To perform a gyro test of general relativity in a satellite and develop associated control technology

NASA Technical Reports Server (NTRS)

Fairbank, W. M.; Everitt, C. W. F.; Debra, D. B.

1977-01-01

A satellite configuration having two gyroscopes with axes parallel to the boresight of a telescope and two at right angles to the telescope and approximately parallel and perpendicular to the earth's axis is proposed for measuring geodetic precessions due to the earth's motion about the sun, higher order geodetic terms calculated from the earth's quadrapole mass moment (0.010 arc-sec/year in a 400 nautical mile polar orbit), and deflection by the sun of the starlight signal for the reference telescope. Data from the experiment also contain large periodic signals due to the annual and orbital aberrations of starlight which are useful in providing a built in reference signal of known amplitude for scaling the relativity signals, and should yield a singularly precise measurement of the parallax of the reference star. The development of the gyroscope and its readout system are discussed, as well as signal integration, drag-free control, and attitude control.

Western Pyrenees geodetic deformation study using the Guipuzcoa GNSS network

NASA Astrophysics Data System (ADS)

Martín, Adriana; Sevilla, Miguel; Zurutuza, Joaquín

2018-07-01

The Basque Country in the north of Spain is located inside the Basque-Cantabrian basin of the western Pyrenees which remarkable seismic-tectonic implications justify the need of geodetic control in the area. In order to perform a crustal deformation study we have analysed all daily observations from the GNSS permanent network of Guipuzcoa and external IGS stations, from January 2007 to November 2011. We have carried out the data processing applying double differences methodology in the automatic processing module BPE (Bernese Processing Engine) from Bernese GNSS software version 5.0. Solution was aligned to geodetic reference framework ITRF2008, by using the IGS08 solution and updated satellite and terrestrial antennas calibration. This five years network study results: Coordinate time series, velocities and baseline lengths variations show internal stability among inner stations and from them with respect to outer IGS stations, concluding that no deformations have been observed.

SIRGAS: the core geodetic infrastructure in Latin America and the Caribbean

NASA Astrophysics Data System (ADS)

Sanchez, L.; Brunini, C.; Drewes, H.; Mackern, V.; da Silva, A.

2013-05-01

Studying, understanding, and modelling geophysical phenomena, such as global change and geodynamics, require geodetic reference frames with (1) an order of accuracy higher than the magnitude of the effects we want to study, (2) consistency and reliability worldwide (the same accuracy everywhere), and (3) a long-term stability (the same order of accuracy at any time). The definition, realisation, maintenance, and wide-utilisation of the International Terrestrial Reference System (ITRS) are oriented to guarantee a globally unified geometric reference frame with reliability at the mm-level, i.e. the International Terrestrial Reference Frame (ITRF). The densification of the global ITRF in Latin America and The Caribbean is given by SIRGAS (Sistema de Referencia Geocéntrico para Las Américas), primary objective of which is to provide the most precise coordinates in the region. Therefore, SIRGAS is the backbone for all regional projects based on the generation, use, and analysis of geo-referenced data at national as well as at international level. Besides providing the reference for a wide range of scientific applications such as the monitoring of Earth's crust deformations, vertical movements, sea level variations, atmospheric studies, etc., SIRGAS is also the platform for practical applications such as engineering projects, digital administration of geographical data, geospatial data infrastructures, etc. According to this, the present contribution describes the main features of SIRGAS, giving special care to those challenges faced to continue providing the best possible, long-term stable and high-precise reference frame for Latin America and the Caribbean.

The Current Status and Tendency of China Millimeter Coordinate Frame Implementation and Maintenance

NASA Astrophysics Data System (ADS)

Cheng, P.; Cheng, Y.; Bei, J.

2017-12-01

China Geodetic Coordinate System 2000 (CGCS2000) was first officially declared as the national standard coordinate system on July 1, 2008. This reference frame was defined in the ITRF97 frame at epoch 2000.0 and included 2600 GPS geodetic control points. The paper discusses differences between China Geodetic Coordinate System 2000 (CGCS2000) and later updated ITRF versions, such as ITRF2014,in terms of technical implementation and maintenance. With the development of the Beidou navigation satellite system, especially third generation of BDS with signal global coverage in the future, and with progress of space geodetic technology, it is possible for us to establish a global millimeter-level reference frame based on space geodetic technology including BDS. The millimeter reference frame implementation concerns two factors: 1) The variation of geocenter motion estimation, and 2) the site nonlinear motion modeling. In this paper, the geocentric inversion methods are discussed and compared among results derived from various technical methods. Our nonlinear site movement modeling focuses on singular spectrum analysis method, which is of apparent advantages over earth physical effect modeling. All presented in the paper expected to provide reference to our future CGCS2000 maintenance.

Unification of height systems in the frame of GGOS

NASA Astrophysics Data System (ADS)

Sánchez, Laura

2015-04-01

Most of the existing vertical reference systems do not fulfil the accuracy requirements of modern Geodesy. They refer to local sea surface levels, are stationary (do not consider variations in time), realize different physical height types (orthometric, normal, normal-orthometric, etc.), and their combination in a global frame presents uncertainties at the metre level. To provide a precise geodetic infrastructure for monitoring the Earth system, the Global Geodetic Observing System (GGOS) of the International Association of Geodesy (IAG), promotes the standardization of the height systems worldwide. The main purpose is to establish a global gravity field-related vertical reference system that (1) supports a highly-precise (at cm-level) combination of physical and geometric heights worldwide, (2) allows the unification of all existing local height datums, and (3) guarantees vertical coordinates with global consistency (the same accuracy everywhere) and long-term stability (the same order of accuracy at any time). Under this umbrella, the present contribution concentrates on the definition and realization of a conventional global vertical reference system; the standardization of the geodetic data referring to the existing height systems; and the formulation of appropriate strategies for the precise transformation of the local height datums into the global vertical reference system. The proposed vertical reference system is based on two components: a geometric component consisting of ellipsoidal heights as coordinates and a level ellipsoid as the reference surface, and a physical component comprising geopotential numbers as coordinates and an equipotential surface defined by a conventional W0 value as the reference surface. The definition of the physical component is based on potential parameters in order to provide reference to any type of physical heights (normal, orthometric, etc.). The conversion of geopotential numbers into metric heights and the modelling of the reference surface (geoid or quasigeoid determination) are considered as steps of the realization. The vertical datum unification strategy is based on (1) the physical connection of height datums to determine their discrepancies, (2) joint analysis of satellite altimetry and tide gauge records to determine time variations of sea level at reference tide gauges, (3) combination of geometrical and physical heights in a well-distributed and high-precise reference frame to estimate the relationship between the individual vertical levels and the global one, and (4) analysis of GNSS time series at reference tide gauges to separate crustal movements from sea level changes. The final vertical transformation parameters are provided by the common adjustment of the observation equations derived from these methods.

Status and Future Developments of SIRGAS

NASA Astrophysics Data System (ADS)

Fortes, L.; Lauría, E.; Brunini, C.; Amaya, W.; Sanchez, L.; Drewes, H.

2007-05-01

This paper presents the status and future developments of the SIRGAS (Geocentric Reference System for the Americas) project. Since its creation, in 1993, SIRGAS has coordinated two continental GPS campaigns in 1995 an 2000, responsible for the establishment of a very accurate 3D reference frame in the region. First focusing on South America, the project has expanded its scope to Latin America since 2001. Currently the maintenance of the SIRGAS reference frame is carried out through more than 80 continuous operating GNSS (Global Navigation Satellite System) stations available in the region, whose data is officially processed by the International GNSS Service (IGS) Regional Network Associate Analysis Centre for SIRGAS (IGS RNACC-SIR), functioning at the DGFI (Deutsches Geodatisches Forschungsinstitut), in Munich, to generate weekly coordinates and velocity information of each continuous GNSS station. Since October 2006, five additional experimental processing centers - located at the Brazilian Institute of Geography and Statistics (IBGE), National Institute of Statistics, Geography and Informatics of Mexico (INEGI), Military Geographic Institute of Argentina (IGM), University of La Plata (UNLP), Argentina, and Geographic Institute Agustín Codazzi, Colombia (IGAC) - have also been processing data from those stations in order to assume the official processing responsibility in near future. Many Latin American countries have already adopted SIRGAS as their new official reference system. Besides, efforts have been carried out in order to have the national geodetic networks of Central American countries connected to the SIRGAS reference frame, which will be accomplished by a GNSS campaign scheduled for the first semester of 2007. In terms of vertical datum, SIRGAS continues to coordinate with each member country all the necessary efforts towards making the geodetic leveling data available together with gravity information in order to support the computation of geopotential numbers, to be unified in a continental adjustment.

Absolute Gravity Datum in the Age of Cold Atom Gravimeters

NASA Astrophysics Data System (ADS)

Childers, V. A.; Eckl, M. C.

2014-12-01

The international gravity datum is defined today by the International Gravity Standardization Net of 1971 (IGSN-71). The data supporting this network was measured in the 1950s and 60s using pendulum and spring-based gravimeter ties (plus some new ballistic absolute meters) to replace the prior protocol of referencing all gravity values to the earlier Potsdam value. Since this time, gravimeter technology has advanced significantly with the development and refinement of the FG-5 (the current standard of the industry) and again with the soon-to-be-available cold atom interferometric absolute gravimeters. This latest development is anticipated to provide improvement in the range of two orders of magnitude as compared to the measurement accuracy of technology utilized to develop ISGN-71. In this presentation, we will explore how the IGSN-71 might best be "modernized" given today's requirements and available instruments and resources. The National Geodetic Survey (NGS), along with other relevant US Government agencies, is concerned about establishing gravity control to establish and maintain high order geodetic networks as part of the nation's essential infrastructure. The need to modernize the nation's geodetic infrastructure was highlighted in "Precise Geodetic Infrastructure, National Requirements for a Shared Resource" National Academy of Science, 2010. The NGS mission, as dictated by Congress, is to establish and maintain the National Spatial Reference System, which includes gravity measurements. Absolute gravimeters measure the total gravity field directly and do not involve ties to other measurements. Periodic "intercomparisons" of multiple absolute gravimeters at reference gravity sites are used to constrain the behavior of the instruments to ensure that each would yield reasonably similar measurements of the same location (i.e. yield a sufficiently consistent datum when measured in disparate locales). New atomic interferometric gravimeters promise a significant increase in accuracy. Our presentation will also explore the impact of such an instrument on our theory of how to constrain the gravity datum and on how to ensure stability, repeatability, and reproducibility across different absolute gravimeter systems.

The First Geodetic VLBI Field Test of LIFT: A 550-km-long Optical Fiber Link for Remote Antenna Synchronization

NASA Astrophysics Data System (ADS)

Perini, Federico; Bortolotti, Claudio; Roma, Mauro; Ambrosini, Roberto; Negusini, Monia; Maccaferri, Giuseppe; Stagni, Matteo; Nanni, Mauro; Clivati, Cecilia; Frittelli, Matteo; Mura, Alberto; Levi, Filippo; Zucco, Massimo; Calonico, Davide; Bertarini, Alessandra; Artz, Thomas

2016-12-01

We present the first field test of the implementation of a coherent optical fiber link for remote antenna synchronization realized in Italy between the Italian Metrological Institute (INRIM) and the Medicina radio observatory of the National Institute for Astrophysics (INAF). The Medicina VLBI antenna participated in the EUR137 experiment carried out in September 2015 using, as reference systems, both the local H-maser and a remote H-maser hosted at the INRIM labs in Turin, separated by about 550 km. In order to assess the quality of the remote clock, the observed radio sources were split into two sets, using either the local or the remote H-maser. A system to switch automatically between the two references was integrated into the antenna field system. The observations were correlated in Bonn and preliminary results are encouraging since fringes were detected with both time references along the full 24 hours of the session. The experimental set-up, the results, and the perspectives for future radio astronomical and geodetic experiments are presented.

Equilibrium figures in geodesy and geophysics.

NASA Astrophysics Data System (ADS)

Moritz, H.

There is an enormous literature on geodetic equilibrium figures, but the various works have not always been interrelated, also for linguistic reasons (English, French, German, Italian, Russian). The author attempts to systematize the various approaches and to use the standard second-order theory for a study of the deviation of the actual earth and of the equipotential reference ellipsoid from an equilibrium figure.

Space Geodetic Technique Co-location in Space: Simulation Results for the GRASP Mission

NASA Astrophysics Data System (ADS)

Kuzmicz-Cieslak, M.; Pavlis, E. C.

2011-12-01

The Global Geodetic Observing System-GGOS, places very stringent requirements in the accuracy and stability of future realizations of the International Terrestrial Reference Frame (ITRF): an origin definition at 1 mm or better at epoch and a temporal stability on the order of 0.1 mm/y, with similar numbers for the scale (0.1 ppb) and orientation components. These goals were derived from the requirements of Earth science problems that are currently the international community's highest priority. None of the geodetic positioning techniques can achieve this goal alone. This is due in part to the non-observability of certain attributes from a single technique. Another limitation is imposed from the extent and uniformity of the tracking network and the schedule of observational availability and number of suitable targets. The final limitation derives from the difficulty to "tie" the reference points of each technique at the same site, to an accuracy that will support the GGOS goals. The future GGOS network will address decisively the ground segment and to certain extent the space segment requirements. The JPL-proposed multi-technique mission GRASP (Geodetic Reference Antenna in Space) attempts to resolve the accurate tie between techniques, using their co-location in space, onboard a well-designed spacecraft equipped with GNSS receivers, a SLR retroreflector array, a VLBI beacon and a DORIS system. Using the anticipated system performance for all four techniques at the time the GGOS network is completed (ca 2020), we generated a number of simulated data sets for the development of a TRF. Our simulation studies examine the degree to which GRASP can improve the inter-technique "tie" issue compared to the classical approach, and the likely modus operandi for such a mission. The success of the examined scenarios is judged by the quality of the origin and scale definition of the resulting TRF.

Global reference frame: Intercomparison of results (SLR, VLBI and GPS)

NASA Technical Reports Server (NTRS)

Ma, Chopo; Watkins, Michael M.; Heflin, M.

1994-01-01

The terrestrial reference frame (TRF) is realized by a set of positions and velocities derived from a combination of the three space geodetic techniques, SLR, VLBI and GPS. The standard International TRF is constructed by the International Earth Rotation Service in such a way that it is stable with time and the addition of new data. An adopted model for overall plate motion, NUVEL-1 NNR, defines the conceptual reference frame in which all the plates are moving. In addition to the measurements made between reference points within the space geodetic instruments, it is essential to have accurate, documented eccentricity measurements from the instrument reference points to ground monuments. Proper local surveys between the set of ground monuments at a site are also critical for the use of the space geodetic results. Eccentricities and local surveys are, in fact, the most common and vexing sources of error in the use of the TRF for such activities as collocation and intercomparison.

Integrating Continuous GPS Time Series and Geodetic Leveling Data to Estimate Secular Vertical Velocity of Taiwan

NASA Astrophysics Data System (ADS)

LAI, Y. R.; Hsu, Y. J.; You, R. J.

2017-12-01

GPS technique services as the most powerful method in monitoring crustal deformation owing to its advantage of temporal continuity. Geodetic leveling is also widely used not only in engineering but also in geophysics applicants due to its high precision in vertical datum determination and spatial continuity advantages. As widely known, the reference frames of GPS and geodetic leveling are different- the former refers to the reference ellipsoid (WGS84 ellipsoid) and the latter refers to the geoid. In order to combine vertical velocity fields from different datums, we decide to examine discrepancy between these two data sets. Moreover, GPS stations and benchmarks always do not locate at the same places. In place of using a spatial reduced function (Ching et.al, JGR, 2011) to find the discrepancy between them, we focused on comparing termporal variation of GPS vertical motions and geodetic leveling displacements. In this study, we analyzed the vertical velocity field from 238 GPS stations and 1634 benchmarks, including the time-period (2000 to 2015) influenced by postseismiceffects from 1999 Chi-Chi earthquake (Mw 7.6), 2003 Chengkung earthquake (Mw 6.8), and so on. After we thoroughly examined all the process and considered coseismic and postseismic deformation of significant earthquakes, we found that the discrepancy of vertical velocity of the GPS station and its nearby benchmarks is about 1 - 2 mm/yr, including several source of errors in data processing. We suggest that this discrepancy of vertical velocity field can be ignored as tolerable error, and two heterogeneous fields can be integrated together without any mathematical presumptions of spatial regression. The result shows that the western coast is suffering sever subsidence with rates up to 40 mm/yr; the Central Range of Taiwan is uplifting with rates about +10 mm/yr and active landslides with significant subsidence of 5-10 mm/yr in local area. A huge velocity contrast of 30 mm;/yr indicating east over west thrusting is shown across the Longitudinal Valley Fault. Estimation of vertical velocity from 2000 to 2015 is consistent with velocities from 2008 to 2015, indicating our modification process is not affected by the Chi-Chi earthquake (Mw 7.6).

The gravity field observations and products at IGFS

NASA Astrophysics Data System (ADS)

Barzaghi, Riccardo; Vergos, George; Bonvalot, Sylvain; Barthelmes, Franz; Reguzzoni, Mirko; Wziontek, Hartmut; Kelly, Kevin

2017-04-01

The International Gravity Field Service (IGFS) is a service of the International Association of Geodesy (IAG) that was established in 2003 at the IAG/IUGG General Assembly in Sapporo (Japan). This service aims at coordinating the actions of the IAG services related to the Earth gravity field, i.e. the Bureau Gravimétrique International (BGI), the International Service for the Geoid (ISG), the International Geodynamics and Earth Tides Service (IGETS), the International Center for Global Earth Models (ICGEM) and the International Digital Elevation Model Service (IDEMS). Also, via its Central Bureau hosted at the Aristotle University of Thessaloniki (Greece), IGFS provides a link to the Global Geodetic Observing System (GGOS) bureaus in order to communicate their requirements and recommendations to the IGFS-Centers. In this work, a presentation is given on the recent activities of the service, namely those related to the contributions to the implementation of: the International Height Reference System/Frame; the Global Geodetic Reference System/Frame; the new Global Absolute Gravity Reference System/Frame. Particularly, the impact that these activities have in improving the estimation of the Earth's gravity field, either at global and local scale, is highlighted also in the framework of GGOS.

A surface spherical harmonic expansion of gravity anomalies on the ellipsoid

NASA Astrophysics Data System (ADS)

Claessens, S. J.; Hirt, C.

2015-10-01

A surface spherical harmonic expansion of gravity anomalies with respect to a geodetic reference ellipsoid can be used to model the global gravity field and reveal its spectral properties. In this paper, a direct and rigorous transformation between solid spherical harmonic coefficients of the Earth's disturbing potential and surface spherical harmonic coefficients of gravity anomalies in ellipsoidal approximation with respect to a reference ellipsoid is derived. This transformation cannot rigorously be achieved by the Hotine-Jekeli transformation between spherical and ellipsoidal harmonic coefficients. The method derived here is used to create a surface spherical harmonic model of gravity anomalies with respect to the GRS80 ellipsoid from the EGM2008 global gravity model. Internal validation of the model shows a global RMS precision of 1 nGal. This is significantly more precise than previous solutions based on spherical approximation or approximations to order or , which are shown to be insufficient for the generation of surface spherical harmonic coefficients with respect to a geodetic reference ellipsoid. Numerical results of two applications of the new method (the computation of ellipsoidal corrections to gravimetric geoid computation, and area means of gravity anomalies in ellipsoidal approximation) are provided.

An Overview of Geodetic and Astrometric VLBI at the Hartebeesthoek Radio Astronomy Observatory

NASA Astrophysics Data System (ADS)

de Witt, A.; Gaylard, M.; Quick, J.; Combrinck, L.

2013-08-01

For astronomical Very Long Baseline Interferometry (VLBI), the Hartebeesthoek Radio Astronomy Observatory (HartRAO), in South Africa operates as part of a number of networks including the European and Australian VLBI networks, global arrays and also space VLBI. HartRAO is the only African representative in the international geodetic VLBI network and participates in regular astrometric and geodetic VLBI programmes. HartRAO will play a major role in the realization of the next generation full-sky celestial reference frame, especially the improvement of the celestial reference frame in the South. The observatory also provides a base for developing the African VLBI Network (AVN), a project to convert redundant satellite Earth-station antennas across Africa to use for radio astronomy. The AVN would greatly facilitate VLBI observations of southern objects. We present an overview of the current capabilities as well as future opportunities for astrometric and geodetic VLBI at HartRAO.

GEOdetic Data assimilation and EStimation of references for climate change InvEstigation. An overall presentation of the French GEODESIE project

NASA Astrophysics Data System (ADS)

Coulot, David; Richard, Jean-Yves

2017-04-01

Many major indicators of climate change are monitored with space observations (sea level rise from satellite altimetry, ice melting from dedicated satellites, etc.). This monitoring is highly dependent on references (positions and velocities of ground observing instruments, orbits of satellites, etc.) that only geodesy can provide. The current accuracy of these references does not permit to fully support the challenges that the constantly evolving Earth system gives rise to, and can consequently limit the accuracy of these indicators. For this reason, in the framework of the Global Geodetic Observing System (GGOS), stringent requirements are fixed to the International Terrestrial Reference Frame (ITRF) for the next decade: an accuracy at the level of 1 mm and a stability at the level of 0.1 mm/yr. This means an improvement of the current quality of ITRF by a factor of 5-10. Improving the quality of the geodetic references is an issue which requires a thorough reassessment of the methodologies involved. The most relevant and promising method to improve this quality is the direct combination (Combination at Observation Level - COL) of the space-geodetic measurements used to compute the official references of the International Earth Rotation and Reference Systems Service (IERS). The GEODESIE project aims at (i) determining highly-accurate global and consistent references (time series of Terrestrial Reference Frames and Celestial Reference Frames, of Earth's Orientation Parameters, and orbits of Earth's observation satellites) and (ii) providing the geophysical and climate research communities with these references, for a better estimation of geocentric sea level rise, ice mass balance and on-going climate changes. Time series of sea levels computed from altimetric data and tide gauge records with these references (orbits of satellite altimeters, Terrestrial Reference Frames and related vertical velocities of stations) will also be provided. The geodetic references will be essential bases for Earth's observation and monitoring to support the challenges of the century. The geocentric time series of sea levels will permit to better apprehend (i) the drivers of the global mean sea level rise and of regional variations of sea level and (ii) the contribution of the global climate change induced by anthropogenic greenhouse gases emissions to these drivers. All the results and computation and quality assessment reports will be available on a Website designed and opened in the Summer of 2017. This project, supported by the French Agence Nationale de la Recherche (ANR) for the period 2017-2020, will be an unprecedented opportunity to provide the French Groupe de Recherche de Géodésie Spatiale (GRGS) with complete simulation and data processing capabilities to prepare the future arrival of space missions such as the European Geodetic Reference Antenna in SPace (E-GRASP) and to significantly contribute to the GGOS with accurate references.

Time Biases in laser ranging measurements; impacts on geodetic products (Reference Frame and Orbitography)

NASA Astrophysics Data System (ADS)

Belli, A.; Exertier, P.; Lemoine, F. G.; Chinn, D. S.; Zelensky, N. P.

2017-12-01

The GGOS objectives are to maintain a geodetic network with an accuracy of 1 mm and a stability of 0.1 mm per year. For years, the laser ranging technique, which provide very accurate absolute distances to geodetic targets enable to determine the scale factor as well as coordinates of the geocenter. In order to achieve this goal, systematic errors appearing in the laser ranging measurements must be considered and solved. In addition to Range Bias (RB), which is the primary source of uncertainty of the technique, Time Bias (TB) has been recently detected by using the Time Transfer by Laser Link (T2L2) space instrument capability on-board the satellite Jason-2. Instead of determining TB through the precise orbit determination that is applied to commonly used geodetic targets like LAGEOS to estimate global geodetic products, we have developed, independently, a dedicated method to transfer time between remote satellite laser ranging stations. As a result, the evolving clock phase shift to UTC of around 30 stations has been determined under the form of time series of time bias per station from 2008 to 2016 with an accuracy of 3-4 ns. It demonstrated the difficulty, in terms of Time & Frequency used technologies, to locally maintain accuracy and long term stability at least in the range of 100 ns that is the current requirement for time measurements (UTC) for the laser ranging technique. Because some laser ranging stations oftently exceed this limit (from 100 ns to a few μs) we have been studying these effects first on the precision orbit determination itself, second on the station positioning. We discuss the impact of TB on LAGEOS and Jason-2 orbits, which appears to affect the along-track component essentially. We also investigate the role of TB in global geodetic parameters as the station coordinates. Finally, we propose to provide the community with time series of time bias of laser ranging stations, under the form of a data- handling-file in order to be included in each orbit determination process that is using laser ranging data since 2008.

GEOdetic Data assimilation and EStimation of references for climate change InvEstigation. An overall presentation of the French GEODESIE project

NASA Astrophysics Data System (ADS)

Nahmani, S.; Coulot, D.; Biancale, R.; Bizouard, C.; Bonnefond, P.; Bouquillon, S.; Collilieux, X.; Deleflie, F.; Garayt, B.; Lambert, S. B.; Laurent-Varin, S.; Marty, J. C.; Mercier, F.; Metivier, L.; Meyssignac, B.; Pollet, A.; Rebischung, P.; Reinquin, F.; Richard, J. Y.; Tertre, F.; Woppelmann, G.

2017-12-01

Many major indicators of climate change are monitored with space observations. This monitoring is highly dependent on references that only geodesy can provide. The current accuracy of these references does not permit to fully support the challenges that the constantly evolving Earth system gives rise to, and can consequently limit the accuracy of these indicators. Thus, in the framework of the GGOS, stringent requirements are fixed to the International Terrestrial Reference Frame (ITRF) for the next decade: an accuracy at the level of 1 mm and a stability at the level of 0.1 mm/yr. This means an improvement of the current quality of ITRF by a factor of 5-10. Improving the quality of the geodetic references is an issue which requires a thorough reassessment of the methodologies involved. The most relevant and promising method to improve this quality is the direct combination of the space-geodetic measurements used to compute the official references of the IERS. The GEODESIE project aims at (i) determining highly-accurate global and consistent references and (ii) providing the geophysical and climate research communities with these references, for a better estimation of geocentric sea level rise, ice mass balance and on-going climate changes. Time series of sea levels computed from altimetric data and tide gauge records with these references will also be provided. The geodetic references will be essential bases for Earth's observation and monitoring to support the challenges of the century. The geocentric time series of sea levels will permit to better apprehend (i) the drivers of the global mean sea level rise and of regional variations of sea level and (ii) the contribution of the global climate change induced by anthropogenic greenhouse gases emissions to these drivers. All the results and computation and quality assessment reports will be available at geodesie_anr.ign.fr.This project, supported by the French Agence Nationale de la Recherche (ANR) for the period 2017-2020, will be an unprecedented opportunity to provide the French Groupe de Recherche de Géodésie Spatiale (GRGS) with complete simulation and data processing capabilities to prepare the future arrival of space missions such as the European Geodetic Reference Antenna in SPace (E-GRASP) and to significantly contribute to the GGOS with accurate references.

Theory and Realization of Global Terrestrial Reference Systems

NASA Technical Reports Server (NTRS)

Ma, C.; Bolotin, S.; Gipson, J.; Gordon, D.; Le Bail, K.; MacMillan, D.

2010-01-01

Comparison of realizations of the terrestrial reference frame. IGN and DGFI both generated realizations of the terrestrial reference frame under the auspices of the IERS from combination of the same space geodetic data. We examined both results for VLBI sites using the full geodetic VLBI data set with respect to site positions and velocities and time series of station positions, baselines and Earth orientation parameters. One of the difficulties encountered was matching episodic breaks and periods of non-linear motion of the two realizations with the VLBI models. Our analysis and conclusions will be discussed.

(abstract) Altimeter Calibration and Geophysical Monitoring from Collocated Measurements at the Harvest Oil Platform

NASA Technical Reports Server (NTRS)

Haines, B. J.; Christensen, E. J.; Norman, R. A.; Parke, M. E.; Born, G. H.; Gill, S. K.

1996-01-01

Prior to the launch of TOPEX/ Poseidon in August 1992, NASA established its primary in situ verification site on the Harvest oil platform located in the Pacific Ocean off the coast of central California. Data from a suite of geodetic and oceanographic instruments attached to the platform have been combined to yield a precise record of absolute sea level simce the beginning of the mission. Critical to the computation of this geocentric sea level record is the precise determination of the platform geodetic height and the vertical velocity in the global terrestrial reference frame.We compare estimates of the platform height and vertical velocity from global positioning system (GPS) data alone and from a combination of GPS and satellite laser ranging (SLR) information. Current estimates suggest the platform is subsiding at a rate of about 8 mm per year. This height information is combined with in situ tide gauge measurements of sea level relative to a platform reference mark in order to produce a continuous record of the local geocentric sea height.

Proposals for Changes in Surveying-Legal Procedures for the Needs of Cadastre in Poland

NASA Astrophysics Data System (ADS)

Mika, Monika

2016-12-01

The aim of this paper is to present the need for changes of geodetic-legal procedures for the cadastre and real estate management. This problem was analyzed both in theoretical and practical terms. In order to better present the analyzed technical and legal procedures, a study of several cases of surveying documentation was made. On their example the problems associated with the surveying services were shows and the formal and legal procedures, on the basis of which described surveying works were done were verified. The problem presented is current and valid not only for the comfort of the surveyor's work, but also from the point of view of the structure and modernization of the real estate cadastre, constituting the backbone of the real estate management. The article emphasized the need to unify the databases of state registers and the digitization of the National Geodetic and Cartographic Resources (PZDGiK). Research has shown that despite the continuous changes of legislation, there are still many shortcomings and gaps, which often complicate the surveying works. The surveyor must analyze and verify all materials he uses, including those obtained from the Centre of Geodetic and Cartographic Documentation (ODGiK). The quality of the geodetic and cartographic elaboration depends largely on the work of the Centre of Geodetic and Cartographic Documentation. The need of modernization of the Land and Buildings Registry, which acts as a cadastre in Poland, has been demonstrated. Furthermore, the unification of data used as reference systems both for plane coordinates and elevation has been proposed.

A high-precision, distributed geodetic strainmeter based on dual coaxial cable Bragg gratings

NASA Astrophysics Data System (ADS)

Fu, J.; Wei, T.; Wei, M.; Shen, Y.

2014-12-01

Observations of surface deformation are essential for understanding a wide range of geophysical problems, including earthquakes, volcanoes, landslides, and glaciers. Current geodetic technologies, such as GPS, InSAR, borehole and laser strainmeters, are costly and limited in their temporal or spatial resolution. Here we present a new type of strainmeter based on coaxial cable Bragg grating (CCBG) sensing technology that provides high-precision, distributed strain measurements at a moderate cost. The coaxial-cable-based strainmeter is designed to cover a long distance (~ km) under harsh environmental conditions such as extreme temperatures. To minimize the environmental noises, two CCBGs are introduced into the geodetic strainmeter: one is used to measure the strain applied on it, and the other acts as a reference only to detect the environmental noises. The environmental noises are removed using the inputs from the strained CCBG and the reference CCBG in a frequency mixer. The test results show that the geodetic strainmeter with dual CCBGs has micron-strain accuracy in the lab.

Status of NGS CORS Network and Its Contribution to the GGOS Infrastructure

NASA Astrophysics Data System (ADS)

Choi, K. K.; Haw, D.; Sun, L.

2017-12-01

Recent advancement of Satellite Geodesy techniques can now contribute to the global frame realization needed to improve worldwide accuracies. These techniques rely on coordinates computed using continuously observed GPS data and corresponding satellite orbits. The GPS-based reference system continues to depend on the physical stability of a ground-based network of points as the primary foundation for these observations. NOAA's National Geodetic Survey (NGS) has been operating Continuously Operating Reference Stations (CORS) to provide direct access to the National Spatial Reference System (NSRS). By virtue of NGS' scientific reputation and leadership in national and international geospatial issues, NGS has determined to increase its participation in the maintenance of the U.S. component of the global GPS tracking network in order to realize a long-term stable national terrestrial reference frame. NGS can do so by leveraging its national leadership role coupled with NGS' scientific expertise, in designating and upgrading a subset of the current tracking network for this purpose. This subset of stations must have the highest operational standards to serve the dual functions: being the U.S. contribution to the international frame, along with providing the link to the national datum. These stations deserve special attention to ensure that the highest possible levels of quality and stability are maintained. To meet this need, NGS is working with the international scientific groups to add and designate these reference stations based on scientific merit such as: colocation with other geodetic techniques, geographic area, and monumentation stability.

Automated and continual determination of radio telescope reference points with sub-mm accuracy: results from a campaign at the Onsala Space Observatory

NASA Astrophysics Data System (ADS)

Lösler, Michael; Haas, Rüdiger; Eschelbach, Cornelia

2013-08-01

The Global Geodetic Observing System (GGOS) requires sub-mm accuracy, automated and continual determinations of the so-called local tie vectors at co-location stations. Co-location stations host instrumentation for several space geodetic techniques and the local tie surveys involve the relative geometry of the reference points of these instruments. Thus, these reference points need to be determined in a common coordinate system, which is a particular challenge for rotating equipment like radio telescopes for geodetic Very Long Baseline Interferometry. In this work we describe a concept to achieve automated and continual determinations of radio telescope reference points with sub-mm accuracy. We developed a monitoring system, including Java-based sensor communication for automated surveys, network adjustment and further data analysis. This monitoring system was tested during a monitoring campaign performed at the Onsala Space Observatory in the summer of 2012. The results obtained in this campaign show that it is possible to perform automated determination of a radio telescope reference point during normal operations of the telescope. Accuracies on the sub-mm level can be achieved, and continual determinations can be realized by repeated determinations and recursive estimation methods.

47 CFR 24.5 - Terms and definitions.

Code of Federal Regulations, 2010 CFR

2010-10-01

... bands. National Geodetic Reference System (NGRS): The name given to all geodetic control data contained... processing system for all Wireless Radio Services. ULS supports electronic filing of all applications and... operating in the 1850-1890 MHz, 1930-1970 MHz, 2130-2150 MHz, and 2180-2200 MHz bands. Effective Radiated...

Enhanced three-dimensional stochastic adjustment for combined volcano geodetic networks

NASA Astrophysics Data System (ADS)

Del Potro, R.; Muller, C.

2009-12-01

Volcano geodesy is unquestionably a necessary technique in studies of physical volcanology and for eruption early warning systems. However, as every volcano geodesist knows, obtaining measurements of the required resolution using traditional campaigns and techniques is time consuming and requires a large manpower. Moreover, most volcano geodetic networks worldwide use a combination of data from traditional techniques; levelling, electronic distance measurements (EDM), triangulation and Global Navigation Satellite Systems (GNSS) but, in most cases, these data are surveyed, analysed and adjusted independently. This then leaves it to the authors’ criteria to decide which technique renders the most realistic results in each case. Herein we present a way of solving the problem of inter-methodology data integration in a cost-effective manner following a methodology were all the geodetic data of a redundant, combined network (e.g. surveyed by GNSS, levelling, distance, angular data, INSAR, extensometers, etc.) is adjusted stochastically within a single three-dimensional referential frame. The adjustment methodology is based on the least mean square method and links the data with its geometrical component providing combined, precise, three-dimensional, displacement vectors, relative to external reference points as well as stochastically-quantified, benchmark-specific, uncertainty ellipsoids. Three steps in the adjustment allow identifying, and hence dismissing, flagrant measurement errors (antenna height, atmospheric effects, etc.), checking the consistency of external reference points and a final adjustment of the data. Moreover, since the statistical indicators can be obtained from expected uncertainties in the measurements of the different geodetic techniques used (i.e. independent of the measured data), it is possible to run a priori simulations of a geodetic network in order to constrain its resolution, and reduce logistics, before the network is even built. In this work we present a first effort to apply this technique to a new volcano geodetic network on Arenal volcano in Costa Rica, using triangulation, EDM and GNSS data from four campaigns. An a priori simulation, later confirmed by field measurements, of the movement detection capacity of different benchmarks within the network, shows how the network design is optimised to detect smaller displacement at the points where these are expected. Data from the four campaigns also proves the repeatability and consistency of the statistical indicators. A preliminary interpretation of the geodetic data relative to Arenal’s volcanic activity could indicate a correlation between displacement velocity and direction with the location and thickness of the recent lava flow field. This then suggests that a deflation caused by the weight of the lava field could be obscuring the effects of possible deep magmatic sources. Although this study is specific to Arenal volcano and its regional tectonic setting, we suggest that the cost-effective, high-quality results we present, prove the methodology’s potential to be incorporated into the design and analysis of volcano geodetic networks worldwide.

Permanent Monitoring of the Reference Point of the 20m Radio Telescope Wettzell

NASA Technical Reports Server (NTRS)

Neidhardt, Alexander; Losler, Michael; Eschelbach, Cornelia; Schenk, Andreas

2010-01-01

To achieve the goals of the VLBI2010 project and the Global Geodetic Observing System (GGOS), an automated monitoring of the reference points of the various geodetic space techniques, including Very Long Baseline Interferometry (VLBI), is desirable. The resulting permanent monitoring of the local-tie vectors at co-location stations is essential to obtain the sub-millimeter level in the combinations. For this reason a monitoring system was installed at the Geodetic Observatory Wettzell by the Geodetic Institute of the University of Karlsruhe (GIK) to observe the 20m VLBI radio telescope from May to August 2009. A specially developed software from GIK collected data from automated total station measurements, meteorological sensors, and sensors in the telescope monument (e.g., Invar cable data). A real-time visualization directly offered a live view of the measurements during the regular observation operations. Additional scintillometer measurements allowed refraction corrections during the post-processing. This project is one of the first feasibility studies aimed at determining significant deformations of the VLBI antenna due to, for instance, changes in temperature.

Multi-geodetic characterization of the seasonal signal at the CERGA geodetic reference, France

NASA Astrophysics Data System (ADS)

Memin, A.; Viswanathan, V.; Fienga, A.; Santamaría-Gómez, A.; Boy, J. P.

2016-12-01

Crustal deformations due to surface-mass loading account for a significant part of the variability in geodetic time series. A perfect understanding of the loading signal observed by geodetic techniques should help in improving terrestrial reference frame (TRF) realizations. Yet, discrepancies between crustal motion estimates from models of surface-mass loading and observations are still too large so that no model is currently recommended by the IERS for reducing the data. We investigate the discrepancy observed in the seasonal variations of the CERGA station, South of France.We characterize the seasonal motions of the reference geodetic station CERGA from GNSS, SLR and LLR. We compare the station motion observed with GNSS and SLR and we estimate changes in the station-to-the-moon distance using an improved processing strategy. We investigate the consistency between these geodetic techniques and compare the observed station motion with that estimated using models of surface-mass change. In that regard, we compute atmospheric loading effects using surface pressure fields from ECMWF, assuming an ocean response according to the classical inverted barometer (IB) assumption, considered to be valid for periods typically exceeding a week. We also used general circulation ocean models (ECCO and GLORYS) forced by wind, heat and fresh water fluxes. The continental water storage is described using GLDAS/Noah and MERRA-land models.Using the surface-mass models, we estimate the amplitude of the seasonal vertical motion of the CERGA station ranging between 5 and 10 mm with a maximum reached in August, mostly due to hydrology. The horizontal seasonal motion of the station may reach up to 3 mm. Such a station motion should induce a change in the distance to the moon reaching up to 10 mm, large enough to be detected in LLR time series and compared to GNSS- and SLR-derived motion.

Seismology and space-based geodesy

NASA Technical Reports Server (NTRS)

Tralli, David M.; Tajima, Fumiko

1993-01-01

The potential of space-based geodetic measurement of crustal deformation in the context of seismology is explored. The achievements of seismological source theory and data analyses, mechanical modeling of fault zone behavior, and advances in space-based geodesy are reviewed, with emphasis on realizable contributions of space-based geodetic measurements specifically to seismology. The fundamental relationships between crustal deformation associated with an earthquake and the geodetically observable data are summarized. The response and spatial and temporal resolution of the geodetic data necessary to understand deformation at various phases of the earthquake cycle is stressed. The use of VLBI, SLR, and GPS measurements for studying global geodynamics properties that can be investigated to some extent with seismic data is discussed. The potential contributions of continuously operating strain monitoring networks and globally distributed geodetic observatories to existing worldwide modern digital seismographic networks are evaluated in reference to mutually addressable problems in seismology, geophysics, and tectonics.

Deriving a geocentric reference frame for satellite positioning and navigation

NASA Technical Reports Server (NTRS)

Malla, R. P.; Wu, S.-C.

1988-01-01

With the advent of Earth-orbiting geodetic satellites, nongeocentric datums or reference frames have become things of the past. Accurate geocentric three-dimensional positioning is now possible and is of great importance for various geodetic and oceanographic applications. While relative positioning accuracy of a few centimeters has become a reality using very long baseline interferometry (VLBI), the uncertainty in the offset of the adopted coordinate system origin from the geocenter is still believed to be on the order of 1 meter. Satellite laser ranging (SLR), however, is capable of determining this offset to better than 10 cm, but this is possible only after years of measurements. Global Positioning System (GPS) measurements provide a powerful tool for an accurate determination of this origin offset. Two strategies are discussed. The first strategy utilizes the precise relative positions that were predetermined by VLBI to fix the frame orientation and the absolute scaling, while the offset from the geocenter is determined from GPS measurements. Three different cases are presented under this strategy. The reference frame thus adopted will be consistent with the VLBI coordinate system. The second strategy establishes a reference frame by holding only the longitude of one of the tracking sites fixed. The absolute scaling is determined by the adopted gravitational constant (GM) of the Earth; and the latitude is inferred from the time signature of the Earth rotation in the GPS measurements. The coordinate system thus defined will be a geocentric Earth-fixed coordinate system.

The combined geodetic network adjusted on the reference ellipsoid - a comparison of three functional models for GNSS observations

NASA Astrophysics Data System (ADS)

Kadaj, Roman

2016-12-01

The adjustment problem of the so-called combined (hybrid, integrated) network created with GNSS vectors and terrestrial observations has been the subject of many theoretical and applied works. The network adjustment in various mathematical spaces was considered: in the Cartesian geocentric system on a reference ellipsoid and on a mapping plane. For practical reasons, it often takes a geodetic coordinate system associated with the reference ellipsoid. In this case, the Cartesian GNSS vectors are converted, for example, into geodesic parameters (azimuth and length) on the ellipsoid, but the simple form of converted pseudo-observations are the direct differences of the geodetic coordinates. Unfortunately, such an approach may be essentially distorted by a systematic error resulting from the position error of the GNSS vector, before its projection on the ellipsoid surface. In this paper, an analysis of the impact of this error on the determined measures of geometric ellipsoid elements, including the differences of geodetic coordinates or geodesic parameters is presented. Assuming that the adjustment of a combined network on the ellipsoid shows that the optimal functional approach in relation to the satellite observation, is to create the observational equations directly for the original GNSS Cartesian vector components, writing them directly as a function of the geodetic coordinates (in numerical applications, we use the linearized forms of observational equations with explicitly specified coefficients). While retaining the original character of the Cartesian vector, one avoids any systematic errors that may occur in the conversion of the original GNSS vectors to ellipsoid elements, for example the vector of the geodesic parameters. The problem is theoretically developed and numerically tested. An example of the adjustment of a subnet loaded from the database of reference stations of the ASG-EUPOS system was considered for the preferred functional model of the GNSS observations.

Towards a Refined Realisation of the Terrestrial Reference System

NASA Astrophysics Data System (ADS)

Angermann, D.; Drewes, H.; Meisel, B.; Kruegel, M.; Tesmer, V.

2004-12-01

Global reference frames provide the framework for scientific investigations of the Earth's system (e.g. plate tectonics, sea level change, seasonal and secular loading signals, atmosphere dynamics, Earth orientation excitation), as well as for many practical applications (e.g. surveying and navigation). Today, space geodetic techniques allow to determine geodetic parameters (e.g. station positions, Earth rotation) with a precision of a few millimeters (or even better). However, this high accuracy is not reflected by current realisations of the terrestrial reference system. To fully exploit the potential of the space geodetic observations for investigations of various global and regional, short-term, seasonal and secular phenomena of the Earth's system, the reference frame must be realised with the highest accuracy, spatial and temporal consistency and stability over decades. Furthermore, future progress in Earth sciences will fundamentally depend on understanding the Earth as a system, into which the three areas of geodetic research (geometry/deformation, Earth rotation, gravity) are to be integrated. The presentation focusses on various aspects that must be considered for a refined realisation of the terrestrial reference system, such as the development of suitable methods for the combination of the contributing space geodetic observations, the realisation of the TRF datum and the parameterisation of site motions. For this purpose we investigated time series of station positions and datum parameters obtained from VLBI, SLR, GPS and DORIS solutions, and compared the results at co-location sites and with other studies. Furthermore, we present results obtained from a TRS realisation based on epoch (weekly/daily) normal equations with station positions and daily Earth Orientation Parameters (EOP) using five years (1999-2004) of VLBI, SLR, GPS and DORIS data. This refined approach has major advantages compared to past TRF realisations based on multi-year solutions with station positions at a given epoch and constant velocities, as for instance non-linear effects of site positions and datum parameters can be considered, and consistency between TRF and EOPs can be achieved. First results of this new approach are promising.

Low-Cost GNSS Receivers for Local Monitoring: Experimental Simulation, and Analysis of Displacements

PubMed Central

Biagi, Ludovico; Grec, Florin Cătălin; Negretti, Marco

2016-01-01

The geodetic monitoring of local displacements and deformations is often needed for civil engineering structures and natural phenomena like, for example, landslides. A local permanent GNSS (Global Navigation Satellite Systems) network can be installed: receiver positions in the interest area are estimated and monitored with respect to reference stations. Usually, GNSS geodetic receivers are adopted and provide results with accuracies at the millimeter level: however, they are very expensive and the initial cost and the risk of damage and loss can discourage this approach. In this paper the accuracy and the reliability of low-cost u-blox GNSS receivers are experimentally investigated for local monitoring. Two experiments are analyzed. In the first, a baseline (65 m long) between one geodetic reference receiver and one u-blox is continuously observed for one week: the data are processed by hourly sessions and the results provide comparisons between two processing packages and a preliminary accuracy assessment. Then, a network composed of one geodetic and two u-blox receivers is set up. One u-blox is installed on a device (slide) that allows to apply controlled displacements. The geodetic and the other u-blox (at about 130 m) act as references. The experiment lasts about two weeks. The data are again processed by hourly sessions. The estimated displacements of the u-blox on the slide are analyzed and compared with the imposed displacements. All of the results are encouraging: in the first experiment the standard deviations of the residuals are smaller than 5 mm both in the horizontal and vertical; in the second, they are slightly worse but still satisfactory (5 mm in the horizontal and 13 mm in vertical) and the imposed displacements are almost correctly identified. PMID:27983707

Low-Cost GNSS Receivers for Local Monitoring: Experimental Simulation, and Analysis of Displacements.

PubMed

Biagi, Ludovico; Grec, Florin Cătălin; Negretti, Marco

2016-12-15

The geodetic monitoring of local displacements and deformations is often needed for civil engineering structures and natural phenomena like, for example, landslides. A local permanent GNSS (Global Navigation Satellite Systems) network can be installed: receiver positions in the interest area are estimated and monitored with respect to reference stations. Usually, GNSS geodetic receivers are adopted and provide results with accuracies at the millimeter level: however, they are very expensive and the initial cost and the risk of damage and loss can discourage this approach. In this paper the accuracy and the reliability of low-cost u-blox GNSS receivers are experimentally investigated for local monitoring. Two experiments are analyzed. In the first, a baseline (65 m long) between one geodetic reference receiver and one u-blox is continuously observed for one week: the data are processed by hourly sessions and the results provide comparisons between two processing packages and a preliminary accuracy assessment. Then, a network composed of one geodetic and two u-blox receivers is set up. One u-blox is installed on a device (slide) that allows to apply controlled displacements. The geodetic and the other u-blox (at about 130 m) act as references. The experiment lasts about two weeks. The data are again processed by hourly sessions. The estimated displacements of the u-blox on the slide are analyzed and compared with the imposed displacements. All of the results are encouraging: in the first experiment the standard deviations of the residuals are smaller than 5 mm both in the horizontal and vertical; in the second, they are slightly worse but still satisfactory (5 mm in the horizontal and 13 mm in vertical) and the imposed displacements are almost correctly identified.

KALREF—A Kalman filter and time series approach to the International Terrestrial Reference Frame realization

NASA Astrophysics Data System (ADS)

Wu, Xiaoping; Abbondanza, Claudio; Altamimi, Zuheir; Chin, T. Mike; Collilieux, Xavier; Gross, Richard S.; Heflin, Michael B.; Jiang, Yan; Parker, Jay W.

2015-05-01

The current International Terrestrial Reference Frame is based on a piecewise linear site motion model and realized by reference epoch coordinates and velocities for a global set of stations. Although linear motions due to tectonic plates and glacial isostatic adjustment dominate geodetic signals, at today's millimeter precisions, nonlinear motions due to earthquakes, volcanic activities, ice mass losses, sea level rise, hydrological changes, and other processes become significant. Monitoring these (sometimes rapid) changes desires consistent and precise realization of the terrestrial reference frame (TRF) quasi-instantaneously. Here, we use a Kalman filter and smoother approach to combine time series from four space geodetic techniques to realize an experimental TRF through weekly time series of geocentric coordinates. In addition to secular, periodic, and stochastic components for station coordinates, the Kalman filter state variables also include daily Earth orientation parameters and transformation parameters from input data frames to the combined TRF. Local tie measurements among colocated stations are used at their known or nominal epochs of observation, with comotion constraints applied to almost all colocated stations. The filter/smoother approach unifies different geodetic time series in a single geocentric frame. Fragmented and multitechnique tracking records at colocation sites are bridged together to form longer and coherent motion time series. While the time series approach to TRF reflects the reality of a changing Earth more closely than the linear approximation model, the filter/smoother is computationally powerful and flexible to facilitate incorporation of other data types and more advanced characterization of stochastic behavior of geodetic time series.

Transformation pipelines for PROJ.4

NASA Astrophysics Data System (ADS)

Knudsen, Thomas; Evers, Kristian

2017-04-01

For more than 2 decades, PROJ.4 has been the globally leading map projection library for open source (and probably also closed source) geospatial software. While focusing on mathematically well defined 2D projections from geographical to planar coordinates, PROJ.4 has nevertheless, since its introduction in the 1980s, provided limited support for more general geodetic datum transformations, and has gradually introduced a higher degree of support for 3D coordinate data and reference systems. The support has, however, been implemented over a long period of time, as need became evident and opportunity was found, by a number of different people, with different needs and at different times. Hence, the PROJ.4 3D support has not been the result of neither deep geodetic, nor careful code architectural considerations. This has resulted in a library that supports only a subset of commonly occurring geodetic transformations. To be more specific: It supports any datum shift that can be completed by a combination of two Helmert shifts (to and from a pivot datum) and, potentially, also a non-linear planar correction derived from interpolation in a correction grid. While this is sufficient for most small scale mapping activities, it is not at all sufficient for operational geodetic use, nor for many of the rapidly emerging high accuracy geospatial applications in agriculture, construction, transportation and utilities. To improve this situation, we have introduced a new framework for implementation of geodetic transformations, which will appear in the next release of the PROJ.4 library. Before describing the details, let us first remark that most cases of geodetic transformations can be expressed as a series of elementary operations, the output of one operation being the input of the next. E.g. when going from UTM zone 32, datum ED50, to UTM zone 32, datum ETRS89, one must, in the simplest case, go through 5 steps: Back-project the UTM coordinates to geographic coordinates Convert the geographic coordinates to 3D cartesian geocentric coordinates Apply a Helmert transformation from ED50 to ETRS89 Convert back from cartesian to geographic coordinates Finally project the geographic coordinates to UTM zone 32 planar coordinates. The homology between these steps and a Unix shell style pipeline is evident. With this as its main architectural inspiration, the primary feature of our implementation is a pipeline driver, that takes as its user supplied arguments, a series of elementary operations, which it strings together in order to implement the full transformation needed. Also, we have added a number of elementary geodetic operations, including Helmert transformations, general high order polynomial shifts (2D Horner's scheme) and the abridged Molodensky transformation. In anticipation of upcoming support for full time-varying transformations, we also introduce a 4D spatiotemporal data type, and a programming interface (API) for handling this. With these improvements in place, we assert that PROJ.4 is now well on its way from being a mostly-map-projection library, to becoming an almost-generic-geodetic-transformation library.

LAGEOS geodetic analysis-SL7.1

NASA Technical Reports Server (NTRS)

Smith, D. E.; Kolenkiewicz, R.; Dunn, P. J.; Klosko, S. M.; Robbins, J. W.; Torrence, M. H.; Williamson, R. G.; Pavlis, E. C.; Douglas, N. B.; Fricke, S. K.

1991-01-01

Laser ranging measurements to the LAGEOS satellite from 1976 through 1989 are related via geodetic and orbital theories to a variety of geodetic and geodynamic parameters. The SL7.1 analyses are explained of this data set including the estimation process for geodetic parameters such as Earth's gravitational constant (GM), those describing the Earth's elasticity properties (Love numbers), and the temporally varying geodetic parameters such as Earth's orientation (polar motion and Delta UT1) and tracking site horizontal tectonic motions. Descriptions of the reference systems, tectonic models, and adopted geodetic constants are provided; these are the framework within which the SL7.1 solution takes place. Estimates of temporal variations in non-conservative force parameters are included in these SL7.1 analyses as well as parameters describing the orbital states at monthly epochs. This information is useful in further refining models used to describe close-Earth satellite behavior. Estimates of intersite motions and individual tracking site motions computed through the network adjustment scheme are given. Tabulations of tracking site eccentricities, data summaries, estimated monthly orbital and force model parameters, polar motion, Earth rotation, and tracking station coordinate results are also provided.

Explicitly computing geodetic coordinates from Cartesian coordinates

NASA Astrophysics Data System (ADS)

Zeng, Huaien

2013-04-01

This paper presents a new form of quartic equation based on Lagrange's extremum law and a Groebner basis under the constraint that the geodetic height is the shortest distance between a given point and the reference ellipsoid. A very explicit and concise formulae of the quartic equation by Ferrari's line is found, which avoids the need of a good starting guess for iterative methods. A new explicit algorithm is then proposed to compute geodetic coordinates from Cartesian coordinates. The convergence region of the algorithm is investigated and the corresponding correct solution is given. Lastly, the algorithm is validated with numerical experiments.

New test of general relativity - Measurement of de Sitter geodetic precession rate for lunar perigee

NASA Technical Reports Server (NTRS)

Bertotti, Bruno; Ciufolini, Ignazio; Bender, Peter L.

1987-01-01

According to general relativity, the calculated rate of motion of lunar perigee should include a contribution of 19.2 msec/yr from geodetic precession. It is shown that existing analyses of lunar-laser-ranging data confirm the general-relativistic rate for geodetic precession with respect to the planetary dynamical frame. In addition, the comparison of earth-rotation results from lunar laser ranging and from VLBI shows that the relative drift of the planetary dynamical frame and the extragalactic VLBI reference frame is small. The estimated accuracy is about 10 percent.

An Analysis of Strain Accumulation in the Western Part of Black Sea Region in Turkey

NASA Astrophysics Data System (ADS)

Deniz, I.; Avsar, N. B.; Deniz, R.; Mekik, C.; Kutoglu, S.

2014-12-01

Turkish National Horizontal Control Network (TNHCN) based on the European Datum 1950 (ED50) was used as the principal geodetic network until 2005 in Turkey. Since 2005, Turkish Large Scale Map and Map Information Production Regulation have required that that all the densification points have been produced within the same datum of Turkish National Fundamental GPS Network (TNFGN) put into practise in 2002 and based on International Terrestrial Reference Frame (ITRF). Hence, the common points were produced in both European Datum 1950 (ED50), and TNFGN.It is known that the geological and geophysical information about the network area can be obtained by the evaluation of the coordinate and scale variations in a geodetic network. For one such evaluation, the coordinate variations and velocities of network points, and also the strains are investigated. However, the principal problem in derivation of velocities arises from two different datums. In this context, the computation of velocities using the coordinate data of the ED50 and TNFGN is not accurate and reliable. Likewise, the analysis of strain from the coordinate differences is not reliable. However, due to the fact that the scale of a geodetic network is independent from datum, the strains can be derived from scale variations accurately and reliably.In this study, a test area limited 39.5°-42.0° northern latitudes and 31.0°-37.0° eastern longitudes was chosen. The benchmarks in this test area are composed of 30 geodetic control points derived with the aim of cadastral and engineering applications. We used data mining to investigate the common benchmarks in both reference systems for this area. Accordingly, the ED50 and TNFGN coordinates refer 1954 and 2005, respectively. Thus, it has been investigated the strain accumulation of 51 years in this region. It should be also noted that since 1954, the earthquakes have not registered greater than magnitude 6.0 in the test area. It is a considerable situation for this evaluation. The finite element analysis is used in order to derive the strain accumulation and rates in the test area (Figure 1). The results have been indicated that the minimum and maximum strains are 17μs and 3041μs, respectively.

Establishing a Modern Ground Network for Space Geodesy Applications

NASA Technical Reports Server (NTRS)

Pearlman, M.; Pavlis, E.; Altamimi, Z.; Noll, C.

2010-01-01

Ground-based networks of co-located space-geodesy techniques (VLBI, SLR, GLASS, DORIS) are the basis for the development and maintenance of the :International Terrestrial deference Frame (ITRE), which is the basis for our metric measurements of global change. The Global Geodetic Observing System (GGOS) within the International Association of Geodesy has established a task to develop a strategy to design, integrate and maintain the fundamental geodetic network and supporting infrastructure in a sustainable way to satisfy the long-term requirements for the reference frame. The GGOS goal is an origin definition at I mm or better and a temporal stability on the order of 0.1 mm/y, with similar numbers for the scale and orientation components. These goals are based on scientific requirements to address sea level rise with confidence. As a first step, simulations focused on establishing the optimal global SLR and VLBI network, since these two techniques alone are sufficient to define the reference frame. The GLASS constellations will then distribute the reference frame to users anywhere on the Earth. Using simulated data to be collected by the future networks, we investigated various designs and the resulting accuracy in the origin, scale and orientation of the resulting ITRF. We present here the results of extensive simulation studies aimed at designing optimal global geodetic networks to support GGOS science products. Current estimates are the network will require 24 - 32 globally distributed co-location sites. Stations in the near global network will require geologically stable sites witla good weather, established infrastructure, and local support and personnel. EGOS will seek groups that are interested in participation. GGOS intends to issues a Call for Participation of groups that would like to take part in the network implementation and operation_ Some examples of integrated stations currently in operation or under development will be presented. We will examine necessary conditions and challenges in designing a co-location station.

Analysis of difference between direct and geodetic mass balance measurements at South Cascade Glacier, Washington

USGS Publications Warehouse

Krimmel, R.M.

1999-01-01

Net mass balance has been measured since 1958 at South Cascade Glacier using the 'direct method,' e.g. area averages of snow gain and firn and ice loss at stakes. Analysis of cartographic vertical photography has allowed measurement of mass balance using the 'geodetic method' in 1970, 1975, 1977, 1979-80, and 1985-97. Water equivalent change as measured by these nearly independent methods should give similar results. During 1970-97, the direct method shows a cumulative balance of about -15 m, and the geodetic method shows a cumulative balance of about -22 m. The deviation between the two methods is fairly consistent, suggesting no gross errors in either, but rather a cumulative systematic error. It is suspected that the cumulative error is in the direct method because the geodetic method is based on a non-changing reference, the bedrock control, whereas the direct method is measured with reference to only the previous year's summer surface. Possible sources of mass loss that are missing from the direct method are basal melt, internal melt, and ablation on crevasse walls. Possible systematic measurement errors include under-estimation of the density of lost material, sinking stakes, or poorly represented areas.

A solution of the geodetic boundary value problem to order e3

NASA Technical Reports Server (NTRS)

Mather, R. S.

1973-01-01

A solution is obtained for the geodetic boundary value problem which defines height anomalies to + or - 5 cm, if the earth were rigid. The solution takes into account the existence of the earth's topography, together with its ellipsoidal shape and atmosphere. A relation is also established between the commonly used solution of Stokes and a development correct to order e cubed. The data requirements call for a complete definition of gravity anomalies at the surface of the earth and a knowledge of elevation characteristics at all points exterior to the geoid. In addition, spherical harmonic representations must be based on geocentric rather than geodetic latitudes.

First-order design of geodetic networks using the simulated annealing method

NASA Astrophysics Data System (ADS)

Berné, J. L.; Baselga, S.

2004-09-01

The general problem of the optimal design for a geodetic network subject to any extrinsic factors, namely the first-order design problem, can be dealt with as a numeric optimization problem. The classic theory of this problem and the optimization methods are revised. Then the innovative use of the simulated annealing method, which has been successfully applied in other fields, is presented for this classical geodetic problem. This method, belonging to iterative heuristic techniques in operational research, uses a thermodynamical analogy to crystalline networks to offer a solution that converges probabilistically to the global optimum. Basic formulation and some examples are studied.

The AuScope geodetic VLBI array

NASA Astrophysics Data System (ADS)

Lovell, J. E. J.; McCallum, J. N.; Reid, P. B.; McCulloch, P. M.; Baynes, B. E.; Dickey, J. M.; Shabala, S. S.; Watson, C. S.; Titov, O.; Ruddick, R.; Twilley, R.; Reynolds, C.; Tingay, S. J.; Shield, P.; Adada, R.; Ellingsen, S. P.; Morgan, J. S.; Bignall, H. E.

2013-06-01

The AuScope geodetic Very Long Baseline Interferometry array consists of three new 12-m radio telescopes and a correlation facility in Australia. The telescopes at Hobart (Tasmania), Katherine (Northern Territory) and Yarragadee (Western Australia) are co-located with other space geodetic techniques including Global Navigation Satellite Systems (GNSS) and gravity infrastructure, and in the case of Yarragadee, satellite laser ranging (SLR) and Doppler Orbitography and Radiopositioning Integrated by Satellite (DORIS) facilities. The correlation facility is based in Perth (Western Australia). This new facility will make significant contributions to improving the densification of the International Celestial Reference Frame in the Southern Hemisphere, and subsequently enhance the International Terrestrial Reference Frame through the ability to detect and mitigate systematic error. This, combined with the simultaneous densification of the GNSS network across Australia, will enable the improved measurement of intraplate deformation across the Australian tectonic plate. In this paper, we present a description of this new infrastructure and present some initial results, including telescope performance measurements and positions of the telescopes in the International Terrestrial Reference Frame. We show that this array is already capable of achieving centimetre precision over typical long-baselines and that network and reference source systematic effects must be further improved to reach the ambitious goals of VLBI2010.

Network global navigation satellite system survey to harmonize water-surface elevation data for the Rainy River Basin

USGS Publications Warehouse

Ziegeweid, Jeffrey R.; Silliker, R. Jason; Densmore, Brenda K.; Krahulik, Justin

2016-08-15

Continuously recording water-level streamgages in Rainy Lake and Namakan Reservoir are used to regulate water levels according to rule curves established in 2000 by the International Joint Commission; however, water levels at streamgages were referenced to a variety of vertical datums, confounding efforts to model the flow of water through the system, regulate water levels during periods of high inflow, and evaluate the effectiveness of the rule curves. In October 2014, the U.S. Geological Survey, Natural Resources Canada, International Joint Commission, and National Park Service began a joint field study with the goal of obtaining precise elevations referenced to a uniform vertical datum for all reference marks used to set water levels at streamgages throughout Rainy Lake and Namakan Reservoir. This report was prepared by the U.S. Geological Survey in cooperation with Natural Resources Canada, International Joint Commission, and National Park Service.Three field crews deployed Global Navigation Satellite System receivers statically over 16 reference marks colocated with active and discontinued water-level streamgages throughout Rainy River, Rainy Lake, Namakan Reservoir, and select tributaries of Rainy Lake and Namakan Reservoir. A Global Navigation Satellite System receiver also was deployed statically over a National Geodetic Survey cooperative base network control station for use as a quality-control reference mark. Satellite data were collected simultaneously during a 5-day period and processed independently by the U.S. Geological Survey and Natural Resources Canada to obtain accurate positioning and elevations for the 17 surveyed reference marks. Processed satellite data were used to convert published water levels to elevations above sea level referenced to the Canadian Geodetic Vertical Datum of 2013 in order to compare water-surface elevations referenced to a uniform vertical datum throughout the study area. In this report, an “offset” refers to the correction applied to published data from a particular streamgage to produce elevation data referenced to a specified vertical datum.Offsets were applied to water-level data from surveyed streamgages to further evaluate the accuracy and utility of updated reference mark elevations presented in this report. Daily mean water levels from active streamgages surveyed in this study were converted to water-surface elevations referenced to the Canadian Geodetic Vertical Datum of 2013. Graphical comparisons of water-surface elevations for streamgages in Namakan Reservoir, Rainy Lake, and selected rivers are presented (referencing the Canadian Geodetic Vertical Datum of 2013). Offsets presented in this report can be used in the evaluation of rule curves and in flood damage curves that fully assess the benefits of one regulation approach over another. In addition, offsets may be used to calibrate hydraulic models developed for four narrows that connect lakes of Namakan Reservoir, refine digital elevation models, and support modeling studies designed to assess the effects of rule curves on aquatic vegetation, benthic invertebrates, northern pike, and walleye.

Long-term mass variations from SLR, VLBI and GPS data

NASA Astrophysics Data System (ADS)

Luceri, Vincenza; Sciarretta, Cecilia; Bianco, Giuseppe

2013-04-01

The second-degree geopotential coefficients reflect the behaviour of the Earth's inertia tensor of order 2 which describes the main mass variations of our planet impacting polar motion and length of day (EOP). SLR, VLBI and GPS allow the estimation of those variations, either directly in the case of SLR through its dynamics, and indirectly, for all the three geodetic techniques, by deriving excitation functions from the EOP estimations. The geodetic estimates include the influence of the Earth's atmosphere and oceans, both from their mass and motion components, which can be modelled using the atmospheric and oceanic angular momenta variations. The different C21, S21 and C20 geodetic time series are compared in order to evaluate their coherence and their response to the mass variations after the removal of the motion terms. Moreover, the residual signal contents of the geodetic values, deprived by the atmospheric and oceanic mass and motion components, will be investigated.

Multi-geodetic characterization of the seasonal signal at the CERGA geodetic reference station, France

NASA Astrophysics Data System (ADS)

Mémin, Anthony; Viswanathan, Vishnu; Fienga, Agnes; Santamarìa-Gómez, Alvaro; Boy, Jean-Paul; Cavalié, Olivier; Deleflie, Florent; Exertier, Pierre; Bernard, Jean-Daniel; Hinderer, Jacques

2017-04-01

Crustal deformations due to surface-mass loading account for a significant part of the variability in geodetic time series. A perfect understanding of the loading signal observed by geodetic techniques should help in improving terrestrial reference frame (TRF) realizations. Yet, discrepancies between crustal motion estimates from models of surface-mass loading and observations are still too large so that no model is currently recommended by the IERS for reducing the observations. We investigate the discrepancy observed in the seasonal variations of the position at the CERGA station, South of France. We characterize the seasonal motions of the reference geodetic station CERGA from GNSS, SLR, LLR and InSAR. We investigate the consistency between the station motions deduced from these geodetic techniques and compare the observed station motion with that estimated using models of surface-mass change. In that regard, we compute atmospheric loading effects using surface pressure fields from ECMWF, assuming an ocean response according to the classical inverted barometer (IB) assumption, considered to be valid for periods typically exceeding a week. We also used general circulation ocean models (ECCO and GLORYS) forced by wind, heat and fresh water fluxes. The continental water storage is described using GLDAS/Noah and MERRA-land models. Using the surface-mass models, we estimate that the seasonal signal due to loading deformation at the CERGA station is about 8-9, 1-2 and 1-2 mm peak-to-peak in Up, North and East component, respectively. There is a very good correlation between GPS observations and non-tidal loading predicted deformation due to atmosphere, ocean and hydrology which is the main driver of seasonal signal at CERGA. Despite large error bars, LLR observations agree reasonably well with GPS and non-tidal loading predictions in Up component. Local deformation as observed by InSAR is very well correlated with GPS observations corrected for non-tidal loading. Finally, we estimate local mass changes using the absolute gravity measurement campaigns available at the station and the global models of surface-mass change. We compute the induced station motion that we compare with the local deformation observed by InSAR and GPS.

Single-frequency receivers as master permanent stations in GNSS networks: precision and accuracy of the positioning in mixed networks

NASA Astrophysics Data System (ADS)

Dabove, Paolo; Manzino, Ambrogio Maria

2015-04-01

The use of GPS/GNSS instruments is a common practice in the world at both a commercial and academic research level. Since last ten years, Continuous Operating Reference Stations (CORSs) networks were born in order to achieve the possibility to extend a precise positioning more than 15 km far from the master station. In this context, the Geomatics Research Group of DIATI at the Politecnico di Torino has carried out several experiments in order to evaluate the achievable precision obtainable with different GNSS receivers (geodetic and mass-market) and antennas if a CORSs network is considered. This work starts from the research above described, in particular focusing the attention on the usefulness of single frequency permanent stations in order to thicken the existing CORSs, especially for monitoring purposes. Two different types of CORSs network are available today in Italy: the first one is the so called "regional network" and the second one is the "national network", where the mean inter-station distances are about 25/30 and 50/70 km respectively. These distances are useful for many applications (e.g. mobile mapping) if geodetic instruments are considered but become less useful if mass-market instruments are used or if the inter-station distance between master and rover increases. In this context, some innovative GNSS networks were developed and tested, analyzing the performance of rover's positioning in terms of quality, accuracy and reliability both in real-time and post-processing approach. The use of single frequency GNSS receivers leads to have some limits, especially due to a limited baseline length, the possibility to obtain a correct fixing of the phase ambiguity for the network and to fix the phase ambiguity correctly also for the rover. These factors play a crucial role in order to reach a positioning with a good level of accuracy (as centimetric o better) in a short time and with an high reliability. The goal of this work is to investigate about the real effect and how is the contribute of L1 mass-market permanent stations to the CORSs Network both for geodetic and low-cost receivers; in particular is described how the use of the network products which are generated by the network (in real-time and post-processing) can improve the accuracy and precision of a rover 5, 10 and 15 km far from the nearest station. Some tests have been carried out considering different types of receivers (geodetic and mass market) and antennas (patch and geodetic). The tests have been conducted considering several positioning approaches (static, stop and go and real time) in order to make the analysis more complete. Good and interesting results were obtained: the followed approach will be useful for many types of applications (landslides monitoring, traffic control), especially where the inter-station distances of GNSS permanent station are greater than 30 km.

The AuScope Project and Trans-Tasman VLBI

NASA Technical Reports Server (NTRS)

Lovell, Jim; Dickey, John; Gulyaev, Sergei; Natusch, Tim; Titov, Oleg; Tingay, Steven

2010-01-01

Three 12-meter radio telescopes are being built in Australia (the AuScope project) and one in New Zealand. These facilities will be fully-equipped for undertaking S and X-band geodetic VLBI observations and correlation will take place on a software correlator (part of the AuScope project). All sites are equipped with permanent GPS receivers to provide co-location of several space geodetic techniques. The following scientific tasks of geodesy and astrometry are considered. 1. Improvement and densification of the International Celestial Reference Frame in the southern hemisphere; 2. Improvement of the International Terrestrial Reference Frame in the region; 3. Measurement of intraplate deformation of the Australian tectonic plate.

A Comparative Study of the Applied Methods for Estimating Deflection of the Vertical in Terrestrial Geodetic Measurements

PubMed Central

Vittuari, Luca; Tini, Maria Alessandra; Sarti, Pierguido; Serantoni, Eugenio; Borghi, Alessandra; Negusini, Monia; Guillaume, Sébastien

2016-01-01

This paper compares three different methods capable of estimating the deflection of the vertical (DoV): one is based on the joint use of high precision spirit leveling and Global Navigation Satellite Systems (GNSS), a second uses astro-geodetic measurements and the third gravimetric geoid models. The working data sets refer to the geodetic International Terrestrial Reference Frame (ITRF) co-location sites of Medicina (Northern, Italy) and Noto (Sicily), these latter being excellent test beds for our investigations. The measurements were planned and realized to estimate the DoV with a level of precision comparable to the angular accuracy achievable in high precision network measured by modern high-end total stations. The three methods are in excellent agreement, with an operational supremacy of the astro-geodetic method, being faster and more precise than the others. The method that combines leveling and GNSS has slightly larger standard deviations; although well within the 1 arcsec level, which was assumed as threshold. Finally, the geoid model based method, whose 2.5 arcsec standard deviations exceed this threshold, is also statistically consistent with the others and should be used to determine the DoV components where local ad hoc measurements are lacking. PMID:27104544

Determination of Galactic Aberration from VLBI Measurements and Its Effect on VLBI Reference Frames and Earth Orientation Parameters.

NASA Astrophysics Data System (ADS)

MacMillan, D. S.

2014-12-01

Galactic aberration is due to the motion of the solar system barycenter around the galactic center. It results in a systematic pattern of apparent proper motion of radio sources observed by VLBI. This effect is not currently included in VLBI analysis. Estimates of the size of this effect indicate that it is important that this secular aberration drift be accounted for in order to maintain an accurate celestial reference frame and allow astrometry at the several microarcsecond level. Future geodetic observing systems are being designed to be capable of producing a future terrestrial reference frame with an accuracy of 1 mm and stability of 0.1 mm/year. We evaluate the effect galactic aberration on attaining these reference frame goals. This presentation will discuss 1) the estimation of galactic aberration from VLBI data and 2) the effect of aberration on the Terrestrial and Celestial Reference Frames and the Earth Orientation Parameters that connect these frames.

Verification of the Polish Geodetic Reference Frame by Means of a New Solution Based on Permanent GNSS Data from the Years 2011-2014

NASA Astrophysics Data System (ADS)

Liwosz, T.; Ryczywolski, M.

2016-12-01

The new solution for the Polish geodetic primary GNSS network was created to verify the currently used reference frame (PL-ETRF2000). The new solution is based on more GNSS data (more daily observation sessions included, a longer data timespan, GLONASS observations added) which were processed in a newer reference frame (IGb08) according to up-to-date methodology and using the latest version of Bernese GNSS Software. The new long-term solution (spanning 3.7 years) was aligned to the IGb08 reference frame using a minimum constraints approach. We categorized Polish reference stations into two categories according to their data length. We obtained good agreement of the new solution with the PL-ETRF2000: for most stations position differences did not exceed 5 mm in horizontal, and 10 mm in vertical components. However, for 30 stations we observed discontinuities in position time series, mostly due to GNSS equipment changes, which occured after the introduction of PL-ETRF2000. Position changes due to the discontinuities reached 9.1 mm in horizontal components, and 26.9 mm in vertical components. The new solution takes into account position discontinuities, and in addition also includes six new stations which were installed after the introduction of the PL-ETRF2000. Therefore, we propose to update the currently-used reference frame for the Polish geodetic primary network (PL-ETRF2000) with the new solution. The new solution was also accepted by the EUREF Technical Working Group as a class A solution (highest accuracy) according to EUREF standards.

A Cost-Effective Geodetic Strainmeter Based on Dual Coaxial Cable Bragg Gratings

PubMed Central

Fu, Jihua; Wang, Xu; Wei, Tao; Wei, Meng; Shen, Yang

2017-01-01

Observations of surface deformation are essential for understanding a wide range of geophysical problems, including earthquakes, volcanoes, landslides, and glaciers. Current geodetic technologies, such as global positioning system (GPS), interferometric synthetic aperture radar (InSAR), borehole and laser strainmeters, are costly and limited in their temporal or spatial resolutions. Here we present a new type of strainmeters based on the coaxial cable Bragg grating (CCBG) sensing technology that provides cost-effective strain measurements. Two CCBGs are introduced into the geodetic strainmeter: one serves as a sensor to measure the strain applied on it, and the other acts as a reference to detect environmental noises. By integrating the sensor and reference signals in a mixer, the environmental noises are minimized and a lower mixed frequency is obtained. The lower mixed frequency allows for measurements to be taken with a portable spectrum analyzer, rather than an expensive spectrum analyzer or a vector network analyzer (VNA). Analysis of laboratory experiments shows that the strain can be measured by the CCBG sensor, and the portable spectrum analyzer can make measurements with the accuracy similar to the expensive spectrum analyzer, whose relative error to the spectrum analyzer R3272 is less than ±0.4%. The outputs of the geodetic strainmeter show a linear relationship with the strains that the CCBG sensor experienced. The measured sensitivity of the geodetic strainmeter is about −0.082 kHz/με; it can cover a large dynamic measuring range up to 2%, and its nonlinear errors can be less than 5.3%. PMID:28417925

A Cost-Effective Geodetic Strainmeter Based on Dual Coaxial Cable Bragg Gratings.

PubMed

Fu, Jihua; Wang, Xu; Wei, Tao; Wei, Meng; Shen, Yang

2017-04-12

Observations of surface deformation are essential for understanding a wide range of geophysical problems, including earthquakes, volcanoes, landslides, and glaciers. Current geodetic technologies, such as global positioning system (GPS), interferometric synthetic aperture radar (InSAR), borehole and laser strainmeters, are costly and limited in their temporal or spatial resolutions. Here we present a new type of strainmeters based on the coaxial cable Bragg grating (CCBG) sensing technology that provides cost-effective strain measurements. Two CCBGs are introduced into the geodetic strainmeter: one serves as a sensor to measure the strain applied on it, and the other acts as a reference to detect environmental noises. By integrating the sensor and reference signals in a mixer, the environmental noises are minimized and a lower mixed frequency is obtained. The lower mixed frequency allows for measurements to be taken with a portable spectrum analyzer, rather than an expensive spectrum analyzer or a vector network analyzer (VNA). Analysis of laboratory experiments shows that the strain can be measured by the CCBG sensor, and the portable spectrum analyzer can make measurements with the accuracy similar to the expensive spectrum analyzer, whose relative error to the spectrum analyzer R3272 is less than ±0.4%. The outputs of the geodetic strainmeter show a linear relationship with the strains that the CCBG sensor experienced. The measured sensitivity of the geodetic strainmeter is about -0.082 kHz/με; it can cover a large dynamic measuring range up to 2%, and its nonlinear errors can be less than 5.3%.

The Australian Geodetic Observing Program. Current Status and Future Plans

NASA Astrophysics Data System (ADS)

Johnston, G.; Dawson, J. H.

2015-12-01

Over the last decade, the Australian government has through programs like AuScope, the Asia Pacific Reference Frame (APREF), and the Pacific Sea Level Monitoring (PSLM) Project made a significant contribution to the Global Geodetic Observing Program. In addition to supporting the national research priorities, this contribution is justified by Australia's growing economic dependence on precise positioning to underpin efficient transportation, geospatial data management, and industrial automation (e.g., robotic mining and precision agriculture) and the consequent need for the government to guarantee provision of precise positioning products to the Australian community. It is also well recognised within Australia that there is an opportunity to exploit our near unique position as being one of the few regions in the world to see all new and emerging satellite navigation systems including Galileo (Europe), GPS III (USA), GLONASS (Russia), Beidou (China), QZSS (Japan) and IRNSS (India). It is in this context that the Australian geodetic program will build on earlier efforts and further develop its key geodetic capabilities. This will include the creation of an independent GNSS analysis capability that will enable Australia to contribute to the International GNSS Service (IGS) and an upgrade of key geodetic infrastructure including the national VLBI and GNSS arrays. This presentation will overview the significant geodetic activities undertaken by the Australian government and highlight its future plans.

Construction Theory and Noise Analysis Method of Global CGCS2000 Coordinate Frame

NASA Astrophysics Data System (ADS)

Jiang, Z.; Wang, F.; Bai, J.; Li, Z.

2018-04-01

The definition, renewal and maintenance of geodetic datum has been international hot issue. In recent years, many countries have been studying and implementing modernization and renewal of local geodetic reference coordinate frame. Based on the precise result of continuous observation for recent 15 years from state CORS (continuously operating reference system) network and the mainland GNSS (Global Navigation Satellite System) network between 1999 and 2007, this paper studies the construction of mathematical model of the Global CGCS2000 frame, mainly analyzes the theory and algorithm of two-step method for Global CGCS2000 Coordinate Frame formulation. Finally, the noise characteristic of the coordinate time series are estimated quantitatively with the criterion of maximum likelihood estimation.

International Laser Ranging Service (ILRS) 2003-2004 Annual Report

NASA Technical Reports Server (NTRS)

Pearlman, Michael (Editor); Noll, Carey (Editor)

2005-01-01

The International Laser Ranging Service (ILRS) organizes and coordinates Satellite Laser Ranging (SLR) and Lunar Laser Ranging (LLR) to support programs in geodetic, geophysical, and lunar research activities and provides the International Earth Rotation and Reference Systems Service (IERS) with products important to the maintenance of an accurate International Terrestrial Reference Frame (ITRF). This reference frame provides the stability through which systematic measurements of the Earth can be made over thousands of kilometers, decades of time, and evolution of measurement technology. This 2003-2004 ILRS annual report is comprised of individual contributions from ILRS components within the international geodetic community for the years 2003-2004. The report documents changes and progress of the ILRS and is also available on the ILRS Web site at http://ilrs.gsfc.nasa.gov/reports/ilrs_reports/ilrsar_2003.html.

Why the Greenwich Meridian Moved

DTIC Science & Technology

2015-08-01

that are related to the geocentric reference frame introduced by the Bureau International de l’Heure (BIH) in 1984. This BIHTerrestrial System provided...the basis for orientation of subsequent geocentric reference frames, including all realizations of theWorld Geodetic Sys- tem 1984 and the...astronomical time. The coordinates of satellite-navigation receivers are provided in reference frames that are related to the geocentric reference

Seafloor Geodetic Observations West off Miyake-jima Island During January to April, 2001

NASA Astrophysics Data System (ADS)

Mochizuki, M.; Sato, M.; Yabuki, T.; Yoshida, Z.; Asada, A.

2001-12-01

An intensive earthquake swarm started under Miyake-jima Island, 180km south off Honshu, Japan, on June 26, 2000. The earthquake swarm migrated towards northwest off from Miyake-jima Island, where numerous earthquakes, more than 100,000, were detected within about two months and an extensive crustal deformation was observed by on-land geodetic observations. We started seafloor geodetic observation in this area to monitor seafloor deformation for the better understandings of underground magmatic activities. This poster presents summary of the observations and preliminary results from them. IIS has been developing a method of seafloor geodesy in corporation with JHD. A combination of kinematic GPS measurements and precise acoustic ranging techniques is employed to achieve centimeter-level seafloor geodesy. First observation site using the method was Kumano trough, where the Philippine Sea Plate subducts beneath Japan Islands arc. It was confirmed that the method could locate horizontal position of the seafloor reference points within 4 cm standard deviation ( Asada and Yabuki, 2001). We apply this seafloor positioning method to the observations conducted in the area west off Miyake-jima Island. Three seafloor reference systems ( Stations A, B, and C ), which consist of three or four acoustic mirror transponders, were built in triangle area surrounded by three islands, Miyake-jima, Nii-jima and Koudu-jima Islands, in November and December, 2000. This area would be deformed remarkably due to underground magma movement including magma injections from deeper part. Distances among three reference systems were set about 15 km. Stations A and B were located on the two sides of NW-SE trending seismically active area. The observations have been conducted three times until present, in January, February and April 2001. We obtained less data than we had expected due to bad sea condition in January and February observations. Also, a fast and quickly varying ocean current prevented us from keeping ship lines as they were planned at the observation in April. Although the amount and quality of the data might be less and worse than projected, analyses are going on by improving software suitable for each data set in order to extract as much information as possible from available data.

Using GPS and leveling data in local precise geoid determination and case study

NASA Astrophysics Data System (ADS)

Erol, B.; Çelik, R. N.; Erol, S.

2003-04-01

As an important result of developments in high technology, satellite based positioning system has become to use in geodesy and surveying professions. These developments made the measurement works more accurate, more practical and more economic. Today, one of the most recent used satellite based positioning system is GPS (Global Positioning System) and it serves to a very wide range of geodetic applications from monitoring earth crustal deformations till building the basis for a GIS (Geographical Information Systems). The most efficient way to utilize GPS measurement system for mentioned aims is having a reliable geodetic infrastructure in working area. Geodetic infrastructure is a extraterrestrial and time system and involved 4D geodetic reference networks. The forth element of mentioned geodetic reference system is time because having an accurate and reliable geodetic infrastructure is needed to up-date according to physical realities of the region. By the help of a well designed geodetic infrastructure accurate and reliable coordinates of a point can be generated economically every time in a global and up-to-date system. Geoid is one of the important parts of a geodetic infrastructure. As it is well known, geoid is the equipotential surface of the Earth's gravity field which best fits, in a least squares sense, global mean sea level and it is reference for physical height systems like orthometric and normal heights. In the most of the applications, vertical position of a point is expressed with orthometric or normal height. Orthometric or normal height is a physical concept and gives vertical position of a point uniquely. On the other hand, vertical position of a point is derived in a geometrical system according to GPS measurements. GPS datum is WGS84 and in this system, an ellipsoidal height of a point is calculated according to WGS84 ellipsoid. So, it is an necessity to transform the ellipsoidal heights to orthometric heights and this procedure is managed with the fundamental mathematical equation; N=h-H. In the equation, "h" is the ellipsoidal height of a point P, "H" is the orthometric height of the same point and "N" is "geoid undulation" value. Normally, "H" orthometric height derived from leveling measurements but these measurements are tiring applications. So, while having a geoid model in the region as the essential part of geodetic infrastructure, number leveling measurements can be reduced from the procedure and by this way time and labor is saved. Geoid determination is modeling of the data in such a way that geoid height can be obtained digital or analog at a point whose horizontal position is known. Geoid models can be developed for local, regional or global regions. Using satellite techniques, especially GPS, in geodetic measurements are increased importance of geoid. Because geoid is a natural tie between high precision geodetic coordinates and coordinates which obtained from satellites. There are several geoid determination methods according to used data and models. GPS/Leveling method, which is also known as geometric method, is one of these methods. This method is appropriate for local precise geoid determination in respectively small areas. In this paper, it is going to be given information about GPS/Leveling geoid determination method and mathematical models, which are used in geoid determination with this method. And Izmir local geoid model will be presented as a case study. Izmir is one of the west metropolitan cities of Turkey and located near Aegean Sea. The topography is extremely rough in the region. There are two different geoid determination studies which were carried out in 1996 and 2001 in Izmir. Both models were accomplished according to GPS/Leveling method. Those two geoid models of Izmir Metropolitan region are investigated in here, the conflict of them were discussed. The relation between distribution of common reference points and differences of geoid undulation values, which are calculated from both models separately, were analyzed and also effects of topography on conflict of both geoid model was investigated. The results of the study and suggestions are going to be given in the paper.

Analysis of Site Position Time Series Derived From Space Geodetic Solutions

NASA Astrophysics Data System (ADS)

Angermann, D.; Meisel, B.; Kruegel, M.; Tesmer, V.; Miller, R.; Drewes, H.

2003-12-01

This presentation deals with the analysis of station coordinate time series obtained from VLBI, SLR, GPS and DORIS solutions. We also present time series for the origin and scale derived from these solutions and discuss their contribution to the realization of the terrestrial reference frame. For these investigations we used SLR and VLBI solutions computed at DGFI with the software systems DOGS (SLR) and OCCAM (VLBI). The GPS and DORIS time series were obtained from weekly station coordinates solutions provided by the IGS, and from the joint DORIS analysis center (IGN-JPL). We analysed the time series with respect to various aspects, such as non-linear motions, periodic signals and systematic differences (biases). A major focus is on a comparison of the results at co-location sites in order to identify technique- and/or solution related problems. This may also help to separate and quantify possible effects, and to understand the origin of still existing discrepancies. Technique-related systematic effects (biases) should be reduced to the highest possible extent, before using the space geodetic solutions for a geophysical interpretation of seasonal signals in site position time series.

A new velocity field for Africa from combined GPS and DORIS space geodetic Solutions: Contribution to the definition of the African reference frame (AFREF)

NASA Astrophysics Data System (ADS)

Saria, E.; Calais, E.; Altamimi, Z.; Willis, P.; Farah, H.

2013-04-01

We analyzed 16 years of GPS and 17 years of Doppler orbitography and radiopositioning integrated by satellite (DORIS) data at continuously operating geodetic sites in Africa and surroundings to describe the present-day kinematics of the Nubian and Somalian plates and constrain relative motions across the East African Rift. The resulting velocity field describes horizontal and vertical motion at 133 GPS sites and 9 DORIS sites. Horizontal velocities at sites located on stable Nubia fit a single plate model with a weighted root mean square residual of 0.6 mm/yr (maximum residual 1 mm/yr), an upper bound for plate-wide motions and for regional-scale deformation in the seismically active southern Africa and Cameroon volcanic line. We confirm significant southward motion ( ˜ 1.5 mm/yr) in Morocco with respect to Nubia, consistent with earlier findings. We propose an updated angular velocity for the divergence between Nubia and Somalia, which provides the kinematic boundary conditions to rifting in East Africa. We update a plate motion model for the East African Rift and revise the counterclockwise rotation of the Victoria plate and clockwise rotation of the Rovuma plate with respect to Nubia. Vertical velocities range from - 2 to +2 mm/yr, close to their uncertainties, with no clear geographic pattern. This study provides the first continent-wide position/velocity solution for Africa, expressed in International Terrestrial Reference Frame (ITRF2008), a contribution to the upcoming African Reference Frame (AFREF). Except for a few regions, the African continent remains largely under-sampled by continuous space geodetic data. Efforts are needed to augment the geodetic infrastructure and openly share existing data sets so that the objectives of AFREF can be fully reached.

Unification of Intercontinental Height Systems based on the Fixed Geodetic Boundary Value Problem - A Case Study in Spherical Approximation

NASA Astrophysics Data System (ADS)

Grombein, T.; Seitz, K.; Heck, B.

2013-12-01

In general, national height reference systems are related to individual vertical datums defined by specific tide gauges. The discrepancy of these vertical datums causes height system biases that range in an order of 1-2 m at a global scale. Continental height systems can be connected by spirit leveling and gravity measurements along the leveling lines as performed for the definition of the European Vertical Reference Frame. In order to unify intercontinental height systems, an indirect connection is needed. For this purpose, global geopotential models derived from recent satellite missions like GOCE provide an important contribution. However, to achieve a highly-precise solution, a combination with local terrestrial gravity data is indispensable. Such combinations result in the solution of a Geodetic Boundary Value Problem (GBVP). In contrast to previous studies, mostly related to the traditional (scalar) free GBVP, the present paper discusses the use of the fixed GBVP for height system unification, where gravity disturbances instead of gravity anomalies are applied as boundary values. The basic idea of our approach is a conversion of measured gravity anomalies to gravity disturbances, where unknown datum parameters occur that can be associated with height system biases. In this way, the fixed GBVP can be extended by datum parameters for each datum zone. By evaluating the GBVP at GNSS/leveling benchmarks, the unknown datum parameters can be estimated in a least squares adjustment. Beside the developed theory, we present numerical results of a case study based on the spherical fixed GBVP and boundary values simulated by the use of the global geopotential model EGM2008. In a further step, the impact of approximations like linearization as well as topographic and ellipsoidal effects is taken into account by suitable reduction and correction terms.

Geodetic VLBI observations at Simeiz station

NASA Astrophysics Data System (ADS)

Volvach, A.; Petrov, L.; Nesterov, N.

Very long baseline interferometry (VLBI) observations under international geodetic programs are carried out at Simeiz station since June 1994. 22-m radiotelescope is equipped by dual-band S/X receivers, hydrogen maser CH-70 and data acquisition terminal Mark-IIIA. Observations are conducted by 24 hours sessions scheduled 6-15 times per year. Observational programs are a part of common efforts for maintenance of terrestrial reference frame, celestial reference frame and monitoring Earth orientation parameters carried out by international community under the auspices of International VLBI Service (IVS). Data are recorded on magnetic tapes which are shipped to correlator centers for further correlation and fringing. Fringed data are archived and are freely available via Internet for scientific analysis after 1-2 months after observations.

Simulations of VLBI observations of a geodetic satellite providing co-location in space

NASA Astrophysics Data System (ADS)

Anderson, James M.; Beyerle, Georg; Glaser, Susanne; Liu, Li; Männel, Benjamin; Nilsson, Tobias; Heinkelmann, Robert; Schuh, Harald

2018-02-01

We performed Monte Carlo simulations of very-long-baseline interferometry (VLBI) observations of Earth-orbiting satellites incorporating co-located space-geodetic instruments in order to study how well the VLBI frame and the spacecraft frame can be tied using such measurements. We simulated observations of spacecraft by VLBI observations, time-of-flight (TOF) measurements using a time-encoded signal in the spacecraft transmission, similar in concept to precise point positioning, and differential VLBI (D-VLBI) observations using angularly nearby quasar calibrators to compare their relative performance. We used the proposed European Geodetic Reference Antenna in Space (E-GRASP) mission as an initial test case for our software. We found that the standard VLBI technique is limited, in part, by the present lack of knowledge of the absolute offset of VLBI time to Coordinated Universal Time at the level of microseconds. TOF measurements are better able to overcome this problem and provide frame ties with uncertainties in translation and scale nearly a factor of three smaller than those yielded from VLBI measurements. If the absolute time offset issue can be resolved by external means, the VLBI results can be significantly improved and can come close to providing 1 mm accuracy in the frame tie parameters. D-VLBI observations with optimum performance assumptions provide roughly a factor of two higher uncertainties for the E-GRASP orbit. We additionally simulated how station and spacecraft position offsets affect the frame tie performance.

An Investigation on the Use of Different Centroiding Algorithms and Star Catalogs in Astro-Geodetic Observations

NASA Astrophysics Data System (ADS)

Basoglu, Burak; Halicioglu, Kerem; Albayrak, Muge; Ulug, Rasit; Tevfik Ozludemir, M.; Deniz, Rasim

2017-04-01

In the last decade, the importance of high-precise geoid determination at local or national level has been pointed out by Turkish National Geodesy Commission. The Commission has also put objective of modernization of national height system of Turkey to the agenda. Meanwhile several projects have been realized in recent years. In Istanbul city, a GNSS/Levelling geoid was defined in 2005 for the metropolitan area of the city with an accuracy of ±3.5cm. In order to achieve a better accuracy in this area, "Local Geoid Determination with Integration of GNSS/Levelling and Astro-Geodetic Data" project has been conducted in Istanbul Technical University and Bogazici University KOERI since January 2016. The project is funded by The Scientific and Technological Research Council of Turkey. With the scope of the project, modernization studies of Digital Zenith Camera System are being carried on in terms of hardware components and software development. Accentuated subjects are the star catalogues, and centroiding algorithm used to identify the stars on the zenithal star field. During the test observations of Digital Zenith Camera System performed between 2013-2016, final results were calculated using the PSF method for star centroiding, and the second USNO CCD Astrograph Catalogue (UCAC2) for the reference star positions. This study aims to investigate the position accuracy of the star images by comparing different centroiding algorithms and available star catalogs used in astro-geodetic observations conducted with the digital zenith camera system.

VLBI tracking of GNSS satellites: recent achievements

NASA Astrophysics Data System (ADS)

Liu, Li; Heinkelmann, Robert; Tornatore, Vincenza; Li, Jinling; Mora-Diaz, Julian; Nilsson, Tobias; Karbon, Maria; Raposo-Pulido, Virginia; Soja, Benedikt; Xu, Minghui; Lu, Cuixian; Schuh, Harald

2014-05-01

While the ITRF (International Terrestrial Reference Frame) is realized by the combination of the various space geodetic techniques, VLBI (Very Long Baseline Interferometry) is the only technique for determining the ICRF (International Celestial Reference Frame) through its observations of extragalactic radio sources. Therefore, small inconsistencies between the two important frames do exist. According to recent comparisons of parameters derived by GNSS (Global Navigation Satellite Systems) and VLBI (e.g. troposphere delays, gradients, UT1-UTC), evidences of discrepancies obtained by the vast amounts of data become obvious. Terrestrial local ties can provide a way to interlink the otherwise independent technique-specific reference frames but only to some degree. It is evident that errors in the determination of the terrestrial ties, e.g. due to the errors when transforming the locally surveyed coordinates into global Cartesian three dimensional coordinates, introduce significant errors in the combined analysis of space geodetic techniques. A new concept for linking the space geodetic techniques might be to introduce celestial ties, e.g. realized by technique co-location on board of satellites. A small satellite carrying a variety of space geodetic techniques is under investigation at GFZ. Such a satellite would provide a new observing platform with its own additional unknowns, such as the orbit or atmospheric drag parameters. A link of the two techniques VLBI and GNSS might be achieved in a more direct way as well: by VLBI tracking of GNSS satellites. Several tests of this type of observation were already successfully carried out. This new kind of hybrid VLBI-GNSS observation would comprise a new direct inter-technique tie without the involvement of surveying methods and would enable improving the consistency of the two space geodetic techniques VLBI and GNSS, in particular of their celestial frames. Recently the radio telescopes Wettzell and Onsala have successfully observed a GNSS satellite for the first time, using also new receiver developments, done at Wettzell. In this contribution we want to develop the motivation for this kind of innovative observation and we will show first results of the test observations.

Three-dimensional stochastic adjustment of volcano geodetic network in Arenal volcano, Costa Rica

NASA Astrophysics Data System (ADS)

Muller, C.; van der Laat, R.; Cattin, P.-H.; Del Potro, R.

2009-04-01

Volcano geodetic networks are a key instrument to understanding magmatic processes and, thus, forecasting potentially hazardous activity. These networks are extensively used on volcanoes worldwide and generally comprise a number of different traditional and modern geodetic surveying techniques such as levelling, distances, triangulation and GNSS. However, in most cases, data from the different methodologies are surveyed, adjusted and analysed independently. Experience shows that the problem with this procedure is the mismatch between the excellent correlation of position values within a single technique and the low cross-correlation of such values within different techniques or when the same network is surveyed shortly after using the same technique. Moreover one different independent network for each geodetic surveying technique strongly increase logistics and thus the cost of each measurement campaign. It is therefore important to develop geodetic networks which combine the different geodetic surveying technique, and to adjust geodetic data together in order to better quantify the uncertainties associated to the measured displacements. In order to overcome the lack of inter-methodology data integration, the Geomatic Institute of the University of Applied Sciences of Western Switzerland (HEIG-VD) has developed a methodology which uses a 3D stochastic adjustment software of redundant geodetic networks, TRINET+. The methodology consists of using each geodetic measurement technique for its strengths relative to other methodologies. Also, the combination of the measurements in a single network allows more cost-effective surveying. The geodetic data are thereafter adjusted and analysed in the same referential frame. The adjustment methodology is based on the least mean square method and links the data with the geometry. Trinet+ also allows to run a priori simulations of the network, hence testing the quality and resolution to be expected for a determined network even before it is built. Moreover, a posterior analysis enables identifying, and hence dismissing, measurement errors (antenna height, atmospheric effects, etc.). Here we present a preliminary effort to apply this technique to volcano deformation. A geodetic network has been developed on the western flank of the Arenal volcano in Costa Rica. It is surveyed with GNSS, angular and EDM (Electronic Distance Measurements) measurements. Three measurement campaigns were carried out between February and June 2008. The results show consistent and accurate output of deformation and uncertainty for each of the 12 benchmarks surveyed. The three campaigns also prove the repeatability and consistency of the statistical indicators and the displacement vectors. Although, this methodology has only recently been applied to volcanoes, we suggest that due to its cost-effective high-quality results it has the potential to be incorporated into the design and analysis of volcano geodetic networks worldwide.

Propagation of uncertainty by Monte Carlo simulations in case of basic geodetic computations

NASA Astrophysics Data System (ADS)

Wyszkowska, Patrycja

2017-12-01

The determination of the accuracy of functions of measured or adjusted values may be a problem in geodetic computations. The general law of covariance propagation or in case of the uncorrelated observations the propagation of variance (or the Gaussian formula) are commonly used for that purpose. That approach is theoretically justified for the linear functions. In case of the non-linear functions, the first-order Taylor series expansion is usually used but that solution is affected by the expansion error. The aim of the study is to determine the applicability of the general variance propagation law in case of the non-linear functions used in basic geodetic computations. The paper presents errors which are a result of negligence of the higher-order expressions and it determines the range of such simplification. The basis of that analysis is the comparison of the results obtained by the law of propagation of variance and the probabilistic approach, namely Monte Carlo simulations. Both methods are used to determine the accuracy of the following geodetic computations: the Cartesian coordinates of unknown point in the three-point resection problem, azimuths and distances of the Cartesian coordinates, height differences in the trigonometric and the geometric levelling. These simulations and the analysis of the results confirm the possibility of applying the general law of variance propagation in basic geodetic computations even if the functions are non-linear. The only condition is the accuracy of observations, which cannot be too low. Generally, this is not a problem with using present geodetic instruments.

Error assessment of local tie vectors in space geodesy

NASA Astrophysics Data System (ADS)

Falkenberg, Jana; Heinkelmann, Robert; Schuh, Harald

2014-05-01

For the computation of the ITRF, the data of the geometric space-geodetic techniques on co-location sites are combined. The combination increases the redundancy and offers the possibility to utilize the strengths of each technique while mitigating their weaknesses. To enable the combination of co-located techniques each technique needs to have a well-defined geometric reference point. The linking of the geometric reference points enables the combination of the technique-specific coordinate to a multi-technique site coordinate. The vectors between these reference points are called "local ties". The realization of local ties is usually reached by local surveys of the distances and or angles between the reference points. Identified temporal variations of the reference points are considered in the local tie determination only indirectly by assuming a mean position. Finally, the local ties measured in the local surveying network are to be transformed into the ITRF, the global geocentric equatorial coordinate system of the space-geodetic techniques. The current IERS procedure for the combination of the space-geodetic techniques includes the local tie vectors with an error floor of three millimeters plus a distance dependent component. This error floor, however, significantly underestimates the real accuracy of local tie determination. To fullfill the GGOS goals of 1 mm position and 0.1 mm/yr velocity accuracy, an accuracy of the local tie will be mandatory at the sub-mm level, which is currently not achievable. To assess the local tie effects on ITRF computations, investigations of the error sources will be done to realistically assess and consider them. Hence, a reasonable estimate of all the included errors of the various local ties is needed. An appropriate estimate could also improve the separation of local tie error and technique-specific error contributions to uncertainties and thus access the accuracy of space-geodetic techniques. Our investigations concern the simulation of the error contribution of each component of the local tie definition and determination. A closer look into the models of reference point definition, of accessibility, of measurement, and of transformation is necessary to properly model the error of the local tie. The effect of temporal variations on the local ties will be studied as well. The transformation of the local survey into the ITRF can be assumed to be the largest error contributor, in particular the orientation of the local surveying network to the ITRF.

LONG-TERM STABILITY OF THE LOCAL GROUND CONTROL NETWORK AT THE CO-LOCATION SITE OF MEDICINA

NASA Astrophysics Data System (ADS)

Abbondanza, C.; Sarti, P.; Legrand, J.

2009-12-01

ITRF combinations rely on the availability of accurate tie vectors linking reference points of space geodetic techniques. Co-located instruments are assumed to move consistently and no local relative motion is taken into account. Instabilities may degrade the quality of the co-location itself and perturb the result of ITRF combinations. This work aims to determine the stability of the local ground control network at Medicina (Italy) with independent surveying methods. The observatory hosts a co-location between a VLBI telescope and two GPS antennas, MEDI and MSEL. It is located in the Po Plain where thick layers of clays are the prevalent soil characteristics. Hence, provision of long term stability of geodetic monuments is a challenge and monitoring their stability is an issue. MEDI and the VLBI station regularly contribute to the determination of ITRF, while MSEL is part of the EUREF network. A set of five tie vectors observations linking the VLBI and MEDI reference points was acquired between 2001 and 2007. It is our main tool for performing local deformation analysis. Additionally, the GPS time series of MEDI and MSEL were used to cross check and confirm the local instability detected by terrestrial methods. To achieve a rigorous and reliable investigation of the local stability, multi-epoch terrestrial observations were homogeneously processed according to common parameterizations in a consistent reference frame. Similarly, continuous GPS observations from MEDI and MSEL were analysed according to the new EPN reprocessing strategy in order to monitor the short baseline between MEDI and MSEL; to spotlight any change in its length. Both approaches confirm differential motions at the site which can be related to monument instabilities originated by the particularly unfavourable local geological setting and the inapt design of the monuments foundation. The monuments move non homogeneously at rates reaching up to 1.6 mm/year, this value being comparable to intra-plate tectonic deformations. Evidences of relative motion between MEDI and MSEL are found: an annual signal with amplitude ≈1.3 mm is detected along the East component and an 80 weeks signal with amplitude ≈1.1 mm is found along the vertical component of the baseline. The combination of the two independent observing techniques confirms the importance of repeatedly performed terrestrial surveys and the presence of intra-technique co-locations at geodetic sites. Although available, VLBI observations were not considered since we are interested in detecting local relative motions in a very restricted area (100m x 100m) avoiding problems of datum consistencies between different space geodetic techniques. In fact, the combination of technique-specific frames might originate local inconsistencies on station positions due to misalignments of tie vectors in the global reference frame. These inconsistencies might degrade the accuracy of the displacement analysis and can be difficult to deal with.

An Approach for High-precision Stand-alone Positioning in a Dynamic Environment

NASA Astrophysics Data System (ADS)

Halis Saka, M.; Metin Alkan, Reha; Ozpercin, Alişir

2015-04-01

In this study, an algorithm is developed for precise positioning in dynamic environment utilizing a single geodetic GNSS receiver using carrier phase data. In this method, users should start the measurement on a known point near the project area for a couple of seconds making use of a single dual-frequency geodetic-grade receiver. The technique employs iono-free carrier phase observations with precise products. The equation of the algorithm is given below; Sm(t(i+1))=SC(ti)+[ΦIF (t(i+1) )-ΦIF (ti)] where, Sm(t(i+1)) is the phase-range between satellites and the receiver, SC(ti) is the initial range computed from the initial known point coordinates and the satellite coordinates and ΦIF is the ionosphere-free phase measurement (in meters). Tropospheric path delays are modelled using the standard tropospheric model. To accomplish the process, an in-house program was coded and some functions were adopted from Easy-Suite available at http://kom.aau.dk/~borre/easy. In order to assess the performance of the introduced algorithm in a dynamic environment, a dataset from a kinematic test measurement was used. The data were collected from a kinematic test measurement in Istanbul, Turkey. In the test measurement, a geodetic dual-frequency GNSS receiver, Ashtech Z-Xtreme, was set up on a known point on the shore and a couple of epochs were recorded for initialization. The receiver was then moved to a vessel and data were collected for approximately 2.5 hours and the measurement was finalized on a known point on the shore. While the kinematic measurement on the vessel were carried out, another GNSS receiver was set up on a geodetic point with known coordinates on the shore and data were collected in static mode to calculate the reference trajectory of the vessel using differential technique. The coordinates of the vessel were calculated for each measurement epoch with the introduced method. With the purpose of obtaining more robust results, all coordinates were calculated once again by inversely, i.e. from the last epoch to the first one. In this way, the estimated coordinates were also controlled. The average of both computed coordinates were used as vessel coordinates and then compared with the known-coordinates those of geodetic receiver epoch by epoch. The results indicate that the calculated coordinates from the introduced method are consistent with the reference trajectory with an accuracy of about 1 decimeter. In contrast, the findings imply lower accuracy for height components with an accuracy of about 2 decimeters. This accuracy level meets the requirement of many applications including some marine applications, precise hydrographic surveying, dredging, attitude control of ships, buoys and floating platforms, marine geodesy, navigation and oceanography.

Applications of Differential Operators in Geodetic Coordinates

NASA Astrophysics Data System (ADS)

Hallam, K. A. T.; Oliveira, V. C., Jr.

2016-12-01

The definition of coordinate systems and frames is an essential step to even start a problem in physical geodesy and geophysics. The commonly used coordinate systems when dealing with problems on (or close to) the surface of the Earth are the geocentric Cartesian coordinates, geocentric spherical coordinates and geodetic coordinates. Transformations between Cartesian and spherical coordinates are widely known and used for several problems. More complex, but not less important, are the transformations between Cartesian and geodetic coordinates. Although most of them utilize an ellipsoidal frame in which the three coordinates are geodetic longitude (λ), geodetic latitude (φ) and the scale factor (u), the latter being a combination of X and Y, not the geometric height (h), the data sets measured on (or close to) the surface of the Earth are given in geodetic coordinates which are usually transformed into Cartesian or spherical coordinates for mathematical developments. It would be useful, however, to preclude coordinate transformations for the subsequent operations. Thus, we derived expressions for the gradient and Laplacian operators in geodetic coordinates in order to make further use on mathematical developments. Results obtained analitically and from numerical simulations validate our expressions. We applied our operators to derive the gravitational field produced by a point mass and used it for representing the regional gravity field in geodetic coordinates. The results obtained with the numerical simulations show that our approach is potentially useful in solving a wide range of problems in physical geodesy and geophysics.

Integration of space geodesy: A US National Geodetic Observatory

NASA Astrophysics Data System (ADS)

Yunck, Thomas P.; Neilan, Ruth E.

2005-11-01

In the interest of improving the performance and efficiency of space geodesy a diverse group in the US, in collaboration with IGGOS, has begun to establish a unified National Geodetic Observatory (NGO). To launch this effort an international team will conduct a multi-year program of research into the technical issues of integrating SLR, VLBI, and GPS geodesy to produce a unified set of global geodetic products. The goal is to improve measurement accuracy by up to an order of magnitude while lowering the cost to current sponsors. A secondary goal is to expand and diversify international sponsorship of space geodesy. Principal benefits will be to open new vistas of research in geodynamics and surface change while freeing scarce NASA funds for scientific studies. NGO will proceed in partnership with, and under the auspices of, the International Association of Geodesy (IAG) as an element of the Integrated Global Geodetic Observation System project. The collaboration will be conducted within, and will make full use of, the IAG's existing international services: the IGS, IVS, ILRS, and IERS. Seed funding for organizational activities and technical analysis will come from NASA's Solid Earth and Natural Hazards Program. Additional funds to develop an integrated geodetic data system known as Inter-service Data Integration for Geodetic Operations (INDIGO), will come from a separate NASA program in Earth science information technology. INDIGO will offer ready access to the full variety of NASA's space geodetic data and will extend the GPS Seamless Archive (GSAC) philosophy to all space geodetic data types.

Interest of the MICROSTAR Accelerometer to improve the GRASP Mission.

NASA Astrophysics Data System (ADS)

Perrot, E.; Lebat, V.; Foulon, B.; Christophe, B.; Liorzou, F.; Huynh, P. A.

2015-12-01

The Geodetic Reference Antenna in Space (GRASP) is a micro satellite mission concept proposed by JPL to improve the definition of the Terrestrial Reference Frame (TRF). GRASP collocates GPS, SLR, VLBI, and DORIS sensors on a dedicated spacecraft in order to establish precise and stable ties between the key geodetic techniques used to define and disseminate the TRF. GRASP also offers a space-based reference antenna for the present and future Global Navigation Satellite Systems (GNSS). By taking advantage of the new testing possibilities offer by the catapult facility at the ZARM drop tower, the ONERA's space accelerometer team proposes an up-dated version, called MICROSTAR, of its ultra sensitive electrostatic accelerometers which have contributed to the success of the last Earth's gravity missions GRACE and GOCE. Built around a cubic proof-mass, it provides the 3 linear accelerations with a resolution better than 10-11 ms-2/Hz1/2 into a measurement bandwidth between 10-3 Hz and 0.1 Hz and the 3 angular accelerations about its 3 orthogonal axes with 5´10-10 rad.s-2/Hz1/2 resolution. Integrated at the centre of mass of the satellite, MICROSTAR improves the Precise Orbit Determination (POD) by accurate measurement of the non-gravitational force acting on the satellite. It offers also the possibility to calibrate the change in the position of the satellite center of mass with an accuracy better than 100 μm as demonstrated in the GRACE mission. Assuming a sufficiently rigid structure between the antennas and the accelerometer, its data can participate to reach the mission objective of 1 mm precision for the TRF position.

Establishment of Karadeniz Technical University Permanent GNSS Station as Reactivated of TRAB IGS Station

NASA Astrophysics Data System (ADS)

Kazancı, Selma Zengin; Kayıkçı, Emine Tanır

2017-12-01

In recent years, Global Navigation Satellite Systems (GNSS) have gained great importance in terms of the benefi ts it provides such as precise geodetic point positioning, determining crustal deformations, navigation, vehicle monitoring systems and meteorological applications etc. As in Turkey, for this purpose, each country has set up its own GNSS station networks like Turkish National Permanent RTK Network analyzed precise station coordinates and velocities together with the International GNSS Service, Turkish National Fundamental GPS Network and Turkish National Permanent GNSS Network (TNPGN) stations not only are utilized as precise positioning but also GNSS meteorology studies so total number of stations are increased. This work is related to the reactivated of the TRAB IGS station which was established in Karadeniz Technical University, Department of Geomatics Engineering. Within the COST ES1206 Action (GNSS4SWEC) KTU analysis center was established and Trop-NET system developed by Geodetic Observatory Pecny (GOP, RIGTC) in order to troposphere monitoring. The project titled "Using Regional GNSS Networks to Strengthen Severe Weather Prediction" was accepted to the scientifi c and technological research council of Turkey (TUBITAK). With this project, we will design 2 new constructed GNSS reference station network. Using observation data of network, we will compare water vapor distribution derived by GNSS Meteorology and GNSS Tomography. At this time, KTU AC was accepted as E-GVAP Analysis Centre in December 2016. KTU reference station is aimed to be a member of the EUREF network with these studies.

On the methodology of Engineering Geodesy

NASA Astrophysics Data System (ADS)

Brunner, Fritz K.

2007-09-01

Textbooks on geodetic surveying usually describe a very small number of principles which should provide the foundation of geodetic surveying. Here, the author argues that an applied field, such as engineering geodesy, has a methodology as foundation rather than a few principles. Ten methodological elements (ME) are identified: (1) Point discretisation of natural surfaces and objects, (2) distinction between coordinate and observation domain, (3) definition of reference systems, (4) specification of unknown parameters and desired precisions, (5) geodetic network and observation design, (6) quality control of equipment, (7) quality control of measurements, (8) establishment of measurement models, (9) establishment of parameter estimation models, (10) quality control of results. Each ME consists of a suite of theoretical developments, geodetic techniques and calculation procedures, which will be discussed. This paper is to be considered a first attempt at identifying the specific elements of the methodology of engineering geodesy. A better understanding of this methodology could lead to an increased objectivity, to a transformation of subjective practical experiences into objective working methods, and consequently to a new structure for teaching this rather diverse subject.

Current status of the EPOS WG4 - GNSS and Other Geodetic Data

NASA Astrophysics Data System (ADS)

Fernandes, Rui; Bastos, Luísa; Bruyninx, Carine; D'Agostino, Nicola; Dousa, Jan; Ganas, Athanassios; Lidberg, Martin; Nocquet, Jean-Mathieu

2013-04-01

WG4 - "EPOS Geodetic Data and Other Geodetic Data" is the Working Group of the EPOS project in charge of defining and preparing the integration of the existing Pan-European Geodetic Infrastructures that will support the European Geosciences, which is the ultimate goal of the EPOS project. The WG4 is formed by representatives of the participating EPOS countries (23) but it is also open to the entire geodetic community. In fact, WG4 also includes members from countries that formally are not part of the current phase of EPOS. In an ongoing effort, the majority of existing GNSS Research Infrastructures in Europe were identified. The current database, available at http://epos-couch.cloudant.com/epos-couch/_design/epos-couch/, lists a total of 50 Research Infrastructures managing a total of 1534 GNSS CORS sites. This presentation intends to detail the work being produced within the working group WG4 related with the definition of strategies towards the implementation of the best solutions that will permit to the end-users, and in particular geo-scientists, to access the geodetic data, derived solutions, and associated metadata using transparent and uniform processes. The first step toward the design of an implementation and business plan is the definition of the core services for geodetic data within EPOS. In this talk, we will present the current status of the discussion about the content of core services. Three levels of core services could be distinguished, for which their content need to be defined. The 3 levels are: (1) the core services associated to data (diffusion, archive, long-term preservation, quality check, rapid analysis) (2) core services associated to geodetic products (analysis, products definition like position time series, velocity field and Zenithal Total Delay) (3) User oriented services (reference frames, real-time solutions for early warning systems, strain rate maps, meteorology, space weather, …). Current propositions and remaining open questions will be discussed.

Examination of global correlations in ground deformation for terrestrial reference frame estimation

NASA Astrophysics Data System (ADS)

Chin, T. M.; Abbondanza, C.; Argus, D. F.; Gross, R. S.; Heflin, M. B.; Parker, J. W.; Wu, X.

2016-12-01

The KALman filter for REFerence frames (KALREF, Wu et al. 2015) has been developed to produce terrestrial reference frame (TRF) solutions. TRFs consist of precise position coordinates and velocity vectors of terrestrial reference sites (with the geocenter as the origin) along with the Earth orientation parameters, and they are produced by combining decades worth of space geodetic data using site tie data. To perform the combination, KALREF relies on stochastic models of the geophysical processes that are causing the Earth's surface to deform and reference sites to be displaced. We are investigating application of the GRACE data to improve the KALREF stochastic models by determining spatial statistics of the deformation of the Earth's surface caused by mass loading. A potential target of improvement is the non-uniform distribution of the geodetic observation sites, which can introduce bias in TRF estimates of the geocenter. The global and relatively uniform coverage of the GRACE measurements is expected to be free of such bias and allow us to improve physical realism of the stochastic model. For such a goal, we examine the spatial correlations in ground deformation derived from several GRACE data sets.[Wu et al. 2015: Journal of Geophysical Research (Solid Earth) 120:3775-3802

GARS O'Higgins as a core station for geodesy in Antarctica

NASA Astrophysics Data System (ADS)

Klügel, Thomas; Diedrich, Erhard; Falk, Reinhard; Hessels, Uwe; Höppner, Kathrin; Kühmstedt, Elke; Metzig, Robert; Plötz, Christian; Reinhold, Andreas; Schüler, Torben; Wojdziak, Reiner

2014-05-01

The German Antarctic Receiving Station GARS O'Higgins at the northern tip of the Antarctic Peninsula is a dual purpose facility for Earth observation since more than 20 years. It serves as a satellite ground station for payload data downlink and telecommanding of remote sensing satellites as well as a geodetic observatory for global reference frames and global change. Both applications use the same 9m diameter radio telescope. For space geodesy and astrometry the radio telescope significantly improves the coverage on the southern hemisphere and plays an essential role within the global Very Long Baseline Interferometry (VLBI) network. In particular the determination of the Earth Orientation Parameters (EOP) and the sky coverage of the International Celectial Reference Frame (ICRF) benefit from the location at high southern latitude. Further geodetic instrumentation includes different permanent GNSS receivers (since 1995), two SAR corner reflectors (since 2013) and in the past a PRARE system (1996 - 2004). In addition absolute gravity measurements were performed in 1997 and 2011. All geodetic reference points are tied together by a local survey network. The various geodetic instrumentation and the long time series at O'Higgins allow a reliable determination of crustal motions. VLBI station velocities, continuous GNSS time series and absolute gravity measurements consistently document an uplift rate of about 5 mm/a. A pressure gauge and a radar tide gauge being refererenced to space by a GNSS antenna on top allow the measurement of sea level changes independently from crustal motions, and the determination of the ellipsoidal height of the sea surface, which is, the geoid height plus the mean dynamic topography. The outstanding location on the Antarctic continent makes GARS O'Higgins also in future attractive for polar orbiting satellite missions and an essential station for the global VLBI network. Future plans envisage a development towards an observatory for environmentally relevant research.

INEGI's Network of GPS permanent stations in Mexico

NASA Astrophysics Data System (ADS)

Gonzalez Franco, G. A.

2013-05-01

The Active National Geodetic Network administered by INEGI (Instituto Nacional de Estadística y Geografía) is a set of 24 GPS permanent stations in Mexico that was established in 1993 for a national rural cadastral project, its has been mainly used for geodetic surveys through Mexico including international borders, and has been progressing to contribute to national, regional and international reference frames through the delivering of GPS data or coordinate solutions from INEGI Processing Center to SIRGAS and NAREF. Recently GAMIT/GLOBK Processing of permanent stations in Mexico was realized from 2007-2011 to determine station's velocity. Related to natural hazards, a subset of INEGI network contributes to the project Real Time Integrated Atmosferic Water Wapor and TEC from GPS. The GPS network planned evolution consider changing to a GNSS network, adding stations to IGS, maintain the services of the present, and contribute to multidisciplinary geodetic studies through data publicly available.

Analysis of the DORIS, GNSS, SLR, VLBI and gravimetric time series at the GGOS core sites

NASA Astrophysics Data System (ADS)

Moreaux, G.; Lemoine, F. G.; Luceri, V.; Pavlis, E. C.; MacMillan, D. S.; Bonvalot, S.; Saunier, J.

2017-12-01

Since June 2016 and the installation of a new DORIS station in Wettzell (Germany), four geodetic sites (Badary, Greenbelt, Wettzell and Yarragadee) are equipped with the four space geodetic techniques (DORIS, GNSS, SLR and VLBI). In line with the GGOS (Global Geodetic Observing System) objective of achieving a terrestrial reference frame at the millimetric level of accuracy, the combination centers of the four space techniques initiated a joint study to assess the level of agreement among these space geodetic techniques. In addition to the four sites, we will consider all the GGOS core sites including the seven sites with at least two space geodetic techniques in addition to DORIS. Starting from the coordinate time series, we will estimate and compare the mean positions and velocities of the co-located instruments. The temporal evolution of the coordinate differences will also be evaluated with respect to the local tie vectors and discrepancies will be investigated. Then, the analysis of the signal content of the time series will be carried out. Amplitudes and phases of the common signals among the techniques, and eventually from gravity data, will be compared. The first objective of this talk is to describe our joint study: the sites, the data, and the objectives. The second purpose is to present the first results obtained from the GGAO (Goddard Geophysical and Astronomic Observatory) site of Greenbelt.

General-altitude transformations between geocentric and geodetic coordinates. [earth's flattening and eccentricity application

NASA Technical Reports Server (NTRS)

Long, S. A. T.

1975-01-01

Formulas for the general-altitude (height above the ellipsoid) transformation from geocentric to geodetic coordinates and vice versa are derived. The set of four formulas is expressed in each of two useful forms: series expansions in powers of the earth's flattening and series expansions in powers of the earth's eccentricity. The error incurred in these expansions is of the order of one part in 30 million.-

Geodesy, a Bibliometric Approach for 2000-2006

NASA Astrophysics Data System (ADS)

Vazquez, G.; Landeros, C. F.

2007-12-01

In recent years, bibliometric science has been frequently applied in the development and evaluation of scientific research. This work presents a bibliometric analysis for the research work performed in the field of geodesy "science of the measurement and mapping of the earth surface including its external gravity field". The objective of this work is to present a complete overview of the generated research on this field to assemble and study the most important publications occurred during the past seven years. The analysis was performed including the SCOPUS and WEB OF SCIENCE databases for all the geodetic scientific articles published between 2000 and 2006. The search profile was designed considering a strategy to seek for titles and article descriptors using the terms geodesy and geodetic and some other terms associated with the topics: geodetic surfaces, vertical measurements, reference systems and frames, modern space-geodetic techniques and satellite missions. Some preliminary results had been achieved specifically Bradford law of distribution for journals and education institutes, and Lotka's law for authors that also includes the cooperation between countries in terms of writing together scientific articles. In the particular case of distributions, the model suggested by Egghe (2002) was adopted for determining the cores.

Some aspects of the analysis of geodetic strain observations in kinematic models

NASA Astrophysics Data System (ADS)

Welsch, W. M.

1986-11-01

Frequently, deformation processes are analyzed in static models. In many cases, this procedure is justified, in particular if the deformation occurring is a singular event. If. however, the deformation is a continuous process, as is the case, for instance, with recent crustal movements, the analysis in kinematic models is more commensurate with the problem because the factor "time" is considered an essential part of the model. Some specialities have to be considered when analyzing geodetic strain observations in kinematic models. They are dealt with in this paper. After a brief derivation of the basic kinematic model and the kinematic strain model, the following subjects are treated: the adjustment of the pointwise velocity field and the derivation of strain-rate parameters; the fixing of the kinematic reference system as part of the geodetic datum; statistical tests of models by testing linear hypotheses; the invariance of kinematic strain-rate parameters with respect to transformations of the coordinate-system and the geodetic datum; the interpolation of strain rates by finite-element methods. After the representation of some advanced models for the description of secular and episodic kinematic processes, the data analysis in dynamic models is regarded as a further generalization of deformation analysis.

Height bias and scale effect induced by antenna gravitational deformations in geodetic VLBI data analysis

NASA Astrophysics Data System (ADS)

Sarti, Pierguido; Abbondanza, Claudio; Petrov, Leonid; Negusini, Monia

2011-01-01

The impact of signal path variations (SPVs) caused by antenna gravitational deformations on geodetic very long baseline interferometry (VLBI) results is evaluated for the first time. Elevation-dependent models of SPV for Medicina and Noto (Italy) telescopes were derived from a combination of terrestrial surveying methods to account for gravitational deformations. After applying these models in geodetic VLBI data analysis, estimates of the antenna reference point positions are shifted upward by 8.9 and 6.7 mm, respectively. The impact on other parameters is negligible. To simulate the impact of antenna gravitational deformations on the entire VLBI network, lacking measurements for other telescopes, we rescaled the SPV models of Medicina and Noto for other antennas according to their size. The effects of the simulations are changes in VLBI heights in the range [-3, 73] mm and a net scale increase of 0.3-0.8 ppb. The height bias is larger than random errors of VLBI position estimates, implying the possibility of significant scale distortions related to antenna gravitational deformations. This demonstrates the need to precisely measure gravitational deformations of other VLBI telescopes, to derive their precise SPV models and to apply them in routine geodetic data analysis.

Precise Orbital and Geodetic Parameter Estimation using SLR Observations for ILRS AAC

NASA Astrophysics Data System (ADS)

Kim, Young-Rok; Park, Eunseo; Oh, Hyungjik Jay; Park, Sang-Young; Lim, Hyung-Chul; Park, Chandeok

2013-12-01

In this study, we present results of precise orbital geodetic parameter estimation using satellite laser ranging (SLR) observations for the International Laser Ranging Service (ILRS) associate analysis center (AAC). Using normal point observations of LAGEOS-1, LAGEOS-2, ETALON-1, and ETALON-2 in SLR consolidated laser ranging data format, the NASA/ GSFC GEODYN II and SOLVE software programs were utilized for precise orbit determination (POD) and finding solutions of a terrestrial reference frame (TRF) and Earth orientation parameters (EOPs). For POD, a weekly-based orbit determination strategy was employed to process SLR observations taken from 20 weeks in 2013. For solutions of TRF and EOPs, loosely constrained scheme was used to integrate POD results of four geodetic SLR satellites. The coordinates of 11 ILRS core sites were determined and daily polar motion and polar motion rates were estimated. The root mean square (RMS) value of post-fit residuals was used for orbit quality assessment, and both the stability of TRF and the precision of EOPs by external comparison were analyzed for verification of our solutions. Results of post-fit residuals show that the RMS of the orbits of LAGEOS-1 and LAGEOS-2 are 1.20 and 1.12 cm, and those of ETALON-1 and ETALON-2 are 1.02 and 1.11 cm, respectively. The stability analysis of TRF shows that the mean value of 3D stability of the coordinates of 11 ILRS core sites is 7.0 mm. An external comparison, with respect to International Earth rotation and Reference systems Service (IERS) 08 C04 results, shows that standard deviations of polar motion XP and YP are 0.754 milliarcseconds (mas) and 0.576 mas, respectively. Our results of precise orbital and geodetic parameter estimation are reasonable and help advance research at ILRS AAC.

Results from the ESA-funded project 'Height System Unification with GOCE'

NASA Astrophysics Data System (ADS)

Sideris, M. G.; Rangelova, E. V.; Gruber, T.; Rummel, R. F.; Woodworth, P. L.; Hughes, C. W.; Ihde, J.; Liebsch, G.; Schäfer, U.; Rülke, A.; Gerlach, C.; Haagmans, R.

2013-12-01

The paper summarizes the main results of a project, supported by the European Space Agency, whose main goal is to identify the impact of GOCE gravity field models on height system unification. In particular, the Technical University Munich, the University of Calgary and the National Oceanography Centre in Liverpool, together with the Bavarian Academy of Sciences, the Federal German Agency for Cartography and Geodesy, and the Geodetic Surveys of Canada, USA and Mexico, have investigated the role of GOCE-derived gravity and geoid models for regional and global height datum connection. GOCE provides three important components of height unification: highly accurate potential differences (geopotential numbers), a global geoid- or quasi-geoid-based reference surface for elevations that is independent of inaccuracies and inconsistencies of local and regional data, and a consistent way to refer to the same datum all the relevant gravimetric, topographic and oceanographic data. We introduce briefly the methodology that has been applied in order to unify height system in North America, North Atlantic Ocean and Europe, and present results obtained using the available GOCE-derived satellite-only geopotential models, and their combination with terrestrial data and ocean models. The effects of various factors, such as data noise, omission errors, indirect bias terms, ocean models and temporal variations, on height datum unification are also presented, highlighting their magnitude and importance in the estimation of offsets between vertical datums. Based on the experiences gained in this project, a general roadmap has been developed for height datum unification in regions with good, as well as poor, coverage in gravity and geodetic height and tide gauge control stations.

Contribution of SELENE-2 geodetic measurements to constrain the lunar internal structure

NASA Astrophysics Data System (ADS)

Matsumoto, K.; Kikuchi, F.; Yamada, R.; Iwata, T.; Kono, Y.; Tsuruta, S.; Hanada, H.; Goossens, S. J.; Ishihara, Y.; Kamata, S.; Sasaki, S.

2012-12-01

Internal structure and composition of the Moon provide important clue and constraints on theories for how the Moon formed and evolved. The Apollo seismic network has contributed to the internal structure modeling. Efforts have been made to detect the lunar core from the noisy Apollo data (e.g., [1], [2]), but there is scant information about the structure below the deepest moonquakes at about 1000 km depth. On the other hand, there have been geodetic studies to infer the deep structure of the Moon. For example, LLR (Lunar Laser Ranging) data analyses detected a displacement of the lunar pole of rotation, indicating that dissipation is acting on the rotation arising from a fluid core [3]. Bayesian inversion using geodetic data (such as mass, moments of inertia, tidal Love numbers k2 and h2, and quality factor Q) also suggests a fluid core and partial melt in the lower mantle region [4]. Further improvements in determining the second-degree gravity coefficients (which will lead to better estimates of moments of inertia) and the Love number k2 will help us to better constrain the lunar internal structure. Differential VLBI (Very Long Baseline Interferometry) technique, which was used in the Japanese lunar exploration mission SELENE (Sept. 2007 - June 2009), is expected to contribute to better determining the second-degree potential Love number k2 and low-degree gravity coefficients. SELENE will be followed by the future lunar mission SELENE-2 which will carry both a lander and an orbiter. We propose to put the SELENE-type radio sources on these spacecraft in order to accurately estimate k2 and the low-degree gravity coefficients. By using the same-beam VLBI tracking technique, these parameters will be retrieved through precision orbit determination of the orbiter with respect to the lander which serves as a reference. The VLBI mission with the radio sources is currently one of the mission candidates for SELENE-2. We have conducted a preliminary simulation study on the anticipated k2 accuracy. With the assumed mission duration of about 3 months and the arc length of 14 days, the k2 accuracy is estimated to be better than 1 %, where the uncertainty is evaluated as 10 times the formal error considering the errors in the non-conservative force modeling and in the lander position. We carried out a feasibility study using Bayesian inversion on how well we can constrain the lunar internal structure by the geodetic data to be improved by SELENE-2. It will be shown that such improved geodetic data contribute to narrow the range of the plausible internal structure models, but there are still trade-offs among crust, mantle, and core structures. Preliminary simulation results will be presented to show that the accuracy of core structure estimation will be improved in consequence of better determination of the mantle structure by combining the geodetic data with the seismic data. References [1] Weber et al. (2011), Science, 331, 309-312, doi:10.1126/science.1199375 [2] Garcia eta l. (2011), PEPI, doi:10.1016/j.pepi.2011.06.015 [3] Williams et al. (2001), JGR, 106, E11, 27,933-27,968 [4] Khan and Mosegaard (2005), GRL, 32, L22203, doi:10.1029/2005GL023985

Upcoming replacements for NAD83, NAVD88 and IGLD85

NASA Astrophysics Data System (ADS)

Smith, D. A.; Snay, R.

2009-05-01

The National Geodetic Survey (NGS), part of the National Oceanic and Atmospheric Administration (NOAA) is responsible for defining, maintaining and providing access to the National Spatial Reference System (NSRS) for the United States. The NSRS is the official system to which all civil federal mapping agencies should refer, and contains, amongst other things, the official geopotential (historically "vertical") datum of NAVD 88, the 3-D geometric reference system (historically "horizontal datum") of NAD 83 and great lakes datum (IGLD 85). Although part of the United States NSRS, all three of these datums have been created through international partnerships across North America. Unfortunately, time has shown both the systematic errors existent within these datums, as well as the inherent weaknesses of relying exclusively on passive monuments to define and provide access to these datums. In recognition of these issues, the National Geodetic Survey has issued a "10 year plan", available online, which outlines steps which will be taken to update NAD 83, NAVD 88 and IGLD 85 concurrently around the year 2018. The primary source of success will be in the refinement of the CORS network and the upcoming execution of the GRAV-D project (Gravity for the Re-definition of the American Vertical Datum). Conversations are ongoing with colleagues in Canada, Mexico, Central America and the Caribbean in order to coordinate all of these efforts across the entire continent. The largest changes expected to occur are the removal of over 2 meters of non-geocentricity in NAD 83; the removal of decimeters of bias and over a meter of tilt in NAVD 88; the addition of the ability to track crustal motions (subsidence, tectonics, etc) in the datums; the removal of leveling as a tool for long-line height differencing; the use of a "best" geoid as the orthometric height reference surface; the addition of datum velocities (motions of the 3-D geometric reference system origin and motions of the geoid); and the use of GNSS technology as the way to access both orthometric and dynamic heights in the vertical datum. This talk will outline the broad plan of action and invite further collaboration along these lines.

EPOS-GNSS - Improving the infrastructure for GNSS data and products in Europe

NASA Astrophysics Data System (ADS)

Fernandes, Rui; Bos, Machiel; Bruyninx, Carine; Crocker, Paul; Dousa, Jan; Socquet, Anne; Walpersdorf, Andrea; Avallone, Antonio; Ganas, Athanassios; Gunnar, Benedikt; Ionescu, Constantin; Kenyeres, Ambrus; Ozener, Haluk; Vergnolle, Mathilde; Lidberg, Martin; Liwosz, Tomek; Soehne, Wolfgang

2017-04-01

EPOS-IP WP10 - "GNSS Data & Products" is the Working Package 10 of the European Plate Observing System - Implementation Phase project in charge of implementing services for the geo-sciences community to access existing Pan-European Geodetic Infrastructures. WP10 is currently formed by representatives of participating European institutions but in the operational phase contributions will be solicited from the entire geodetic community. In fact, WP10 also includes members from other institutions/countries that formally are not participating in the EPOS-IP but will be key players in the future services to be provided by EPOS. Additionally, several partners are also key partners at EUREF, which is also actively collaborating with EPOS. The geodetic component of EPOS is dealing essentially with implementing an e-infrastructure to store and disseminate the continuous GNSS data from existing Research Infrastructures. Present efforts are on developing geodetic tools to support Solid Earth research by optimizing the existing resources. However, other research and technical applications (e.g., reference frames, meteorology, space weather) can also benefit in the future from the optimization of the geodetic resources in Europe. We present and discuss the status of the implementation of the thematic and core services (TCS) for GNSS data within EPOS and the related business plan. We explain the tools and web-services being developed towards the implementation of the best solutions that will permit to the end-users, and in particular geo-scientists, to access the geodetic data, derived solutions, and associated metadata using a transparent and standardized processes. We also detail the different DDSS (Data, Data-Products, Services, Software) that will be made available for the Operational Phase of EPOS, which will start to be tested and made available during 2017 and 2018.

How well can online GPS PPP post-processing services be used to establish geodetic survey control networks?

NASA Astrophysics Data System (ADS)

Ebner, R.; Featherstone, W. E.

2008-09-01

Establishing geodetic control networks for subsequent surveys can be a costly business, even when using GPS. Multiple stations should be occupied simultaneously and post-processed with scientific software. However, the free availability of online GPS precise point positioning (PPP) post-processing services offer the opportunity to establish a whole geodetic control network with just one dual-frequency receiver and one field crew. To test this idea, we compared coordinates from a moderate-sized (~550 km by ~440 km) geodetic network of 46 points over part of south-western Western Australia, which were processed both with the Bernese v5 scientific software and with the CSRS (Canadian Spatial Reference System) PPP free online service. After rejection of five stations where the antenna type was not recognised by CSRS, the PPP solutions agreed on average with the Bernese solutions to 3.3 mm in east, 4.8 mm in north and 11.8 mm in height. The average standard deviations of the Bernese solutions were 1.0 mm in east, 1.2 mm in north and 6.2 mm in height, whereas for CSRS they were 3.9 mm in east, 1.9 mm in north and 7.8 mm in height, reflecting the inherently lower precision of PPP. However, at the 99% confidence level, only one CSRS solution was statistically different to the Bernese solution in the north component, due to a data interruption at that site. Nevertheless, PPP can still be used to establish geodetic survey control, albeit with a slightly lower quality because of the larger standard deviations. This approach may be of particular benefit in developing countries or remote regions, where geodetic infrastructure is sparse and would not normally be established without this approach.

Accurate determination of the geoid undulation N

NASA Astrophysics Data System (ADS)

Lambrou, E.; Pantazis, G.; Balodimos, D. D.

2003-04-01

This work is related to the activities of the CERGOP Study Group Geodynamics of the Balkan Peninsula, presents a method for the determination of the variation ΔN and, indirectly, of the geoid undulation N with an accuracy of a few millimeters. It is based on the determination of the components xi, eta of the deflection of the vertical using modern geodetic instruments (digital total station and GPS receiver). An analysis of the method is given. Accuracy of the order of 0.01arcsec in the estimated values of the astronomical coordinates Φ and Δ is achieved. The result of applying the proposed method in an area around Athens is presented. In this test application, a system is used which takes advantage of the capabilities of modern geodetic instruments. The GPS receiver permits the determination of the geodetic coordinates at a chosen reference system and, in addition, provides accurate timing information. The astronomical observations are performed through a digital total station with electronic registering of angles and time. The required accuracy of the values of the coordinates is achieved in about four hours of fieldwork. In addition, the instrumentation is lightweight, easily transportable and can be setup in the field very quickly. Combined with a stream-lined data reduction procedure and the use of up-to-date astrometric data, the values of the components xi, eta of the deflection of the vertical and, eventually, the changes ΔN of the geoid undulation are determined easily and accurately. In conclusion, this work demonstrates that it is quite feasible to create an accurate map of the geoid undulation, especially in areas that present large geoid variations and other methods are not capable to give accurate and reliable results.

The role of topography in geodetic gravity field modelling

NASA Technical Reports Server (NTRS)

Forsberg, R.; Sideris, M. G.

1989-01-01

Masses associated with the topography, bathymetry, and its isostatic compensation are a dominant source of gravity field variations, especially at shorter wavelengths. On global scales the topographic/isostatic effects are also significant, except for the lowest harmonics. In practice, though, global effects need not be taken into account as such effects are included in the coefficients of the geopotential reference fields. On local scales, the short-wavelength gravity variations due to the topography may, in rugged terrain, be an order of magnitude larger than other effects. In such cases, explicit or implicit terrain reduction procedures are mandatory in order to obtain good prediction results. Such effects may be computed by space-domain integration or by fast Fourier transformation (FFT) methods. Numerical examples are given for areas of the Canadian Rockies. In principle, good knowledge of the topographic densities is required to produce the smoothest residual field. Densities may be determined from sample measurements or by gravimetric means, but both are somewhat troublesome methods in practice. The use of a standard density, e.g., 2.67 g/cu cm, may often yield satisfactory results and may be put within a consistent theoretical framework. The independence of density assumptions is the key point of the classical Molodensky approach to the geodetic boundary value problem. The Molodensky solutions take into account that land gravity field observations are done on a non-level surface. Molodensky's problem may be solved by integral expansions or more effective FFT methods, but the solution should not be intermixed with the use of terrain reductions. The methods are actually complimentary and may both be required in order to obtain the smoothest possible signal, least prone to aliasing and other effects coming from sparse data coverage, typical of rugged topography.

Annual Geocenter Motion from Space Geodesy and Models

NASA Astrophysics Data System (ADS)

Ries, J. C.

2013-12-01

Ideally, the origin of the terrestrial reference frame and the center of mass of the Earth are always coincident. By construction, the origin of the reference frame is coincident with the mean Earth center of mass, averaged over the time span of the satellite laser ranging (SLR) observations used in the reference frame solution, within some level of uncertainty. At shorter time scales, tidal and non-tidal mass variations result in an offset between the origin and geocenter, called geocenter motion. Currently, there is a conventional model for the tidally-coherent diurnal and semi-diurnal geocenter motion, but there is no model for the non-tidal annual variation. This annual motion reflects the largest-scale mass redistribution in the Earth system, so it essential to observe it for a complete description of the total mass transport. Failing to model it can also cause false signals in geodetic products such as sea height observations from satellite altimeters. In this paper, a variety of estimates for the annual geocenter motion are presented based on several different geodetic techniques and models, and a ';consensus' model from SLR is suggested.

Comprehensive geo-spatial data creation for Najran region in the KSA

NASA Astrophysics Data System (ADS)

Alrajhi, M.; Hawarey, M.

2009-04-01

The General Directorate for Surveying and Mapping (GDSM) of the Deputy Ministry for Land and Surveying (DMLS) of the Ministry of Municipal and Rural Affairs (MOMRA) in the Kingdom of Saudi Arabia (KSA) has the exclusive mandate to carry out aerial photography and produce large-scale detailed maps for about 220 cities and villages in the KSA. This presentation is about the comprehensive geo-spatial data creation for the Najran region, South KSA, that was founded on country-wide horizontal geodetic ground control using Global Navigation Satellite Systems (GNSS) within the MOMRA's Terrestrial Reference Frame 2000 (MTRF2000) that is tied to International Terrestrial Reference Frame 2000 (ITRF2000) Epoch 2004.0, and vertical geodetic ground control using precise digital leveling in reference to Jeddah 1969 mean sea level, and included aerial photography of area 917 km2 at 1:5,500 scale and 14,304 km2 at 1:45,000 scale, full aerial triangulation, and production of orthophoto maps at scale of 1:10,000 (298 sheets) for 14,304 km2, with aerial photography lasting from May 2006 until July 2006.

Comprehensive geo-spatial data creation for Ar-Riyadh region in the KSA

NASA Astrophysics Data System (ADS)

Alrajhi, M.; Hawarey, M.

2009-04-01

The General Directorate for Surveying and Mapping (GDSM) of the Deputy Ministry for Land and Surveying (DMLS) of the Ministry of Municipal and Rural Affairs (MOMRA) in the Kingdom of Saudi Arabia (KSA) has the exclusive mandate to carry out aerial photography and produce large-scale detailed maps for about 220 cities and villages in the KSA. This presentation is about the comprehensive geo-spatial data creation for the Ar-Riyadh region, Central KSA, that was founded on country-wide horizontal geodetic ground control using Global Navigation Satellite Systems (GNSS) within the MOMRA's Terrestrial Reference Frame 2000 (MTRF2000) that is tied to International Terrestrial Reference Frame 2000 (ITRF2000) Epoch 2004.0, and vertical geodetic ground control using precise digital leveling in reference to Jeddah 1969 mean sea level, and included aerial photography of area 3,000 km2 at 1:5,500 scale and 10,000 km2 at 1:45,000 scale, full aerial triangulation, and production of orthophoto maps at scale of 1:10,000 (480 sheets) for 10,000 km2, with aerial photography lasting from July 2007 thru August 2007.

Comprehensive geo-spatial data creation for Asir region in the KSA

NASA Astrophysics Data System (ADS)

Alrajhi, M.; Hawarey, M.

2009-04-01

The General Directorate for Surveying and Mapping (GDSM) of the Deputy Ministry for Land and Surveying (DMLS) of the Ministry of Municipal and Rural Affairs (MOMRA) in the Kingdom of Saudi Arabia (KSA) has the exclusive mandate to carry out aerial photography and produce large-scale detailed maps for about 220 cities and villages in the KSA. This presentation is about the comprehensive geo-spatial data creation for the Asir region, South West KSA, that was founded on country-wide horizontal geodetic ground control using Global Navigation Satellite Systems (GNSS) within the MOMRA's Terrestrial Reference Frame 2000 (MTRF2000) that is tied to International Terrestrial Reference Frame 2000 (ITRF2000) Epoch 2004.0, and vertical geodetic ground control using precise digital leveling in reference to Jeddah 1969 mean sea level, and included aerial photography of area 2,188 km2 at 1:5,500 scale and 32,640 km2 at 1:45,000 scale, full aerial triangulation, and production of orthophoto maps at scale of 1:10,000 (680 sheets) for 32,640 km2, with aerial photography lasting from July 2007 thru October 2007.

NASA's Next Generation Space Geodesy Network

NASA Technical Reports Server (NTRS)

Desai, S. D.; Gross, R. S.; Hilliard, L.; Lemoine, F. G.; Long, J. L.; Ma, C.; McGarry, J. F.; Merkowitz, S. M.; Murphy, D.; Noll, C. E.;

Contribution to defining a geodetic reference frame for Africa (AFREF): Geodynamics implications

NASA Astrophysics Data System (ADS)

Saria, Elifuraha E.

African Reference Frame (AFREF) is the proposed regional three-dimensional standard frame, which will be used to reference positions and velocities for geodetic sites in Africa and surrounding. This frame will play a crucial role in scientific application for example plate motion and crustal deformation studies, and also in mapping when it involves for example national boundary surveying, remote sensing, GIS, engineering projects and other development programs in Africa. To contribute to the definition of geodetic reference frame for Africa and provide the first continent-wide position/velocity solution for Africa, we processed and analyzed 16 years of GPS and 17 years of DORIS data at 133 GPS sites and 9 DORIS sites continuously operating geodetic sites in Africa and surroundings to describe the present-day kinematics of the Nubian and Somalian plates and constrain relative motions across the East African Rift. We use the resulting horizontal velocities to determine the level of rigidity of Nubia and updated a plate motion model for the East African Rift and revise the counter clockwise rotation of the Victoria plate and clockwise rotation of the Rovuma plate with respect to Nubia. The vertical velocity ranges from -2 to +2 mm/yr, close to their uncertainties with no clear geographical pattern. This study provides the first continent-wide position/velocity solution for Africa, expressed in International Terrestrial Reference Frame (ITRF2008), a contribution to the upcoming African Reference Frame (AFREF). In the next step we used the substantial increase in the geologic, geophysical and geodetic data in Africa to improve our understanding of the rift geometry and the block kinematics of the EAR. We determined the best-fit fault structure of the rift in terms of the locking depth and dip angle and use a block modeling approach where observed velocities are described as the contribution of rigid block rotation and strain accumulation on locked faults. Our results show a better fit with three sub-plates (Victoria, Rovuma and Lwandle) between the major plates Nubia and Somalia. We show that the earthquake slip vectors provide information that is consistent with the GPS velocities and significantly help reduce the uncertainties in plate angular velocity estimates. However, we find that 3.16 My average spreading rates along the Southwest Indian Ridge (SWIR) from MORVEL model are systematically faster than GPS-derived motions across that ridge, possibly reflecting the need to revise the MORVEL outward displacement correction. In the final step, we attempt to understand the hydrological loading in Africa, which may affect our geodetic estimates, particularly the uplift rates. In this work, we analyze 10 years (2002 - 2012) of continuous GPS measurements operating in Africa, and compare with the modeled hydrological loading deformation inferred from the Gravity Recovery and Climate Experiment (GRACE) at the same GPS location and for the same time period. We estimated hydrological loading deformation based on the Equivalent Water Height (EWH) derived from the 10-days interval reprocessed GRACE solution second release (RL02). We took in to account in both GPS and GRACE the systematic errors from atmospheric pressure and non-tidal ocean loading effects and model the Earth as perfect elastic and compute the deformation using appropriate Greens function. We analyze the strength of association between the observation (GPS) and the model (GRACE) in terms of annual amplitude and phase as well as the original data (time-series). We find a good correlation mainly in regions associated with strong seasonal hydrological variations. To improve the correlation between the two solutions, we subtract the GRACE-derived vertical displacement from GPS-observed time series and determine the variance reduction. Our solution shows average variance between the model and the observation reduced to ~40%. (Abstract shortened by UMI.)

On differential transformations between Cartesian and curvilinear (geodetic) coordinates

NASA Technical Reports Server (NTRS)

Soler, T.

1976-01-01

Differential transformations are developed between Cartesian and curvilinear orthogonal coordinates. Only matrix algebra is used for the presentation of the basic concepts. After defining the reference systems used the rotation (R), metric (H), and Jacobian (J) matrices of the transformations between cartesian and curvilinear coordinate systems are introduced. A value of R as a function of H and J is presented. Likewise an analytical expression for J(-1) as a function of H(-2) and R is obtained. Emphasis is placed on showing that differential equations are equivalent to conventional similarity transformations. Scaling methods are discussed along with ellipsoidal coordinates. Differential transformations between elipsoidal and geodetic coordinates are established.

Current Limitations on VLBI Accuracy

NASA Technical Reports Server (NTRS)

Ma, Chopo; Gipson, John; MacMillan, Daniel

1998-01-01

The contribution of VLBI to geophysics and geodesy arises from its ability to measure distances between stations in a network and to determine the orientation of stations in the network as well as the orientation of the network with respect to the external reference frame of extragalactic radio objects. Integrating nearly two decades of observations provides useful information about station positions and velocities and the orientation of the Earth, but the complications of the real world and the limitations of observing, modeling and analysis prevent recovery of all effects. Of the factors that limit the accuracy of seemingly straightforward geodetic parameters, the neutral propagation medium has been subject to the greatest scrutiny, but the treatment of the mapping function, the wet component and spatial/temporal inhomogeneities is still improving. These affect both the terrestrial scale and consistency over time. The modeling of non-secular site motions (tides and loading) has increased in sophistication, but there are some differences between the models and the observations. VLBI antennas are massive objects, so their behavior is quite unlike GPS monuments, but antenna deformations add some (generally) unmodeled signal. Radio sources used in geodetic VLBI observations are selected for strength and (relative) absence of structure, but apparent changes in position can leak into geodetic parameters. A linear rate of change of baseline or site parameters is the simplest model and its error improves with time span. However, in most cases the VLBI data distribution is insufficient to look for real non-linear behavior that might affect the average rate. A few sites have multiple VLBI antennas, and some show small differences in rate. VLBI intrinsically measures relative positions and velocities, but individual site positions and velocities are generally more useful. The creation of the VLBI terrestrial reference frame, which transforms relative information into individual results, is an empirical process that has intrinsic errors. While UT1 is uniquely measured by VLBI, the geographical distribution and availability of VLBI stations, especially in the southern hemisphere, and the consistency of the VLBI terrestrial reference frame may limit the accuracy of Earth orientation measurements. The effects of particular error sources on geodetic and geophysical parameters derived from VLBI data will be illustrated.

The Contribution of GGOS to Understanding Dynamic Earth Processes

NASA Astrophysics Data System (ADS)

Gross, Richard

2017-04-01

Geodesy is the science of the Earth's shape, size, gravity and rotation, including their evolution in time. Geodetic observations play a major role in the solid Earth sciences because they are fundamental for the understanding and modeling of Earth system processes. Changes in the Earth's shape, its gravitational field, and its rotation are caused by external forces acting on the Earth system and internal processes involving mass transfer and exchange of angular and linear momentum. Thus, variations in these geodetic quantities of the Earth reflect and constrain mechanical and thermo-dynamic processes in the Earth system. Mitigating the impact on human life and property of natural hazards such as earthquakes, volcanic eruptions, debris flows, landslides, land subsidence, sea level change, tsunamis, floods, storm surges, hurricanes and extreme weather is an important scientific task to which geodetic observations make fundamental contributions. Geodetic observations can be used to monitor the pre-eruptive deformation of volcanoes and the pre-seismic deformation of earthquake fault zones, aiding in the issuance of volcanic eruption and earthquake warnings. They can also be used to rapidly estimate earthquake fault motion, aiding in the modeling of tsunami genesis and the issuance of tsunami warnings. Geodetic observations are also used in other areas of the Earth sciences, not just the solid Earth sciences. For example, geodesy contributes to atmospheric science by supporting both observation and prediction of the weather by geo-referencing meteorological observing data and by globally tracking change in stratospheric mass and lower tropospheric water vapor fields. Geodetic measurements of refraction profiles derived from satellite occultation data are routinely assimilated into numerical weather prediction models. Geodesy contributes to hydrologic studies by providing a unique global reference system for measurements of: sub-seasonal, seasonal and secular movements of continental and basin-scale water masses; loading and unloading of the land surface due to seasonal changes of groundwater; measurement of water level of major lakes and rivers by satellite altimetry; and improved digital terrain models as basis for flux modeling of surface water and flood modeling. Geodesy is crucial for cryospheric studies because of its ability to measure the motions of ice masses and changes in their volumes. Ice sheets, glaciers, and sea ice are intricately linked to the Earth's climate system. They store a record of past climate; they strongly affect surface energy budget, global water cycle, and sea-level change; and they are sensitive indicators of climate change. Geodesy is at the heart of all present-day ocean studies. Geodetic observations uniquely produce accurate, quantitative, and integrated observations of gravity, ocean circulation, sea surface height, ocean bottom pressure, and mass exchanges among the ocean, cryosphere, and land. Geodetic observations have made fundamental contributions to monitoring and understanding physical ocean processes. In particular, geodesy is the basic technique used to determine an accurate geoid model, allowing for the determination of absolute surface geostrophic currents, which are necessary to quantify heat transport of the ocean. Geodesy also provides the absolute reference for tide gauge measurements, allowing those measurements to be merged with satellite altimetric measurements to provide a coherent worldwide monitoring system for sea level change. In this presentation, selected examples of the contribution of geodetic observations to understanding the dynamic Earth system will be presented.

The Contribution of the IGS to a Globally Integrated Geodetic Observing System

NASA Astrophysics Data System (ADS)

WEBER, R.

2002-05-01

The dedicated goal of the International GPS Service (IGS) is 'to provide a service to support geodetic and geophysical research activities through GPS data and data products'. To accomplish its mission IGS began routine operations in Jan 1994. Nowadays operations are based on a large number of components like a globally distributed tracking network of about 200 stations, local and regional data centers as well as eight analysis centers. This presentation summarizes the measurement principles of the GPS and GLONASS microwave satellite navigation systems. An overview of current IGS-products will be given and factors limiting the accuracy of these products are discussed. Moreover IGS serves as one of the technique center of the IERS and therefore the delivered products follow designated IERS standards as close as possible. It can be anticipated that the IGS will also play an important role within the framework of an upcoming Globally Integrated Geodetic Observing System. Even today there are a number of scientific crosslinks to other space geodetic techniques and services e.g. to the ILRS in the determination of the geocentre or to the IVS in questions of a temporal and spatial densification of the reference frame. The above-mentioned initiative will strengthen further the cooperation and increase the scientific outcome.

A Unified Global Reference Frame of Vertical Crustal Movements by Satellite Laser Ranging.

PubMed

Zhu, Xinhui; Wang, Ren; Sun, Fuping; Wang, Jinling

2016-02-08

Crustal movement is one of the main factors influencing the change of the Earth system, especially in its vertical direction, which affects people's daily life through the frequent occurrence of earthquakes, geological disasters, and so on. In order to get a better study and application of the vertical crustal movement,as well as its changes, the foundation and prerequisite areto devise and establish its reference frame; especially, a unified global reference frame is required. Since SLR (satellite laser ranging) is one of the most accurate space techniques for monitoring geocentric motion and can directly measure the ground station's geocentric coordinates and velocities relative to the centre of the Earth's mass, we proposed to take the vertical velocity of the SLR technique in the ITRF2008 framework as the reference frame of vertical crustal motion, which we defined as the SLR vertical reference frame (SVRF). The systematic bias between other velocity fields and the SVRF was resolved by using the GPS (Global Positioning System) and VLBI (very long baseline interferometry) velocity observations, and the unity of other velocity fields and SVRF was realized,as well. The results show that it is feasible and suitable to take the SVRF as a reference frame, which has both geophysical meanings and geodetic observations, so we recommend taking the SLR vertical velocity under ITRF2008 as the global reference frame of vertical crustal movement.

A Unified Global Reference Frame of Vertical Crustal Movements by Satellite Laser Ranging

PubMed Central

Zhu, Xinhui; Wang, Ren; Sun, Fuping; Wang, Jinling

2016-01-01

Crustal movement is one of the main factors influencing the change of the Earth system, especially in its vertical direction, which affects people’s daily life through the frequent occurrence of earthquakes, geological disasters, and so on. In order to get a better study and application of the vertical crustal movement, as well as its changes, the foundation and prerequisite areto devise and establish its reference frame; especially, a unified global reference frame is required. Since SLR (satellite laser ranging) is one of the most accurate space techniques for monitoring geocentric motion and can directly measure the ground station’s geocentric coordinates and velocities relative to the centre of the Earth’s mass, we proposed to take the vertical velocity of the SLR technique in the ITRF2008 framework as the reference frame of vertical crustal motion, which we defined as the SLR vertical reference frame (SVRF). The systematic bias between other velocity fields and the SVRF was resolved by using the GPS (Global Positioning System) and VLBI (very long baseline interferometry) velocity observations, and the unity of other velocity fields and SVRF was realized, as well. The results show that it is feasible and suitable to take the SVRF as a reference frame, which has both geophysical meanings and geodetic observations, so we recommend taking the SLR vertical velocity under ITRF2008 as the global reference frame of vertical crustal movement. PMID:26867197

On the long-term stability of terrestrial reference frame solutions based on Kalman filtering

NASA Astrophysics Data System (ADS)

Soja, Benedikt; Gross, Richard S.; Abbondanza, Claudio; Chin, Toshio M.; Heflin, Michael B.; Parker, Jay W.; Wu, Xiaoping; Nilsson, Tobias; Glaser, Susanne; Balidakis, Kyriakos; Heinkelmann, Robert; Schuh, Harald

2018-06-01

The Global Geodetic Observing System requirement for the long-term stability of the International Terrestrial Reference Frame is 0.1 mm/year, motivated by rigorous sea level studies. Furthermore, high-quality station velocities are of great importance for the prediction of future station coordinates, which are fundamental for several geodetic applications. In this study, we investigate the performance of predictions from very long baseline interferometry (VLBI) terrestrial reference frames (TRFs) based on Kalman filtering. The predictions are computed by extrapolating the deterministic part of the coordinate model. As observational data, we used over 4000 VLBI sessions between 1980 and the middle of 2016. In order to study the predictions, we computed VLBI TRF solutions only from the data until the end of 2013. The period of 2014 until 2016.5 was used to validate the predictions of the TRF solutions against the measured VLBI station coordinates. To assess the quality, we computed average WRMS values from the coordinate differences as well as from estimated Helmert transformation parameters, in particular, the scale. We found that the results significantly depend on the level of process noise used in the filter. While larger values of process noise allow the TRF station coordinates to more closely follow the input data (decrease in WRMS of about 45%), the TRF predictions exhibit larger deviations from the VLBI station coordinates after 2014 (WRMS increase of about 15%). On the other hand, lower levels of process noise improve the predictions, making them more similar to those of solutions without process noise. Furthermore, our investigations show that additionally estimating annual signals in the coordinates does not significantly impact the results. Finally, we computed TRF solutions mimicking a potential real-time TRF and found significant improvements over the other investigated solutions, all of which rely on extrapolating the coordinate model for their predictions, with WRMS reductions of almost 50%.

Dynamic rupture models of earthquakes on the Bartlett Springs Fault, Northern California

USGS Publications Warehouse

Lozos, Julian C.; Harris, Ruth A.; Murray, Jessica R.; Lienkaemper, James J.

2015-01-01

The Bartlett Springs Fault (BSF), the easternmost branch of the northern San Andreas Fault system, creeps along much of its length. Geodetic data for the BSF are sparse, and surface creep rates are generally poorly constrained. The two existing geodetic slip rate inversions resolve at least one locked patch within the creeping zones. We use the 3-D finite element code FaultMod to conduct dynamic rupture models based on both geodetic inversions, in order to determine the ability of rupture to propagate into the creeping regions, as well as to assess possible magnitudes for BSF ruptures. For both sets of models, we find that the distribution of aseismic creep limits the extent of coseismic rupture, due to the contrast in frictional properties between the locked and creeping regions.

Connecting kinematic and dynamic reference frames by D-VLBI

NASA Astrophysics Data System (ADS)

Schuh, Harald; Plank, Lucia; Madzak, Matthias; Böhm, Johannes

2012-08-01

In geodetic and astrometric practice, terrestrial station coordinates are usually provided in the kinematic International Terrestrial Reference Frame (ITRF) and radio source coordinates in the International Celestial Reference Frame (ICRF), whereas measurements of space probes such as satellites and spacecrafts, or planetary ephemerides rest upon dynamical theories. To avoid inconsistencies and errors during measurement and calculation procedures, exact frame ties between quasi - inertial, kinematic and dynamic reference frames have to be secured. While the Earth Orientation Parameters (EOP), e.g. measured by VLBI, link the ITRF to the ICRF, the ties with the dynamic frames can be established with the differential Very Long Baseline Interferometry (D - VLBI) method. By observing space probes alternately t o radio sources, the relative position of the targets to each other on the sky can be determined with high accuracy. While D - VLBI is a common technique in astrophysics (source imaging) and deep space navigation, just recently there have been several effort s to use it for geodetic purposes. We present investigations concerning possible VLBI observations to satellites. This includes the potential usage of available GNNS satellites as well as specifically designed missions, as e.g. the GRASP mission proposed b y JPL/NASA and an international consortium, where the aspect of co - location in space of various techniques (VLBI, SLR, GNSS, DORIS) is the main focus.

NKG201xGIA - first results for a new model of glacial isostatic adjustment in Fennoscandia

NASA Astrophysics Data System (ADS)

Steffen, Holger; Barletta, Valentina; Kollo, Karin; Milne, Glenn A.; Nordman, Maaria; Olsson, Per-Anders; Simpson, Matthew J. R.; Tarasov, Lev; Ågren, Jonas

2016-04-01

Glacial isostatic adjustment (GIA) is a dominant process in northern Europe, which is observed with several geodetic and geophysical methods. The observed land uplift due to this process amounts to about 1 cm/year in the northern Gulf of Bothnia. GIA affects the establishment and maintenance of reliable geodetic and gravimetric reference networks in the Nordic countries. To support a high level of accuracy in the determination of position, adequate corrections have to be applied with dedicated models. Currently, there are efforts within a Nordic Geodetic Commission (NKG) activity towards a model of glacial isostatic adjustment for Fennoscandia. The new model, NKG201xGIA, to be developed in the near future will complement the forthcoming empirical NKG land uplift model, which will substitute the currently used empirical land uplift model NKG2005LU (Ågren & Svensson, 2007). Together, the models will be a reference for vertical and horizontal motion, gravity and geoid change and more. NKG201xGIA will also provide uncertainty estimates for each field. Following former investigations, the GIA model is based on a combination of an ice and an earth model. The selected reference ice model, GLAC, for Fennoscandia, the Barents/Kara seas and the British Isles is provided by Lev Tarasov and co-workers. Tests of different ice and earth models will be performed based on the expertise of each involved modeler. This includes studies on high resolution ice sheets, different rheologies, lateral variations in lithosphere and mantle viscosity and more. This will also be done in co-operation with scientists outside NKG who help in the development and testing of the model. References Ågren, J., Svensson, R. (2007): Postglacial Land Uplift Model and System Definition for the New Swedish Height System RH 2000. Reports in Geodesy and Geographical Information Systems Rapportserie, LMV-Rapport 4, Lantmäteriet, Gävle.

GPS inferred geocentric reference frame for satellite positioning and navigation

NASA Technical Reports Server (NTRS)

Malla, Rajendra P.; Wu, Sien-Chong

1989-01-01

Accurate geocentric three-dimensional positioning is of great importance for various geodetic and oceanographic applications. While relative positioning accuracy of a few centimeters has become a reality using Very Long Baseline Interferometry (VLBI), the uncertainty in the offset of the adopted coordinate system origin from the geocenter is still believed to be of the order of one meter. Satellite Laser Ranging (SLR) is capable of determining this offset to better than 10 cm, though, because of the limited number of satellites, this requires a long arc of data. The Global Positioning System (GPS) measurements provide a powerful alternative for an accurate determination of this origin offset in relatively short period of time. Two strategies are discussed, the first utilizes the precise relative positions predetermined by VLBI, whereas the second establishes a reference frame by holding only one of the tracking sites longitude fixed. Covariance analysis studies indicate that geocentric positioning to an accuracy of a few centimeters can be achieved with just one day of precise GPS pseudorange and carrier phase data.

GEODYN system support program, volume 4. [computer program for trajectory analysis of artificial satellites

NASA Technical Reports Server (NTRS)

Mullins, N. E.

1972-01-01

The GEODYN Orbit Determination and Geodetic Parameter Estimation System consists of a set of computer programs designed to determine and analyze definitive satellite orbits and their associated geodetic and measurement parameters. This manual describes the Support Programs used by the GEODYN System. The mathematics and programming descriptions are detailed. The operational procedures of each program are presented. GEODYN ancillary analysis programs may be grouped into three different categories: (1) orbit comparison - DELTA (2) data analysis using reference orbits - GEORGE, and (3) pass geometry computations - GROUNDTRACK. All of the above three programs use one or more tapes written by the GEODYN program in either a data reduction or orbit generator run.

Mass Intrusion at Mount St. Helens (WA) From Temporal Gravity Variations

NASA Astrophysics Data System (ADS)

Battaglia, M.; Lisowski, M.; Dzurisin, D.; Poland, M. P.; Schilling, S. P.; Diefenbach, A. K.; Wynn, J.

2015-12-01

Repeated high-precision gravity measurements made at Mount St. Helens (WA) have revealed systematic temporal variations in the gravity field several years after the end of the 2004-2008 dome-building eruption. Changes in gravity with respect to a stable reference station 36 km NW of the volcano were measured at 10 sites on the volcanic edifice and at 4 sites far afield (10 to 36 km) from the summit in August 2010, August 2012 and August 2014. After simulating and removing the gravity signal associated with changes in mass of the crater glacier, the local hydrothermal aquifer, and vertical deformation, the residual gravity field observed at sites near the volcano's summit significantly increased with respect to the stable reference site during 2010-2012 (maximum change 48 ± 15 mgal). No significant change was measured during 2012-2014. The pattern of gravity increase is radially symmetrical, with a half-width of about 2.5 km and a point of maximum change centered at the 2004-2008 lava dome. Forward modeling of residual gravity data using the same source geometry, depth, and location as that inferred from geodetic data (a spheroidal source centered 7.5 km beneath the 2004-2008 dome) indicates a mass increase rate of the order of 1011 kg/year. For a reasonable magma density (~2250 kg/m3), the volume rate of magma intrusion beneath the summit region inferred from gravity (~ 0.1 km3/yr) greatly exceeds the volume inferred from inversion of geodetic data (0.001 km3/yr between 2008-2011), suggesting that either magma compressibility or other processes are important aspects of magma storage at Mount St. Helens, or that the data argue for a different source.

Next Generation NASA Initiative for Space Geodesy

NASA Technical Reports Server (NTRS)

Merkowitz, S. M.; Desai, S.; Gross, R. S.; Hilliard, L.; Lemoine, F. G.; Long, J. L.; Ma, C.; McGarry J. F.; Murphy, D.; Noll, C. E.;

Research in Application of Geodetic GPS Receivers in Time Synchronization

NASA Astrophysics Data System (ADS)

Zhang, Q.; Zhang, P.; Sun, Z.; Wang, F.; Wang, X.

2018-04-01

In recent years, with the development of satellite orbit and clock parameters accurately determining technology and the popularity of geodetic GPS receivers, Common-View (CV) which proposed in 1980 by Allan has gained widespread application and achieved higher accuracy time synchronization results. GPS Common View (GPS CV) is the technology that based on multi-channel geodetic GPS receivers located in different place and under the same common-view schedule to receiving same GPS satellite signal at the same time, and then calculating the time difference between respective local receiver time and GPST by weighted theory, we will obtain the difference between above local time of receivers that installed in different station with external atomic clock. Multi-channel geodetic GPS receivers have significant advantages such as higher stability, higher accuracy and more common-view satellites in long baseline time synchronization application over the single-channel geodetic GPS receivers. At present, receiver hardware delay and surrounding environment influence are main error factors that affect the accuracy of GPS common-view result. But most error factors will be suppressed by observation data smoothing and using of observation data from different satellites in multi-channel geodetic GPS receiver. After the SA (Selective Availability) cancellation, using a combination of precise satellite ephemeris, ionospheric-free dual-frequency P-code observations and accurately measuring of receiver hardware delay, we can achieve time synchronization result on the order of nanoseconds (ns). In this paper, 6 days observation data of two IGS core stations with external atomic clock (PTB, USNO distance of two stations about 6000 km) were used to verify the GPS common-view theory. Through GPS observation data analysis, there are at least 2-4 common-view satellites and 5 satellites in a few tracking periods between two stations when the elevation angle is 15°, even there will be at least 2 common-view satellites for each tracking period when the elevation angle is 30°. Data processing used precise GPS satellite ephemeris, double-frequency P-code combination observations without ionosphere effects and the correction of the Black troposphere Delay Model. the weighted average of all common-viewed GPS satellites in the same tracking period is taken by weighting the root-mean-square error of each satellite, finally a time comparison data between two stations is obtained, and then the time synchronization result between the two stations (PTB and USNO) is obtained. It can be seen from the analysis of time synchronization result that the root mean square error of REFSV (the difference between the local frequency standard at the mid-point of the actual tracking length and the tracked satellite time in unit of 0.1 ns) shows a linear change within one day, However the jump occurs when jumping over the day which is mainly caused by satellites position being changed due to the interpolation of two-day precise satellite ephemeris across the day. the overall trend of time synchronization result is declining and tends to be stable within a week-long time. We compared the time synchronization results (without considering the hardware delay correction) with those published by the International Bureau of Weights and Measures (BIPM), and the comparing result from a week earlier shows that the trend is same but there is a systematic bias which was mainly caused by hardware delays of geodetic GPS receiver. Regardless of the hardware delay, the comparing result is about between 102 ns and 106 ns. the vast majority of the difference within 2 ns but the difference of individual moment does not exceed 4ns when taking into account the systemic bias which mainly caused by hardware delay. Therefore, it is feasible to use the geodetic GPS receiver to achieve the time synchronization result in nanosecond order between two stations which separated by thousands kilometers, and multi-channel geodetic GPS receivers have obvious advantages over single-channel geodetic GPS receivers in the number of common-viewing satellites. In order to obtain higher precision (e.g sub-nanosecond order) time synchronization results, we shall take account into carrier phase observations, hardware delay ,and more error-influencing factors should be considered such as troposphere delay correction, multipath effects, and hardware delays changes due to temperature changes.

Multi-disciplinary contributions of HartRAO to global geodesy and geodynamics

NASA Astrophysics Data System (ADS)

Combrinck, Ludwig

2015-04-01

The Hartebeesthoek Radio Astronomy Observatory (South Africa) supports global initiatives in both geodesy and geodynamics through an active programme of science platform provision in Africa, the Atlantic Ocean, Indian Ocean and Antarctica. Our involvement ranges from the installation of tide gauges, Global Navigation Satellite Systems stations, seismometers and accelerometers on remote islands to the installation of radar reflectors in Antarctica which enable accurate, geo-referenced maps of the Antarctic coast line to be made. Currently we also participate in the African VLBI Network (AVN), with the aim to densify not only astronomical observatories in Africa, but to improve the geometry and distribution of advanced geodetic and geophysical equipment to facilitate development of research platforms in Africa, which can be used for geodynamics and related sciences, supporting international projects such as the WEGENER initiative. We present our multi-disciplinary activities during the last decade and sketch the way forward. Participation of Africa in the global arena of astronomy, geodesy, geodynamics and related fields will receive a major boost during the next decade. This is partially due to the development of a component of the Square Kilometre Array (SKA) in Africa but also due to the Global Geodetic Observing System (GGOS) project and the international objectives of higher geodetic accuracies and more stable reference frames. Consequent spinoffs into many disciplines relying on global reference frames and sub-cm positional accuracies stand to benefit and Africa can play a major role in improving both science and network geometries.

E-GRASP/Eratosthenes: GRGS numerical simulations and millimetric TRF realization

NASA Astrophysics Data System (ADS)

Pollet, A.; Coulot, D.; Biancale, R.; Mandea, M.

2017-12-01

To accurately measuring and understanding changes in sea level, ice sheets and other elements of the dynamic Earth system, a stable Terrestrial Reference Frame (TRF) is needed. To reach the goals for the TRF realization of 1 mm accuracy and 0.1 mm/year stability (GGOS, Meeting the Requirements of a Global Society on a Changing Planet in 2020, Plag and Pearlman, 2009), The European - Geodetic Reference Antenna in Space (E-GRASP) has been recently proposed to the ESA EE9 call. This space mission is designed to build an enduring and stable TRF, by carrying very precise sensor systems for all the key geodetic techniques used to define and monitor the TRF (DORIS, GNSS, SLR and VLBI).In this study, we present the numerical simulations carried out by the French Groupe de Recherche en Géodésie Spatiale (GRGS). We simulated the measurements of the four geodetic techniques (DORIS and SLR measurements to E-GRASP, VLBI interferometric measurements on E-GRASP and GPS measurements from ground stations and from E-GRASP) over five years. Next, we have evaluated the expected exactitude and stability of the TRF provided by the processing of these measurements. In addition, we show the expected impact of the on-board instrument calibration on the TRF. Finally, we simulated the measurements of the two LAGEOS and four DORIS satellites, quasars for VLBI and we computed two multi-technique combinations, one with E-GRASP measurements and one without, to evaluate the contribution of this satellite to a combination.

Coastal sea level measurements using a single geodetic GPS receiver

NASA Astrophysics Data System (ADS)

Larson, Kristine M.; Löfgren, Johan S.; Haas, Rüdiger

2013-04-01

This paper presents a method to derive local sea level variations using data from a single geodetic-quality Global Navigation Satellite System (GNSS) receiver using GPS (Global Positioning System) signals. This method is based on multipath theory for specular reflections and the use of Signal-to-Noise Ratio (SNR) data. The technique could be valuable for altimeter calibration and validation. Data from two test sites, a dedicated GPS tide gauge at the Onsala Space Observatory (OSO) in Sweden and the Friday Harbor GPS site of the EarthScope Plate Boundary Observatory (PBO) in USA, are analyzed. The sea level results are compared to independently observed sea level data from nearby and in situ tide gauges. For OSO, the Root-Mean-Square (RMS) agreement is better than 5 cm, while it is in the order of 10 cm for Friday Harbor. The correlation coefficients are better than 0.97 for both sites. For OSO, the SNR-based results are also compared with results from a geodetic analysis of GPS data of a two receivers/antennae tide gauge installation. The SNR-based analysis results in a slightly worse RMS agreement with respect to the independent tide gauge data than the geodetic analysis (4.8 cm and 4.0 cm, respectively). However, it provides results even for rough sea surface conditions when the two receivers/antennae installation no longer records the necessary data for a geodetic analysis.

NChina16: A stable geodetic reference frame for geological hazard studies in North China

NASA Astrophysics Data System (ADS)

Wang, Guoquan; Bao, Yan; Gan, Weijun; Geng, Jianghui; Xiao, Gengru; Shen, Jack S.

2018-04-01

We have developed a stable North China Reference Frame 2016 (NChina16) using five years of continuous GPS observations (2011.8-2016.8) from 12 continuously operating reference stations (CORS) fixed to the North China Craton. Applications of NChina16 in landslide and subsidence studies are illustrated in this article. A method for realizing a regional geodetic reference frame is introduced. The primary result of this study is the seven parameters for transforming Cartesian ECEF (Earth-Centered, Earth-Fixed) coordinates X, Y, and Z from the International GNSS Service Reference Frame 2008 (IGS08) to NChina16. The seven parameters include the epoch that is used to align the regional reference frame to IGS08 and the time derivatives of three translations and three rotations. The GIPSY-OASIS (V6.4) software package was used to obtain the precise point positioning (PPP) daily solutions with respect to IGS08. The frame stability of NChina16 is approximately 0.5 mm/year in both horizontal and vertical directions. This study also developed a regional model for correcting seasonal motions superimposed into the vertical component of the GPS-derived displacement time series. Long-term GPS observations (1999-2016) from five CORS in North China were used to develop the seasonal model. According to this study, the PPP daily solutions with respect to NChina16 could achieve 2-3 mm horizontal accuracy and 4-5 mm vertical accuracy after being modified by the regional model. NChina16 will be critical to study geodynamic problems in North China, such as earthquakes, faulting, subsidence, and landslides. The regional reference frame will be periodically updated every few years to mitigate degradation of the frame with time and be synchronized with the update of IGS reference frame.

Α Deformation study in Central Greece using 20 years of GPS data

NASA Astrophysics Data System (ADS)

Marinou, Aggeliki; Papazissi, Kaliopi; Mitsakaki, Christiana; Paradissis, Demitris; Papanikolaou, Xanthos; Anastasiou, Demitris

2015-04-01

Central Greece is a region recognized for its intense tectonic activity with the main characterics being the extension in the North-South direction. This extension is revealed mainly in the form of large parallel grabens. Among these rifts is the Corinth Gulf, which is the most active tectonically, the basin between Parnassos and Kallidromo Mt, the Locris basin and the graben of North Evoikos Gulf, while in the south lays the Thebes basin and the South Evoikos Gulf. Since the late eighties the Laboratory of Higher Geodesy and the Dionysos Satellite Observatory of the National Technical University of Athens, in cooperation with several National and International Universities and Institutions have established, in various Greek areas, of high seismic activity, geodetic networks in order to monitor tectonic displacements. These geodetic networks were observed periodically using Satellite Geodesy techniques and in recent years almost entirely GPS. In this study all the available GPS data, referring to the broader area of Evia, Attiki and Viotia, for the years 1989 to 2008, are analyzed. The displacement field and its temporal changes for the area between the two major geological features, the Corinth Gulf and the Evoikos Gulf, are investigated. Αll the kinematic models that were used do not confirm that the area of study is deforming homogeneously, while an indication of a discontinuity has been detected.

A methodology for design of a linear referencing system for surface transportation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Vonderohe, A.; Hepworth, T.

1997-06-01

The transportation community has recently placed significant emphasis on development of data models, procedural standards, and policies for management of linearly-referenced data. There is an Intelligent Transportation Systems initiative underway to create a spatial datum for location referencing in one, two, and three dimensions. Most recently, a call was made for development of a unified linear reference system to support public, private, and military surface transportation needs. A methodology for design of the linear referencing system was developed from geodetic engineering principles and techniques used for designing geodetic control networks. The method is founded upon the law of propagation ofmore » random error and the statistical analysis of systems of redundant measurements, used to produce best estimates for unknown parameters. A complete mathematical development is provided. Example adjustments of linear distance measurement systems are included. The classical orders of design are discussed with regard to the linear referencing system. A simple design example is provided. A linear referencing system designed and analyzed with this method will not only be assured of meeting the accuracy requirements of users, it will have the potential for supporting delivery of error estimates along with the results of spatial analytical queries. Modeling considerations, alternative measurement methods, implementation strategies, maintenance issues, and further research needs are discussed. Recommendations are made for further advancement of the unified linear referencing system concept.« less

International global network of fiducial stations: Scientific and implementation issues

NASA Astrophysics Data System (ADS)

1991-11-01

In this report, an ad hoc panel of the National Research Council's Committee on Geodesy, Board of Earth Sciences and Resources (1) evaluates the scientific importance of a global network of fiducial sites, monitored very precisely, using a combination of surface- and space-geodetic techniques; (2) examines strategies for implementing and operating such a network; and (3) assesses whether such a network would provide a suitable global infrastructure for geodetic and other geophysical systems of the next century. The panel concludes that a global network of fiducial sites would be a valuable tool for addressing global change issues and play a critical role in providing a reference frame for scientific Earth missions. The panel suggests that existing global networks be integrated and anticipates that such a network would grow from about 30 to the ultimate size of about 200 fiducial sites. It is noted that such a global network will provide a long-term infrastructure for geodetic and geophysical studies. The panel expects that these fiducial sites would evolve into terrestrial observatories or laboratories that would permit more comprehensive studies of the Earth than those now possible.

International global network of fiducial stations: Scientific and implementation issues

NASA Technical Reports Server (NTRS)

1991-01-01

In this report, an ad hoc panel of the National Research Council's Committee on Geodesy, Board of Earth Sciences and Resources (1) evaluates the scientific importance of a global network of fiducial sites, monitored very precisely, using a combination of surface- and space-geodetic techniques; (2) examines strategies for implementing and operating such a network; and (3) assesses whether such a network would provide a suitable global infrastructure for geodetic and other geophysical systems of the next century. The panel concludes that a global network of fiducial sites would be a valuable tool for addressing global change issues and play a critical role in providing a reference frame for scientific Earth missions. The panel suggests that existing global networks be integrated and anticipates that such a network would grow from about 30 to the ultimate size of about 200 fiducial sites. It is noted that such a global network will provide a long-term infrastructure for geodetic and geophysical studies. The panel expects that these fiducial sites would evolve into terrestrial observatories or laboratories that would permit more comprehensive studies of the Earth than those now possible.

Production and Uses of Multi-Decade Geodetic Earth Science Data Records

NASA Astrophysics Data System (ADS)

Bock, Y.; Kedar, S.; Moore, A. W.; Fang, P.; Liu, Z.; Sullivan, A.; Argus, D. F.; Jiang, S.; Marshall, S. T.

2017-12-01

The Solid Earth Science ESDR System (SESES) project funded under the NASA MEaSUREs program produces and disseminates mature, long-term, calibrated and validated, GNSS based Earth Science Data Records (ESDRs) that encompass multiple diverse areas of interest in Earth Science, such as tectonic motion, transient slip and earthquake dynamics, as well as meteorology, climate, and hydrology. The ESDRs now span twenty-five years for the earliest stations and today are available for thousands of global and regional stations. Using a unified metadata database and a combination of GNSS solutions generated by two independent analysis centers, the project currently produces four long-term ESDR's: Geodetic Displacement Time Series: Daily, combined, cleaned and filtered, GIPSY and GAMIT long-term time series of continuous GPS station positions (global and regional) in the latest version of ITRF, automatically updated weekly. Geodetic Velocities: Weekly updated velocity field + velocity field histories in various reference frames; compendium of all model parameters including earthquake catalog, coseismic offsets, and postseismic model parameters (exponential or logarithmic). Troposphere Delay Time Series: Long-term time series of troposphere delay (30-min resolution) at geodetic stations, necessarily estimated during position time series production and automatically updated weekly. Seismogeodetic records for historic earthquakes: High-rate broadband displacement and seismic velocity time series combining 1 Hz GPS displacements and 100 Hz accelerometer data for select large earthquakes and collocated cGPS and seismic instruments from regional networks. We present several recent notable examples of the ESDR's usage: A transient slip study that uses the combined position time series to unravel "tremor-less" slow tectonic transient events. Fault geometry determination from geodetic slip rates. Changes in water resources across California's physiographic provinces at a spatial resolution of 75 km. Retrospective study of a southern California summer monsoon event.

Crowdsourced Contributions to the Nation's Geodetic Elevation Infrastructure

NASA Astrophysics Data System (ADS)

Stone, W. A.

2014-12-01

NOAA's National Geodetic Survey (NGS), a United States Department of Commerce agency, is engaged in providing the nation's fundamental positioning infrastructure - the National Spatial Reference System (NSRS) - which includes the framework for latitude, longitude, and elevation determination as well as various geodetic models, tools, and data. Capitalizing on Global Navigation Satellite System (GNSS) technology for improved access to the nation's precise geodetic elevation infrastructure requires use of a geoid model, which relates GNSS-derived heights (ellipsoid heights) with traditional elevations (orthometric heights). NGS is facilitating the use of crowdsourced GNSS observations collected at published elevation control stations by the professional surveying, geospatial, and scientific communities to help improve NGS' geoid modeling capability. This collocation of published elevation data and newly collected GNSS data integrates together the two height systems. This effort in turn supports enhanced access to accurate elevation information across the nation, thereby benefiting all users of geospatial data. By partnering with the public in this collaborative effort, NGS is not only helping facilitate improvements to the elevation infrastructure for all users but also empowering users of NSRS with the capability to do their own high-accuracy positioning. The educational outreach facet of this effort helps inform the public, including the scientific community, about the utility of various NGS tools, including the widely used Online Positioning User Service (OPUS). OPUS plays a key role in providing user-friendly and high accuracy access to NSRS, with optional sharing of results with NGS and the public. All who are interested in helping evolve and improve the nationwide elevation determination capability are invited to participate in this nationwide partnership and to learn more about the geodetic infrastructure which is a vital component of viable spatial data for many disciplines, including the geosciences.

Repeated Seafloor Geodetic Observation west off Miyake-jima volcanic island

NASA Astrophysics Data System (ADS)

Mochizuki, M.; Sato, M.; Fujita, M.; Katayama, M.; Yoshida, Z.; Yabuki, T.; Asada, A.

2003-12-01

An intensive earthquake swarm started under Miyake-jima island, 180 km south off Japan main island, on June 26, 2000. The earthquake swarm migrated towards northwest off Miyake-jima island, where numerous earthquakes, more than 100,000, were detected within about two months and an extensive crustal deformation was observed by on-land geodetic observations. Inst. of Industrial Science, Univ. of Tokyo and Hydrographic and Oceanographic Dept, Japan Coast Guard deployed three seafloor geodetic reference stations (St.A, St.B & St.C) in triangle area surrounded by three islands, Miyake-jima, Nii-jima and Kouzu-jima islands, in November and December, 2000, and have been conducting observations using these three stations to monitor seafloor deformation for the better understandings of underground magmatic activities. The observations have been conducted thirteen times until present. Fast and quickly varying ocean current in this area prevented us from stable observation. The surface current makes the pole, which connects the GPS antenna and the ship-board transducer, bend. This bending of the pole gave uncertainty to the analyses of locating the positions of the seafloor geodetic reference stations. The pole was replaced new, more rigid pole to overcome the problem in August 2002. The first observation with this new system was conducted at the reference station in the Sagami-bay. Smaller amount of bending with the new pole than that with the old one against both roll and pitch components could be seen in the data from this observation. This shows that the replacement of the pole provided stability to the observation system. We started to adopt the new system to the observation at the three stations west-off Miyake-jima island area, too. Station C, that is located nearest one to the Miyake-jima island, is one where we had most frequent observation after improvement of the system. The observations with the new system have been conducted four times in September, December 2002, April and August 2003 there. We have been processing and analyzing the data from these four observations at Station C. More stable analyses have been done with the data from the observations which the new system was employed than with ones observed by the old system. In this poster, we will present the repeatability of the observation system with the new pole, as well as discuss the preliminary results from them.

The International Geomagnetic Reference Field, 2005

USGS Publications Warehouse

Rukstales, Kenneth S.; Love, Jeffrey J.

2007-01-01

This is a set of five world charts showing the declination, inclination, horizontal intensity, vertical component, and total intensity of the Earth's magnetic field at mean sea level at the beginning of 2005. The charts are based on the International Geomagnetic Reference Field (IGRF) main model for 2005 and secular change model for 2005-2010. The IGRF is referenced to the World Geodetic System 1984 ellipsoid. Additional information about the USGS geomagnetism program is available at: http://geomag.usgs.gov/

Theoretical and Applied Research in the Field of Higher Geodesy Conducted in Rzeszow

NASA Astrophysics Data System (ADS)

Kadaj, Roman; Świętoń, Tomasz

2016-06-01

Important qualitative changes were taking place in polish geodesy in last few years. It was related to application of new techniques and technologies and to introduction of European reference frames in Poland. New reference stations network ASG-EUPOS, together with Internet services which helps in precise positioning was created. It allows to fast setting up precise hybrid networks. New, accurate satellite networks became the basis of new definitions in the field of reference systems. Simultaneously arise the need of new software, which enables to execute the geodetic works in new technical conditions. Authors had an opportunity to participate in mentioned undertakings, also under the aegis of GUGiK, by creation of methods, algorithms and necessary software tools. In this way the automatic postprocessing module (APPS) in POZGEO service, a part of ASG-EUPOS system came into being. It is an entirely polish product which works in Trimble environment. Universal software for transformation between PLETRF89, PL-ETRF2000, PULKOWO'42 reference systems as well as defined coordinate systems was created (TRANSPOL v. 2.06) and published as open product. An essential functional element of the program is the quasi-geoid model PL-geoid-2011, which has been elaborated by adjustment (calibration) of the global quasi-geoid model EGM2008 to 570 geodetic points (satellite-leveling points). Those and other studies are briefly described in this paper.

Monitoring Coral Growth - the Dichotomy Between Underwater Photogrammetry and Geodetic Control Network

NASA Astrophysics Data System (ADS)

Neyer, F.; Nocerino, E.; Gruen, A.

2018-05-01

Creating 3-dimensional (3D) models of underwater scenes has become a common approach for monitoring coral reef changes and its structural complexity. Also in underwater archeology, 3D models are often created using underwater optical imagery. In this paper, we focus on the aspect of detecting small changes in the coral reef using a multi-temporal photogrammetric modelling approach, which requires a high quality control network. We show that the quality of a good geodetic network limits the direct change detection, i.e., without any further registration process. As the photogrammetric accuracy is expected to exceed the geodetic network accuracy by at least one order of magnitude, we suggest to do a fine registration based on a number of signalized points. This work is part of the Moorea Island Digital Ecosystem Avatar (IDEA) project that has been initiated in 2013 by a group of international researchers (https://mooreaidea.ethz.ch/).

Paradoxes of the comparative analysis of ground-based and satellite geodetic measurements in recent geodynamics

NASA Astrophysics Data System (ADS)

Kuzmin, Yu. O.

2017-11-01

The comparative analysis of the Earth's surface deformations measured by ground-based and satellite geodetic methods on the regional and zonal measurement scales is carried out. The displacement velocities and strain rates are compared in the active regions such as Turkmenian-Iranian zone of interaction of the Arabian and Eurasian lithospheric plates and the Kamchatka segment of the subduction of the Pacific Plate beneath the Okotsk Plate. The comparison yields a paradoxical result. With the qualitatively identical kinematics of the motion, the quantitative characteristics of the displacement velocities and rates of strain revealed by the observations using the global navigational satellite system (GNSS) are by 1-2 orders of magnitude higher than those estimated by the more accurate methods of ground-based geodesy. For resolving the revealed paradoxes, it is required to set up special studies on the joint analysis of ground-based and satellite geodetic data from the combined observation sites.

Dynamic rupture modeling of the M7.2 2010 El Mayor-Cucapah earthquake: Comparison with a geodetic model

USGS Publications Warehouse

Kyriakopoulos, Christos; Oglesby, David D.; Funning, Gareth J.; Ryan, Kenneth

2017-01-01

The 2010 Mw 7.2 El Mayor-Cucapah earthquake is the largest event recorded in the broader Southern California-Baja California region in the last 18 years. Here we try to analyze primary features of this type of event by using dynamic rupture simulations based on a multifault interface and later compare our results with space geodetic models. Our results show that starting from homogeneous prestress conditions, slip heterogeneity can be achieved as a result of variable dip angle along strike and the modulation imposed by step over segments. We also considered effects from a topographic free surface and find that although this does not produce significant first-order effects for this earthquake, even a low topographic dome such as the Cucapah range can affect the rupture front pattern and fault slip rate. Finally, we inverted available interferometric synthetic aperture radar data, using the same geometry as the dynamic rupture model, and retrieved the space geodetic slip distribution that serves to constrain the dynamic rupture models. The one to one comparison of the final fault slip pattern generated with dynamic rupture models and the space geodetic inversion show good agreement. Our results lead us to the following conclusion: in a possible multifault rupture scenario, and if we have first-order geometry constraints, dynamic rupture models can be very efficient in predicting large-scale slip heterogeneities that are important for the correct assessment of seismic hazard and the magnitude of future events. Our work contributes to understanding the complex nature of multifault systems.

Hydrological signal in polar motion excitation from a combination of geophysical and gravimetric series

NASA Astrophysics Data System (ADS)

Nastula, Jolanta; Winska, Malgorzata; Salstein, David A.

2015-08-01

One can estimate the hydrological signal in polar motion excitation as a residual, namely the difference between observed geodetic excitation functions (Geodetic Angular Momentum, GAM) and the sum of Atmospheric Angular Momentum (AAM) and Oceanic Angular Momentum (OAM).The aim of this study is to find the optimal model and results for hydrological excitation functions in terms of their agreement with the computed difference between GAM and atmospheric and oceanic signals.The atmospheric and oceanic model-based data that we use in this study are the geophysical excitation functions of AAM, OAM available from the Special Bureaus for the Atmosphere and Oceans of the Geophysical Global Fluids Center (GGFC) of the International Earth Rotation and Reference Systems Service (IERS). For the atmosphere and ocean, these functions are based on the mass and motion fields of the fluids.Global models of land hydrology are used to estimate hydrological excitation functions of polar motion (Hydrological Angular Momentum - HAM). These HAM series are the mass of water substance determined from the various types of land-based hydrological reservoirs. In addition the HAM are estimated from spherical harmonic coefficients of the Earth’s gravity field. We use several sets of degree-2, order-1 harmonics of the Earth’s gravity field, derived from the Gravity Recovery and Climate Experiment (GRACE), Satellite Laser Ranging (SLR), and Global Navigation Satellite Systems (GNSS) data.Finally, these several different HAM series are used to determine the best model of hydrological excitation of polar motion. The model is found by looking for the combination of these series that fits the geodetic residuals using the least-square method.In addition, we will access model results from the Coupled Model Intercomparison Project, fifth experiment (CMIP-5) to examine atmospheric excitations from the twentieth century and estimates for the twenty-first century to see the possible signals and trends of these excitation series to help understand the potential range in the derived of hydrological excitation results.

Vertical motions in Northern Victoria Land inferred from GPS: A comparison with a glacial isostatic adjustment model

USGS Publications Warehouse

Mancini, F.; Negusini, M.; Zanutta, A.; Capra, A.

2007-01-01

Following the densification of GPS permanent and episodic trackers in Antarctica, geodetic observations are playing an increasing role in geodynamics research and the study of the glacial isostatic adjustment (GIA). The improvement in geodetic measurements accuracy suggests their use in constraining GIA models. It is essential to have a deeper knowledge on the sensitivity of GPS data to motionsrelated to long-term ice mass changes and the present-day mass imbalance of the ice sheets. In order to investigate the geodynamic phenomena in Northern Victoria Land (NVL), GPS geodetic observations were made during the last decade within the VLNDEF (Victoria Land Network for Deformation control) project. The processed data provided a picture of the motions occurring in NVL with a high level of accuracy and depicts, for the whole period, a well defined pattern of vertical motion. The comparison between GPS-derived vertical displacementsand GIA is addressed, showing a good degree of agreement and highlighting the future use of geodetic GPS measurements as constraints in GIA models. In spite of this agreement, the sensitivity of GPS vertical rates to non-GIA vertical motions has to be carefully evaluated.

NChina16: A stable geodetic reference frame for geological hazard studies in north China

NASA Astrophysics Data System (ADS)

Wang, G.; Yan, B.; Gan, W.; Geng, J.

2017-12-01

This study established a stable North China Reference Frame 2016 (NChina16) using five years of continuous GPS observations (2011.8 to 2016.8) from 12 continuously operating reference stations (CORS) fixed to the stable interior of the North China Craton. Applications of NChina16 in landslide, subsidence, and post-seismic displacement studies are illustrated. The primary result of this study is the seven parameters for transforming Cartesian ECEF (Earth-Centered, Earth-Fixed) coordinates X, Y, and Z from the International GNSS Service Reference Frame 2008 (IGS08) to NChina16. The seven parameters include the epoch that is used to tie the regional reference frame to IGS08 and the time derivatives of three translations and three rotations. A method for developing a regional geodetic reference frame is introduced in detail. The GIPSY-OASIS (V6.4) software package was used to obtain the precise point positioning (PPP) time series with respect to IGS08. The stability (accuracy) of NChina16 is about 0.5 mm/year in both vertical and horizontal directions. This study also developed a regional seasonal model for correcting vertical displacement time series data derived from the PPP solutions. Long-term GPS observations (1999-2016) from five CORS in north China were used to develop the seasonal model. According to this study, the PPP daily solutions with respect to NChina16 could achieve 2-3 mm horizontal accuracy and 4-5 mm vertical accuracy after being modified by the regional model. NChina16 will be critical to the long-term landslide, subsidence, fault, and structural monitoring in north China and for ongoing post-seismic crustal deformation studies in Japan. NChina16 will be incrementally improved and synchronized with the IGS reference frame update.

Global Positioning System surveys of storm-surge sensors deployed during Hurricane Ike, Seadrift, Texas, to Lake Charles, Louisiana, 2008

USGS Publications Warehouse

Payne, Jason; Woodward, Brenda K.; Storm, John B.

2009-01-01

The U.S. Geological Survey installed a network of pressure sensors at 65 sites along the Gulf Coast from Seadrift, Texas, northeast to Lake Charles, Louisiana, to record the timing, areal extent, and magnitude of inland storm surge and coastal flooding caused by Hurricane Ike in September 2008. A Global Positioning System was used to obtain elevations of reference marks near each sensor. A combination of real-time kinematic (RTK) and static Global Positioning System surveys were done to obtain elevations of reference marks. Leveling relative to reference marks was done to obtain elevations of sensor orifices above the reference marks. This report summarizes the Global Positioning System data collected and processed to obtain reference mark and storm-sensor-orifice elevations for 59 storm-surge sensors recovered from the original 65 installed as a necessary prelude to computation of storm-surge elevations. National Geodetic Survey benchmarks were used for RTK surveying. Where National Geodetic Survey benchmarks were not within 12 kilometers of a sensor site, static surveying was done. Additional control points for static surveying were in the form of newly established benchmarks or reestablished existing benchmarks. RTK surveying was used to obtain positions and elevations of reference marks for 29 sensor sites. Static surveying was used to obtain positions and elevations of reference marks for 34 sensor sites; four sites were surveyed using both methods. Multiple quality checks on the RTK-survey and static-survey data were applied. The results of all quality checks indicate that the desired elevation accuracy for the surveys of this report, less than 0.1-meter error, was achieved.

Height system unification based on the Fixed Geodetic Boundary Value Problem with limited availability of gravity data

NASA Astrophysics Data System (ADS)

Porz, Lucas; Grombein, Thomas; Seitz, Kurt; Heck, Bernhard; Wenzel, Friedemann

2017-04-01

Regional height reference systems are generally related to individual vertical datums defined by specific tide gauges. The discrepancies of these vertical datums with respect to a unified global datum cause height system biases that range in an order of 1-2 m at a global scale. One approach for unification of height systems relates to the solution of a Geodetic Boundary Value Problem (GBVP). In particular, the fixed GBVP, using gravity disturbances as boundary values, is solved at GNSS/leveling benchmarks, whereupon height datum offsets can be estimated by least squares adjustment. In spherical approximation, the solution of the fixed GBVP is obtained by Hotine's spherical integral formula. However, this method relies on the global availability of gravity data. In practice, gravity data of the necessary resolution and accuracy is not accessible globally. Thus, the integration is restricted to an area within the vicinity of the computation points. The resulting truncation error can reach several meters in height, making height system unification without further consideration of this effect unfeasible. This study analyzes methods for reducing the truncation error by combining terrestrial gravity data with satellite-based global geopotential models and by modifying the integral kernel in order to accelerate the convergence of the resulting potential. For this purpose, EGM2008-derived gravity functionals are used as pseudo-observations to be integrated numerically. Geopotential models of different spectral degrees are implemented using a remove-restore-scheme. Three types of modification are applied to the Hotine-kernel and the convergence of the resulting potential is analyzed. In a further step, the impact of these operations on the estimation of height datum offsets is investigated within a closed loop simulation. A minimum integration radius in combination with a specific modification of the Hotine-kernel is suggested in order to achieve sub-cm accuracy for the estimation of height datum offsets.

Slip Distribution of the 2011 Tohoku-oki Earthquake obtained by Geodetic and Tsunami Data and with a 3-D Finite Element Model

NASA Astrophysics Data System (ADS)

Romano, F.; Trasatti, E.; Lorito, S.; Ito, Y.; Piatanesi, A.; Lanucara, P.; Hirata, K.; D'Agostino, N.; Cocco, M.

2012-12-01

The rupture process of the Great 2011 Tohoku-oki earthquake has been particularly well studied by using an unprecedented collection of geophysical data. There is a general agreement among the different source models obtained by modeling seismological, geodetic and tsunami data. A slip patch of nearly 40÷50 meters has been imaged and located around and up-dip from the hypocenter by most of published models, while some differences exist in the slip pattern retrieved at shallow depths near the trench, likely due to the different resolving power of distinct data sets and to the adopted fault geometry. It is well known that the modeling of great subduction earthquakes requires the use of 3-D structural models in order to properly account for the effects of topography, bathymetry and the geometrical variations of the plate interface as well as for the effects of elastic contrasts between the subducting plate and the continental lithosphere. In this study we build a 3-D Finite Element (FE) model of the Tohoku-oki area in order to infer the slip distribution of the 2011 earthquake by performing a joint inversion of geodetic (GPS and seafloor observations) and tsunami (ocean bottom pressure sensors, DART and GPS buoys) data. The FE model is used to compute the geodetic and tsunami Green's functions. In order to understand how geometrical and elastic heterogeneities control the inferred slip distribution of the Tohoku-oki earthquake, we compare the slip patterns obtained using both homogeneous and heterogeneous structural models. The goal of this study is to better constrain the slip distribution and the maximum slip amplitudes. In particular, we aim to focus on the rupture process in the shallower part of the fault plane and near the trench, which is crucial to model the tsunami data and to assess the tsunamigenic potential of earthquakes in this region.

International Laser Ranging Service (ILRS): Terms of Reference

NASA Technical Reports Server (NTRS)

Husson, Van; Noll, Carey

2000-01-01

The International Laser Ranging Service (ILRS) is an established Service within Section II , Advanced Space Technology, of the International Association of Geodesy (IAG). The primary objective of the ILRS is to provide a service to support, through Satellite and Lunar Laser Ranging data and related products, geodetic and geophysical research activities as well as International Earth Rotation Service (IERS) products important to the maintenance of an accurate International Terrestrial Reference Frame (ITRF). The service also develops the necessary standards/specifications and encourages international adherence to its conventions.

Current Trends and Challenges in Satellite Laser Ranging

NASA Astrophysics Data System (ADS)

Appleby, Graham M.; Bianco, Giuseppe; Noll, Carey E.; Pavlis, Erricos C.; Pearlman, Michael R.

2016-12-01

Satellite Laser Ranging (SLR) is used to measure accurately the distance from ground stations to retro-reflectors on satellites and on the Moon. SLR is one of the fundamental space-geodetic techniques that define the International Terrestrial Reference Frame (ITRF), which is the basis upon which many aspects of global change over space, time, and evolving technology are measured; with VLBI the two techniques define the scale of the ITRF; alone the SLR technique defines its origin (geocenter). The importance of the reference frame has recently been recognized at the inter-governmental level through the United Nations, which adopted in February 2015 the Resolution "Global Geodetic Reference Frame for Sustainable Development." Laser Ranging provides precision orbit determination and instrument calibration and validation for satellite-borne altimeters for the better understanding of sea level change, ocean dynamics, ice mass-balance, and terrestrial topography. It is also a tool to study the dynamics of the Moon and fundamental constants and theories. With the exception of the currently in-orbit GPS constellation, all GNSS satellites now carry retro-reflectors for improved orbit determination, harmonization of reference frames, and in-orbit co-location and system performance validation; the next generation of GPS satellites due for launch from 2019 onwards will also carry retro-reflectors. The ILRS delivers weekly realizations that are accumulated sequentially to extend the ITRF and the Earth Orientation Parameter series with a daily resolution. SLR technology continues to evolve towards the next-generation laser ranging systems and it is expected to successfully meet the challenges of the GGOS2020 program for a future Global Space Geodetic Network. Ranging precision is improving as higher repetition rate, narrower pulse lasers, and faster detectors are implemented within the network. Automation and pass interleaving at some stations is expanding temporal coverage and greatly enhancing efficiency. Discussions are ongoing with some missions that will allow the SLR network stations to provide crucial, but energy-safe, range measurements to optically vulnerable satellites. New retro-reflector designs are improving the signal link and enable daylight ranging that is now the norm for many stations. We discuss many of these laser ranging activities and some of the tough challenges that the SLR network currently faces.

Reference frame access under the effects of great earthquakes: a least squares collocation approach for non-secular post-seismic evolution

NASA Astrophysics Data System (ADS)

Gómez, D. D.; Piñón, D. A.; Smalley, R.; Bevis, M.; Cimbaro, S. R.; Lenzano, L. E.; Barón, J.

2016-03-01

The 2010, (Mw 8.8) Maule, Chile, earthquake produced large co-seismic displacements and non-secular, post-seismic deformation, within latitudes 28°S-40°S extending from the Pacific to the Atlantic oceans. Although these effects are easily resolvable by fitting geodetic extended trajectory models (ETM) to continuous GPS (CGPS) time series, the co- and post-seismic deformation cannot be determined at locations without CGPS (e.g., on passive geodetic benchmarks). To estimate the trajectories of passive geodetic benchmarks, we used CGPS time series to fit an ETM that includes the secular South American plate motion and plate boundary deformation, the co-seismic discontinuity, and the non-secular, logarithmic post-seismic transient produced by the earthquake in the Posiciones Geodésicas Argentinas 2007 (POSGAR07) reference frame (RF). We then used least squares collocation (LSC) to model both the background secular inter-seismic and the non-secular post-seismic components of the ETM at the locations without CGPS. We tested the LSC modeled trajectories using campaign and CGPS data that was not used to generate the model and found standard deviations (95 % confidence level) for position estimates for the north and east components of 3.8 and 5.5 mm, respectively, indicating that the model predicts the post-seismic deformation field very well. Finally, we added the co-seismic displacement field, estimated using an elastic finite element model. The final, trajectory model allows accessing the POSGAR07 RF using post-Maule earthquake coordinates within 5 cm for ˜ 91 % of the passive test benchmarks.

Accuracy Assessment in Determining the Location of Corners of Building Structures Using a Combination of Various Measurement Methods

NASA Astrophysics Data System (ADS)

Krzyżek, Robert; Przewięźlikowska, Anna

2017-12-01

When surveys of corners of building structures are carried out, surveyors frequently use a compilation of two surveying methods. The first one involves the determination of several corners with reference to a geodetic control using classical methods of surveying field details. The second method relates to the remaining corner points of a structure, which are determined in sequence from distance-distance intersection, using control linear values of the wall faces of the building, the so-called tie distances. This paper assesses the accuracy of coordinates of corner points of a building structure, determined using the method of distance-distance intersection, based on the corners which had previously been determined by the conducted surveys tied to a geodetic control. It should be noted, however, that such a method of surveying the corners of building structures from linear measures is based on the details of the first-order accuracy, while the regulations explicitly allow such measurement only for the details of the second- and third-order accuracy. Therefore, a question arises whether this legal provision is unfounded, or whether surveyors are acting not only against the applicable standards but also without due diligence while performing surveys? This study provides answers to the formulated problem. The main purpose of the study was to verify whether the actual method which is used in practice for surveying building structures allows to obtain the required accuracy of coordinates of the points being determined, or whether it should be strictly forbidden. The results of the conducted studies clearly demonstrate that the problem is definitely more complex. Eventually, however, it might be assumed that assessment of the accuracy in determining a location of corners of a building using a combination of two different surveying methods will meet the requirements of the regulation [MIA, 2011), subject to compliance with relevant baseline criteria, which have been presented in this study. Observance of the proposed boundary conditions would allow for frequent performance of surveys of building structures by surveyors (from tie distances), while maintaining the applicable accuracy criteria. This would allow for the inclusion of surveying documentation into the national geodetic and cartographic documentation center database pursuant to the legal bases.

High-Precision Global Geodetic Systems: Revolution And Revelation In Fluid And 'Solid' Earth Tracking (Invited)

NASA Astrophysics Data System (ADS)

Minster, J. H.; Altamimi, Z.; Blewitt, G.; Carter, W. E.; Cazenave, A. A.; Davis, J. L.; Dragert, H.; Feary, D. A.; Herring, T.; Larson, K. M.; Ries, J. C.; Sandwell, D. T.; Wahr, J. M.

2009-12-01

Over the past half-century, space geodetic technologies have changed profoundly the way we look at the planet, not only in the matter of details and accuracy, but also in the matter of how the entire planet changes with time, even on “human” time scales. The advent of space geodesy has provided exquisite images of the ever-changing land and ocean topography and global gravity field of the planet. We now enjoy an International Terrestrial Reference System with a time-dependent geocenter position accurate to a few millimeters. We can image small and large tectonic deformations of the surface before, during, and after earthquakes and volcanic eruptions. We measure both the past subtle changes as well as the recent dramatic changes in the ice sheets, and track global and regional sea-level change to a precision of a millimeter per year or better. The remarkable achievements of Earth observing missions over the past two decades, and the success of future international missions described in the Decadal Survey depend both implicitly and explicitly on the continued availability and enhancement of a reliable and resilient global infrastructure for precise geodesy, and on ongoing advances in geodetic science that are linked to it. This allows us to deal with global scientific, technological and social issues such as climate change and natural hazards, but the impact of the global precise geodetic infrastructure also permeates our everyday lives. Nowadays drivers, aviators, and sailors can determine their positions inexpensively to meter precision in real time, anywhere on the planet. In the foreseeable future, not only will we be able to know a vehicle’s position to centimeter accuracy in real time, but also to control that position, and thus introduce autonomous navigation systems for many tasks which are beyond the reach of “manual” navigation capabilities. This vision will only be realized with sustained international support of the precise global geodetic infrastructure, of the associated technological advances, and of the concomitant fundamental geodetic research.

Geodetic Network Design and Optimization on the Active Tuzla Fault (Izmir, Turkey) for Disaster Management

PubMed Central

Halicioglu, Kerem; Ozener, Haluk

2008-01-01

Both seismological and geodynamic research emphasize that the Aegean Region, which comprises the Hellenic Arc, the Greek mainland and Western Turkey is the most seismically active region in Western Eurasia. The convergence of the Eurasian and African lithospheric plates forces a westward motion on the Anatolian plate relative to the Eurasian one. Western Anatolia is a valuable laboratory for Earth Science research because of its complex geological structure. Izmir is a large city in Turkey with a population of about 2.5 million that is at great risk from big earthquakes. Unfortunately, previous geodynamics studies performed in this region are insufficient or cover large areas instead of specific faults. The Tuzla Fault, which is aligned trending NE–SW between the town of Menderes and Cape Doganbey, is an important fault in terms of seismic activity and its proximity to the city of Izmir. This study aims to perform a large scale investigation focusing on the Tuzla Fault and its vicinity for better understanding of the region's tectonics. In order to investigate the crustal deformation along the Tuzla Fault and Izmir Bay, a geodetic network has been designed and optimizations were performed. This paper suggests a schedule for a crustal deformation monitoring study which includes research on the tectonics of the region, network design and optimization strategies, theory and practice of processing. The study is also open for extension in terms of monitoring different types of fault characteristics. A one-dimensional fault model with two parameters – standard strike-slip model of dislocation theory in an elastic half-space – is formulated in order to determine which sites are suitable for the campaign based geodetic GPS measurements. Geodetic results can be used as a background data for disaster management systems. PMID:27873783

Geodetic Network Design and Optimization on the Active Tuzla Fault (Izmir, Turkey) for Disaster Management.

PubMed

Halicioglu, Kerem; Ozener, Haluk

2008-08-19

Both seismological and geodynamic research emphasize that the Aegean Region, which comprises the Hellenic Arc, the Greek mainland and Western Turkey is the most seismically active region in Western Eurasia. The convergence of the Eurasian and African lithospheric plates forces a westward motion on the Anatolian plate relative to the Eurasian one. Western Anatolia is a valuable laboratory for Earth Science research because of its complex geological structure. Izmir is a large city in Turkey with a population of about 2.5 million that is at great risk from big earthquakes. Unfortunately, previous geodynamics studies performed in this region are insufficient or cover large areas instead of specific faults. The Tuzla Fault, which is aligned trending NE-SW between the town of Menderes and Cape Doganbey, is an important fault in terms of seismic activity and its proximity to the city of Izmir. This study aims to perform a large scale investigation focusing on the Tuzla Fault and its vicinity for better understanding of the region's tectonics. In order to investigate the crustal deformation along the Tuzla Fault and Izmir Bay, a geodetic network has been designed and optimizations were performed. This paper suggests a schedule for a crustal deformation monitoring study which includes research on the tectonics of the region, network design and optimization strategies, theory and practice of processing. The study is also open for extension in terms of monitoring different types of fault characteristics. A one-dimensional fault model with two parameters - standard strike-slip model of dislocation theory in an elastic half-space - is formulated in order to determine which sites are suitable for the campaign based geodetic GPS measurements. Geodetic results can be used as a background data for disaster management systems.

Geodetic measurement of deformation in California. Ph.D. Thesis - Massachusetts Inst. of Technology

NASA Technical Reports Server (NTRS)

Sauber, Jeanne

1989-01-01

The very long baseline interferometry (VLBI) measurements made in the western U.S. since 1979 as part of the NASA Crustal Dynamics Project provide discrete samples of the temporal and spatial deformation field. The interpretation of the VLBI-derived rates of deformation requires an examination of geologic information and more densely sampled ground-based geodetic data. In the first two of three related studies, triangulation and trilateration data measured on two regional networks, one in the central Mojave Desert and one in the Coast Ranges east of the San Andreas fault, have been processed. At the spatial scales spanned by these local geodetic networks, auxiliary geologic and geophysical data have been utilized to examine the relation between measured incremental strain and the accommodation of strain seen in local geological structures, strain release in earthquakes, and principal stress directions inferred from in situ measurements. In a third study, the geocentric position vectors from a set of 77 VLBI experiments beginning in October 1982 have been used to estimate the tangential rate of change of station positions in the western U.S. in a North-America-Fixed reference frame.

The African Reference Frame (AFREF) project: a fundamental geodetic tool for Africa

NASA Astrophysics Data System (ADS)

Farah, H.

2009-04-01

AFREF has as objective the establishment and maintenance of a unified geodetic reference frame for Africa, which will support and facilitate fundamental scientific and technical projects. The installation of observation systems all over Africa will provide important data that can be used in many different scientific fields (e.g., geodynamics, meteorological). Furthermore, AFREF will create an uniform frame that will support development projects, uniform environmental and mapping programmes as well as aid in resolving current and future international boundary disputes. This reference frame will be based on the International Terrestrial Reference Frame (ITRF) and will be realised through the establishment of a network of permanent Global Navigation Satellite System (GNSS) receivers. In close collaboration with several institutional role players, AFREF is an initiative of the United Nations Economic Commission for Africa (UNECA) Committee on Development Information (CODI). A steering committee is currently responsible for the over-all management and coordination of the implementation of AFREF. Implementation of AFREF is envisaged to be at national level in collaboration with National Mapping Organizations. Furthermore, many scientific Institutions are contributing for the densification of the network. The current status of the AFREF network will be discussed in detail. Several CORS systems have been installed to support AFREF specifically. In addition, most or all of the IGS stations located in Africa will automatically qualify as AFREF core stations. Furthermore, we will show examples of interaction between specific projects and AFREF that are contributing for the development of science in Africa.

Mapping the Coastline Limits of the Mexican State Sinaloa Using GPS

NASA Astrophysics Data System (ADS)

Vazquez, G. E.

2007-12-01

This research work presents the delimitation of the coastline limits of Sinaloa (one of the richest states of northwestern Mexico). In order to achieve this big task, it was required to use GPS (Global Positioning System) together with leveling spirit measurements. Based on the appropriate selection of the cited measurement techniques, the objective was to map the Sinaloa's state coastline to have the cartography of approximate 1600 km of littoral. The GPS measurements were performed and referred with respect to a GPS network located across the state. This GPS network consists of at least one first-order-site at each of the sixteen counties that constitute the state, and three to four second-order-sites of the ten counties of the state surrounded by sea. The leveling spirit measurements were referred to local benchmarks pre-established by the Mexican agency SEMARNAT (SEcretaría Del Medio Ambiente y Recursos NATurales). Within the main specifications of the GPS measurements and equipment, we used geodetic-dual-frequency GPS receivers in kinematic mode for both base stations (first and second order sites of the GPS state network) and rover stations (points forming the state littoral) with 5-sec log-rate interval and 10 deg cut-off angle. The GPS data processing was performed using the commercial software Trimble Geomatics Office (TGO) with Double Differences (DD) in post-processing mode. To this point, the field measurements had been totally covered including the cartography (scale 1:1000) and this includes the specifications and appropriate labeling according to the Mexican norm NOM-146-SEMARNAT-2005.

The International GPS Service (IGS) as a Continuous Reference System for Precise GPS Positioning

NASA Technical Reports Server (NTRS)

Neilan, Ruth; Heflin, Michael; Watkins, Michael; Zumberge, James

1996-01-01

The International GPS Service for Geodynamics (IGS) is an organization which operates under the auspices of the International Association of Geodesy (IAG) and has been operational since January 1994. The primary objective of the IGS is to provide precise GPS data and data products to support geodetic and geophysical research activities.

Direct determination of geocenter motion by combining SLR, VLBI, GNSS, and DORIS time series

NASA Astrophysics Data System (ADS)

Wu, X.; Abbondanza, C.; Altamimi, Z.; Chin, T. M.; Collilieux, X.; Gross, R. S.; Heflin, M. B.; Jiang, Y.; Parker, J. W.

2013-12-01

The longest-wavelength surface mass transport includes three degree-one spherical harmonic components involving hemispherical mass exchanges. The mass load causes geocenter motion between the center-of-mass of the total Earth system (CM) and the center-of-figure of the solid Earth surface (CF), and deforms the solid Earth. Estimation of the degree-1 surface mass changes through CM-CF and degree-1 deformation signatures from space geodetic techniques can thus complement GRACE's time-variable gravity data to form a complete change spectrum up to a high resolution. Currently, SLR is considered the most accurate technique for direct geocenter motion determination. By tracking satellite motion from ground stations, SLR determines the motion between CM and the geometric center of its ground network (CN). This motion is then used to approximate CM-CF and subsequently for deriving degree-1 mass changes. However, the SLR network is very sparse and uneven in global distribution. The average number of operational tracking stations is about 20 in recent years. The poor network geometry can have a large CN-CF motion and is not ideal for the determination of CM-CF motion and degree-1 mass changes. We recently realized an experimental Terrestrial Reference Frame (TRF) through station time series using the Kalman filter and the RTS smoother. The TRF has its origin defined at nearly instantaneous CM using weekly SLR measurement time series. VLBI, GNSS and DORIS time series are combined weekly with those of SLR and tied to the geocentric (CM) reference frame through local tie measurements and co-motion constraints on co-located geodetic stations. The unified geocentric time series of the four geodetic techniques provide a much better network geometry for direct geodetic determination of geocenter motion. Results from this direct approach using a 90-station network compares favorably with those obtained from joint inversions of GPS/GRACE data and ocean bottom pressure models. We will also show that a previously identified discrepancy in X-component between direct SLR orbit-tracking and inverse determined geocenter motions is largely reconciled with the new unified network.

Development of web tools to disseminate space geodesy data-related products

NASA Astrophysics Data System (ADS)

Soudarin, Laurent; Ferrage, Pascale; Mezerette, Adrien

2015-04-01

In order to promote the products of the DORIS system, the French Space Agency CNES has developed and implemented on the web site of the International DORIS Service (IDS) a set of plot tools to interactively build and display time series of site positions, orbit residuals and terrestrial parameters (scale, geocenter). An interactive global map is also available to select sites, and to get access to their information. Besides the products provided by the CNES Orbitography Team and the IDS components, these tools allow comparing time evolutions of coordinates for collocated DORIS and GNSS stations, thanks to the collaboration with the Terrestrial Frame Combination Center of the International GNSS Service (IGS). A database was created to improve robustness and efficiency of the tools, with the objective to propose a complete web service to foster data exchange with the other geodetic services of the International Association of Geodesy (IAG). The possibility to visualize and compare position time series of the four main space geodetic techniques DORIS, GNSS, SLR and VLBI is already under way at the French level. A dedicated version of these web tools has been developed for the French Space Geodesy Research Group (GRGS). It will give access to position time series provided by the GRGS Analysis Centers involved in DORIS, GNSS, SLR and VLBI data processing for the realization of the International Terrestrial Reference Frame. In this presentation, we will describe the functionalities of these tools, and we will address some aspects of the time series (content, format).

Geodetic Earth Observation

NASA Astrophysics Data System (ADS)

Rothacher, Markus

2017-04-01

Mankind is constantly threatened by a variety of natural disasters and global change phenomena. In order to be able to better predict and assess these catastrophic and disastrous events a continuous observation and monitoring of the causative Earth processes is a necessity. These processes may happen in time scales from extremely short (earthquakes, volcano eruptions, land slides, ...) to very long (melting of ice sheets, sea level change, plate tectonics, ...). Appropriate monitoring and early warning systems must allow, therefore, the detection and quantification of catastrophic events in (near) real-time on the one hand and the reliable identification of barely noticeable, but crucial long-term trends (e.g., sea level rise) on the other hand. The Global Geodetic Observing System (GGOS), established by the International Association of Geodesy (IAG) in 2003, already now contributes in a multitude of ways to meet this challenge, e.g., by providing a highly accurate and stable global reference frame, without which the measurement of a sea level rise of 2-3 mm/y would not be possible; by measuring displacements in near real-time and deformations over decades that offer valuable clues to plate tectonics, earthquake processes, tsunamis, volcanos, land slides, and glaciers dynamics; by observing the mass loss of ice sheets with gravity satellite missions; and by estimating essential variables such as the amount of water vapor in the troposphere relevant for weather predictions and climate and the content of free electrons in the ionosphere crucial for space weather.

VERA Geodetic Activities

NASA Technical Reports Server (NTRS)

Jike, Takaaki; Tamura, Yoshiaki; Shizugami, Makoto

2013-01-01

This report briefly describes the geodetic activities of VERA in the year 2012. The regular geodetic observations are carried out both in K- and S/X-bands. The frequency of regular observations is three times a month-twice for the VERA internal observations in K-band. The networks of the S/X sessions are JADE of GSI and IVS-T2. The raw data of the T2 and JADE sessions are electronically transferred to the Bonn, Haystack, and GSI correlators via Internet. Gravimetric observations are carried out at the VERA stations. An SG was installed at Mizusawa and placed in the vicinity of the VERA antenna in order to monitor vertical displacement at the end of 2008, and the observations continued throughout the year. Also at the VERA-Ishigakijima station, continuous operation of the SG started in 2012. The crustal movements generated by the 2011 earthquake off the Pacific coast of Tohoku continued during 2012, and displacement of the VERA-Mizusawa position by post-seismic creeping continued.

NASA directory of observation station locations, volume 1

NASA Technical Reports Server (NTRS)

1971-01-01

Geodetic information is presented for NASA tracking stations and observation stations in the NASA geodetic satellites program. A geodetic data sheet is provided for each station, giving the position of the station and describing briefly how it was established. Geodetic positions and geocentric coordinates of these stations are tabulated on local or major geodetic datums, and on selected world geodetic systems when available information permits.

NASA directory of observation station locations, volume 2

NASA Technical Reports Server (NTRS)

1971-01-01

The directory documents geodetic information for NASA tracking stations and observation stations in the NASA Geodetic Satellites Program, including stations participating in the National Geodetic Satellite Program. Station positions of these facilities are given on local or preferred major datums, and on the Modified Mercury Datum 1968. A geodetic data sheet is provided for each station, giving the position of the station and describing briefly how it was established. Geodetic positions and geocentric coordinates of these stations are tabulated on local or major geodetic datums, and on selected world geodetic systems when available information permits.

Evaluating Pseudorange Multipath at CGPS Stations Spanning Mexico

NASA Astrophysics Data System (ADS)

Vazquez, G.; Bennett, R. A.; Spinler, J. C.

2013-12-01

A research study was conducted in order to quantify and analyze the amount of pseudorange multipath at continuous Global Positioning System (CGPS) stations spanning Mexico. These CGPS stations are administered by a variety of organizations, including government agencies and public universities, and thus serve a wide range of positioning needs. Despite the diversity of the networks and their intended audiences, a core function of all of the networks is to provide a stable framework for high-precision positioning in support of diverse commercial and scientific applications. CGPS data from a large number of publicly available networks located in Mexico were studied. These include the RGNA (National Active Geodetic Network) administered by INEGI (National Institute of Statistics and Geography), the PBO network (Plate Boundary Observatory) funded by the National Science Foundation (NSF) and operated by UNAVCO (University NAVstar Consortium), the Southern California Integrated GPS Network (SCIGN), which is a collaboration effort of the United States Geological Survey (USGS), Scripps Institution of Oceanography and the Jet Propulsion Laboratory (JPL), the UNAM network, operated by the National Seismological System (SSN) and the Institute of Geophysics of the National Autonomous University of Mexico (UNAM), the Suominet Geodetic Network (SNG) and the CORS (Continuously Operating Reference Station) network, operated by the Federal Aviation Administration (FAA). A total of 54 CGPS stations were evaluated, where dual-frequency geodetic-grade receivers collected GPS data continuously during the period from 1994 to 2013. It is usually assumed that despite carefully selected locations, all CGPS stations are to some extent, affected by the presence of signal multipath. In addition, the geographic distribution of stations provides a nation-wide access to the International Terrestrial Reference Frame (ITRF). For real-time kinematic (RTK) and rapid static applications that depend on the pseudo-range observable, the accuracy with which a roaming user may locate their assets with respect to the ITRF may be limited by site-specific multipath. The issue is particularly critical for users depending on pseudorange measurements for 'real-time' (or 'near-real-time') kinematic GPS positioning, where ambiguity resolution is a critical step. Therefore, to identify the most and the least affected GPS stations we analyzed the averaged daily root mean square pseudorange multipath variations (MP1-RMS and MP2-RMS) for all feasible satellites tracked by the CGPS networks. We investigated the sources of multipath, including changes associated with hardware replacement (i.e., receiver and antenna type) and receiver firmware upgrades.

Round-Trip System Available to Measure Path Length Variation in Korea VLBI System for Geodesy

NASA Technical Reports Server (NTRS)

Oh, Hongjong; Kondo, Tetsuro; Lee, Jinoo; Kim, Tuhwan; Kim, Myungho; Kim, Suchul; Park, Jinsik; Ju, Hyunhee

2010-01-01

The construction project of Korea Geodetic VLBI officially started in October 2008. The construction of all systems will be completed by the end of 2011. The project was named Korea VLBI system for Geodesy (KVG), and its main purpose is to maintain the Korea Geodetic Datum. In case of the KVG system, an observation room with an H-maser frequency standard is located in a building separated from the antenna by several tens of meters. Therefore KVG system will adopt a so-called round-trip system to transmit reference signals to the antenna with reduction of the effect of path length variations. KVG s round-trip system is designed not only to use either metal or optical fiber cables, but also to measure path length variations directly. We present this unique round trip system for KVG.

Reference coordinate systems: An update. Supplement 11

NASA Technical Reports Server (NTRS)

Mueller, Ivan I.

1988-01-01

A common requirement for all geodetic investigations is a well-defined coordinate system attached to the earth in some prescribed way, as well as a well-defined inertial coordinate system in which the motions of the terrestrial frame can be monitored. The paper deals with the problems encountered when establishing such coordinate systems and the transformations between them. In addition, problems related to the modeling of the deformable earth are discussed. This paper is an updated version of the earlier work, Reference Coordinate Systems for Earth Dynamics: A Preview, by the author.

Interferometric investigations with the S1 constellation: an application to the Vesuvius/Campi Flegrei volcanic test site

NASA Astrophysics Data System (ADS)

Borgstrom, Sven; Del Gaudio, Carlo; De Martino, Prospero; Siniscalchi, Valeria; Prats-Iraola, Pau; Nannini, Matteo; Yague-Martinez, Nestor; Pinheiro, Muriel; Kim, Jun-Su; Vecchioli, Francesco; Minati, Federico; Costantini, Mario; Foumelis, Michael; Desnos, Yves-Louis

2017-04-01

The contribution focuses on the current status of the ESA study entitled "INSARAP Sentinel-1 Constellation Study" and investigates the interferometric performance of the S1A/S1B units. In particular, we refer to the Vesuvius/Campi Flegrei (Southern Italy) volcanic test site, where the continuous inflation (about 35 cm from 2011 to date) and the huge availability of ground-based geodetic data (continuous GPS - cGPS - leveling, tiltmetric, gravimetric, etc.) from the INGV-Osservatorio Vesuviano monitoring networks have allowed to get a clear deformation signal, besides the comparison between S1A/S1B and geodetic data. In this regard, the integration between InSAR and geodetic measurements is crucial for a continuous and extended monitoring of such an active volcanic area, as InSAR investigations allow to get an information on wide areas, whereas permanent networks (e.g., cGPS), allow to provide a continuous information complementing InSAR, which is limited by its revisiting time. Comparisons between S1 constellation data and geodetic measurements, with a particular focus on cGPS, will be presented, exploiting both LOS and inverted (E-W and vertical inversion) InSAR data starting from October, 2014. In addition, as a next step we are planning to model the deformation source of the area by exploiting the S1 time series results. Ultimately, very encouraging results suggest for a continuation of this activity also for the future, showing the great potential of S1 constellation data for monitoring active volcanic areas and, in general, to retrieve a very high quality deformation signal.

VLBI Observations of Geostationary Satellites

NASA Astrophysics Data System (ADS)

Artz, T.; Nothnagel, A.; La Porta, L.

2013-08-01

For a consistent realization of a Global Geodetic Observing System (GGOS), a proper tie between the individual global reference systems used in the analysis of space-geodetic observations is a prerequisite. For instance, the link between the terrestrial, the celestial and the dynamic reference system of artificial Earth orbiters may be realized by Very Long O Baseline Interferometry (VLBI) observations of one or several satellites. In the preparation phase for a dedicated satellite mission, one option to realize this is using a geostationary (GEO) satellite emitting a radio signal in X-Band and/or S-Band and, thus, imitating a quasar. In this way, the GEO satellite can be observed by VLBI together with nearby quasars and the GEO orbit can, thus, be determined in a celestial reference frame. If the GEO satellite is, e.g., also equipped with a GNSS-type transmitter, a further tie between GNSS and VLBI may be realized. In this paper, a concept for the generation of a radio signal is shown. Furthermore, simulation studies for estimating the GEO position are presented with a GEO satellite included in the VLBI schedule. VLBI group delay observations are then simulated for the quasars as well as for the GEO satellite. The analysis of the simulated observations shows that constant orbit changes are adequately absorbed by estimated orbit parameters. Furthermore, the post-fit residuals are comparable to those from real VLBI sessions.

An improved model of the Earth's gravitational field: GEM-T1

NASA Technical Reports Server (NTRS)

Marsh, J. G.; Lerch, F. J.; Christodoulidis, D. C.; Putney, B. H.; Felsentreger, T. L.; Sanchez, B. V.; Smith, D. E.; Klosko, S. M.; Martin, T. V.; Pavlis, E. C.

1987-01-01

Goddard Earth Model T1 (GEM-T1), which was developed from an analysis of direct satellite tracking observations, is the first in a new series of such models. GEM-T1 is complete to degree and order 36. It was developed using consistent reference parameters and extensive earth and ocean tidal models. It was simultaneously solved for gravitational and tidal terms, earth orientation parameters, and the orbital parameters of 580 individual satellite arcs. The solution used only satellite tracking data acquired on 17 different satellites and is predominantly based upon the precise laser data taken by third generation systems. In all, 800,000 observations were used. A major improvement in field accuracy was obtained. For marine geodetic applications, long wavelength geoidal modeling is twice as good as in earlier satellite-only GEM models. Orbit determination accuracy has also been substantially advanced over a wide range of satellites that have been tested.

Evaluation of a New Prototype Geodetic Astrolabe for Measuring Deflections of the Vertical

NASA Astrophysics Data System (ADS)

Slater, J. A.; Thompson, N.; Angell, L. E.; Belenkii, M. S.; Bruns, D. G.; Johnson, D. O.

2009-12-01

During the last three years, the National Geospatial-Intelligence Agency (NGA), with assistance from the U.S. Naval Observatory (USNO), sponsored the development of a new electronic geodetic astrolabe for measuring deflections of the vertical (DoV). NGA’s current operational astrolabes, built in 1995, have a number of undesirable features including the need for a pool of liquid mercury as a reflecting surface. The new state-of-the-art prototype instrument, completed by Trex Enterprises in early 2009, was designed to meet a 0.2 arcsec accuracy requirement. It reduces the weight, eliminates the mercury, and dramatically reduces observation times. The new astrolabe consists of a 101 mm aperture telescope with a 1.5° field of view and an inclinometer mounted inside a 92-cm high, 30-cm diameter tube, an external GPS receiver for timing, and a laptop computer that controls and monitors the instrument and performs the computations. Star images are recorded by an astronomical-grade camera with a 2,048 x 2,048 pixel CCD sensor that is externally triggered by time pulses from the GPS receiver. The prototype was designed for nighttime observation of visible stars equal to or brighter than magnitude 10.0. The inclinometer is a system of two orthogonal pendula that define the local gravitational vertical, each consisting of a brass plumb bob suspended from an aluminized polymer ribbon set between two electrodes. An internal reference collimator is rigidly tied to the inclinometer and projects an array of reference points of light onto the CCD sensor. After the astrolabe is coarsely leveled to within 20 arcsec, voice coil actuators automatically adjust and maintain the inclinometer vertical to within 0.02 arcsec. Independent images are collected at 6 second intervals using a 200 msec exposure time. The CCD coordinates are determined for each star and a collimator reference point on each image. Stars are identified by referencing a customized star catalog produced by USNO. A plate model is fitted to the topocentric coordinates of the stars, and then used to solve for the astronomical latitude and longitude of the vertical reference point on the CCD. The average of 100-150 individual image solutions (10-15 minutes) defines the astronomical position for the observation session. In order to remove an azimuthal orientation bias, the astrolabe is rotated 180°, a new observation session solution is produced for that orientation and then averaged with the first solution to get the final astronomical position of the site. By combining these coordinates with GPS-derived geodetic latitude and longitude, one obtains the DoV. Initial testing of the prototype at a known astronomic position has been completed. The tests evaluated the session-to-session and day-to-day repeatability of the solutions, the number of observations required for a solution, the accuracy with respect to the known position, and the operational robustness of the hardware and software. Based on the field tests, Trex will make improvements to the prototype hardware and software and then produce operational units for use by NGA.

Atomic clocks for geodesy.

PubMed

Mehlstäubler, Tanja E; Grosche, Gesine; Lisdat, Christian; Schmidt, Piet O; Denker, Heiner

2018-06-01

We review experimental progress on optical atomic clocks and frequency transfer, and consider the prospects of using these technologies for geodetic measurements. Today, optical atomic frequency standards have reached relative frequency inaccuracies below 10 -17 , opening new fields of fundamental and applied research. The dependence of atomic frequencies on the gravitational potential makes atomic clocks ideal candidates for the search for deviations in the predictions of Einstein's general relativity, tests of modern unifying theories and the development of new gravity field sensors. In this review, we introduce the concepts of optical atomic clocks and present the status of international clock development and comparison. Besides further improvement in stability and accuracy of today's best clocks, a large effort is put into increasing the reliability and technological readiness for applications outside of specialized laboratories with compact, portable devices. With relative frequency uncertainties of 10 -18 , comparisons of optical frequency standards are foreseen to contribute together with satellite and terrestrial data to the precise determination of fundamental height reference systems in geodesy with a resolution at the cm-level. The long-term stability of atomic standards will deliver excellent long-term height references for geodetic measurements and for the modelling and understanding of our Earth.

Atomic clocks for geodesy

NASA Astrophysics Data System (ADS)

Mehlstäubler, Tanja E.; Grosche, Gesine; Lisdat, Christian; Schmidt, Piet O.; Denker, Heiner

2018-06-01

We review experimental progress on optical atomic clocks and frequency transfer, and consider the prospects of using these technologies for geodetic measurements. Today, optical atomic frequency standards have reached relative frequency inaccuracies below 10‑17, opening new fields of fundamental and applied research. The dependence of atomic frequencies on the gravitational potential makes atomic clocks ideal candidates for the search for deviations in the predictions of Einstein’s general relativity, tests of modern unifying theories and the development of new gravity field sensors. In this review, we introduce the concepts of optical atomic clocks and present the status of international clock development and comparison. Besides further improvement in stability and accuracy of today’s best clocks, a large effort is put into increasing the reliability and technological readiness for applications outside of specialized laboratories with compact, portable devices. With relative frequency uncertainties of 10‑18, comparisons of optical frequency standards are foreseen to contribute together with satellite and terrestrial data to the precise determination of fundamental height reference systems in geodesy with a resolution at the cm-level. The long-term stability of atomic standards will deliver excellent long-term height references for geodetic measurements and for the modelling and understanding of our Earth.

Leveraging geodetic data to reduce losses from earthquakes

USGS Publications Warehouse

Murray, Jessica R.; Roeloffs, Evelyn A.; Brooks, Benjamin A.; Langbein, John O.; Leith, William S.; Minson, Sarah E.; Svarc, Jerry L.; Thatcher, Wayne R.

2018-04-23

Seismic hazard assessments that are based on a variety of data and the best available science, coupled with rapid synthesis of real-time information from continuous monitoring networks to guide post-earthquake response, form a solid foundation for effective earthquake loss reduction. With this in mind, the Earthquake Hazards Program (EHP) of the U.S. Geological Survey (USGS) Natural Hazards Mission Area (NHMA) engages in a variety of undertakings, both established and emergent, in order to provide high quality products that enable stakeholders to take action in advance of and in response to earthquakes. Examples include the National Seismic Hazard Model (NSHM), development of tools for improved situational awareness such as earthquake early warning (EEW) and operational earthquake forecasting (OEF), research about induced seismicity, and new efforts to advance comprehensive subduction zone science and monitoring. Geodetic observations provide unique and complementary information directly relevant to advancing many aspects of these efforts (fig. 1). EHP scientists have long leveraged geodetic data for a range of influential studies, and they continue to develop innovative observation and analysis methods that push the boundaries of the field of geodesy as applied to natural hazards research. Given the ongoing, rapid improvement in availability, variety, and precision of geodetic measurements, considering ways to fully utilize this observational resource for earthquake loss reduction is timely and essential. This report presents strategies, and the underlying scientific rationale, by which the EHP could achieve the following outcomes: The EHP is an authoritative source for the interpretation of geodetic data and its use for earthquake loss reduction throughout the United States and its territories.The USGS consistently provides timely, high quality geodetic data to stakeholders.Significant earthquakes are better characterized by incorporating geodetic data into USGS event response products and by expanded use of geodetic imaging data to assess fault rupture and source parameters.Uncertainties in the NSHM, and in regional earthquake models, are reduced by fully incorporating geodetic data into earthquake probability calculations.Geodetic networks and data are integrated into the operations and earthquake information products of the Advanced National Seismic System (ANSS).Earthquake early warnings are improved by more rapidly assessing ground displacement and the dynamic faulting process for the largest earthquakes using real-time geodetic data.Methodology for probabilistic earthquake forecasting is refined by including geodetic data when calculating evolving moment release during aftershock sequences and by better understanding the implications of transient deformation for earthquake likelihood.A geodesy program that encompasses a balanced mix of activities to sustain missioncritical capabilities, grows new competencies through the continuum of fundamental to applied research, and ensures sufficient resources for these endeavors provides a foundation by which the EHP can be a leader in the application of geodesy to earthquake science. With this in mind the following objectives provide a framework to guide EHP efforts:Fully utilize geodetic information to improve key products, such as the NSHM and EEW, and to address new ventures like the USGS Subduction Zone Science Plan.Expand the variety, accuracy, and timeliness of post-earthquake information products, such as PAGER (Prompt Assessment of Global Earthquakes for Response), through incorporation of geodetic observations.Determine if geodetic measurements of transient deformation can significantly improve estimates of earthquake probability.Maintain an observational strategy aligned with the target outcomes of this document that includes continuous monitoring, recording of ephemeral observations, focused data collection for use in research, and application-driven data processing and analysis systems.Collaborate on research, development, and operation of affordable, high-precision seafloor geodetic methods that improve earthquake forecasting and event response.Advance computational techniques and instrumentation to enable use of strategies like repeat-pass imagery and low-cost geodetic sensors for earthquake response, monitoring, and research.Engage stakeholders and collaborate with partner institutions to foster operational and research objectives and to safeguard the continued health of geodetic infrastructure upon which we mutually depend.Maintaining a vibrant internal research program provides the foundation by which the EHP can remain an effective and trusted source for earthquake science. Exploiting abundant new data sources, evaluating and assimilating the latest science, and pursuing novel avenues of investigation are means to fulfilling the EHP’s core responsibilities and realizing the important scientific advances envisioned by its scientists. Central to the success of such a research program is engaging personnel with a breadth of competencies and a willingness and ability to adapt these to the program’s evolving priorities, enabling current staff to expand their skills and responsibilities, and planning holistically to meet shared workforce needs. In parallel, collaboration with external partners to support scientific investigations that complement ongoing internal research enables the EHP to strengthen earthquake information products by incorporating alternative perspectives and approaches and to study topics and geographic regions that cannot be adequately covered internally.With commensurate support from technical staff who possess diverse skills, including engineering, information technology, and proficiency in quantitative analysis combined with basic geophysical knowledge, the EHP can achieve the geodetic outcomes identified in this document.

Designing the Next Generation Global Geodetic Network for GGOS

NASA Astrophysics Data System (ADS)

Pavlis, Erricos C.; Kuzmicz-Cieslak, Magdalena; König, Daniel; MacMillan, Daniel S.

2014-05-01

The U.S. National Research Council report "Precise Geodetic Infrastructure: National Requirements for a Shared Resource" (2010) recommended that we 'make a long-term commitment to maintain the International Terrestrial Reference Frame (ITRF) to ensure its continuity and stability'. It further determined that to ensure this, a network of about ~30 globally distributed "core" observatories with state of the art equipment was necessary and should be deployed over the next decade or so. The findings were based on simulation studies using conceptual networks where Satellite Laser Ranging (SLR) and Very Long Baseline Interferometry (VLBI) equipment of the next generation quality were deployed and operated 24/7. Since then, GGOS—the Global Geodetic Observing System, has embarked in an international effort to organize this future network, soliciting contributions from around the world, through an open solicitation "Call for Proposals—CfP". After a critical number of proposals were received, the results were evaluated and a data base was established where the likely sites are ranked in terms of the available equipment, local environment and weather, probability of completion and the relevant date, etc. The renewal process is expected to evolve smoothly over many years, from the current (legacy) state to the next generation ("GGOS-class") equipment. In order to design the optimal distribution of the proposed sites and to determine any gaps in the final network, simulations have been called for again, only this time the site locations are identical to those listed in the compiled data base, and the equipment at each site is in accordance to what is described in the data base for each point in time. The main objective of the simulations addresses the quality of the ITRF product from a network we expect to have in place about five and ten years after the NRC report (2016/2020). A secondary but equally important simulation task is the study of trade-offs when deploying new sites, e.g. comparing possible alternatives from several proposed sites in a region, or the order in time of deployment of future sites so that the transition is seamless and the ITRF suffers no degradation. As a first step, the simulation process was validated against the prior realization of the ITRF, using simulated SLR, VLBI and GNSS information based on two years of real data contributing to ITRF. We present the results of these simulation studies and examine the likelihood that the designed networks will successfully meet the GGOS goal of 1 mm or better accuracy at epoch and a temporal stability on the order of 0.1 mm/y, with similar numbers for the scale and orientation components of the ITRF.

Historical Review of Astro-Geodetic Observations in Serbia

NASA Astrophysics Data System (ADS)

Ogrizovic, V.; Delcev, S.; Vasilic, V.; Gucevic, J.

2008-10-01

Astro-geodetic determinations of vertical deflections in Serbia began during the first years of 20th century. The first field works were led by S. Bo\\vsković. After the 2nd World War, Military Geographic Institute, Department of Geodesy from the Faculty of Civil Engineering, and Federal Geodetic Directorate continued the determinations, needed for reductions of terrestrial geodetic measurements and the astro-geodetic geoid determination. Last years improvements of the astro-geodetic methods are carried out in the area of implementing modern measurement equipment and technologies.

A New Global Geodetic Strain Rate Model

NASA Astrophysics Data System (ADS)

Kreemer, C.; Blewitt, G.; Klein, E. C.; Shen, Z.; Wang, M.; Estey, L.; Wier, S.

2013-12-01

As part of the Global Earthquake Model (GEM) effort to improve global seismic hazard models, we present a new global geodetic strain rate model. This model (GSRM v. 2) is a vast improvement on the previous model from 2004 (v. 1.2). The model is still based on a finite-element type approach and has deforming cells in between the assumed rigid plates. The new model contains ~144,700 cells of 0.25° by 0.2° dimension. We redefined the geometries of the deforming zones based on the definitions of Bird (2003) and Chamot-Rooke and Rabaute (2006). We made some adjustments to the grid geometry at places where seismicity and/or GPS velocities suggested either the presence of deforming areas or a rigid block where those previous studies did not. GSRM v.2 includes 50 plates and blocks, including many not considered by Bird (2003). The new GSRM model is based on over 20,700 horizontal geodetic velocities at over 17,000 unique locations. The GPS velocity field consists of a 1) Over 6500 velocities derived by the University of Nevada, Reno, for CGPS stations for which >2.5 years of RINEX data are available until April 2013, 2) ~1200 velocities for China from a new analysis of all data from the Crustal Movement Network of China (CMONOC), and 3) about 13,000 velocities from 212 studies published in the literature or made otherwise available to us. Velocities from all studies were combined into the same reference frame by a 6-parameter transformation using velocities at collocated stations. We model co-seismic jumps while estimating velocities, ignore periods of post-seismic deformation, and exclude time-series that reflect magmatic and anthropogenic activity. GPS velocities were used to estimate angular velocities for 36 of the 50 rigid plates and blocks (the rest being taken from the literature), and these were used as boundary conditions in the strain rate calculations. For the strain rate calculations we used the method of Haines and Holt. In order to fit the data equally well in slowly and rapidly deforming areas, we first calculated a very smooth model by setting the a priori variances of the strain rate components very low. We then used this model as a proxy for the a priori standard deviations of the final model, at least for the areas that are well constrained by the GPS data. We will show examples of the strain rate and velocity field results. We will also highlight how and where the results can be viewed and accessed through a dedicated webportal (gsrm2.unavco.org). New GPS velocities (in any reference frame) can be uploaded to a new tool and displayed together with velocities used in GSRM v.2 in 53 reference frames (http://facility.unavco.org/data/maps/GPSVelocityViewer/GSRMViewer.html) .

Two-dimensional analysis of post-seismic deformation of the 2011 Tohoku-Oki earthquake with rate-and-state friction and non-linear rock rheology

NASA Astrophysics Data System (ADS)

Muto, J.; Moore, J. D. P.; Barbot, S.; Iinuma, T.; Ohta, Y.; Horiuchi, S.; Hikaru, I.

2017-12-01

We conduct a two-dimensional (2D) analysis of the post-seismic deformation of the 2011 Tohoku-Oki earthquake with the nonlinear coupling between frictional afterslip and viscoelastic flow. We consider slip on the plate boundary and distributed viscous flow of the lower crust and mantle. We created 2D transects across the Miyagi-Yamagata area where the largest coseismic slip was observed. We use the stress change by the coseismic slip model of Iinuma et al. (2012) to drive the post-seismic relaxation. The simulation is performed by the integral method (Lambert & Barbot, 2016) expanded to plane strain (Barbot, Moore, & Lambert, 2017). Despite the simple 2D approximation, we look for a realistic model compatible with mineral physics to explain geodetic observations including 5 years of seafloor observations (Tomita et al., 2017). In the ductile regions, the model employs a bi-viscous Burgers rheology with power-law flow (Masuti et al., 2016). The steady-state viscosity is estimated based on a thermal structure obtained by thermal-flow model including the wedge corner flow (Horiuchi & Iwamori, 2016). We model afterslip by the regularized rate-strengthening approximation of the rate-and-state dependent friction law (Barbot et al., 2009). The combination of power-law rheology with stress-driven afterslip explains the observed 2D displacement fields well during the 5-year post-seismic period. We also find that the model requires a low viscosity ( 1018 Pas) body beneath the quaternary volcano (Mt. Naruko) to reproduce the localized subsidence detected in the 9-month post-seismic period (Muto et al., 2016). The introduction of the low-viscosity body also reproduces quick recovery of the subsidence in the 5-year period. Equipped with a reference model that fits available geodetic observations, we discuss the importance of the mechanical coupling between afterslip and viscoelastic flow. We find that ignoring the traction change on the fault by viscoelastic flow introduces variations of the order of 20% on the amplitude of afterslip. This effect is most pronounced late in the post-seismic relaxation. Our model reconciles laboratory constraints on rock rheology and geophysical observations after the earthquake and serves as a first-order reference to better understand the dynamics of subduction at the Japan trench.

RTX Correction Accuracy and Real-Time Data Processing of the New Integrated SeismoGeodetic System with Real-Time Acceleration and Displacement Measurements for Earthquake Characterization Based on High-Rate Seismic and GPS Data

NASA Astrophysics Data System (ADS)

Zimakov, L. G.; Raczka, J.; Barrientos, S. E.

2016-12-01

We will discuss and show the results obtained from an integrated SeismoGeodetic System, model SG160-09, installed in the Chile (Chilean National Network), Italy (University of Naples Network), and California. The SG160-09 provides the user high rate GNSS and accelerometer data, full epoch-by-epoch measurement integrity and the ability to create combined GNSS and accelerometer high-rate (200Hz) displacement time series in real-time. The SG160-09 combines seismic recording with GNSS geodetic measurement in a single compact, ruggedized case. The system includes a low-power, 220-channel GNSS receiver powered by the latest Trimble-precise Maxwell™6 technology and supports tracking GPS, GLONASS and Galileo signals. The receiver incorporates on-board GNSS point positioning using Real-Time Precise Point Positioning (PPP) technology with satellite clock and orbit corrections delivered over IP networks. The seismic recording includes an ANSS Class A, force balance accelerometer with the latest, low power, 24-bit A/D converter, producing high-resolution seismic data. The SG160-09 processor acquires and packetizes both seismic and geodetic data and transmits it to the central station using an advanced, error-correction protocol providing data integrity between the field and the processing center. The SG160-09 has been installed in three seismic stations in different geographic locations with different Trimble global reference stations coverage The hardware includes the SG160-09 system, external Zephyr Geodetic-2 GNSS antenna, both radio and high-speed Internet communication media. Both acceleration and displacement data was transmitted in real-time to the centralized Data Acquisition Centers for real-time data processing. Command/Control of the field station and real-time GNSS position correction are provided via the Pivot platform. Data from the SG160-09 system was used for seismic event characterization along with data from traditional seismic and geodetic stations installed in the network. Our presentation will focus on the key improvements of the network installation with the SG160-09 system, RTX correction accuracy obtained from Trimble Global RTX tracking network, rapid data transmission, and real-time data processing for strong seismic events and aftershock characterization.

The effect of meteorological data on atmospheric pressure loading corrections in VLBI data analysis

NASA Astrophysics Data System (ADS)

Balidakis, Kyriakos; Glaser, Susanne; Karbon, Maria; Soja, Benedikt; Nilsson, Tobias; Lu, Cuixian; Anderson, James; Liu, Li; Andres Mora-Diaz, Julian; Raposo-Pulido, Virginia; Xu, Minghui; Heinkelmann, Robert; Schuh, Harald

2015-04-01

Earth's crustal deformation is a manifestation of numerous geophysical processes, which entail the atmosphere and ocean general circulation and tidal attraction, climate change, and the hydrological circle. The present study deals with the elastic deformations induced by atmospheric pressure variations. At geodetic sites, APL (Atmospheric Pressure Loading) results in displacements covering a wide range of temporal scales which is undesirable when rigorous geodetic/geophysical analysis is intended. Hence, it is of paramount importance that the APL signal are removed at the observation level in the space geodetic data analysis. In this study, elastic non-tidal components of loading displacements were calculated in the local topocentric frame for all VLBI (Very Long Baseline Interferometry) stations with respect to the center-of-figure of the solid Earth surface and the center-of-mass of the total Earth system. The response of the Earth to the load variation at the surface was computed by convolving Farrell Green's function with the homogenized in situ surface pressure observations (in the time span 1979-2014) after the subtraction of the reference pressure and the S1, S2 and S3 thermal tidal signals. The reference pressure was calculated through a hypsometric adjustment of the absolute pressure level determined from World Meteorological Organization stations in the vicinity of each VLBI observatory. The tidal contribution was calculated following the 2010 International Earth Rotation and Reference Systems Service conventions. Afterwards, this approach was implemented into the VLBI software VieVS@GFZ and the entirety of available VLBI sessions was analyzed. We rationalize our new approach on the basis that the potential error budget is substantially reduced, since several common errors are not applicable in our approach, e.g. those due to the finite resolution of NWM (Numerical Weather Models), the accuracy of the orography model necessary for adjusting the former as well as the inconsistencies between them, and the interpolation scheme which yields the elastic deformations. Differences of the resulting TRF (Terrestrial Reference Frame) determinations and other products derived from VLBI analysis between the approach followed here and the one employing NWM's data for obtaining the input pressure fields, are illustrated. The providers of the atmospheric pressure loading models employed for our comparisons are GSFC/NASA, the University of Luxembourg, the University of Strasbourg, the Technical University of Vienna and GeoForschungsZentrum of Potsdam.

Moving to a Modernized Height Reference System in Canada: Rationale, Status and Plans

NASA Astrophysics Data System (ADS)

Veronneau, M.; Huang, J.

2007-05-01

A modern society depends on a common coordinate reference system through which geospatial information can be interrelated and exploited reliably. For height measurements this requires the ability to measure mean sea level elevations easily, accurately, and at the lowest possible cost. The current national reference system for elevations, the Canadian Geodetic Vertical Datum of 1928 (CGVD28), offers only partial geographic coverage of the Canadian territory and is affected by inaccuracies that are becoming more apparent as users move to space- based technologies such as GPS. Furthermore, the maintenance and expansion of the national vertical network using spirit-levelling, a costly, time consuming and labour intensive proposition, has only been minimally funded over the past decade. It is now generally accepted that the most sustainable alternative for the realization of a national vertical datum is a gravimetric geoid model. This approach defines the datum in relation to an ellipsoid, making it compatible with space-based technologies for positioning. While simplifying access to heights above mean sea level all across the Canadian territory, this approach imposes additional demands on the quality of the geoid model. These are being met by recent and upcoming space gravimetry missions that have and will be measuring the Earth`s gravity field with increasing and unprecedented accuracy. To maintain compatibility with the CGVD28 datum materialized at benchmarks, the current first-order levelling can be readjusted by constraining geoid heights at selected stations of the Canadian Base Network. The new reference would change CGVD28 heights of benchmarks by up to 1 m across Canada. However, local height differences between benchmarks would maintain a relative precision of a few cm or better. CGVD28 will co-exist with the new height reference as long as it will be required, but it will undoubtedly disappear as benchmarks are destroyed over time. The adoption of GNSS technologies for positioning should naturally move users to the new height reference and offer the possibility of transferring heights over longer distances, within the precision of the geoid model. This transition will also reduce user dependency on a dense network of benchmarks and offer the possibility for geodetic agencies to provide the reference frame with a reduced number of 3D control points. While the rationale for moving to a modernized height system is easily understood, the acceptance of the new system by users will only occur gradually as they adopt new technologies and procedures to access the height reference. A stakeholder consultation indicates user readiness and an implementation plan is starting to unfold. This presentation will look at the current state of the geoid model and control networks that will support the modernized height system. Results of the consultation and the recommendations regarding the roles and responsibilities of the various stakeholders involved in implementing the transition will also be reported.

Ellipsoidal terrain correction based on multi-cylindrical equal-area map projection of the reference ellipsoid

NASA Astrophysics Data System (ADS)

Ardalan, A. A.; Safari, A.

2004-09-01

An operational algorithm for computation of terrain correction (or local gravity field modeling) based on application of closed-form solution of the Newton integral in terms of Cartesian coordinates in multi-cylindrical equal-area map projection of the reference ellipsoid is presented. Multi-cylindrical equal-area map projection of the reference ellipsoid has been derived and is described in detail for the first time. Ellipsoidal mass elements with various sizes on the surface of the reference ellipsoid are selected and the gravitational potential and vector of gravitational intensity (i.e. gravitational acceleration) of the mass elements are computed via numerical solution of the Newton integral in terms of geodetic coordinates {λ,ϕ,h}. Four base- edge points of the ellipsoidal mass elements are transformed into a multi-cylindrical equal-area map projection surface to build Cartesian mass elements by associating the height of the corresponding ellipsoidal mass elements to the transformed area elements. Using the closed-form solution of the Newton integral in terms of Cartesian coordinates, the gravitational potential and vector of gravitational intensity of the transformed Cartesian mass elements are computed and compared with those of the numerical solution of the Newton integral for the ellipsoidal mass elements in terms of geodetic coordinates. Numerical tests indicate that the difference between the two computations, i.e. numerical solution of the Newton integral for ellipsoidal mass elements in terms of geodetic coordinates and closed-form solution of the Newton integral in terms of Cartesian coordinates, in a multi-cylindrical equal-area map projection, is less than 1.6×10-8 m2/s2 for a mass element with a cross section area of 10×10 m and a height of 10,000 m. For a mass element with a cross section area of 1×1 km and a height of 10,000 m the difference is less than 1.5×10-4m2/s2. Since 1.5× 10-4 m2/s2 is equivalent to 1.5×10-5m in the vertical direction, it can be concluded that a method for terrain correction (or local gravity field modeling) based on closed-form solution of the Newton integral in terms of Cartesian coordinates of a multi-cylindrical equal-area map projection of the reference ellipsoid has been developed which has the accuracy of terrain correction (or local gravity field modeling) based on the Newton integral in terms of ellipsoidal coordinates.

A preliminary geodetic data model for geographic information systems

NASA Astrophysics Data System (ADS)

Kelly, K. M.

2009-12-01

Our ability to gather and assimilate integrated data collections from multiple disciplines is important for earth system studies. Moreover, geosciences data collection has increased dramatically, with pervasive networks of observational stations on the ground, in the oceans, in the atmosphere and in space. Contemporary geodetic observations from several space and terrestrial technologies contribute to our knowledge of earth system processes and thus are a valuable source of high accuracy information for many global change studies. Assimilation of these geodetic observations and numerical models into models of weather, climate, oceans, hydrology, ice, and solid Earth processes is an important contribution geodesists can make to the earth science community. Clearly, the geodetic observations and models are fundamental to these contributions. ESRI wishes to provide leadership in the geodetic community to collaboratively build an open, freely available content specification that can be used by anyone to structure and manage geodetic data. This Geodetic Data Model will provide important context for all geographic information. The production of a task-specific geodetic data model involves several steps. The goal of the data model is to provide useful data structures and best practices for each step, making it easier for geodesists to organize their data and metadata in a way that will be useful in their data analyses and to their customers. Built on concepts from the successful Arc Marine data model, we introduce common geodetic data types and summarize the main thematic layers of the Geodetic Data Model. These provide a general framework for envisioning the core feature classes required to represent geodetic data in a geographic information system. Like Arc Marine, the framework is generic to allow users to build workflow or product specific geodetic data models tailored to the specific task(s) at hand. This approach allows integration of the data with other existing geophysical datasets, thus facilitating creation of multi-tiered models. The Geodetic Data Model encourages data assimilation and analysis and facilitates data interoperability, coordination and integration in earth system modeling. It offers a basic set of data structures organized in a simple and homogeneous way and can streamline access to and processing of geodetic data. It can aid knowledge discovery through the use of GIS technology to enable identification and understanding of relationships and provide well-established tools and methods to communicate complex technical knowledge with non-specialist audiences. The Geodetic Data Model comprise the base classes for using workflow driven ontology (WDO) techniques for specifying the computation of complex geodetic products along with the ability to capture provenance information. While we do not specify WDO for any given geodetic product, we recognize that structured geodetic data is essential for generating any geodetic WDO, a task that can be streamlined in some GIS software.

Contribution of Starlette, Stella, and AJISAI to the SLR-derived global reference frame

NASA Astrophysics Data System (ADS)

Sośnica, Krzysztof; Jäggi, Adrian; Thaller, Daniela; Beutler, Gerhard; Dach, Rolf

2014-08-01

The contribution of Starlette, Stella, and AJISAI is currently neglected when defining the International Terrestrial Reference Frame, despite a long time series of precise SLR observations and a huge amount of available data. The inferior accuracy of the orbits of low orbiting geodetic satellites is the main reason for this neglect. The Analysis Centers of the International Laser Ranging Service (ILRS ACs) do, however, consider including low orbiting geodetic satellites for deriving the standard ILRS products based on LAGEOS and Etalon satellites, instead of the sparsely observed, and thus, virtually negligible Etalons. We process ten years of SLR observations to Starlette, Stella, AJISAI, and LAGEOS and we assess the impact of these Low Earth Orbiting (LEO) SLR satellites on the SLR-derived parameters. We study different orbit parameterizations, in particular different arc lengths and the impact of pseudo-stochastic pulses and dynamical orbit parameters on the quality of the solutions. We found that the repeatability of the East and North components of station coordinates, the quality of polar coordinates, and the scale estimates of the reference are improved when combining LAGEOS with low orbiting SLR satellites. In the multi-SLR solutions, the scale and the component of geocenter coordinates are less affected by deficiencies in solar radiation pressure modeling than in the LAGEOS-1/2 solutions, due to substantially reduced correlations between the geocenter coordinate and empirical orbit parameters. Eventually, we found that the standard values of Center-of-mass corrections (CoM) for geodetic LEO satellites are not valid for the currently operating SLR systems. The variations of station-dependent differential range biases reach 52 and 25 mm for AJISAI and Starlette/Stella, respectively, which is why estimating station-dependent range biases or using station-dependent CoM, instead of one value for all SLR stations, is strongly recommended. This clearly indicates that the ILRS effort to produce CoM corrections for each satellite, which are site-specific and depend on the system characteristics at the time of tracking, is very important and needs to be implemented in the SLR data analysis.

NASA directory of observation station locations, volume 1

NASA Technical Reports Server (NTRS)

1973-01-01

Geodetic information for NASA tracking stations and for observation stations cooperating in NASA geodetic satellite programs is presented. A Geodetic Data Sheet is provided for each station, giving the position of the station and describing briefly how it was established. Geodetic positions and geocentric coordinates of these stations are tabulated on local or major geodetic datums and on selected world geodetic systems. The principal tracking facilities used by NASA, including the Spaceflight Tracking and Data Network, the Deep Space Network, and several large radio telescopes are discussed. Positions of these facilities are tabulated on their local or national datums, the Mercury Spheroid 1960, the Modified Mercury Datum 1968, and the Spaceflight Tracking and Data Network System. Observation stations in the NASA Geodetic Satellites Program are included along with stations participating in the National Geodetic Satellite Program. Positions of these facilities are given on local or preferred major datums, and on the Modified Mercury Datum 1968.

Review of current GPS methodologies for producing accurate time series and their error sources

NASA Astrophysics Data System (ADS)

He, Xiaoxing; Montillet, Jean-Philippe; Fernandes, Rui; Bos, Machiel; Yu, Kegen; Hua, Xianghong; Jiang, Weiping

2017-05-01

The Global Positioning System (GPS) is an important tool to observe and model geodynamic processes such as plate tectonics and post-glacial rebound. In the last three decades, GPS has seen tremendous advances in the precision of the measurements, which allow researchers to study geophysical signals through a careful analysis of daily time series of GPS receiver coordinates. However, the GPS observations contain errors and the time series can be described as the sum of a real signal and noise. The signal itself can again be divided into station displacements due to geophysical causes and to disturbing factors. Examples of the latter are errors in the realization and stability of the reference frame and corrections due to ionospheric and tropospheric delays and GPS satellite orbit errors. There is an increasing demand on detecting millimeter to sub-millimeter level ground displacement signals in order to further understand regional scale geodetic phenomena hence requiring further improvements in the sensitivity of the GPS solutions. This paper provides a review spanning over 25 years of advances in processing strategies, error mitigation methods and noise modeling for the processing and analysis of GPS daily position time series. The processing of the observations is described step-by-step and mainly with three different strategies in order to explain the weaknesses and strengths of the existing methodologies. In particular, we focus on the choice of the stochastic model in the GPS time series, which directly affects the estimation of the functional model including, for example, tectonic rates, seasonal signals and co-seismic offsets. Moreover, the geodetic community continues to develop computational methods to fully automatize all phases from analysis of GPS time series. This idea is greatly motivated by the large number of GPS receivers installed around the world for diverse applications ranging from surveying small deformations of civil engineering structures (e.g., subsidence of the highway bridge) to the detection of particular geophysical signals.

Combining Real-time Seismic and Geodetic Data to Improve Rapid Earthquake Information

NASA Astrophysics Data System (ADS)

Murray, M. H.; Neuhauser, D. S.; Gee, L. S.; Dreger, D. S.; Basset, A.; Romanowicz, B.

2002-12-01

The Berkeley Seismological Laboratory operates seismic and geodetic stations in the San Francisco Bay area and northern California for earthquake and deformation monitoring. The seismic systems, part of the Berkeley Digital Seismic Network (BDSN), include strong motion and broadband sensors, and 24-bit dataloggers. The data from 20 GPS stations, part of the Bay Area Regional Deformation (BARD) network of more than 70 stations in northern California, are acquired in real-time. We have developed methods to acquire GPS data at 12 stations that are collocated with the seismic systems using the seismic dataloggers, which have large on-site data buffer and storage capabilities, merge it with the seismic data stream in MiniSeed format, and continuously stream both data types using reliable frame relay and/or radio modem telemetry. Currently, the seismic data are incorporated into the Rapid Earthquake Data Integration (REDI) project to provide notification of earthquake magnitude, location, moment tensor, and strong motion information for hazard mitigation and emergency response activities. The geodetic measurements can provide complementary constraints on earthquake faulting, including the location and extent of the rupture plane, unambiguous resolution of the nodal plane, and distribution of slip on the fault plane, which can be used, for example, to refine strong motion shake maps. We are developing methods to rapidly process the geodetic data to monitor transient deformation, such as coseismic station displacements, and for combining this information with the seismic observations to improve finite-fault characterization of large earthquakes. The GPS data are currently processed at hourly intervals with 2-cm precision in horizontal position, and we are beginning a pilot project in the Bay Area in collaboration with the California Spatial Reference Center to do epoch-by-epoch processing with greater precision.

Local Deformation Precursors of Large Earthquakes Derived from GNSS Observation Data

NASA Astrophysics Data System (ADS)

Kaftan, Vladimir; Melnikov, Andrey

2017-12-01

Research on deformation precursors of earthquakes was of immediate interest from the middle to the end of the previous century. The repeated conventional geodetic measurements, such as precise levelling and linear-angular networks, were used for the study. Many examples of studies referenced to strong seismic events using conventional geodetic techniques are presented in [T. Rikitake, 1976]. One of the first case studies of geodetic earthquake precursors was done by Yu.A. Meshcheryakov [1968]. Rare repetitions, insufficient densities and locations of control geodetic networks made difficult predicting future places and times of earthquakes occurrences. Intensive development of Global Navigation Satellite Systems (GNSS) during the recent decades makes research more effective. The results of GNSS observations in areas of three large earthquakes (Napa M6.1, USA, 2014; El Mayor Cucapah M7.2, USA, 2010; and Parkfield M6.0, USA, 2004) are treated and presented in the paper. The characteristics of land surface deformation before, during, and after earthquakes have been obtained. The results prove the presence of anomalous deformations near their epicentres. The temporal character of dilatation and shear strain changes show existence of spatial heterogeneity of deformation of the Earth’s surface from months to years before the main shock close to it and at some distance from it. The revealed heterogeneities can be considered as deformation precursors of strong earthquakes. According to historical data and proper research values of critical deformations which are offered to be used for seismic danger scale creation based on continuous GNSS observations are received in a reference to the mentioned large earthquakes. It is shown that the approach has restrictions owing to uncertainty of the moment in the beginning of deformation accumulation and the place of expectation of another seismic event. Verification and clarification of the derived conclusions are proposed.

Basic research for the geodynamics program

NASA Technical Reports Server (NTRS)

1984-01-01

Some objectives of this geodynamic program are: (1) optimal utilization of laser and VLBI observations as reference frames for geodynamics, (2) utilization of range difference observations in geodynamics, and (3) estimation techniques in crustal deformation analysis. The determination of Earth rotation parameters from different space geodetic systems is studied. Also reported on is the utilization of simultaneous laser range differences for the determination of baseline variation. An algorithm for the analysis of regional or local crustal deformation measurements is proposed along with other techniques and testing procedures. Some results of the reference from comparisons in terms of the pole coordinates from different techniques are presented.

Gravity data of Nevada

USGS Publications Warehouse

Ponce, David A.

1997-01-01

Gravity data for the entire state of Nevada and adjacent parts of California, Utah, and Arizona are available on this CD-ROM. About 80,000 gravity stations were compiled primarily from the National Geophysical Data Center and the U.S. Geological Survey. Gravity data was reduced to the Geodetic Reference System of 1967 and adjusted to the Gravity Standardization Net 1971 gravity datum. Data were processed to complete Bouguer and isostatic gravity anomalies by applying standard gravity corrections including terrain and isostatic corrections. Selected principal fact references and a list of sources for data from the National Geophysical Data Center are included.

Development of web tools to disseminate space geodesy data-related products

NASA Astrophysics Data System (ADS)

Soudarin, L.; Ferrage, P.; Mezerette, A.

2014-12-01

In order to promote the products of the DORIS system, the French Space Agency CNES has developed and implemented on the web site of the International DORIS Service (IDS) a set of plot tools to interactively build and display time series of site positions, orbit residuals and terrestrial parameters (scale, geocenter). An interactive global map is also available to select sites, and to get access to their information. Besides the products provided by the CNES Orbitography Team and the IDS components, these tools allow comparing time evolutions of coordinates for collocated DORIS and GNSS stations, thanks to the collaboration with the Terrestrial Frame Combination Center of the International GNSS Service (IGS). The next step currently in progress is the creation of a database to improve robustness and efficiency of the tools, with the objective to propose a complete web service to foster data exchange with the other geodetic services of the International Association of Geodesy (IAG). The possibility to visualize and compare position time series of the four main space geodetic techniques DORIS, GNSS, SLR and VLBI is already under way at the French level. A dedicated version of these web tools has been developed for the French Space Geodesy Research Group (GRGS). It will give access to position time series provided by the GRGS Analysis Centers involved in DORIS, GNSS, SLR and VLBI data processing for the realization of the International Terrestrial Reference Frame. In this presentation, we will describe the functionalities of these tools, and we will address some aspects of the time series (content, format).

Validation of the ASTER Global Digital Elevation Model Version 2 over the conterminous United States

USGS Publications Warehouse

Gesch, Dean B.; Oimoen, Michael J.; Zhang, Zheng; Meyer, David J.; Danielson, Jeffrey J.

2012-01-01

The ASTER Global Digital Elevation Model Version 2 (GDEM v2) was evaluated over the conterminous United States in a manner similar to the validation conducted for the original GDEM Version 1 (v1) in 2009. The absolute vertical accuracy of GDEM v2 was calculated by comparison with more than 18,000 independent reference geodetic ground control points from the National Geodetic Survey. The root mean square error (RMSE) measured for GDEM v2 is 8.68 meters. This compares with the RMSE of 9.34 meters for GDEM v1. Another important descriptor of vertical accuracy is the mean error, or bias, which indicates if a DEM has an overall vertical offset from true ground level. The GDEM v2 mean error of -0.20 meters is a significant improvement over the GDEM v1 mean error of -3.69 meters. The absolute vertical accuracy assessment results, both mean error and RMSE, were segmented by land cover to examine the effects of cover types on measured errors. The GDEM v2 mean errors by land cover class verify that the presence of aboveground features (tree canopies and built structures) cause a positive elevation bias, as would be expected for an imaging system like ASTER. In open ground classes (little or no vegetation with significant aboveground height), GDEM v2 exhibits a negative bias on the order of 1 meter. GDEM v2 was also evaluated by differencing with the Shuttle Radar Topography Mission (SRTM) dataset. In many forested areas, GDEM v2 has elevations that are higher in the canopy than SRTM.

Conversion of time-varying Stokes coefficients into mass anomalies at the Earth's surface considering the Earth's oblateness

NASA Astrophysics Data System (ADS)

Ditmar, Pavel

2018-02-01

Time-varying Stokes coefficients estimated from GRACE satellite data are routinely converted into mass anomalies at the Earth's surface with the expression proposed for that purpose by Wahr et al. (J Geophys Res 103(B12):30,205-30,229, 1998). However, the results obtained with it represent mass transport at the spherical surface of 6378 km radius. We show that the accuracy of such conversion may be insufficient, especially if the target area is located in a polar region and the signal-to-noise ratio is high. For instance, the peak values of mean linear trends in 2003-2015 estimated over Greenland and Amundsen Sea embayment of West Antarctica may be underestimated in this way by about 15%. As a solution, we propose an updated expression for the conversion of Stokes coefficients into mass anomalies. This expression is based on the assumptions that: (i) mass transport takes place at the reference ellipsoid and (ii) at each point of interest, the ellipsoidal surface is approximated by the sphere with a radius equal to the current radial distance from the Earth's center ("locally spherical approximation"). The updated expression is nearly as simple as the traditionally used one but reduces the inaccuracies of the conversion procedure by an order of magnitude. In addition, we remind the reader that the conversion expressions are defined in spherical (geocentric) coordinates. We demonstrate that the difference between mass anomalies computed in spherical and ellipsoidal (geodetic) coordinates may not be negligible, so that a conversion of geodetic colatitudes into geocentric ones should not be omitted.

A stress-constrained geodetic inversion method for spatiotemporal slip of a slow slip event with earthquake swarm

NASA Astrophysics Data System (ADS)

Hirose, H.; Tanaka, T.

2017-12-01

Geodetic inversions have been performed by using GNSS data and/or tiltmeter data in order to estimate spatio-temporal fault slip distributions. They have been applied for slow slip events (SSEs), which are episodic fault slip lasting for days to years (e.g., Ozawa et al., 2001; Hirose et al., 2014). Although their slip distributions are important information in terms of inferring strain budget and frictional characteristics on a subduction plate interface, inhomogeneous station coverage generally yields spatially non-uniform slip resolution, and in a worse case, a slip distribution can not be recovered. It is known that an SSE which accompanies an earthquake swarm around the SSE slip area, such as the Boso Peninsula SSEs (e.g., Hirose et al., 2014). Some researchers hypothesize that these earthquakes are triggered by a stress change caused by the accompanying SSE (e.g., Segall et al., 2006). Based on this assumption, it is possible that a conventional geodetic inversion which impose a constraint on the stress change that promotes earthquake activities may improve the resolution of the slip distribution. Here we develop an inversion method based on the Network Inversion Filter technique (Segall and Matthews, 1997), incorporating a constraint on a positive change in Coulomb failure stress (Delta-CFS) at the accompanied earthquakes. In addition, we apply this new method to synthetic data in order to check the effectiveness of the method and the characteristics of the inverted slip distributions. The results show that there is a case in which the reproduction of a slip distribution is better with earthquake information than without it. That is, it is possible to improve the reproducibility of a slip distribution of an SSE with this new inversion method if an earthquake catalog for the accompanying earthquake activity can be used when available geodetic data are insufficient.

Assessment of the possible contribution of space ties on-board GNSS satellites to the terrestrial reference frame

NASA Astrophysics Data System (ADS)

Bruni, Sara; Rebischung, Paul; Zerbini, Susanna; Altamimi, Zuheir; Errico, Maddalena; Santi, Efisio

2018-04-01

The realization of the international terrestrial reference frame (ITRF) is currently based on the data provided by four space geodetic techniques. The accuracy of the different technique-dependent materializations of the frame physical parameters (origin and scale) varies according to the nature of the relevant observables and to the impact of technique-specific errors. A reliable computation of the ITRF requires combining the different inputs, so that the strengths of each technique can compensate for the weaknesses of the others. This combination, however, can only be performed providing some additional information which allows tying together the independent technique networks. At present, the links used for that purpose are topometric surveys (local/terrestrial ties) available at ITRF sites hosting instruments of different techniques. In principle, a possible alternative could be offered by spacecrafts accommodating the positioning payloads of multiple geodetic techniques realizing their co-location in orbit (space ties). In this paper, the GNSS-SLR space ties on-board GPS and GLONASS satellites are thoroughly examined in the framework of global reference frame computations. The investigation focuses on the quality of the realized physical frame parameters. According to the achieved results, the space ties on-board GNSS satellites cannot, at present, substitute terrestrial ties in the computation of the ITRF. The study is completed by a series of synthetic simulations investigating the impact that substantial improvements in the volume and quality of SLR observations to GNSS satellites would have on the precision of the GNSS frame parameters.

The Dams and Monitoring Systems and Case Study: Ataturk and Karakaya Dams

NASA Astrophysics Data System (ADS)

Kalkan, Y.; Bilgi, S.; Gülnerman, A. G.

2017-12-01

Dams are among the most important engineering structures used for flood controls, agricultural purposes as well as drinking and hydroelectric power. Especially after the Second World War, developments on the construction technology, increase the construction of larger capacity dams. There are more than 150.000 dams in the world and almost 1000 dams in Turkey, according to international criteria. Although dams provide benefits to humans, they possess structural risks too. To determine the performance of dams on structural safety, assessing the spatial data is very important. These are movement, water pressure, seepage, reservoir and tail-water elevations, local seismic activities, total pressure, stress and strain, internal concrete temperature, ambient temperature and precipitation. These physical data are measured and monitored by the instruments and equipment. Dams and their surroundings have to be monitored by using essential methods at periodic time intervals in order to determine the possible changes that may occur over the time. Monitoring programs typically consist of; surveillance or visual observation. These programs on dams provide information for evaluating the dam's performance related to the design intent and expected changes that could affect the safety performance of the dam. Additionally, these programs are used for investigating and evaluating the abnormal or degrading performance where any remedial action is necessary. Geodetic and non-geodetic methods are used for monitoring. Monitoring the performance of the dams is critical for producing and maintaining the safe dams. This study provides some general information on dams and their different monitoring systems by taking into account two different dams and their structural specifications with the required information. The case study in this paper depends on a comparison of the monitoring surveys on Atatürk Dam and Karakaya Dam, which are constructed on Firat River with two different structural type in Turkey. In addition, brief information is given about these dams and the methods of geodetic and non-geodetic monitoring measurements applied by various disciplines. The last part of the study focuses on the inference of the geodetic monitoring methods, which depend on a seven years of geodetic monitoring.

Laboratory volcano geodesy

NASA Astrophysics Data System (ADS)

Færøvik Johannessen, Rikke; Galland, Olivier; Mair, Karen

2014-05-01

Magma transport in volcanic plumbing systems induces surface deformation, which can be monitored by geodetic techniques, such as GPS and InSAR. These geodetic signals are commonly analyzed through geodetic models in order to constrain the shape of, and the pressure in, magma plumbing systems. These models, however, suffer critical limitations: (1) the modelled magma conduit shapes cannot be compared with the real conduits, so the geodetic models cannot be tested nor validated; (2) the modelled conduits only exhibit shapes that are too simplistic; (3) most geodetic models only account for elasticity of the host rock, whereas substantial plastic deformation is known to occur. To overcome these limitations, one needs to use a physical system, in which (1) both surface deformation and the shape of, and pressure in, the underlying conduit are known, and (2) the mechanical properties of the host material are controlled and well known. In this contribution, we present novel quantitative laboratory results of shallow magma emplacement. Fine-grained silica flour represents the brittle crust, and low viscosity vegetable oil is an analogue for the magma. The melting temperature of the oil is 31°C; the oil solidifies in the models after the end of the experiments. At the time of injection the oil temperature is 50°C. The oil is pumped from a reservoir using a volumetric pump into the silica flour through a circular inlet at the bottom of a 40x40 cm square box. The silica flour is cohesive, such that oil intrudes it by fracturing it, and produces typical sheet intrusions (dykes, cone sheets, etc.). During oil intrusion, the model surface deforms, mostly by doming. These movements are measured by an advanced photogrammetry method, which uses 4 synchronized fixed cameras that periodically image the surface of the model from different angles. We apply particle tracking method to compute the 3D ground deformation pattern through time. After solidification of the oil, the intrusion can be excavated and photographed from several angles to compute its 3D shape with the same photogrammetry method. Then, the surface deformation pattern can be directly compared with the shape of underlying intrusion. This quantitative dataset is essential to quantitatively test and validate classical volcano geodetic models.

Global Biomass Variation and its Geodynamic Effects, 1982-1998

NASA Technical Reports Server (NTRS)

Rodell, M.; Chao, B. F.; Au, A. Y.; Kimball, J. S.; McDonald, K. C.

2005-01-01

Redistribution of mass near Earth's surface alters its rotation, gravity field, and geocenter location. Advanced techniques for measuring these geodetic variations now exist, but the ability to attribute the observed modes to individual Earth system processes has been hampered by a shortage of reliable global data on such processes, especially hydrospheric processes. To address one aspect of this deficiency, 17 yrs of monthly, global maps of vegetation biomass were produced by applying field-based relationships to satellite-derived vegetation type and leaf area index. The seasonal variability of biomass was estimated to be as large as 5 kg m(exp -2). Of this amount, approximately 4 kg m(exp -2) is due to vegetation water storage variations. The time series of maps was used to compute geodetic anomalies, which were then compared with existing geodetic observations as well as the estimated measurement sensitivity of the Gravity Recovery and Climate Experiment (GRACE). For gravity, the seasonal amplitude of biomass variations may be just within GRACE'S limits of detectability, but it is still an order of magnitude smaller than current observation uncertainty using the satellite-laser-ranging technique. The contribution of total biomass variations to seasonal polar motion amplitude is detectable in today's measurement, but it is obscured by contributions from various other sources, some of which are two orders of magnitude larger. The influence on the length of day is below current limits of detectability. Although the nonseasonal geodynamic signals show clear interannual variability, they are too small to be detected.

Real-time and rapid GNSS solutions from the M8.2 September 2017 Tehuantepec Earthquake and implications for Earthquake and Tsunami Early Warning Systems

NASA Astrophysics Data System (ADS)

Mencin, D.; Hodgkinson, K. M.; Mattioli, G. S.

2017-12-01

In support of hazard research and Earthquake Early Warning (EEW) Systems UNAVCO operates approximately 800 RT-GNSS stations throughout western North America and Alaska (EarthScope Plate Boundary Observatory), Mexico (TLALOCNet), and the pan-Caribbean region (COCONet). Our system produces and distributes raw data (BINEX and RTCM3) and real-time Precise Point Positions via the Trimble PIVOT Platform (RTX). The 2017-09-08 earthquake M8.2 located 98 km SSW of Tres Picos, Mexico is the first great earthquake to occur within the UNAVCO RT-GNSS footprint, which allows for a rigorous analysis of our dynamic and static processing methods. The need for rapid geodetic solutions ranges from seconds (EEW systems) to several minutes (Tsunami Warning and NEIC moment tensor and finite fault models). Here, we compare and quantify the relative processing strategies for producing static offsets, moment tensors and geodetically determined finite fault models using data recorded during this event. We also compare the geodetic solutions with the USGS NEIC seismically derived moment tensors and finite fault models, including displacement waveforms generated from these models. We define kinematic post-processed solutions from GIPSY-OASISII (v6.4) with final orbits and clocks as a "best" case reference to evaluate the performance of our different processing strategies. We find that static displacements of a few centimeters or less are difficult to resolve in the real-time GNSS position estimates. The standard daily 24-hour solutions provide the highest-quality data-set to determine coseismic offsets, but these solutions are delayed by at least 48 hours after the event. Dynamic displacements, estimated in real-time, however, show reasonable agreement with final, post-processed position estimates, and while individual position estimates have large errors, the real-time solutions offer an excellent operational option for EEW systems, including the use of estimated peak-ground displacements or directly inverting for finite-fault solutions. In the near-field, we find that the geodetically-derived moment tensors and finite fault models differ significantly with seismically-derived models, highlighting the utility of using geodetic data in hazard applications.

A Seafloor Test of the A-0-A Approach to Calibrating Pressure Sensors for Vertical Geodesy

NASA Astrophysics Data System (ADS)

Wilcock, W. S. D.; Manalang, D.; Harrington, M.; Cram, G.; Tilley, J.; Burnett, J.; Martin, D.; Paros, J. M.

2017-12-01

Seafloor geodetic observations are critical for understanding the locking and slip of the megathrust in Cascadia and other subduction zones. Differences of bottom pressure time series have been used successfully in several subduction zones to detect slow-slip earthquakes centered offshore. Pressure sensor drift rates are much greater than the long-term rates of strain build-up and thus, in-situ calibration is required to measure secular strain. One approach to calibration is to use a dead-weight tester, a laboratory apparatus that produces an accurate reference pressure, to calibrate a pressure sensor deployed on the seafloor by periodically switching between the external pressure and the deadweight tester (Cook et al, this session). The A-0-A method replaces the dead weight tester by using the internal pressure of the instrument housing as the reference pressure. We report on the first non-proprietary ocean test of this approach on the MARS cabled observatory at a depth of 900 m depth in Monterey Bay. We use the Paroscientific Seismic + Oceanic Sensors module that is designed for combined geodetic, oceanographic and seismic observations. The module comprises a three-component broadband accelerometer, two pressure sensors that for this deployment measure ocean pressures, A, up to 2000 psia (14 MPa), and a barometer to measure the internal housing reference pressure, 0. A valve periodically switches between external and internal pressures for 5 minute calibrations. The seafloor test started in mid-June and the results of 30 calibrations collected over the first 6 weeks of operation are very encouraging. After correcting for variations in the internal temperature of the housing, the offset of the pressure sensors from the barometer reading as a function of time, can be fit with a straight line for each sensor with a rms misfit of 0.1 hPa (1 mm of water). The slopes of these lines (-4 cm/yr and -0.4 cm/yr) vary by an order of magnitude but the difference in the span (external minus internal pressure) of the two sensors is constant to 0.05 hPa. We will present the results for the first 6 months of A-0-A calibrations for vertical geodesy and also discuss the performance of the pressure sensors and accelerometer for monitoring seismic activity, tilt and ocean infragravity waves.

MOLA: The Future of Mars Global Cartography

NASA Technical Reports Server (NTRS)

Duxbury, T. C.; Smith, D. E.; Zuber, M. T.; Frey, H. V.; Garvin, J. B.; Head, J. W.; Muhleman, D. O.; Pettengill, G. H.; Phillips, R. J.; Solomon, S. C.

1999-01-01

The MGS Orbiter is carrying the high-precision Mars Orbiter Laser Altimeter (MOLA) which, when combined with precision reconstructed orbital data and telemetered attitude data, provides a tie between inertial space and Mars-fixed coordinates to an accuracy of 100 m in latitude / longitude and 10 m in radius (1 sigma), orders of magnitude more accurate than previous global geodetic/ cartographic control data. Over the 2 year MGS mission lifetime, it is expected that over 30,000 MOLA Global Cartographic Control Points will be produced to form the basis for new and re-derived map and geodetic products, key to the analysis of existing and evolving MGS data as well as future Mars exploration. Additional information is contained in the original extended abstract.

Determination of bench-mark elevations at Bethel Island and vicinity, Contra Costa and San Joaquin counties, California, 1987

USGS Publications Warehouse

Blodgett, J.C.; Ikehara, M.E.; McCaffrey, William F.

1988-01-01

Elevations of 49 bench marks in the southwestern part of the Sacramento-San Joaquin River Delta were determined during October and November 1987. A total of 58 miles of level lines were run in the vicinity of Bethel Island and the community of Discovery Bay. The datum of these surveys is based on a National Geodetic Survey bench mark T934 situated on bedrock 10.5 mi east of Mount Diablo and near Marsh Creek Reservoir. The accuracy of these levels, based on National Geodetic Survey standards, was of first, second, and third order, depending on the various segments surveyed. Several bench marks were noted as possibly being stable, but most show evidence of instability. (USGS)

International Laser Ranging Service (ILRS) 1999 Annual Report

NASA Technical Reports Server (NTRS)

Pearlman, Michael (Editor); Taggert, Linda (Editor)

2000-01-01

This 1999 Annual Report of the International Laser Ranging Service (ILRS) is comprised of individual contributions from ILRS components within the international geodetic community. This report documents the work of the ILRS components from the inception of the Service through December 31,1999. Since the service has only recently been established, the ILRS associates decided to publish this Annual report as a reference to our organization and its components.

NOAA Photo Library - Historical Coast & Geodetic Survey Collection

Science.gov Websites

;gs photos The Historic Coast and Geodetic Survey Collection is composed of over 3,000 images of many aspects of Coast and Geodetic Survey operations including geodesy, nautical and aeronautical charting geophysics and oceanography. The Historic Coast and Geodetic Survey Collection chronicles this rich heritage

Strategies for Space-Geodetic Monitoring of Infraseismic and Subseismic Transient Deformations

NASA Technical Reports Server (NTRS)

Jordan, Thomas H.

1996-01-01

The utility of space-geodetic data in elucidating infraseismic and subseismic phenomena is assessed. Existing seismological, geodetic, and other data to characterize the distribution of infraseismic and subseismic transients are used. Strategies for space-geodetic monitoring of infraseismic and subseismic transients along major plate boundaries are developed.

Integrating Analysis Goals for EOP, CRF and TRF

NASA Technical Reports Server (NTRS)

Ma, Chopo; MacMillan, Daniel; Petrov, Leonid

2002-01-01

In a simplified, idealized way the TRF (Terrestrial Reference Frame) can be considered a set of positions at epoch and corresponding linear rates of change while the CRF (Celestial Reference Frame) is a set of fixed directions in space. VLBI analysis can be optimized for CRF and TRF separately while handling some of the complexity of geodetic and astrometric reality. For EOP (Earth Orientation Parameter) time series both CRF and TRF should be accurate at the epoch of interest and well defined over time. The optimal integration of EOP, TRF and CRF in a single VLBI solution configuration requires a detailed consideration of the data set and the possibly conflicting nature of the reference frames. A possible approach for an integrated analysis is described.

Observing APOD with the AuScope VLBI Array

PubMed Central

Sun, Jing; Cao, Jianfeng

2018-01-01

The possibility to observe satellites with the geodetic Very Long Baseline Interferometry (VLBI) technique is vividly discussed in the geodetic community, particularly with regard to future co-location satellite missions. The Chinese APOD-A nano satellite can be considered as a first prototype—suitable for practical observation tests—combining the techniques Satellite Laser Ranging (SLR), Global Navigation Satellite Systems (GNSS) and VLBI on a single platform in a Low Earth Orbit (LEO). Unfortunately, it has hardly been observed by VLBI, so major studies towards actual frame ties could not be performed. The main reason for the lack of observations was that VLBI observations of satellites are non-standard, and suitable observing strategies were not in place for this mission. This work now presents the first serious attempt to observe the satellite with a VLBI network over multiple passes. We introduce a series of experiments with the AuScope geodetic VLBI array which were carried out in November 2016, and describe all steps integrated in the established process chain: the experiment design and observation planning, the antenna tracking and control scheme, correlation and derivation of baseline-delays, and the data analysis yielding delay residuals on the level of 10 ns. The developed procedure chain can now serve as reference for future experiments, hopefully enabling the global VLBI network to be prepared for the next co-location satellite mission. PMID:29772732

Observing APOD with the AuScope VLBI Array.

PubMed

Hellerschmied, Andreas; McCallum, Lucia; McCallum, Jamie; Sun, Jing; Böhm, Johannes; Cao, Jianfeng

2018-05-16

The possibility to observe satellites with the geodetic Very Long Baseline Interferometry (VLBI) technique is vividly discussed in the geodetic community, particularly with regard to future co-location satellite missions. The Chinese APOD-A nano satellite can be considered as a first prototype-suitable for practical observation tests-combining the techniques Satellite Laser Ranging (SLR), Global Navigation Satellite Systems (GNSS) and VLBI on a single platform in a Low Earth Orbit (LEO). Unfortunately, it has hardly been observed by VLBI, so major studies towards actual frame ties could not be performed. The main reason for the lack of observations was that VLBI observations of satellites are non-standard, and suitable observing strategies were not in place for this mission. This work now presents the first serious attempt to observe the satellite with a VLBI network over multiple passes. We introduce a series of experiments with the AuScope geodetic VLBI array which were carried out in November 2016, and describe all steps integrated in the established process chain: the experiment design and observation planning, the antenna tracking and control scheme, correlation and derivation of baseline-delays, and the data analysis yielding delay residuals on the level of 10 ns. The developed procedure chain can now serve as reference for future experiments, hopefully enabling the global VLBI network to be prepared for the next co-location satellite mission.

On the Cause of Geodetic Satellite Accelerations and Other Correlated Unmodeled Phenomena

NASA Astrophysics Data System (ADS)

Mayer, A. F.

2005-12-01

An oversight in the development of the Einstein field equations requires a well-defined amendment to general relativity that very slightly modifies the weak-field Schwarzschild geometry yielding unambiguous new predictions of gravitational relativistic phenomena. The secular accelerations of LAGEOS, Etalon and other geodetic satellites are definitively explained as a previously unmodeled relativistic effect of the gravitational field. Observed dynamic variations may be correlated to the complex dynamic relationship between the satellite angular momentum vector and the solar gravitational gradient associated with the orbital motion of the Earth and the natural precession of the satellite orbit. The Pioneer Anomaly, semidiurnal saw-toothed pseudo-range residuals of GPS satellites, peculiar results of radio occultation experiments, secular accelerations of Solar System moons, the conspicuous excess redshift of white dwarf stars and other documented empirical observations are all correlated to the same newly modeled subtle relativistic energy effect. Modern challenges in the determination and maintenance of an accurate and reliable terrestrial reference frame, difficulties with global time synchronization at nanosecond resolution and the purported existence of unlikely excessive undulations of the Geoid relative to the Ellipsoid are all related to this previously unknown phenomenon inherent to the gravitational field. Doppler satellite measurements made by the TRANSIT system (the precursor to GPS) were significantly affected; WGS 84 coordinates and other geodetic data now assumed to be correct to high accuracy require correction based on the new theoretical developments.

Interoperable web applications for sharing data and products of the International DORIS Service

NASA Astrophysics Data System (ADS)

Soudarin, L.; Ferrage, P.

2017-12-01

The International DORIS Service (IDS) was created in 2003 under the umbrella of the International Association of Geodesy (IAG) to foster scientific research related to the French satellite tracking system DORIS and to deliver scientific products, mostly related to the International Earth rotation and Reference systems Service (IERS). Since its start, the organization has continuously evolved, leading to additional and improved operational products from an expanded set of DORIS Analysis Centers. In addition, IDS has developed services for sharing data and products with the users. Metadata and interoperable web applications are proposed to explore, visualize and download the key products such as the position time series of the geodetic points materialized at the ground tracking stations. The Global Geodetic Observing System (GGOS) encourages the IAG Services to develop such interoperable facilities on their website. The objective for GGOS is to set up an interoperable portal through which the data and products produced by the IAG Services can be served to the user community. We present the web applications proposed by IDS to visualize time series of geodetic observables or to get information about the tracking ground stations and the tracked satellites. We discuss the future plans for IDS to meet the recommendations of GGOS. The presentation also addresses the needs for the IAG Services to adopt common metadata thesaurus to describe data and products, and interoperability standards to share them.

AAPSilver System Performance Validation

DTIC Science & Technology

2012-12-01

10 APPENDIX A. NATIONAL GEODETIC SURVEY FORWARD OUTPUT FOR BPP ALPHA ... A-1...APPENDIX B. NATIONAL GEODETIC SURVEY FORWARD OUTPUT FOR BPP BRAVO ...B-1 APPENDIX C. NATIONAL GEODETIC SURVEY FORWARD OUTPUT FOR BPP CHARLIE...SURVEY FORWARD OUTPUT FOR BPP DELTA ... D-1 APPENDIX E. NATIONAL GEODETIC SURVEY FORWARD OUTPUT FOR BPP ECHO ......E-1 AAPSilver System Performance

Added-value joint source modelling of seismic and geodetic data

NASA Astrophysics Data System (ADS)

Sudhaus, Henriette; Heimann, Sebastian; Walter, Thomas R.; Krueger, Frank

2013-04-01

In tectonically active regions earthquake source studies strongly support the analysis of the current faulting processes as they reveal the location and geometry of active faults, the average slip released or more. For source modelling of shallow, moderate to large earthquakes often a combination of geodetic (GPS, InSAR) and seismic data is used. A truly joint use of these data, however, usually takes place only on a higher modelling level, where some of the first-order characteristics (time, centroid location, fault orientation, moment) have been fixed already. These required basis model parameters have to be given, assumed or inferred in a previous, separate and highly non-linear modelling step using one of the these data sets alone. We present a new earthquake rupture model implementation that realizes a fully combined data integration of surface displacement measurements and seismic data in a non-linear optimization of simple but extended planar ruptures. The model implementation allows for fast forward calculations of full seismograms and surface deformation and therefore enables us to use Monte Carlo global search algorithms. Furthermore, we benefit from the complementary character of seismic and geodetic data, e. g. the high definition of the source location from geodetic data and the sensitivity of the resolution of the seismic data on moment releases at larger depth. These increased constraints from the combined dataset make optimizations efficient, even for larger model parameter spaces and with a very limited amount of a priori assumption on the source. A vital part of our approach is rigorous data weighting based on the empirically estimated data errors. We construct full data error variance-covariance matrices for geodetic data to account for correlated data noise and also weight the seismic data based on their signal-to-noise ratio. The estimation of the data errors and the fast forward modelling opens the door for Bayesian inferences of the source model parameters. The source model product then features parameter uncertainty estimates and reveals parameter trade-offs that arise from imperfect data coverage and data errors. We applied our new source modelling approach to the 2010 Haiti earthquake for which a number of apparently different seismic, geodetic and joint source models has been reported already - mostly without any model parameter estimations. We here show that the variability of all these source models seems to arise from inherent model parameter trade-offs and mostly has little statistical significance, e.g. even using a large dataset comprising seismic and geodetic data the confidence interval of the fault dip remains as wide as about 20 degrees.

Single Platform Geolocation of Radio Frequency Emitters

DTIC Science & Technology

2015-03-26

Error SNR Signal to Noise Ratio SOI Signal of Interest STK Systems Tool Kit UCA Uniform Circular Array WGS World Geodetic System xv SINGLE PLATFORM...Section 2.6 describes a method to visualize the confidence of estimated parameters. 2.1 Coordinate Systems and Reference Frames The following...be used to visualize the confidence surface using the method developed in Section 2.6. The NLO method will be shown to be the minimization of the

Proposed satellite laser ranging and very long baseline interferometry sites for crustal dynamics investigations

NASA Technical Reports Server (NTRS)

Lowman, P. D.; Allenby, R. J.; Frey, H. V.

1979-01-01

Recommendations are presented for a global network of 125 sites for geodetic measurements by satellite laser ranging and very long baseline interferometry. The sites were proposed on the basis of existing facilities and scientific value for investigation of crustal dynamics as related to earthquake hazards. Tectonic problems are discussed for North America peripheral regions and for the world. The sites are presented in tables and maps, with bibliographic references.

Forecasting magma-chamber rupture at Santorini volcano, Greece.

PubMed

Browning, John; Drymoni, Kyriaki; Gudmundsson, Agust

2015-10-28

How much magma needs to be added to a shallow magma chamber to cause rupture, dyke injection, and a potential eruption? Models that yield reliable answers to this question are needed in order to facilitate eruption forecasting. Development of a long-lived shallow magma chamber requires periodic influx of magmas from a parental body at depth. This redistribution process does not necessarily cause an eruption but produces a net volume change that can be measured geodetically by inversion techniques. Using continuum-mechanics and fracture-mechanics principles, we calculate the amount of magma contained at shallow depth beneath Santorini volcano, Greece. We demonstrate through structural analysis of dykes exposed within the Santorini caldera, previously published data on the volume of recent eruptions, and geodetic measurements of the 2011-2012 unrest period, that the measured 0.02% increase in volume of Santorini's shallow magma chamber was associated with magmatic excess pressure increase of around 1.1 MPa. This excess pressure was high enough to bring the chamber roof close to rupture and dyke injection. For volcanoes with known typical extrusion and intrusion (dyke) volumes, the new methodology presented here makes it possible to forecast the conditions for magma-chamber failure and dyke injection at any geodetically well-monitored volcano.

Pathway to 2022: The Ongoing Modernization of the United States National Spatial Reference System

NASA Astrophysics Data System (ADS)

Stone, W. A.; Caccamise, D.

2017-12-01

The National Oceanic and Atmospheric Administration's National Geodetic Survey (NGS) mission is "to define, maintain and provide access to the National Spatial Reference System (NSRS) to meet our nation's economic, social, and environmental needs." The NSRS is an assemblage of geophysical and geodetic models, tools, and data, with the most-visible components being the North American Datum of 1983 (NAD83) and the North American Vertical Datum of 1988 (NAVD88), which together provide a consistent spatial reference framework for myriad geospatial applications and positioning requirements throughout the United States. The NGS is engaged in an ongoing and comprehensive multi-year project of modernizing the NSRS, a makeover necessitated by technological developments and user accuracy requirements, all with a goal of providing a modern, accurate, accessible, and globally aligned national positioning framework exploiting the substantial power and utility of the Global Navigation Satellite System - of both today and tomorrow. The modernized NSRS will include four new-generation geometric terrestrial reference frames (replacing NAD83) and a technically unprecedented geopotential datum (replacing NAVD88), all to be released in 2022 (anticipated). This poster/presentation will describe the justification for this modernization effort and will update the status and planned evolution of the NSRS as 2022 draws ever closer. Also discussed will be recent developments, including the publication of "blueprint" documents addressing technical details of various facets of the modernized NSRS and a continued series of public Geospatial Summits. Supporting/ancillary projects such as Gravity for the Redefinition of the American Vertical Datum (GRAV-D), which will result in the generation of a highly accurate gravimetric geoid - or definitional reference surface (zero elevation) - for the future geopotential datum, and Geoid Slope Validation Surveys (GSVS), which are exploring the achievable accuracy of the new geopotential datum, will be summarized. Also included will be suggestions of user preparation for transition to the NSRS of tomorrow.

First opportunity to synchronize the ILRS network thanks to T2L2 on Jason-2

NASA Astrophysics Data System (ADS)

Exertier, Pierre; Belli, Alexandre; Courde, Clément; Vernotte, François

2016-07-01

The Time Transfer by Laser Link (T2L2, on-board the oceanographic satellite Jason-2 at 1335 km) experiment allows us to synchronize remote clocks of Satellite Laser Ranging (SLR) stations throughout the whole ILRS (International Laser Ranging Service) network. We have developed a time transfer processing dedicated to non Common View (CV) cases, i.e. time transfer between stations from the Americas, Asia, Europe and Oceania. The main difficulty is to take into account the complex behaviour of the on-board Ultra Stable Oscillator (USO) over more than 1,500 s and up to a few thousands seconds. By integrating a recently published model describing the frequency responses of the USO to physical effects, as temperature and radiations, we show that it is possible to propagate the phase (time) of the on-board clock for an orbital revolution (1 rev = 6,700 s) or two with an error of a few nanoseconds (ns). Scheme of stages of this process is presented. The non CV time transfer process is applied in order to synchronize a plurality of remote stations involved in the T2L2/Jason-2 tracking by laser. The ground-to-space time transfers which we have processed over recent years (from 2013 to 2015) are all contributing to the development of a synthetic on-board time scale. The resulting ground-to-ground time transfers, computed between remote clocks of SLR stations, show differences of 250-300 ns up to a few microseconds ± 3-4 ns. The T2L2 space experiment is thus the first opportunity to estimate, quasi-instantaneously and to the ns level, time differences between clocks of the SLR stations which form one of the basis of the International Terrestrial Reference Frame (ITRF). This result would help the laser ranging community (time & frequency metrology of stations, analysis centres, and applications to the precise orbit and positioning) to achieve the GGOS (Global Geodetic Observing System) requirements in terms of accuracy and long-term stability of geodetic references.

Analysis of the geodetic residuals as differences between geodetic and sum of the atmospheric and ocean excitation of polar motion

NASA Astrophysics Data System (ADS)

Kolaczek, B.; Pasnicka, M.; Nastula, J.

2012-12-01

Up to now studies of geophysical excitation of polar motion containing AAM (Atmospheric Angular Momentum), OAM (Oceanic Angular Momentum) and HAM (Hydrological Angular Momentum) excitation functions of polar motion have not achieved the total agreement between geophysical and determined geodetic excitation (GAM, Geodetic AngularMomentum) functions of polar motion...

Generation of Global Geodetic Networks for GGOS

NASA Astrophysics Data System (ADS)

MacMillan, Daniel; Pavlis, Erricos C.; Kuzmicz-Cieslak, Magda; Koenig, Daniel

2016-12-01

We simulated future networks of VLBI+SLR sites to assess their performance. The objective is to build a global network of geographically well distributed, co-located next-generation sites from each of the space geodetic techniques. The network is being designed to meet the GGOS terrestrial reference frame goals of 1 mm in accuracy and 0.1 mm/yr in stability. We simulated the next generation networks that should be available in five years and in ten years to assess the likelihood that these networks will meet the reference frame goals. Simulations were based on the expectation that 17 broadband VLBI stations will be available in five years and 27 stations in ten years. We also consider the improvement resulting from expanding the network by six additional VLBI sites to improve the global distribution of the network. In the simulations, the networks will operate continuously, but we account for station downtime for maintenance or because of bad weather. We ran SLR+VLBI combination TRF solutions, where site ties were used to connect the two networks in the same way as in combination solutions with observed data. The strengths of VLBI and SLR allows them to provide the necessary reference frame accuracy in scale, geocenter, and orientation. With the +10-year extended network operating for ten years, simulations indicate that scale, origin, and orientation accuracies will be at the level of 0.02 ppb, 0.2 mm, and 6 μas. Combining the +5-year and +10-year network realizations will provide better estimates of accuracy and estimates of stability.

Comprehensive geo-spatial data creation for Qassim region in the KSA

NASA Astrophysics Data System (ADS)

Alrajhi, M.; Hawarey, M.

2009-04-01

The General Directorate for Surveying and Mapping (GDSM) of the Deputy Ministry for Land and Surveying (DMLS) of the Ministry of Municipal and Rural Affairs (MOMRA) in the Kingdom of Saudi Arabia (KSA) has the exclusive mandate to carry out aerial photography and produce large-scale detailed maps for about 220 cities and villages in the KSA. This presentation is about the comprehensive geo-spatial data creation for the Qassim region, North KSA, that was founded on country-wide horizontal geodetic ground control using Global Navigation Satellite Systems (GNSS) within the MOMRA's Terrestrial Reference Frame 2000 (MTRF2000) that is tied to International Terrestrial Reference Frame 2000 (ITRF2000) Epoch 2004.0, and vertical geodetic ground control using precise digital leveling in reference to Jeddah 1969 mean sea level, and included aerial photography of 1,505 km2 at 1:5,500 scale, 4,081 km2 at scale 22,500 and 22,224 km2 at 1:45,000 scale, full aerial triangulation, production of orthophoto maps at scale of 1:10,000 (463 sheets) for 22,224 km2, and production of GIS-oriented highly-detailed digital line maps in various formats at scales of 1:1,000 (1,534 sheets) and 1:2,500 (383 sheets) for 1,150 km2, 1:10,000 (161 sheets) for 7,700 km2, and 1:20,000 (130 sheets) for 22,000 km2. While aerial photography lasted from Feb 2003 thru May 2003, the line mapping continued May 2005 until December 2008.

On the energy integral for first post-Newtonian approximation

NASA Astrophysics Data System (ADS)

O'Leary, Joseph; Hill, James M.; Bennett, James C.

2018-07-01

The post-Newtonian approximation for general relativity is widely adopted by the geodesy and astronomy communities. It has been successfully exploited for the inclusion of relativistic effects in practically all geodetic applications and techniques such as satellite/lunar laser ranging and very long baseline interferometry. Presently, the levels of accuracy required in geodetic techniques require that reference frames, planetary and satellite orbits and signal propagation be treated within the post-Newtonian regime. For arbitrary scalar W and vector gravitational potentials W^j (j=1,2,3), we present a novel derivation of the energy associated with a test particle in the post-Newtonian regime. The integral so obtained appears not to have been given previously in the literature and is deduced through algebraic manipulation on seeking a Jacobi-like integral associated with the standard post-Newtonian equations of motion. The new integral is independently verified through a variational formulation using the post-Newtonian metric components and is subsequently verified by numerical integration of the post-Newtonian equations of motion.

GPS application to mapping, charting and geodesy

NASA Technical Reports Server (NTRS)

Senus, W. J.; Hill, R. W.

1981-01-01

GPSPAC, a receiver being developed for space applications by the Defense Mapping Agency and NASA, will use signals from GPS constellations to generate real-time values of host vehicle position and velocity. The GPSPAC has an L-band antenna and preamp capable of receiving the 1575 MHz and 1227 MHz spread spectrum signals; its stable oscillator at 5.115 MHz provides the basic frequency reference, resulting in a long term drift of less than one part in 10 to the -10th day. The GPSPAC performs many functions on board the spacecraft which were previously relegated to large-scale ground-based computer/receiver systems. A positional accuracy of better than 8 can be achieved for those periods when four or more NAVSTAR satellites are visible to the host satellite. The GPS geodetic receiver development, which will provide prototype receivers for utilization in terrestrial surveying operations, has the potential to significantly enhance the accuracy of point geodetic surveys over the current user hardware capability.

Height unification using GOCE

NASA Astrophysics Data System (ADS)

Rummel, R.

2012-12-01

With the gravity field and steady-state ocean circulation explorer (GOCE) (preferably combined with the gravity field and climate experiment (GRACE)) a new generation of geoid models will become available for use in height determination. These models will be globally consistent, accurate (<3 cm) and with a spatial resolution up to degree and order 200, when expressed in terms of a spherical harmonic expansion. GOCE is a mission of the European Space Agency (ESA). It is the first satellite equipped with a gravitational gradiometer, in the case of GOCE it measures the gradient components Vxx , Vyy, Vzzand Vxz. The GOCE gravitational sensor system comprises also a geodetic global positioning system (GPS)-receiver, three star sensors and ion-thrusters for drag compensation in flight direction. GOCE was launched in March 2009 and will fly till the end of 2013. Several gravity models have been derived from its data, their maximum degree is typically between 240 and 250. In summer 2012 a first re-processing of all level-1b data took place. One of the science objectives of GOCE is the unification of height systems. The existing height offsets among the datum zones can be determined by least-squares adjustment. This requires several precise geodetic reference points available in each height datum zone, physical heights from spirit levelling (plus gravimetry), the GOCE geoid and, in addition, short wavelength geoid refinement from terrestrial gravity anomalies. GOCE allows for important simplifications of the functional and stochastic part of the adjustment model. The future trend will be the direct determination of physical heights (orthometric as well as normal) from precise global navigation satellite system (GNSS)-positioning in combination with a next generation combined satellite-terrestrial high-resolution geoid model.

Contributions of satellite-determined gravity results in geodesy

NASA Technical Reports Server (NTRS)

Khan, M. A.

1974-01-01

Different forms of the theoretical gravity formula are summarized and methods of standardization of gravity anomalies obtained from satellite gravity and terrestrial gravity data are discussed in the context of three most commonly used reference figures, e.g., International Reference Ellipsoid, Reference Ellipsoid 1967, and Equilibrium Reference Ellipsoid. These methods are important in the comparison and combination of satellite gravity and gravimetric data as well as the integration of surface gravity data, collected with different objectives, in a single reference system. For ready reference, tables for such reductions are computed. Nature of the satellite gravity anomalies is examined to aid the geophysical and geodetic interpretation of these anomalies in terms of the tectonic features of the earth and the structure of the earth's crust and mantle. Computation of the Potsdam correction from satellite-determined geopotential is reviewed. The contribution of the satellite gravity results in decomposing the total observed gravity anomaly into components of geophysical interest is discussed. Recent work on the possible temporal variations in the geogravity field is briefly reviewed.

The Geodetic Signature of the Earthquake Cycle at Subduction Zones: Model Constraints on the Deep Processes

NASA Astrophysics Data System (ADS)

Govers, R.; Furlong, K. P.; van de Wiel, L.; Herman, M. W.; Broerse, T.

2018-03-01

Recent megathrust events in Tohoku (Japan), Maule (Chile), and Sumatra (Indonesia) were well recorded. Much has been learned about the dominant physical processes in megathrust zones: (partial) locking of the plate interface, detailed coseismic slip, relocking, afterslip, viscoelastic mantle relaxation, and interseismic loading. These and older observations show complex spatial and temporal patterns in crustal deformation and displacement, and significant differences among different margins. A key question is whether these differences reflect variations in the underlying processes, like differences in locking, or the margin geometry, or whether they are a consequence of the stage in the earthquake cycle of the margin. Quantitative models can connect these plate boundary processes to surficial and far-field observations. We use relatively simple, cyclic geodynamic models to isolate the first-order geodetic signature of the megathrust cycle. Coseismic and subsequent slip on the subduction interface is dynamically (and consistently) driven. A review of global preseismic, coseismic, and postseismic geodetic observations, and of their fit to the model predictions, indicates that similar physical processes are active at different margins. Most of the observed variability between the individual margins appears to be controlled by their different stages in the earthquake cycle. The modeling results also provide a possible explanation for observations of tensile faulting aftershocks and tensile cracking of the overriding plate, which are puzzling in the context of convergence/compression. From the inversion of our synthetic GNSS velocities we find that geodetic observations may incorrectly suggest weak locking of some margins, for example, the west Aleutian margin.

On the impact of reducing global geophysical fluid model deformations in SLR data processing

NASA Astrophysics Data System (ADS)

Weigelt, Matthias; Thaller, Daniela

2016-04-01

Mass redistributions in the atmosphere, oceans and the continental hydrology cause elastic loading deformations of the Earth's crust and thus systematically influence Earth-bound observation systems such as VLBI, GNSS or SLR. Causing non-linear station variations, these loading deformations have a direct impact on the estimated station coordinates and an indirect impact on other parameters of global space-geodetic solutions, e.g. Earth orientation parameters, geocenter coordinates, satellite orbits or troposphere parameters. Generally, the impact can be mitigated by co-parameterisation or by reducing deformations derived from global geophysical fluid models. Here, we focus on the latter approach. A number of data sets modelling the (non-tidal) loading deformations are generated by various groups. They show regionally and locally significant differences and consequently the impact on the space-geodetic solutions heavily depends on the available network geometry. We present and discuss the differences between these models and choose SLR as the speace-geodetic technique of interest in order to discuss the impact of atmospheric, oceanic and hydrological loading on the parameters of space-geodetic solutions when correcting for the global geophysical fluid models at the observation level. Special emphasis is given to a consistent usage of models for geometric and gravimetric corrections during the data processing. We quantify the impact of the different deformation models on the station coordinates and discuss the improvement in the Earth orientation parameters and the geocenter motion. We also show that a significant reduction in the RMS of the station coordinates can be achieved depending on the model of choice.

The PBO Nucleus: Integration of the Existing Continuous GPS Networks in the Western U.S.

NASA Astrophysics Data System (ADS)

Blume, F.; Anderson, G.; Freymueller, J. T.; Herring, T. A.; Melbourne, T. I.; Murray, M. H.; Prescott, W. H.; Smith, R. B.; Wernicke, B.

2004-12-01

Tectonic and earthquake research in the US has experienced a quiet revolution over the last decade precipitated by the recognition that slow-motion faulting events can both trigger and be triggered by regular earthquakes. Transient motion has now been found in essentially all tectonic environments, and the detection and analysis of such events is the first-order science target of the EarthScope Project. Because of this and a host of other fundamental tectonics questions that can be answered only with long-duration geodetic time series, the incipient 1400-station EarthScope Plate Boundary Observatory (PBO) network has been designed to leverage 432 existing continuous GPS stations whose measurements extend back over a decade. The irreplaceable recording history of these stations will accelerate EarthScope scientific return by providing the highest possible resolution. This resolution will be used to detect and understand transients, to determine the three-dimensional velocity field (particularly vertical motion), and to improve measurement precision by understanding the complex noise sources inherent in GPS. The PBO Nucleus Project is designed operate, maintain and upgrade a subset of six western U.S. geodetic networks: the Alaska Deformation Array (AKDA), Bay Area Regional Deformation network (BARD), the Basin and Range Geodetic Network (BARGEN), the Eastern Basin and Range/Yellowstone network (EBRY), the Pacific Northwest Geodetic Array (PANGA), and the Southern California Integrated Geodetic Network (SCIGN), until they are subsumed by PBO in 2008. Uninterrupted data flow from these stations will effectively double the time-series length of PBO over the expected life of EarthScope, and create, for the first time, a single GPS-based geodetic network in the US. Other existing sites will remain in operation under support from non-NSF sources (e.g. the USGS), and EarthScope will benefit from their continued operation. On the grounds of relevance to EarthScope science goals, geographic distribution and data quality, 209 of the 432 existing stations have been selected as the nucleus upon which to build PBO. We have begun converting these stations to a PBO-compatible mode of operation; data now flow directly to PBO archives and processing centers while maintenance, operations, and meta-data requirements are currently under upgrade to PBO standards.

Comparison between geodetic and oceanographic approaches to estimate mean dynamic topography for vertical datum unification: evaluation at Australian tide gauges

NASA Astrophysics Data System (ADS)

Filmer, M. S.; Hughes, C. W.; Woodworth, P. L.; Featherstone, W. E.; Bingham, R. J.

2018-04-01

The direct method of vertical datum unification requires estimates of the ocean's mean dynamic topography (MDT) at tide gauges, which can be sourced from either geodetic or oceanographic approaches. To assess the suitability of different types of MDT for this purpose, we evaluate 13 physics-based numerical ocean models and six MDTs computed from observed geodetic and/or ocean data at 32 tide gauges around the Australian coast. We focus on the viability of numerical ocean models for vertical datum unification, classifying the 13 ocean models used as either independent (do not contain assimilated geodetic data) or non-independent (do contain assimilated geodetic data). We find that the independent and non-independent ocean models deliver similar results. Maximum differences among ocean models and geodetic MDTs reach >150 mm at several Australian tide gauges and are considered anomalous at the 99% confidence level. These differences appear to be of geodetic origin, but without additional independent information, or formal error estimates for each model, some of these errors remain inseparable. Our results imply that some ocean models have standard deviations of differences with other MDTs (using geodetic and/or ocean observations) at Australian tide gauges, and with levelling between some Australian tide gauges, of ˜ ± 50 mm . This indicates that they should be considered as an alternative to geodetic MDTs for the direct unification of vertical datums. They can also be used as diagnostics for errors in geodetic MDT in coastal zones, but the inseparability problem remains, where the error cannot be discriminated between the geoid model or altimeter-derived mean sea surface.

The Neural Network In Coordinate Transformation

NASA Astrophysics Data System (ADS)

Urusan, Ahmet Yucel

2011-12-01

In international literature, Coordinate operations is divided into two categories. They are coordinate conversion and coordinate transformation. Coordinates converted from coordinate system A to coordinate system B in the same datum (mean origine, scale and axis directions are same) by coordinate conversion. There are two different datum in coordinate transformation. The basis of each datum to a different coordinate reference system. In Coordinate transformation, coordinates are transformed from coordinate reference system A to coordinate referance system B. Geodetic studies based on physical measurements. Coordinate transformation needs identical points which were measured in each coordinate reference system (A and B). However it is difficult (and need a big reserved budget) to measure in some places like as top of mountain, boundry of countries and seaside. In this study, this sample problem solution was researched. The method of learning which is one of the neural network methods, was used for solution of this problem.

Strain Analysis in Horizontal Geodetic Network of Dams for Control of Stability and Monitoring Deformation

NASA Astrophysics Data System (ADS)

Roohi, S.; Ardalan, A. A.; Khodakarami, M.

2009-04-01

Dams as one of the engineering structures play very important role in human life. Because, from primary human needs such as providing drinking water to professional needs such as water powerhouse creation in order to provide power for industrial centers, hospitals, manufactures and agriculture, have considerable dependent on dams. In addition destruction of a dam can be as dangerous as earthquake. Therefore maintenance, stability control and monitoring deformation of them is indispensable. In order to control stability of dams and their around lands and monitoring deformation a network is created by surveyor, geologist and dam experts on crest and body of dam or on land near the dam. Geodetic observations are done in this network by precise surveying instrument in deferent time then by using linear least square parametric adjustment method, adjusted coordinates with their variance- covariance matrix and error ellipses, redundancy numbers for observation, blunders and … are estimated in each epoch. Then displacement vectors are computed in each point of network, After that by use of Lagrangeian deformation idea and constitution of deformation equations movement, displacement model is determined and strain tensor is computed. we can induce deformation information from strain tensor in different ways such as strain ellipse then interpret deformation that happen in each point of network. Also we can compute rigid rotation from anti-symmetric part of displacement gradient tensor. After processing tow consequence epochs observations of horzontal geodetic network of Hnna dam in southwest of Esfahan, the most semi-major axis of error ellipse is estimated about 0.9mm for point D10, largest displacement is 1.4mm for point C3 that it's semimajor axis of displacement error ellipse is 1.3mm and there is different shear in all of network points exceptional points D2,C3 and C2. There is different dilatation in most of points. These amount of maximum shear and dilatation are justified because of horizontal displacement and subsidence of dam due to pressure of water that conserve behind it. Key word: strain tensor, monitoring deformation, Geodetic network, deformation equation movement, error ellipse, strain ellipse, shear, dilatation

A Recommendation on SLR Ranging to Future Global Navigation Satellite Systems

NASA Astrophysics Data System (ADS)

Labrecque, J. L.; Miller, J. J.; Pearlman, M.

2008-12-01

The multi-agency US Geodetic Requirements Working Group has recommended that Satellite Laser Retro- reflectors be installed on GPS III satellites as a principal component of the Positioning, Navigation, and Timing mandate of the Global Positioning System. The Working Group, which includes NASA, NGA, NOAA, NRL, USGS, and the USNO, echoes the Global Geodetic Observing System recommendation that SLR retro- reflectors be installed on all GNSS satellites. It is further recommended that the retro-reflectors conform to and hopefully exceed the minimum standard of the International Laser Ranging Service for retro-reflector cross sections of 100 million square meters for the HEO GNSS satellites to insure sufficiently accurate ranging by the global network of satellite laser ranging systems. The objective of this recommendation is to contribute to the improvement in the International Terrestrial Reference Frame, and its derivative the WGS84 reference frame, through continuing improvements in the characterization of the GPS orbits and clocks. Another objective is to provide an independent means of assessing the interoperability and accuracy of the GNSS systems and regional augmentation systems. The ranging to GNSS-mounted retro-reflectors will constitute a significant new means of space-based collocation to constrain the tie between the GPS and SLR networks that constitute over 50% of the data from which the ITRF is derived. The recommendation for the installation of SLR retro-reflectors aboard future GPS satellites is one of a number of efforts aimed at improving the accuracy and stability of ITRF. These steps are being coordinated with and supportive of the efforts of the GGOS and its services such at the VLBI2010 initiative, developing a next generation geodetic network, near real-time GPS positioning and EOP determination, and numerous efforts in the improvement of geodetic algorithms for GPS, SLR, VLBI, DORIS, and the determination of the ITRF. If past is prologue, the requirements of accuracy placed upon GNSS systems will continue to evolve at a factor of ten per decade for the lifetime of the GPS III, extending to 2025 and beyond. Global societal priorities such as sea level change measurement already require a factor of ten or more improvement in the accuracy and stability of the ITRF. Increasing accuracy requirements by civilian users for precision positioning and time keeping will certainly continue to grow at an exponential rate. The PNT accuracy of our GNSS systems will keep pace with these societal needs only if we equip the GNSS systems with the capability to identify and further reduce systematic errors.

Effects of Full Order Geopotential Hessian on Precision Orbit Determination of Geodetic Satellites

DTIC Science & Technology

2014-08-01

Astrodynamics, geopotential, geodesy 16. SECURITY CLASSIFICATION OF: 17. LIMITATION OF ABSTRACT UU 18. NUMBER OF PAGES 12 19a. NAME OF RESPONSIBLE PERSON...Tech. rep., DTIC Document, 2010. 15Kanner, L. and Associates, “Translation of ’Le satellite de geodesie ’Starlette’,’ Groupe de Recherches de Geodesie

IERS Conventions (2003)

DTIC Science & Technology

2004-01-01

International Earth Rotation and Reference Systems Service (IERS) Service International de la Rotation Terrestre et des Systèmes de Référence IERS...Equation for the determination of the density of moist air (1981/91),” Metrologia , 29, pp. 67–70. Giacomo, P., 1982, “Equation for the determination of...the density of moist air (1981),” Metrologia , 18, pp. 33–40. Herring, T. A., 1992, “Modeling Atmospheric Delays in the Analysis of Space Geodetic Data

Three-D multilateration: A precision geodetic measurement system

NASA Technical Reports Server (NTRS)

Escobal, P. R.; Ong, K. M.; Vonroos, O. H.; Shumate, M. S.; Jaffe, R. M.; Fliegel, H. F.; Muller, P. M.

1973-01-01

A technique of satellite geodesy for determining the relative three dimensional coordinates of ground stations within one centimeter over baselines of 20 to 10,000 kilometers is discussed. The system is referred to as 3-D Multilateration and has applications in earthquake hazard assessment, precision surveying, plate tectonics, and orbital mechanics. The accuracy is obtained by using pulsed lasers to obtain simultaneous slant ranges between several ground stations and a moving retroreflector with known trajectory for aiming the lasers.

A Global Terrestrial Reference Frame from simulated VLBI and SLR data in view of GGOS

NASA Astrophysics Data System (ADS)

Glaser, Susanne; König, Rolf; Ampatzidis, Dimitrios; Nilsson, Tobias; Heinkelmann, Robert; Flechtner, Frank; Schuh, Harald

2017-07-01

In this study, we assess the impact of two combination strategies, namely local ties (LT) and global ties (GT), on the datum realization of Global Terrestrial Reference Frames in view of the Global Geodetic Observing System requiring 1 mm-accuracy. Simulated Very Long Baseline Interferometry (VLBI) and Satellite Laser Ranging (SLR) data over a 7 year time span was used. The LT results show that the geodetic datum can be best transferred if the precision of the LT is at least 1 mm. Investigating different numbers of LT, the lack of co-located sites on the southern hemisphere is evidenced by differences of 9 mm in translation and rotation compared to the solution using all available LT. For the GT, the combination applying all Earth rotation parameters (ERP), such as pole coordinates and UT1-UTC, indicates that the rotation around the Z axis cannot be adequately transferred from VLBI to SLR within the combination. Applying exclusively the pole coordinates as GT, we show that the datum can be transferred with mm-accuracy within the combination. Furthermore, adding artificial stations in Tahiti and Nigeria to the current VLBI network results in an improvement in station positions by 13 and 12%, respectively, and in ERP by 17 and 11%, respectively. Extending to every day VLBI observations leads to 65% better ERP estimates compared to usual twice-weekly VLBI observations.

New Developments in Geodetic Data Management Systems for Fostering International Collaborations in the Geosciences

NASA Astrophysics Data System (ADS)

Meertens, Charles; Boler, Fran; Miller, M. Meghan

2015-04-01

UNAVCO community investigators are actively engaged in using space and terrestrial geodetic techniques to study earthquake processes, mantle properties, active magmatic systems, plate tectonics, plate boundary zone deformation, intraplate deformation, glacial isostatic adjustment, and hydrologic and atmospheric processes. The first GPS field projects were conducted over thirty years ago, and from the beginning these science investigations and the UNAVCO constituency as a whole have been international and collaborative in scope and participation. Collaborations were driven by the nature of the scientific problems being addressed, the capability of the technology to make precise measurements over global scales, and inherent technical necessity for sharing of GPS tracking data across national boundaries. The International GNSS Service (IGS) was formed twenty years ago as a voluntary federation to share GPS data from now hundreds of locations around the globe to facilitate realization of global reference frames, ties to regional surveys, precise orbits, and to establish and improve best practices in analysis and infrastructure. Recently, however, numbers of regional stations have grown to the tens of thousands, often with data that are difficult to access. UNAVCO has been working to help remove technical barriers by providing open source tools such as the Geodetic Seamless Archive Centers software to facilitate cross-project data sharing and discovery and by developing Dataworks software to manage network data. Data web services also provide the framework for UNAVCO contributions to multi-technique, inter-disciplinary, and integrative activities such as CoopEUS, GEO Supersites, EarthScope, and EarthCube. Within the geodetic community, metadata standards and data exchange formats have been developed and evolved collaboratively through the efforts of global organizations such as the IGS. A new generation of metadata and data exchange formats, as well as the software tools that utilize these formats and that support more efficient exchange of the highest quality data and metadata, are currently being developed and deployed through multiple international efforts.

Integrated geodetic monitoring of subsidence due to groundwater abstraction in the Perth Basin, Western Australia

NASA Astrophysics Data System (ADS)

Parker, A. L.; Filmer, M. S.; Featherstone, W. E.; Pigois, J. P.; Lyon, T.

2016-12-01

Small-magnitude subsidence due to groundwater abstraction was first observed in Perth, Western Australia, in the 2000s. Ongoing monitoring of ground deformation is required to avoid infrastructure damage, increased risk of seawater inundation and compromised integrity of geodetic benchmarks (e.g. tide-gauges). Subsidence measurements will also be used to provide constraints on aquifer storage properties, which is of significance to groundwater-resource management and proposed managed aquifer recharge. To these ends, a geodetic monitoring system in the Perth Basin has been established incorporating repeat levelling, continuous GPS and >20 years of InSAR data, including four years of TerraSAR-X (2012 to 2016), plus the first Sentinel-1A interferograms over Western Australia. The magnitude of subsidence ( 2-5 mm/yr) is at the limit detectable with InSAR, but through integration with high-precision repeat levelling, groundwater level records and geological information, we are able to constrain and interpret the spatial and temporal characteristics of the deformation field. InSAR datasets reveal a narrow subsiding coastal strip proximal to abstraction bores that came online since the early 2000s. Subsidence is also identified at the eastern margin of the Perth Basin, where seasonal variations of 10 mm measured with repeat-levelling are attributed to expansion and contraction of shallow clays. Elsewhere in the basin, high-resolution time-series from TerraSAR-X record non-linear, often seasonal vertical land motion, which correlates with changes in water levels at artesian monitoring bores. SAR coverage of the Perth Basin is ongoing and is now complemented by corner reflectors co-located with continuous GPS to tie measurements to a consistent reference frame. The ongoing collection of these and other geodetic data ensures that we are well placed to measure and monitor vertical land motion across the Perth Basin, including any effects of proposed managed aquifer recharge.

NASA's Next Generation Space Geodesy Program

NASA Technical Reports Server (NTRS)

Pearlman, M. R.; Frey, H. V.; Gross, R. S.; Lemoine, F. G.; Long, J. L.; Ma, C.; McGarry J. F.; Merkowitz, S. M.; Noll, C. E.; Pavilis, E. C.;

NASA's Next Generation Space Geodesy Program

NASA Technical Reports Server (NTRS)

Merkowitz, S. M.; Desai, S. D.; Gross, R. S.; Hillard, L. M.; Lemoine, F. G.; Long, J. L.; Ma, C.; McGarry, J. F.; Murphy, D.; Noll, C. E.;

Towards a first realization of the International Height Reference System (IHRS)

NASA Astrophysics Data System (ADS)

Sanchez, Laura; Ihde, Johannes; Pail, Roland; Gruber, Thomas; Barzaghi, Riccardo; Marti, Urs; Agren, Jonas; Sideris, Michael; Novak, Pavel

2017-04-01

The IAG Resolution No. 1 released during the IUGG 2015 General Assembly outlines five conventions for the definition of the International Height Reference System (IHRS). The definition is given in terms of potential parameters: the vertical coordinates are geopotential numbers referring to an equipotential surface of the Earth's gravity field realized by the conventional value W0 = 62 636 853.4 m2s-2. The spatial reference of the position P for the potential W(P) = W(X) is given by coordinates X of the International Terrestrial Reference Frame (ITRF). This Resolution also states that parameters, observations, and data shall be related to the mean tidal system/mean crust. At present, the main challenge is the realization of the IHRS; i.e., the establishment of the International Height Reference Frame (IHRF). It is expected that the IHRF follows the same structure as the ITRF: a global network with regional and national densifications, whose geopotential numbers referring to the global IHRS are known. According to the GGOS objectives, the target accuracy of these global geopotential numbers is 1 x 10-2 m2s-2. In practice, the precise realization of the IHRS is limited by different aspects; for instance, no unified standards or methods for the determination of the potential values W(P); application of different conventions for the gravity field modelling and the estimation of the position vectors X; inhomogeneous distribution of the geodetic infrastructure; restricted accessibility to terrestrial gravity data to increase the GGM resolution; insufficient modelling of geodynamic phenomena, etc. This may restrict the expected accuracy of 1 x 10-2 m2s-2 to some orders lower (from 10 x 10-2 m2s-2 to 100 x 10-2 m2s-2). This contribution discusses the required steps to outline a sustainable realization of the IHRS.

Comparison of Realizations of the Terrestrial Reference Frame

NASA Technical Reports Server (NTRS)

Ma, C.; Macmillan, D.; Bolotin, S.; Le Bail, K.; Gordon, D.; Gipson, J.

2015-01-01

IGN and DGFI both generated realizations of the terrestrial reference frame under the auspices of the IERS from combination of the same space geodetic data. We compared the IGN and DGFI TRFs with a GSFC CALC/SOLVE TRF. WRMS position and velocity differences for the 40 most frequently observed sites were 2-3 mm and 0.3-0.4 mm/year. There was a scale difference of 0.39/0.09 ppb between the IGN/DGFI realizations and the GSFC solution. When we fixed positions and velocities to either the IGN or DGFI values in CALC/SOLVE solutions, the resulting EOP estimates were not significantly different from the estimates from a standard TRF solution.

Basic research and data analysis for the National Geodetic Satellite program and for the Earth Surveys program

NASA Technical Reports Server (NTRS)

1972-01-01

Current research is reported on precise and accurate descriptions of the earth's surface and gravitational field and on time variations of geophysical parameters. A new computer program was written in connection with the adjustment of the BC-4 worldwide geometric satellite triangulation net. The possibility that an increment to accuracy could be transferred from a super-control net to the basic geodetic (first-order triangulation) was investigated. Coordinates of the NA9 solution were computed and were transformed to the NAD datum, based on GEOS 1 observations. Normal equations from observational data of several different systems and constraint equations were added and a single solution was obtained for the combined systems. Transformation parameters with constraints were determined, and the impact of computers on surveying and mapping is discussed.

Techniques and methods to guarantee Bologna-conform higher education in GNSS

NASA Astrophysics Data System (ADS)

Mayer, M.

2012-04-01

The Bologna Declaration is aiming for student-centered, outcome-related, and competence-based teaching. In order to fulfill these demands, deep level learning techniques should be used to meet the needs of adult-compatible and self-determined learning. The presentation will summarize selected case studies carried out in the framework of the lecture course "Introduction into GNSS positioning" of the Geodetic Institute of the Karlsruhe Institute of Technology (Karlsruhe, Germany). The lecture course "Introduction into GNSS positioning" is a compulsory part of the Bachelor study course "Geodesy and Geoinformatics" and also a supplementary module of the Bachelor study course "Geophysics". Within the lecture course, basic knowledge and basic principles of Global Navigation Satellite Systems, like GPS, are imparted. The lecture course was migrated starting from a classically designed geodetic lecture course, which consisted of a well-adapted combination of teacher-centered classroom lectures and practical training (e.g., field exercises). The recent Bologna-conform blended learning concepts supports and motivates students to learn more sustainable using online and classroom learning methods. Therefore, an appropriate combination of - classroom lectures: Students and teacher give lectures - practical training: Students select topics individually - online learning: ILIAS (learning management system) is used as data, result, and communication platform. The framing didactical method is based on the so-called anchored instruction approach. Within this approach, an up-to-date scientific GNSS-related paper dealing with the large-scale geodetic project "Fehmarn Belt Fixed Link" is used as anchor. The students have to read the paper individually in the beginning of the semester. This enables them to realize a lot of not-known GNSS-related facts. Therefore, questions can be formulated. The lecture course deals with these questions, in order to answer them. At the end of the lecture course, the author of the scientific paper gave a concluding lecture. Within the presentation, the didactical concept of the enriched blended learning approach is discussed in detail in order to gain insight into the didactical design of the lecture course and the higher education principles taken into account in order to guarantee Bologna-conform teaching and learning.

Error Propagation in the four terrestrial reference frames of the 2022 Modernized National Spatial Reference System

NASA Astrophysics Data System (ADS)

Roman, D. R.; Smith, D. A.

2017-12-01

In 2022, the National Geodetic Survey will replace all three NAD 83 reference frames with four new terrestrial reference frames. Each frame will be named after a tectonic plate (North American, Pacific, Caribbean and Mariana) and each will be related to the IGS frame through three Euler Pole parameters (EPPs). This talk will focus on three main areas of error propagation when defining coordinates in these four frames. Those areas are (1) use of the small angle approximation to relate true rotation about an Euler Pole to small rotations about three Cartesian axes (2) The current state of the art in determining the Euler Poles of these four plates and (3) the combination of both IGS Cartesian coordinate uncertainties and EPP uncertainties into coordinate uncertainties in the four new frames. Discussion will also include recent efforts at improving the Euler Poles for these frames and expected dates when errors in the EPPs will cause an unacceptable level of uncertainty in the four new terrestrial reference frames.

76 FR 49676 - Final Flood Elevation Determinations

Federal Register 2010, 2011, 2012, 2013, 2014

2011-08-11

... shoreline......... *26 City of Deltona. * National Geodetic Vertical Datum. + North American Vertical Datum... Boulevard. * National Geodetic Vertical Datum. + North American Vertical Datum. Depth in feet above ground... feet +1000 upstream of Southeast 45th Street. * National Geodetic Vertical Datum. + North American...

Forecasting magma-chamber rupture at Santorini volcano, Greece

PubMed Central

Browning, John; Drymoni, Kyriaki; Gudmundsson, Agust

2015-01-01

How much magma needs to be added to a shallow magma chamber to cause rupture, dyke injection, and a potential eruption? Models that yield reliable answers to this question are needed in order to facilitate eruption forecasting. Development of a long-lived shallow magma chamber requires periodic influx of magmas from a parental body at depth. This redistribution process does not necessarily cause an eruption but produces a net volume change that can be measured geodetically by inversion techniques. Using continuum-mechanics and fracture-mechanics principles, we calculate the amount of magma contained at shallow depth beneath Santorini volcano, Greece. We demonstrate through structural analysis of dykes exposed within the Santorini caldera, previously published data on the volume of recent eruptions, and geodetic measurements of the 2011–2012 unrest period, that the measured 0.02% increase in volume of Santorini’s shallow magma chamber was associated with magmatic excess pressure increase of around 1.1 MPa. This excess pressure was high enough to bring the chamber roof close to rupture and dyke injection. For volcanoes with known typical extrusion and intrusion (dyke) volumes, the new methodology presented here makes it possible to forecast the conditions for magma-chamber failure and dyke injection at any geodetically well-monitored volcano. PMID:26507183

Geodetic mass balance of key glaciers across High Mountain Asia: a multi-decadal survey

NASA Astrophysics Data System (ADS)

Maurer, J. M.; Schaefer, J. M.; Rupper, S.; Corley, A. D.

2016-12-01

Glaciers in High Mountain Asia (HMA) supply seasonal meltwater for large populations, yet field observations are scarce and glacier sensitivities are poorly understood. In order to link complex atmospheric driving factors with heterogeneous glacier responses, detailed remote sensing observations of past changes in ice volume are needed. Here we compile a spatially and temporally extensive satellite-based remote sensing record to quantify multi-decadal geodetic mass balance of large mountain glaciers across key regions in HMA, including the Pamir, Himachal Pradesh, Uttarakhand, Nepal, Sikkim, and Bhutan regions. By utilizing declassified spy satellite imagery from the 1970's, ASTER scenes spanning 2000-present, and the ALOS global digital surface model, a methodologically homogenous assessment of regional and individual glacier responses to climate change over several decades is obtained. Although gaps due to low radiometric contrast result in significant uncertainties, the consistent approach across the HMA provides a useful comparison of relative geodetic changes between climatically diverse regions. Various patterns of ice loss are observed, including dynamic retreat of clean-ice glaciers and downwasting of debris-covered glaciers. In particular, we highlight the pronounced thinning and retreat of glaciers undergoing calving into proglacial lakes, which has important implications regarding ongoing and future ice loss of HMA glaciers.

An Investigation on the Crustal Deformations in Istanbul after Eastern Marmara Earthquakes in 1999

NASA Astrophysics Data System (ADS)

Ozludemir, M.; Ozyasar, M.

2008-12-01

Since the introduction of the GPS technique in mid 1970's there has been great advances in positioning activities. Today such Global Navigational Satellite Systems (GNSS) based positioning techniques are widely used in daily geodetic applications. High order geodetic network measurements are one of such geodetic applications. Such networks are established to provide reliable infrastructures for all kind of geodetic work from the production of cadastral plans to the surveying processes during the construction of engineering structures. In fact such positional information obtained in such engineering surveys could be useful for other studies as well. One of such fields is geodynamic studies where such positional information could be valuable to understand the characteristics of tectonic movements. In Turkey being located in a tectonically active zones and having major earthquakes quite frequently, the positional information obtained in engineering surveys could be very useful for earthquake related studies. In this paper an example of such engineering surveys is discussed. This example is the Istanbul GPS (Global Positioning System) Network, first established in 1997 and remeasured in 2005. Between these two measurement processes two major earthquakes took place, on August 17 and November 12, 1999 with magnitudes of 7.4 and 7.2, respectively. In the first measurement campaign in 1997, a network of about 700 points was measured, while in the second campaign in 2005 more than 1800 points were positioned. In these two campaigns are existing common points. The network covers the whole Istanbul area of about 6000 km2. All network points are located on the Eurasian plate to the north of the North Anatolian Fault Zone. In this study, the horizontal and vertical movements are presented and compared with the results obtained in geodynamic studies.

On the establishment and maintenance of a modern conventional terrestrial reference system

NASA Technical Reports Server (NTRS)

Bock, Y.; Zhu, S. Y.

1982-01-01

The frame of the Conventional Terrestrial Reference System (CTS) is defined by an adopted set of coordinates, at a fundamental epoxh, of a global network of stations which contribute the vertices of a fundamental polyhedron. A method to estimate this set of coordinates using a combination of modern three dimensional geodetic systems is presented. Once established, the function of the CTS is twofold. The first is to monitor the external (or global) motions of the polyhedron with respect to the frame of a Conventional Inertial Reference System, i.e., those motions common to all stations. The second is to monitor the internal motions (or deformations) of the polyhedron, i.e., those motions that are not common to all stations. Two possible estimators for use in earth deformation analysis are given and their statistical and physical properties are described.

Geometric Modeling for Computer Vision

DTIC Science & Technology

1974-10-01

within a distance R of a locus X ,Y,Z; spatial uniqueness refers to the property that physical solids can not occupy the same space simultaneously. A...density functions W«p( X ,Y,Z). Unfortunately such density functions can no» be writtrn out for objects such as a typing chair or a plastic horse...be approximated by a surface function 2 = F( X ,Y). For example landscape may be represented by geodetic maps in such a 2-D fashion. By definition, a

Leveling

USGS Publications Warehouse

1966-01-01

Geodetic leveling by the U.S. Geological Survey provides a framework of accurate elevations for topographic mapping. Elevations are referred to the Sea Level Datum of 1929. Lines of leveling may be run either with automatic or with precise spirit levels, by either the center-wire or the three-wire method. For future use, the surveys are monumented with bench marks, using standard metal tablets or other marking devices. The elevations are adjusted by least squares or other suitable method and are published in lists of control.

Subsidence at the Fairport Harbor Water Level Gauge

NASA Astrophysics Data System (ADS)

Conner, D. A.

2014-12-01

SUBSIDENCE AT THE FAIRPORT HARBOR WATER LEVEL GAUGE I will provide information on methods being used to monitor Lake Erie water levels and earth movement at Fairport Harbor, Ohio. Glacial Isostatic Adjustment (GIA) is responsible for vertical movement throughout the Great Lakes region. Fairport Harbor is also experiencing vertical movement due to salt mining, so the nearby water level gauge operated by the National Oceanic and Atmospheric Administration (NOAA) is affected by both GIA and mining. NOAA's National Geodetic Survey (NGS) defines and maintains the National Spatial Reference System (NSRS). The NSRS includes a network of permanently marked points; a consistent, accurate, and up-to-date national shoreline; a network of Continuously Operating Reference Stations (CORS) which supports three-dimensional positioning activities; and a set of accurate models describing dynamic, geophysical processes that affect spatial measurements. The NSRS provides the spatial reference foundation for transportation, mapping, charting and a multitude of scientific and engineering applications. Fundamental elements of geodetic infrastructure include GPS CORS (3-D), water level and tide gauges (height) and a system of vertical bench marks (height). When two or more of these elements converge they may provide an independent determination of position and vertical stability as is the case here at the Fairport Harbor water level gauge. Analysis of GPS, leveling and water level data reveal that this gauge is subsiding at about 2-3 mm/year, independent of the effects of GIA. Analysis of data from the nearby OHLA GPS CORS shows it subsiding at about 4 mm/yr, four times faster than expected due to GIA alone. A long history of salt mine activity in the area is known to geologists but it came as a surprise to other scientists.

First steps of processing VLBI data of space probes with VieVS

NASA Astrophysics Data System (ADS)

Plank, L.; Böhm, J.; Schuh, H.

2011-07-01

Since 2008 the VLBI group at the Institute of Geodesy and Geophysics (IGG) of the Vienna University of Technology has developed the Vienna VLBI Software VieVS which is capable to process geodetic VLBI data in NGS format. Constantly we are working on upgrading the new software, e.g. by developing a scheduling tool or extending the software from single session solution to a so-called global solution, allowing the joint analysis of many sessions covering several years. In this presentation we report on first steps to enable the processing of space VLBI data with the software. Driven by the recently increasing number of space VLBI applications, our goal is the geodetic usage of such data, primarily concerning frame ties between various reference frames, e. g. by connecting the dynamic reference frame of a space probe with the kinematically defined International Celestial Reference Frame (ICRF). Main parts of the software extension w.r.t. the existing VieVS are the treatment of fast moving targets, the implementation of a delay model for radio emitters at finite distances, and the adequate mathematical model and adjustment of the particular unknowns. Actual work has been done for two mission scenarios so far: On the one hand differential VLBI (D-VLBI) data from the two sub-satellites of the Japanese lunar mission Selene were processed, on the other hand VLBI observations of GNSS satellites were modelled in VieVS. Besides some general aspects, we give details on the calculation of the theoretical delay (delay model for moving sources at finite distances) and its realization in VieVS. First results with real data and comparisons with best fit mission orbit data are also presented.'

75 FR 43479 - Proposed Flood Elevation Determinations

Federal Register 2010, 2011, 2012, 2013, 2014

2010-07-26

.... * National Geodetic Vertical Datum. + North American Vertical Datum. Depth in feet above ground. [caret] Mean... Evelyns Drive. * National Geodetic Vertical Datum. + North American Vertical Datum. Depth in feet above.... * National Geodetic Vertical Datum. + North American Vertical Datum. Depth in feet above ground. [caret] Mean...

Consistent realization of Celestial and Terrestrial Reference Frames

NASA Astrophysics Data System (ADS)

Kwak, Younghee; Bloßfeld, Mathis; Schmid, Ralf; Angermann, Detlef; Gerstl, Michael; Seitz, Manuela

2018-03-01

The Celestial Reference System (CRS) is currently realized only by Very Long Baseline Interferometry (VLBI) because it is the space geodetic technique that enables observations in that frame. In contrast, the Terrestrial Reference System (TRS) is realized by means of the combination of four space geodetic techniques: Global Navigation Satellite System (GNSS), VLBI, Satellite Laser Ranging (SLR), and Doppler Orbitography and Radiopositioning Integrated by Satellite. The Earth orientation parameters (EOP) are the link between the two types of systems, CRS and TRS. The EOP series of the International Earth Rotation and Reference Systems Service were combined of specifically selected series from various analysis centers. Other EOP series were generated by a simultaneous estimation together with the TRF while the CRF was fixed. Those computation approaches entail inherent inconsistencies between TRF, EOP, and CRF, also because the input data sets are different. A combined normal equation (NEQ) system, which consists of all the parameters, i.e., TRF, EOP, and CRF, would overcome such an inconsistency. In this paper, we simultaneously estimate TRF, EOP, and CRF from an inter-technique combined NEQ using the latest GNSS, VLBI, and SLR data (2005-2015). The results show that the selection of local ties is most critical to the TRF. The combination of pole coordinates is beneficial for the CRF, whereas the combination of Δ UT1 results in clear rotations of the estimated CRF. However, the standard deviations of the EOP and the CRF improve by the inter-technique combination which indicates the benefits of a common estimation of all parameters. It became evident that the common determination of TRF, EOP, and CRF systematically influences future ICRF computations at the level of several μas. Moreover, the CRF is influenced by up to 50 μas if the station coordinates and EOP are dominated by the satellite techniques.

Assessment of the accuracy of global geodetic satellite laser ranging observations and estimated impact on ITRF scale: estimation of systematic errors in LAGEOS observations 1993-2014

NASA Astrophysics Data System (ADS)

Appleby, Graham; Rodríguez, José; Altamimi, Zuheir

2016-12-01

Satellite laser ranging (SLR) to the geodetic satellites LAGEOS and LAGEOS-2 uniquely determines the origin of the terrestrial reference frame and, jointly with very long baseline interferometry, its scale. Given such a fundamental role in satellite geodesy, it is crucial that any systematic errors in either technique are at an absolute minimum as efforts continue to realise the reference frame at millimetre levels of accuracy to meet the present and future science requirements. Here, we examine the intrinsic accuracy of SLR measurements made by tracking stations of the International Laser Ranging Service using normal point observations of the two LAGEOS satellites in the period 1993 to 2014. The approach we investigate in this paper is to compute weekly reference frame solutions solving for satellite initial state vectors, station coordinates and daily Earth orientation parameters, estimating along with these weekly average range errors for each and every one of the observing stations. Potential issues in any of the large number of SLR stations assumed to have been free of error in previous realisations of the ITRF may have been absorbed in the reference frame, primarily in station height. Likewise, systematic range errors estimated against a fixed frame that may itself suffer from accuracy issues will absorb network-wide problems into station-specific results. Our results suggest that in the past two decades, the scale of the ITRF derived from the SLR technique has been close to 0.7 ppb too small, due to systematic errors either or both in the range measurements and their treatment. We discuss these results in the context of preparations for ITRF2014 and additionally consider the impact of this work on the currently adopted value of the geocentric gravitational constant, GM.

A 10-Year Comparison of Water Levels Measured with a Geodetic GPS Receiver Versus a Conventional Tide Gauge

NASA Technical Reports Server (NTRS)

Larson, Kristine M.; Ray, Richard D.; Williams, Simon D. P.

2017-01-01

A standard geodetic GPS receiver and a conventional Aquatrak tide gauge, collocated at Friday Harbor, Washington, are used to assess the quality of 10 years of water levels estimated from GPS sea surface reflections.The GPS results are improved by accounting for (tidal) motion of the reflecting sea surface and for signal propagation delay by the troposphere. The RMS error of individual GPS water level estimates is about 12 cm. Lower water levels are measured slightly more accurately than higher water levels. Forming daily mean sea levels reduces the RMS difference with the tide gauge data to approximately 2 cm. For monthly means, the RMS difference is 1.3 cm. The GPS elevations, of course, can be automatically placed into a well-defined terrestrial reference frame. Ocean tide coefficients, determined from both the GPS and tide gauge data, are in good agreement, with absolute differences below 1 cm for all constituents save K1 and S1. The latter constituent is especially anomalous, probably owing to daily temperature-induced errors in the Aquatrak tide gauge

23 CFR 630.402 - Policy.

Code of Federal Regulations, 2010 CFR

2010-04-01

... 23 Highways 1 2010-04-01 2010-04-01 false Policy. 630.402 Section 630.402 Highways FEDERAL HIGHWAY... Geodetic Markers § 630.402 Policy. (a) Geodetic surveys along Federal-aid highway routes may be programmed as Federal-aid highway projects. (b) All geodetic survey work performed as a Federal-aid highway...

Modeling and Simulation Network Data Standards

DTIC Science & Technology

2011-09-30

COMBATXXI Movement Logger Data Output Dictionary. Field # Geocentric Coordinates (GCC) Heading Geodetic Coordinates (GDC) Heading Universal...B-8 Field # Geocentric Coordinates (GCC) Heading Geodetic Coordinates (GDC) Heading Universal Transverse Mercator (UTM) Heading...FKSM Fort Knox Supplemental Material FM field manual GCC geocentric coordinates GDC geodetic coordinates GIG global information grid

Hartebeesthoek Radio Astronomy Observatory (HartRAO)

NASA Technical Reports Server (NTRS)

Nickola, Marisa; Gaylard, Mike; Quick, Jonathan; Combrinck, Ludwig

2013-01-01

HartRAO provides the only fiducial geodetic site in Africa, and it participates in global networks for VLBI, GNSS, SLR, and DORIS. This report provides an overview of geodetic VLBI activities at HartRAO during 2012, including the conversion of a 15-m alt-az radio telescope to an operational geodetic VLBI antenna.

Fallon, Nevada FORGE Geodetic Data

DOE Data Explorer

Blankenship, Doug; Eneva, Mariana; Hammond, William

2018-02-01

Fallon FORGE InSAR and geodetic GPS deformation data. InSAR shapefiles are packaged together as .MPK (ArcMap map package, compatible with other GIS platforms), and as .CSV comma-delimited plaintext. GPS data and additional metadata are linked to the Nevada Geodetic Laboratory database at the Univ. of Nevada, Reno (UNR).

Using competence-based and project-related approaches to support students individually - An engineering science experience report

NASA Astrophysics Data System (ADS)

Mayer, M.

2009-04-01

The recent education of engineers, using the example of satellite geodesy at the Geodetic Institute of the University Karlsruhe (Germany), is still suffering from time pressure as well as from heavy curriculum content loading. Within this education field, where the academic teachers have to fulfill high requests from the new generation of students as well as from industry and from research institutions respectively, advanced satellite geodetic knowledge has to be transferred effectively and sustainably. In order to enable the students to train newest aspects related to satellite geodesy as well as important key competences, e.g. capacity for independent and academic work, reflection and evaluation skills, presentation skills, an innovative teaching concept was developed, tested, and evaluated. This teaching concept makes use of very different teaching techniques like portfolio assignment, project work, input from experts, jig saw, advance and post organizer. The concept will be presented and discussed in detail.

Comparison of Polar Motion Excitation Series Derived from GRACE and from Analyses of Geophysical Fluids

NASA Technical Reports Server (NTRS)

Nastula, J.; Ponte, R. M.; Salstein, D. A.

2007-01-01

Three sets of degree-2, order-1 harmonics of the gravity field, derived from the Gravity Recovery and Climate Experiment (GRACE) data processed at the Center for Space Research (CSR), Jet Propulsion Laboratory (JPL) and GeoforschungsZentrum (GFZ), are used to compute polar motion excitation functions X1 and X2. The GFZ and JPL excitations and the CSR X2, excitation compare generally well with geodetically observed excitation after removal of effects of oceanic currents and atmospheric winds. The agreement considerably exceeds that from previous GRACE data releases. For the JPL series, levels of correlation with the geodetic observations and the variance explained are comparable to, but still lower than, those obtained independently from available models and analyses of the atmosphere, ocean, and land hydrology. Improvements in data quality of gravity missions are still needed to deliver even tighter constraints on mass-related excitation of polar motion.

Comparison of polar motion excitation series derived from GRACE and from analyses of geophysical fluids

NASA Astrophysics Data System (ADS)

Nastula, J.; Ponte, R. M.; Salstein, D. A.

2007-06-01

Three sets of degree-2, order-1 harmonics of the gravity field, derived from the Gravity Recovery and Climate Experiment (GRACE) data processed at the Center for Space Research (CSR), Jet Propulsion Laboratory (JPL) and GeoforschungsZentrum (GFZ), are used to compute polar motion excitation functions χ 1 and χ 2. The GFZ and JPL excitations and the CSR χ 2 excitation compare generally well with geodetically observed excitation after removal of effects of oceanic currents and atmospheric winds. The agreement considerably exceeds that from previous GRACE data releases. For the JPL series, levels of correlation with the geodetic observations and the variance explained are comparable to, but still lower than, those obtained independently from available models and analyses of the atmosphere, ocean, and land hydrology. Improvements in data quality of gravity missions are still needed to deliver even tighter constraints on mass-related excitation of polar motion.

Plate Motions, Regional Deformation, and Time-Variation of Plate Motions

NASA Technical Reports Server (NTRS)

Gordon, R. G.

1998-01-01

The significant results obtained with support of this grant include the following: (1) Using VLBI data in combination with other geodetical, geophysical, and geological data to bound the present rotation of the Colorado Plateau, and to evaluate to its implications for the kinematics and seismogenic potential of the western half of the conterminous U.S. (2) Determining realistic estimates of uncertainties for VLBI data and then applying the data and uncertainties to obtain an upper bound on the integral of deformation within the "stable interior" of the North American and other plates and thus to place an upper bound on the seismogenic potential within these regions. (3) Combining VLBI data with other geodetic, geophysical, and geologic data to estimate the motion of coastal California in a frame of reference attached to the Sierra Nevada-Great Valley microplate. This analysis has provided new insights into the kinematic boundary conditions that may control or at least strongly influence the locations of asperities that rupture in great earthquakes along the San Andreas transform system. (4) Determining a global tectonic model from VLBI geodetic data that combines the estimation of plate angular velocities with individual site linear velocities where tectonically appropriate. and (5) Investigation of the some of the outstanding problems defined by the work leading to global plate motion model NUVEL-1. These problems, such as the motion between the Pacific and North American plates and between west Africa and east Africa, are focused on regions where the seismogenic potential may be greater than implied by published plate tectonic models.

Further characterization of the time transfer capabilities of precise point positioning (PPP): the Sliding Batch Procedure.

PubMed

Guyennon, Nicolas; Cerretto, Giancarlo; Tavella, Patrizia; Lahaye, François

2009-08-01

In recent years, many national timing laboratories have installed geodetic Global Positioning System receivers together with their traditional GPS/GLONASS Common View receivers and Two Way Satellite Time and Frequency Transfer equipment. Many of these geodetic receivers operate continuously within the International GNSS Service (IGS), and their data are regularly processed by IGS Analysis Centers. From its global network of over 350 stations and its Analysis Centers, the IGS generates precise combined GPS ephemeredes and station and satellite clock time series referred to the IGS Time Scale. A processing method called Precise Point Positioning (PPP) is in use in the geodetic community allowing precise recovery of GPS antenna position, clock phase, and atmospheric delays by taking advantage of these IGS precise products. Previous assessments, carried out at Istituto Nazionale di Ricerca Metrologica (INRiM; formerly IEN) with a PPP implementation developed at Natural Resources Canada (NRCan), showed PPP clock solutions have better stability over short/medium term than GPS CV and GPS P3 methods and significantly reduce the day-boundary discontinuities when used in multi-day continuous processing, allowing time-limited, campaign-style time-transfer experiments. This paper reports on follow-on work performed at INRiM and NRCan to further characterize and develop the PPP method for time transfer applications, using data from some of the National Metrology Institutes. We develop a processing procedure that takes advantage of the improved stability of the phase-connected multi-day PPP solutions while allowing the generation of continuous clock time series, more applicable to continuous operation/monitoring of timing equipment.

Using portfolio assignment to support students individually and sustainably -There's always a first time

NASA Astrophysics Data System (ADS)

Mayer, M.

2009-04-01

The recent education of engineers, using the example of satellite geodesy at the Geodetic Institute of the University Karlsruhe (GIK, Germany), is still suffering from time pressure as well as from heavy curriculum content loading. Within this education students, where the academic teachers have to fulfill high requests from the new generation of students as well as from industry and from research institutions respectively, advanced satellite geodetic knowledge has to be transferred effectively and sustainably. In order to enable the students to train newest aspects related to satellite geodesy as well as important key competences, e.g. capacity for independent and academic work, reflection and evaluation skills, presentation skills, an innovative teaching concept was developed, tested, and evaluated. This teaching concept makes use of very different teaching techniques like portfolio assignment, project work, input from experts, jig saw, advance and post organizer. This presentation will focus on the portfolio assignment component. This teaching technique was used at the GIK during the last two years for the first time, in order to support students individually. The lessons learnt within this teaching experiment are going to be presented.

Research-related intercultural higher education in satellite geodesy

NASA Astrophysics Data System (ADS)

Mayer, M.; Heck, B.; Krueger, C. P.

2009-04-01

In order to improve the education of young researchers (master degree, PhD, PostDocs) a cooperation between the Department of Geomatics (DGEOM), Federal University of Paraná (UFPR), Curitiba (Brazil) and the Geodetic Institute (GIK), University Karlsruhe (TH), Karlsruhe (Germany) was established which now exists since more than five years. The joint venture is actually called "PROBRAL: Precise positioning and height determination by means of GPS: Modeling of errors and transformation into physical heights" and focuses on research and education within the field of satellite geodesy. PROBRAL is funded by the Brazilian academic exchange service CAPES and the German academic exchange service DAAD. The geodetic aim of the research project is to validate and improve the quality of 3d positions derived from observations related to satellite navigation systems like GPS. In order to fulfill this ambitious goal sustainably, research has to be carried out in close cooperation. At the same time, e.g. to guarantee continuous success, a coordinated education has to be ensured. Besides technical education aspects key competences (e.g. language, capacity for teamwork, project management skills) are trained. Within the presentation the lessons which were learned from this project are discussed in detail.

Haystack Analysis Center

NASA Technical Reports Server (NTRS)

Niell, Arthur; Cappallo, Roger; Corey, Brian; Titus, Mike

2013-01-01

Analysis activities at Haystack Observatory are directed towards improving the accuracy of geodetic measurements, whether these are from VLBI, GNSS, SLR, or any other technique. Those analysis activities that are related to technology development are reported elsewhere in this volume. In this report, a preliminary analysis of the first geodetic sessions with the new broadband geodetic VLBI system is reported.

Plate motions and deformations from geologic and geodetic data

NASA Technical Reports Server (NTRS)

Jordan, Thomas H.

1990-01-01

An analysis of geodetic data in the vicinity of the Crustal Dynamics Program (CDP) site at Vandenberg Air Force Base (VNDN) is presented. The utility of space-geodetic data in the monitoring of transient strains associated with earthquakes in tectonically active areas like California is investigated. Particular interest is in the possibility that space-geodetic methods may be able to provide critical new data on deformations precursory to large seismic events. Although earthquake precursory phenomena are not well understood, the monitoring of small strains in the vicinity of active faults is a promising technique for studying the mechanisms that nucleate large earthquakes and, ultimately, for earthquake prediction. Space-geodetic techniques are now capable of measuring baselines of tens to hundreds of kilometers with a precision of a few parts in 108. Within the next few years, it will be possible to record and analyze large-scale strain variations with this precision continuously in real time. Thus, space-geodetic techniques may become tools for earthquake prediction. In anticipation of this capability, several questions related to the temporal and spatial scales associated with subseismic deformation transients are examined.

Compact Integration of a GSM-19 Magnetic Sensor with High-Precision Positioning using VRS GNSS Technology

PubMed Central

Martín, Angel; Padín, Jorge; Anquela, Ana Belén; Sánchez, Juán; Belda, Santiago

2009-01-01

Magnetic data consists of a sequence of collected points with spatial coordinates and magnetic information. The spatial location of these points needs to be as exact as possible in order to develop a precise interpretation of magnetic anomalies. GPS is a valuable tool for accomplishing this objective, especially if the RTK approach is used. In this paper the VRS (Virtual Reference Station) technique is introduced as a new approach for real-time positioning of magnetic sensors. The main advantages of the VRS approach are, firstly, that only a single GPS receiver is needed (no base station is necessary), reducing field work and equipment costs. Secondly, VRS can operate at distances separated 50–70 km from the reference stations without degrading accuracy. A compact integration of a GSM-19 magnetometer sensor with a geodetic GPS antenna is presented; this integration does not diminish the operational flexibility of the original magnetometer and can work with the VRS approach. The coupled devices were tested in marshlands around Gandia, a city located approximately 100 km South of Valencia (Spain), thought to be the site of a Roman cemetery. The results obtained show adequate geometry and high-precision positioning for the structures to be studied (a comparison with the original low precision GPS of the magnetometer is presented). Finally, the results of the magnetic survey are of great interest for archaeological purposes. PMID:22574055

EUPOS - Satellite multifunctional system of reference stations in Central and Eastern Europe

NASA Astrophysics Data System (ADS)

Sledzinski, J.

2003-04-01

The European project EUPOS (European Position Determination System) of establishment of a system of multifunctional satellite reference stations in Central and Eastern Europe is described in the paper. Fifteen countries intend to participate in the project: Bulgaria, Croatia, Czech Republic, Estonia, Germany, Hungary, Latvia, Lithuania, Macedonia, Poland, Romania, Russia, Serbia, Slovak Republic and Slovenia. One common project will be prepared for all countries, however it will include the existing or developed infrastructure in particular countries. The experiences of establishing and operating of the German network SAPOS as well as experiences gained by other countries will be used. The European network of stations will be compatible with the system SAPOS and future European system Galileo. The network of reference stations will provide signal for both positioning of the geodetic control points and for land, air and marine navigation. Several levels of positioning accuracy will be delivered.

Focus Upon Implementing the GGOS Decadal Vision for Geohazards Monitoring

NASA Astrophysics Data System (ADS)

LaBrecque, John; Stangl, Gunter

2017-04-01

The Global Geodetic Observing System of the IAG identified present and future roles for Geodesy in the development and well being of the global society. The GGOS is focused upon the development of infrastructure, information, analysis, and educational systems to advance the International Global Reference Frame, the International Celestial Reference System, the International Height Reference System, atmospheric dynamics, sea level change and geohazards monitoring. The geohazards initiative is guided by an eleven nation working group initially focused upon the development and integration of regional multi-GNSS networks and analysis systems for earthquake and tsunami early warning. The opportunities and challenges being addressed by the Geohazards working group include regional network design, algorithm development and implementation, communications, funding, and international agreements on data access. This presentation will discuss in further detail these opportunities and challenges for the GGOS focus upon earthquake and tsunami early warning.

Development of a composite geodetic structure for space construction, phase 2

NASA Technical Reports Server (NTRS)

1981-01-01

Primary physical and mechanical properties were defined for pultruded hybrid HMS/E-glass P1700 rod material used for the fabrication of geodetic beams. Key properties established were used in the analysis, design, fabrication, instrumentation, and testing of a geodetic parameter cylinder and a lattice cone closeout joined to a short cylindrical geodetic beam segment. Requirements of structural techniques were accomplished. Analytical procedures were refined and extended to include the effect of rod dimensions for the helical and longitudinal members on local buckling, and the effect of different flexural and extensional moduli on general instability buckling.

GEODYN system description, volume 1. [computer program for estimation of orbit and geodetic parameters

NASA Technical Reports Server (NTRS)

Chin, M. M.; Goad, C. C.; Martin, T. V.

1972-01-01

A computer program for the estimation of orbit and geodetic parameters is presented. The areas in which the program is operational are defined. The specific uses of the program are given as: (1) determination of definitive orbits, (2) tracking instrument calibration, (3) satellite operational predictions, and (4) geodetic parameter estimation. The relationship between the various elements in the solution of the orbit and geodetic parameter estimation problem is analyzed. The solution of the problems corresponds to the orbit generation mode in the first case and to the data reduction mode in the second case.

The contribution of engineering surveys by means of GPS to the determination of crustal movements in Istanbul

NASA Astrophysics Data System (ADS)

Özyaşar, M.; Özlüdemir, M. T.

2011-06-01

Global Navigation Satellite Systems (GNSS) are space based positioning techniques and widely used in geodetic applications. Geodetic networking accomplished by engineering surveys constitutes one of these tasks. Geodetic networks are used as the base of all kinds of geodetic implementations, Co from the cadastral plans to the relevant surveying processes during the realization of engineering applications. Geodetic networks consist of control points positioned in a defined reference frame. In fact, such positional information could be useful for other studies as well. One of such fields is geodynamic studies that use the changes of positions of control stations within a network in a certain time period to understand the characteristics of tectonic movements. In Turkey, which is located in tectonically active zones and struck by major earthquakes quite frequently, the positional information obtained in engineering surveys could be very useful for earthquake related studies. For this purpose, a GPS (Global Positioning System) network of 650 stations distributed over Istanbul (Istanbul GPS Triangulation Network; abbreviated IGNA) covering the northern part of the North Anatolian Fault Zone (NAFZ) was established in 1997 and measured in 1999. From 1998 to 2004, the IGNA network was extended to 1888 stations covering an area of about 6000 km2, the whole administration area of Istanbul. All 1888 stations within the IGNA network were remeasured in 2005. In these two campaigns there existed 452 common points, and between these two campaigns two major earthquakes took place, on 17 August and 12 November 1999 with a Richter scale magnitude of 7.4 and 7.2, respectively. Several studies conducted for estimating the horizontal and vertical displacements as a result of these earthquakes on NAFZ are discussed in this paper. In geodynamic projects carried out before the earthquakes in 1999, an annual average velocity of 2-2.5 cm for the stations along the NAFZ were estimated. Studies carried out using GPS observations in the same area after these earthquakes indicated that point displacements vary depending on their distance to the epicentres of the earthquakes. But the directions of point displacements are similar. The results obtained through the analysis of the IGNA network also show that there is a common trend in the directions of point displacements in the study area. In this paper, the past studies about the tectonics of Marmara region are summarised and the results of the displacement analysis on the IGNA network are discussed.

A Geodetic Strain Rate Model for the East African Rift System.

PubMed

Stamps, D S; Saria, E; Kreemer, C

2018-01-15

Here we describe the new Sub-Saharan Africa Geodetic Strain Rate Model v.1.0 (SSA-GSRM v.1.0), which provides fundamental constraints on long-term tectonic deformation in the region and an improved seismic hazards assessment in Sub-Saharan Africa. Sub-Saharan Africa encompasses the East African Rift System, the active divergent plate boundary between the Nubian and Somalian plates, where strain is largely accommodated along the boundaries of three subplates. We develop an improved geodetic strain rate field for sub-Saharan Africa that incorporates 1) an expanded geodetic velocity field, 2) redefined regions of deforming zones guided by seismicity distribution, and 3) updated constraints on block rotations. SSA-GSRM v.1.0 spans longitudes 22° to 55.5° and latitudes -52° to 20° with 0.25° (longitude) by 0.2° (latitude) spacing. For plates/sub-plates, we assign rigid block rotations as constraints on the strain rate calculation that is determined by fitting bicubic Bessel splines to a new geodetic velocity solution for an interpolated velocity gradient tensor field. We derive strain rates, velocities, and vorticity rates from the velocity gradient tensor field. A comparison with the Global Geodetic Strain Rate model v2.1 reveals regions of previously unresolved spatial heterogeneities in geodetic strain rate distribution, which indicates zones of elevated seismic risk.

Bounding the moment deficit rate on crustal faults using geodetic data: Methods

DOE PAGES

Maurer, Jeremy; Segall, Paul; Bradley, Andrew Michael

2017-08-19

Here, the geodetically derived interseismic moment deficit rate (MDR) provides a first-order constraint on earthquake potential and can play an important role in seismic hazard assessment, but quantifying uncertainty in MDR is a challenging problem that has not been fully addressed. We establish criteria for reliable MDR estimators, evaluate existing methods for determining the probability density of MDR, and propose and evaluate new methods. Geodetic measurements moderately far from the fault provide tighter constraints on MDR than those nearby. Previously used methods can fail catastrophically under predictable circumstances. The bootstrap method works well with strong data constraints on MDR, butmore » can be strongly biased when network geometry is poor. We propose two new methods: the Constrained Optimization Bounding Estimator (COBE) assumes uniform priors on slip rate (from geologic information) and MDR, and can be shown through synthetic tests to be a useful, albeit conservative estimator; the Constrained Optimization Bounding Linear Estimator (COBLE) is the corresponding linear estimator with Gaussian priors rather than point-wise bounds on slip rates. COBE matches COBLE with strong data constraints on MDR. We compare results from COBE and COBLE to previously published results for the interseismic MDR at Parkfield, on the San Andreas Fault, and find similar results; thus, the apparent discrepancy between MDR and the total moment release (seismic and afterslip) in the 2004 Parkfield earthquake remains.« less

Bounding the moment deficit rate on crustal faults using geodetic data: Methods

DOE Office of Scientific and Technical Information (OSTI.GOV)

Maurer, Jeremy; Segall, Paul; Bradley, Andrew Michael

Here, the geodetically derived interseismic moment deficit rate (MDR) provides a first-order constraint on earthquake potential and can play an important role in seismic hazard assessment, but quantifying uncertainty in MDR is a challenging problem that has not been fully addressed. We establish criteria for reliable MDR estimators, evaluate existing methods for determining the probability density of MDR, and propose and evaluate new methods. Geodetic measurements moderately far from the fault provide tighter constraints on MDR than those nearby. Previously used methods can fail catastrophically under predictable circumstances. The bootstrap method works well with strong data constraints on MDR, butmore » can be strongly biased when network geometry is poor. We propose two new methods: the Constrained Optimization Bounding Estimator (COBE) assumes uniform priors on slip rate (from geologic information) and MDR, and can be shown through synthetic tests to be a useful, albeit conservative estimator; the Constrained Optimization Bounding Linear Estimator (COBLE) is the corresponding linear estimator with Gaussian priors rather than point-wise bounds on slip rates. COBE matches COBLE with strong data constraints on MDR. We compare results from COBE and COBLE to previously published results for the interseismic MDR at Parkfield, on the San Andreas Fault, and find similar results; thus, the apparent discrepancy between MDR and the total moment release (seismic and afterslip) in the 2004 Parkfield earthquake remains.« less

GGOS and the EOP - the key role of SLR for a stable estimation of highly accurate Earth orientation parameters

NASA Astrophysics Data System (ADS)

Bloßfeld, Mathis; Panzetta, Francesca; Müller, Horst; Gerstl, Michael

2016-04-01

The GGOS vision is to integrate geometric and gravimetric observation techniques to estimate consistent geodetic-geophysical parameters. In order to reach this goal, the common estimation of station coordinates, Stokes coefficients and Earth Orientation Parameters (EOP) is necessary. Satellite Laser Ranging (SLR) provides the ability to study correlations between the different parameter groups since the observed satellite orbit dynamics are sensitive to the above mentioned geodetic parameters. To decrease the correlations, SLR observations to multiple satellites have to be combined. In this paper, we compare the estimated EOP of (i) single satellite SLR solutions and (ii) multi-satellite SLR solutions. Therefore, we jointly estimate station coordinates, EOP, Stokes coefficients and orbit parameters using different satellite constellations. A special focus in this investigation is put on the de-correlation of different geodetic parameter groups due to the combination of SLR observations. Besides SLR observations to spherical satellites (commonly used), we discuss the impact of SLR observations to non-spherical satellites such as, e.g., the JASON-2 satellite. The goal of this study is to discuss the existing parameter interactions and to present a strategy how to obtain reliable estimates of station coordinates, EOP, orbit parameter and Stokes coefficients in one common adjustment. Thereby, the benefits of a multi-satellite SLR solution are evaluated.

A Community-based Partnership for a Sustainable GNSS Geodetic Network

NASA Astrophysics Data System (ADS)

Dokka, R. K.

2009-12-01

Geodetic networks offer unparalleled opportunities to monitor and understand many of the rhythms of the Earth most vital to the sustainability of modern and future societies, i.e., crustal motions, sea-level, and the weather. For crustal deformation studies, the advantage is clear. Modern measurements allow us to document not only the permanent strains incurred over a seismic cycle, for example, but also the ephemeral strains that are critical for understanding the underlying physical mechanism. To be effective for science, however, geodetic networks must be properly designed, capitalized, and maintained over sufficient time intervals to fully capture the processes in action. Unfortunately, most networks lack interoperability and lack a business plan to ensure long term sustainability. The USA, for example, lacks a unified nation-wide GNSS network that can sustain its self over the coming years, decades, and century. Current federal priorities do not yet envision such a singular network. Publicly and privately funded regional networks exist, but tend to be parochial in scope, and optimized for a special user community, e.g., surveying, crustal motions, etc. Data sharing is common, but the lack of input at the beginning limits the functionality of the system for non-primary users. Funding for private networks depend heavily on the user demand, business cycle, and regulatory requirements. Agencies funding science networks offer no guarantee of sustained support. An alternative model (GULFNet) developed in Louisiana is meeting user needs, is sustainable, and is helping engineers, surveyors, and geologists become more spatially enabled. The common denominator among all participants is the view that accurate, precise, and timely geodetic data have tangible value for all segments of society. Although operated by a university (LSU), GULFNet is a community-based partnership between public and private sectors. GULFNet simultaneously achieves scientific goals by providing data to multiple user communities, supports National Spatial Reference System needs through NGS CORS, and serves the private sector by helping to make it become more profitable. The private sector participates through direct support that sustains operations, but most importantly by raising awareness among policy makers and federal and state appropriators.

High rate GPS positioning , JASON altimetry and marine gravimetry : monitoring the Antarctic Circumpolar Current (ACC) through the DRAKE campaigns.

NASA Astrophysics Data System (ADS)

Melachroinos, S. A.; Biancale, R.; Menard, Y.; Sarrailh, M.

2008-12-01

The Drake campaign which took place from Jan 14, 2006 - 08 Feb, 2006 has been a very successful mission in collecting a wide range of GPS and marine gravity data all along JASON altimetry ground track n° 104. The same campaign will be repeated in 2009 along 028 and 104 JASON-2 ground track. The Drake Passage (DP) chokepoint is not only well suited geographically, as the Antarctic Circumpolar Current (ACC) is constricted to its narrowest extent of 700 km, but observations and models suggest that dynamical balances are particular effective in this area. Furthermore the space geodesy observations and their products provided from several altimetry missions (currently operating ENVISAT, JASON 1 and 2, GFO, ERS and other plannified for the future such as Altika, SWOT) require the cross comparison with independent geodetic techniques at the DP. The current experiment comprises a kinematic GPS and marine gravimetry Cal/Val geodetic approach and it aims to : validate with respect to altimetry data and surface models such a kinematic high frequency GPS technique for measuring sea state and sea surface height (SSH), compare the GPS SSH profiles with altimetry mean dynamic topography (MDT) and mean sea surface (MSS) models, give recommendations for future "offshore" Cal/Val activities on the ground tracks of altimeter satellites such as JASON-2, GFO, Altika using the GNSS technology etc. The GPS observations are collected from GPS antennas installed on a wave-rider buoy , aboard the R/V "Polarstern" and from continuous geodetic reference stations in the proximity. We also analyse problems related to the ship's attitude variations in roll, pitch and yaw and a way to correct them. We also give emphasis on the impact of the ship's acceleration profiles on the so called "squat effect" and ways to deal with it. The project will in particular benefit the GOCE mission by proposing to integrate GOCE in the ocean circulation study and validate GOCE products with our independent geodetic data set. The high rate GPS SSH solutions are derived using two different GPS kinematic software, GINS (CNES) and TRACK (MIT).

Development of a composite geodetic structure for space construction, phase 1A

NASA Technical Reports Server (NTRS)

1980-01-01

The development of a geodetic beam and beam builder for on orbit construction of large truss type space structures is discussed. The geodetic beam is a lightweight, open lattice structure composed of an equilateral gridwork of crisscrossing rods. The beam provides a high degree of stiffness and minimizes structural distortion, due to temperature gradients, through the incorporation of a new graphite and glass reinforced thermoplastic composite material with a low coefficient of thermal expansion. A low power consuming, high production rate, beam builder automatically fabricates the geodetic beams in space using rods preprocessed on Earth. Three areas of the development are focused upon; (1) geodetic beam designs for local attachment of equipment or beam to beam joining in a parallel or crossing configurations, (2) evaluation of long life pultruded rods capable of service temperatures higher than possible with the HMS/P1700 rod material, and (3) evalaution of high temperature joint encapsulant materials.

Interaction of marine geodesy, satellite technology and ocean physics

NASA Technical Reports Server (NTRS)

Mourad, A. G.; Fubara, D. M. J.

1972-01-01

The possible applications of satellite technology in marine geodesy and geodetic related ocean physics were investigated. Four major problems were identified in the areas of geodesy and ocean physics: (1) geodetic positioning and control establishment; (2) sea surface topography and geoid determination; (3) geodetic applications to ocean physics; and (4) ground truth establishment. It was found that satellite technology can play a major role in their solution. For solution of the first problem, the use of satellite geodetic techniques, such as Doppler and C-band radar ranging, is demonstrated to fix the three-dimensional coordinates of marine geodetic control if multi-satellite passes are used. The second problem is shown to require the use of satellite altimetry, along with accurate knowledge of ocean-dynamics parameters such as sea state, ocean tides, and mean sea level. The use of both conventional and advanced satellite techniques appeared to be necessary to solve the third and fourth problems.

Support time-dependent transformations for surveying and GIS : current status and upcoming challenges

NASA Astrophysics Data System (ADS)

Mahmoudabadi, H.; Lercier, D.; Vielliard, S.; Mein, N.; Briggs, G.

2016-12-01

The support of time-dependent transformations for surveying and GIS is becoming a critical issue. We need to convert positions from the realizations of the International Terrestrial Reference Frame to any national reference frame. This problem is easy to solve when all of the required information is available. But it becomes really complicated in a worldwide context. We propose an overview of the current ITRF-aligned reference frames and we describe a global solution to support time-dependent transformations between them and the International Terrestrial Reference Frame. We focus on the uncertainties of station velocities used. In a first approximation, we use a global tectonic plate model to calculate point velocities. We show the impact of the velocity model on the coordinate accuracies. Several countries, particularly in active regions, are developing semi-dynamic reference frames. These frames include local displacement models updated regularly and/or after major events (such as earthquakes). Their integration into surveying or GIS applications is an upcoming challenge. We want to encourage the geodetic community to develop and use standard formats.

GEOS observation systems intercomparison investigation results

NASA Technical Reports Server (NTRS)

Berbert, J. H.

1974-01-01

The results of an investigation designed to determine the relative accuracy and precision of the different types of geodetic observation systems used by NASA is presented. A collocation technique was used to minimize the effects of uncertainties in the relative station locations and in the earth's gravity field model by installing accurate reference tracking systems close to the systems to be compared, and by precisely determining their relative survey. The Goddard laser and camera systems were shipped to selected sites, where they tracked the GEOS satellite simultaneously with other systems for an intercomparison observation.

Fifty year canon of solar eclipses: 1986-2035

NASA Technical Reports Server (NTRS)

Espenak, Fred

1986-01-01

A reference of moderately detailed eclipse predictions and maps for use by the professional astronomical community is provided. The general characteristics of every solar eclipse and a detailed set of cylindrical project world maps which show the umbral paths of every solar eclipse from 1901 to 2100 are presented. The geodetic path coordinates and local circumstance on the center line, and a series of orthographic projection maps which show the regions of visibility of both partial and central phases for every eclipse from 1986 through 2035 are also provided.

Some problems concerned with the geodetic use of high precision altimeter data

NASA Technical Reports Server (NTRS)

Lelgemann, D.

1976-01-01

The definition of the geoid in view of different height systems is discussed. A definition is suggested which makes it possible to take into account the influence of the unknown corrections to the various height systems on the solution of Stokes' problem. A solution to Stokes' problem with an accuracy of 10 cm is derived which allows the inclusion of the results of satellite geodesy. In addition equations are developed for the determination of spherical harmonies using altimeter measurements. The influence of the ellipticity of the reference surface is considered.

Prototype Evaluation of Sluiceway Aeration System Libby Dam, Kootenai River, Montana.

DTIC Science & Technology

1984-03-01

VICKSBURG MS H DRA.. R G MCGEE UNCLASSIFIED MAR 84 WES/TR/HL-84-2 F/G 13/13 NL- DE E-EullEI EEEEEIIIENEIII II I IE EEIImmiEmhihhhEEEI mEEmhEEihhEEm 1j...report of findings was published * All elevations ( el ) cited herein are in feet referred to the National Geodetic Vertical Datum (NGVD). 6 r.W (Hart...1981). Data derived from the test program were used as criteria for de - sign of a more efficient air vent system. 6. The resulting modification to the

Principal facts for a gravity survey of the Double Hot Springs Known Geothermal Resource Area, Humboldt County, Nevada

DOE Office of Scientific and Technical Information (OSTI.GOV)

Peterson, D.L.; Kaufmann, H.E.

1978-01-01

During July 1977, forty-nine gravity stations were obtained in the Double Hot Springs Known Geothermal Resource Area and vicinity, northwestern Nevada. The gravity observations were made with a Worden gravimeter having a scale factor of about 0.5 milligal per division. No terrain corrections have been applied to these data. The earth tide correction was not used in drift reduction. The Geodetic Reference System 1967 formula (International Association of Geodesy, 1967) was used to compute theoretical gravity.

Characterization of Unstable Rock Slopes Through Passive Seismic Measurements

NASA Astrophysics Data System (ADS)

Kleinbrod, Ulrike; Burjánek, Jan; Fäh, Donat

2014-05-01

Catastrophic rock slope failures have high social impact, causing significant damage to infrastructure and many casualties throughout the world each year. Both detection and characterization of rock instabilities are therefore of key importance. Analysing unstable rock slopes by means of ambient vibrations might be a new alternative to the already existing methods as for example geotechnical displacement measurements. A systematic measurement campaign has been initiated recently in Switzerland in order to study the seismic response of potential rockslides concerning a broad class of slope failure mechanisms and material conditions. First results are presented in this contribution. Small aperture seismic arrays were deployed at sites of interest for a short period of time (several hours) in order to record ambient vibrations. During each measurement a reference station was installed on a stable part close to the instability. The total number of stations used varies from 16 down to 2, depending on the site scope and resource availability. Instable rock slopes show a highly directional ground motion which is significantly amplified with respect to stable areas. These effects are strongest at certain frequencies which are identified as eigenfrequencies of the unstable rock mass. The eigenfrequencies and predominant directions have been estimated by frequency dependent polarization analysis. Site-to-reference spectral ratios have been calculated as well in order to estimate the relative amplification of ground motion at unstable parts. The retrieved results were compared with independent in-situ observations and other available data. The directions of maximum amplification are in most cases perpendicular to open cracks mapped on the surface and in good agreement with the deformation directions obtained by geodetic measurements. The interpretation of the observed wave field is done through numerical modelling of seismic wave propagation in fractured media with complex topography. For example, a potential relation between eigenfrequencies and unstable rock mass volume is investigated.

The OSU 275 system of satellite tracking station coordinates

NASA Technical Reports Server (NTRS)

Mueller, I. I.; Kumar, M.

1975-01-01

A brief review of the methods and data used in the OSU 275 geodetic system is given along with the summary of the results. Survey information regarding the tracking stations in the system is given in tabular form along with the geodetic and geophysical parameters, origin and orientation, Cartisian coordinates, and systematic differences with global and nonglobal geodetic systems.

Development of a Mathematical Model to Assess the Accuracy of Difference between Geodetic Heights

ERIC Educational Resources Information Center

Gairabekov, Ibragim; Kliushin, Evgenii; Gayrabekov, Magomed-Bashir; Ibragimova, Elina; Gayrabekova, Amina

2016-01-01

The article includes the results of theoretical studies of the accuracy of geodetic height survey and marks points on the Earth's surface using satellite technology. The dependence of the average square error of geodetic heights difference survey from the distance to the base point was detected. It is being proved that by using satellite…

Reference Ellipsoid and Geoid in Chronometric Geodesy

NASA Astrophysics Data System (ADS)

Kopeikin, Sergei M.

2016-02-01

Chronometric geodesy applies general relativity to study the problem of the shape of celestial bodies including the earth, and their gravitational field. The present paper discusses the relativistic problem of construction of a background geometric manifold that is used for describing a reference ellipsoid, geoid, the normal gravity field of the earth and for calculating geoid's undulation (height). We choose the perfect fluid with an ellipsoidal mass distribution uniformly rotating around a fixed axis as a source of matter generating the geometry of the background manifold through the Einstein equations. We formulate the post-Newtonian hydrodynamic equations of the rotating fluid to find out the set of algebraic equations defining the equipotential surface of the gravity field. In order to solve these equations we explicitly perform all integrals characterizing the interior gravitational potentials in terms of elementary functions depending on the parameters defining the shape of the body and the mass distribution. We employ the coordinate freedom of the equations to choose these parameters to make the shape of the rotating fluid configuration to be an ellipsoid of rotation. We derive expressions of the post-Newtonian mass and angular momentum of the rotating fluid as functions of the rotational velocity and the parameters of the ellipsoid including its bare density, eccentricity and semi-major axes. We formulate the post-Newtonian Pizzetti and Clairaut theorems that are used in geodesy to connect the parameters of the reference ellipsoid to the polar and equatorial values of force of gravity. We expand the post-Newtonian geodetic equations characterizing the reference ellipsoid into the Taylor series with respect to the eccentricity of the ellipsoid, and discuss the small-eccentricity approximation. Finally, we introduce the concept of relativistic geoid and its undulation with respect to the reference ellipsoid, and discuss how to calculate it in chronometric geodesy by making use of the anomalous gravity potential.

Evaluation of Integration Degree of the ASG-EUPOS Polish Reference Networks With Ukrainian GeoTerrace Network Stations in the Border Area

NASA Astrophysics Data System (ADS)

Siejka, Zbigniew

2017-09-01

GNSS systems are currently the basic tools for determination of the highest precision station coordinates (e.g. basic control network stations or stations used in the networks for geodynamic studies) as well as for land, maritime and air navigation. All of these tasks are carried out using active, large scale, satellite geodetic networks which are complex, intelligent teleinformatic systems offering post processing services along with corrections delivered in real-time for kinematic measurements. Many countries in the world, also in Europe, have built their own multifunctional networks and enhance them with their own GNSS augmentation systems. Nowadays however, in the era of international integration, there is a necessity to consider collective actions in order to build a unified system, covering e.g. the whole Europe or at least some of its regions. Such actions have already been undertaken in many regions of the world. In Europe such an example is the development for EUPOS which consists of active national networks built in central eastern European countries. So far experience and research show, that the critical areas for connecting these networks are border areas, in which the positioning accuracy decreases (Krzeszowski and Bosy, 2011). This study attempts to evaluate the border area compatibility of Polish ASG-EUPOS (European Position Determination System) reference stations and Ukrainian GeoTerrace system reference stations in the context of their future incorporation into the EUPOS. The two networks analyzed in work feature similar hardware parameters. In the ASG-EUPOS reference stations network, during the analyzed period, 2 stations (WLDW and CHEL) used only one system (GPS), while, in the GeoTerrace network, all the stations were equipped with both GPS and GLONASS receivers. The ASG EUPOS reference station network (95.6%) has its average completeness greater by about 6% when compared to the GeoTerrace network (89.8%).

Celestial reference frames and the gauge freedom in the post-Newtonian mechanics of the Earth-Moon system

NASA Astrophysics Data System (ADS)

Kopeikin, Sergei; Xie, Yi

2010-11-01

We introduce the Jacobi coordinates adopted to the advanced theoretical analysis of the relativistic Celestial Mechanics of the Earth-Moon system. Theoretical derivation utilizes the relativistic resolutions on reference frames adopted by the International Astronomical Union (IAU) in 2000. The resolutions assume that the Solar System is isolated and space-time is asymptotically flat at infinity and the primary reference frame covers the entire space-time, has its origin at the Solar System barycenter (SSB) with spatial axes stretching up to infinity. The SSB frame is not rotating with respect to a set of distant quasars that are assumed to be at rest on the sky forming the International Celestial Reference Frame (ICRF). The second reference frame has its origin at the Earth-Moon barycenter (EMB). The EMB frame is locally inertial and is not rotating dynamically in the sense that equation of motion of a test particle moving with respect to the EMB frame, does not contain the Coriolis and centripetal forces. Two other local frames—geocentric and selenocentric—have their origins at the center of mass of Earth and Moon respectively and do not rotate dynamically. Each local frame is subject to the geodetic precession both with respect to other local frames and with respect to the ICRF because of their relative motion with respect to each other. Theoretical advantage of the dynamically non-rotating local frames is in a more simple mathematical description of the metric tensor and relative equations of motion of the Moon with respect to Earth. Each local frame can be converted to kinematically non-rotating one after alignment with the axes of ICRF by applying the matrix of the relativistic precession as recommended by the IAU resolutions. The set of one global and three local frames is introduced in order to decouple physical effects of gravity from the gauge-dependent effects in the equations of relative motion of the Moon with respect to Earth.

Aftershock distribution as a constraint on the geodetic model of coseismic slip for the 2004 Parkfield earthquake

USGS Publications Warehouse

Bennington, Ninfa; Thurber, Clifford; Feigl, Kurt; ,

2011-01-01

Several studies of the 2004 Parkfield earthquake have linked the spatial distribution of the event’s aftershocks to the mainshock slip distribution on the fault. Using geodetic data, we find a model of coseismic slip for the 2004 Parkfield earthquake with the constraint that the edges of coseismic slip patches align with aftershocks. The constraint is applied by encouraging the curvature of coseismic slip in each model cell to be equal to the negative of the curvature of seismicity density. The large patch of peak slip about 15 km northwest of the 2004 hypocenter found in the curvature-constrained model is in good agreement in location and amplitude with previous geodetic studies and the majority of strong motion studies. The curvature-constrained solution shows slip primarily between aftershock “streaks” with the continuation of moderate levels of slip to the southeast. These observations are in good agreement with strong motion studies, but inconsistent with the majority of published geodetic slip models. Southeast of the 2004 hypocenter, a patch of peak slip observed in strong motion studies is absent from our curvature-constrained model, but the available GPS data do not resolve slip in this region. We conclude that the geodetic slip model constrained by the aftershock distribution fits the geodetic data quite well and that inconsistencies between models derived from seismic and geodetic data can be attributed largely to resolution issues.

A Comparison of Geodetic and Geologic Rates Prior to Large Strike-Slip Earthquakes: A Diversity of Earthquake-Cycle Behaviors?

NASA Astrophysics Data System (ADS)

Dolan, James F.; Meade, Brendan J.

2017-12-01

Comparison of preevent geodetic and geologic rates in three large-magnitude (Mw = 7.6-7.9) strike-slip earthquakes reveals a wide range of behaviors. Specifically, geodetic rates of 26-28 mm/yr for the North Anatolian fault along the 1999 MW = 7.6 Izmit rupture are ˜40% faster than Holocene geologic rates. In contrast, geodetic rates of ˜6-8 mm/yr along the Denali fault prior to the 2002 MW = 7.9 Denali earthquake are only approximately half as fast as the latest Pleistocene-Holocene geologic rate of ˜12 mm/yr. In the third example where a sufficiently long pre-earthquake geodetic time series exists, the geodetic and geologic rates along the 2001 MW = 7.8 Kokoxili rupture on the Kunlun fault are approximately equal at ˜11 mm/yr. These results are not readily explicable with extant earthquake-cycle modeling, suggesting that they may instead be due to some combination of regional kinematic fault interactions, temporal variations in the strength of lithospheric-scale shear zones, and/or variations in local relative plate motion rate. Whatever the exact causes of these variable behaviors, these observations indicate that either the ratio of geodetic to geologic rates before an earthquake may not be diagnostic of the time to the next earthquake, as predicted by many rheologically based geodynamic models of earthquake-cycle behavior, or different behaviors characterize different fault systems in a manner that is not yet understood or predictable.

First results of DORIS data analysis at Geodetic Observatory Pecný

NASA Astrophysics Data System (ADS)

Štěpánek, Petr; Hugentobler, Urs; Le Bail, Karine

2006-11-01

In a cooperation between the Astronomical Institute, University of Bern (AIUB), the Geodetic Observatory Pecný (GOPE), and the Institut Géographique National (IGN), DORIS data analysis capabilities were implemented into a development version of the Bernese GPS software. The DORIS Doppler observables are reformulated such that they are similar to global navigation satellite system (GNSS) carrier-phase observations, allowing the use of the same observation models and algorithms as for GNSS carrier-phase data analysis with only minor software modifications. As such, the same algorithms may be used to process DORIS carrier-phase observations. First results from the analysis of 3 weeks of DORIS data (September 2004, five DORIS-equipped satellites) at GOPE are promising and are presented here. They include the comparison of station coordinates with coordinate estimates derived by the Laboratoire d’Etudes en Géophysique et Océanographie Spatiale/Collecte Localisation Satellites analysis centre (LCA) and the Institut Géographique National/Jet Propulsion Laboratory (IGN/JPL), and the comparison of Earth orientation parameters (EOPs) with the International Earth Rotation and Reference Frames Service (IERS) C04 model. The modified Bernese results are of a slightly lower, but comparable, quality than corresponding solutions routinely computed within the IDS (International DORIS Service). The weekly coordinate repeatability RMS is of the order of 2 3 cm for each 3D station coordinate. Comparison with corresponding estimates of station coordinates from current IDS analysis centers demonstrates similar precision. Daily pole component estimates show a mean difference from IERS-C04 of 0.6 mas in X p and - 0.5 mas in Y p and a RMS of 0.8 mas in X p and 0.9 mas in Y p (mean removed). An automatic analysis procedure is under development at GOPE, and routine DORIS data processing will be implemented in the near future.

Software development and its description for Geoid determination based on Spherical-Cap-Harmonics Modelling using digital-zenith camera and gravimetric measurements hybrid data

NASA Astrophysics Data System (ADS)

Morozova, K.; Jaeger, R.; Balodis, J.; Kaminskis, J.

2017-10-01

Over several years the Institute of Geodesy and Geoinformatics (GGI) was engaged in the design and development of a digital zenith camera. At the moment the camera developments are finished and tests by field measurements are done. In order to check these data and to use them for geoid model determination DFHRS (Digital Finite element Height reference surface (HRS)) v4.3. software is used. It is based on parametric modelling of the HRS as a continous polynomial surface. The HRS, providing the local Geoid height N, is a necessary geodetic infrastructure for a GNSS-based determination of physcial heights H from ellipsoidal GNSS heights h, by H=h-N. The research and this publication is dealing with the inclusion of the data of observed vertical deflections from digital zenith camera into the mathematical model of the DFHRS approach and software v4.3. A first target was to test out and validate the mathematical model and software, using additionally real data of the above mentioned zenith camera observations of deflections of the vertical. A second concern of the research was to analyze the results and the improvement of the Latvian quasi-geoid computation compared to the previous version HRS computed without zenith camera based deflections of the vertical. The further development of the mathematical model and software concerns the use of spherical-cap-harmonics as the designed carrier function for the DFHRS v.5. It enables - in the sense of the strict integrated geodesy approach, holding also for geodetic network adjustment - both a full gravity field and a geoid and quasi-geoid determination. In addition, it allows the inclusion of gravimetric measurements, together with deflections of the vertical from digital-zenith cameras, and all other types of observations. The theoretical description of the updated version of DFHRS software and methods are discussed in this publication.

Considerations for ICRF-3

NASA Astrophysics Data System (ADS)

Ma, Chopo; MacMillan, Daniel; Gordon, David

2015-08-01

The Second Realization of the International Celestial Reference Frame (ICRF) used dual-frequency VLBI data acquired for geodetic and astrometric purposes from 1979-2009 by organizations now coordinated by the International VLBI Service for Geodesy and Astrometry (IVS) and analyzed according to the Conventions of the International Earth Rotation and Reference Systems Service (IERS). Since 2009 the data set has been significantly broadened, especially by observations in the Southern Hemisphere, and modeling of astronomical, geophysical and tropospheric effects has progressed. The new southern data appear to cause a systematic zonal declination change in the catalog positions. Over the three decades of the ICRF data set the effect of galactic aberration may be significant. Geophysical and tropospheric models also may affect the source positions. All these effects need to be addressed in preparation for ICRF-3.

Development of a System to Generate Near Real Time Tropospheric Delay and Precipitable Water Vapor in situ at Geodetic GPS Stations, to Improve Forecasting of Severe Weather Events

NASA Astrophysics Data System (ADS)

Moore, A. W.; Bock, Y.; Geng, J.; Gutman, S. I.; Laber, J. L.; Morris, T.; Offield, D. G.; Small, I.; Squibb, M. B.

2012-12-01

We describe a system under development for generating ultra-low latency tropospheric delay and precipitable water vapor (PWV) estimates in situ at a prototype network of geodetic GPS sites in southern California, and demonstrating their utility in forecasting severe storms commonly associated with flooding and debris flow events along the west coast of North America through infusion of this meteorological data at NOAA National Weather Service (NWS) Forecast Offices and the NOAA Earth System Research Laboratory (ESRL). The first continuous geodetic GPS network was established in southern California in the early 1990s and much of it was converted to real-time (latency <1s) high-rate (1Hz) mode over the following decades. GPS stations are multi-purpose and can also provide estimates of tropospheric zenith delays, which can be converted into mm-accuracy PWV using collocated pressure and temperature measurements, the basis for GPS meteorology (Bevis et al. 1992, 1994; Duan et al. 1996) as implemented by NOAA with a nationwide distribution of about 300 GPS-Met stations providing PW estimates at subhourly resolution currently used in operational weather forecasting in the U.S. We improve upon the current paradigm of transmitting large quantities of raw data back to a central facility for processing into higher-order products. By operating semi-autonomously, each station will provide low-latency, high-fidelity and compact data products within the constraints of the narrow communications bandwidth that often occurs in the aftermath of natural disasters. The onsite ambiguity-resolved precise point positioning solutions are enabled by a power-efficient, low-cost, plug-in Geodetic Module for fusion of data from in situ sensors including GPS and a low-cost MEMS meteorological sensor package. The decreased latency (~5 minutes) PW estimates will provide the detailed knowledge of the distribution and magnitude of PW that NWS forecasters require to monitor and predict severe winter storms, landfalling atmospheric rivers, and summer thunderstorms associated with the North American monsoon. On the national level, the ESRL will evaluate the utility of ultra-low resolution GNSS observations to improve NOAA's warning and forecast capabilities. The overall objective is to better forecast, assess, and mitigate natural hazards through the flow of information from multiple geodetic stations to scientists, mission planners, decision makers, and first responders.

Optimal Geoid Modelling to determine the Mean Ocean Circulation - Project Overview and early Results

NASA Astrophysics Data System (ADS)

Fecher, Thomas; Knudsen, Per; Bettadpur, Srinivas; Gruber, Thomas; Maximenko, Nikolai; Pie, Nadege; Siegismund, Frank; Stammer, Detlef

2017-04-01

The ESA project GOCE-OGMOC (Optimal Geoid Modelling based on GOCE and GRACE third-party mission data and merging with altimetric sea surface data to optimally determine Ocean Circulation) examines the influence of the satellite missions GRACE and in particular GOCE in ocean modelling applications. The project goal is an improved processing of satellite and ground data for the preparation and combination of gravity and altimetry data on the way to an optimal MDT solution. Explicitly, the two main objectives are (i) to enhance the GRACE error modelling and optimally combine GOCE and GRACE [and optionally terrestrial/altimetric data] and (ii) to integrate the optimal Earth gravity field model with MSS and drifter information to derive a state-of-the art MDT including an error assessment. The main work packages referring to (i) are the characterization of geoid model errors, the identification of GRACE error sources, the revision of GRACE error models, the optimization of weighting schemes for the participating data sets and finally the estimation of an optimally combined gravity field model. In this context, also the leakage of terrestrial data into coastal regions shall be investigated, as leakage is not only a problem for the gravity field model itself, but is also mirrored in a derived MDT solution. Related to (ii) the tasks are the revision of MSS error covariances, the assessment of the mean circulation using drifter data sets and the computation of an optimal geodetic MDT as well as a so called state-of-the-art MDT, which combines the geodetic MDT with drifter mean circulation data. This paper presents an overview over the project results with focus on the geodetic results part.

Assessment of 3D hydrologic deformation using GRACE and GPS

NASA Astrophysics Data System (ADS)

Watson, C. S.; Tregoning, P.; Fleming, K.; Burgette, R. J.; Featherstone, W. E.; Awange, J.; Kuhn, M.; Ramillien, G.

2009-12-01

Hydrological processes cause variations in gravitational potential and surface deformations, both of which are detectable with ever increasing precision using space geodetic techniques. By comparing the elastic deformation computed from continental water load estimates derived from the Gravity Recovery and Climate Experiment (GRACE), with three-dimensional surface deformation derived from GPS observations, there is clear potential to better understand global to regional hydrological processes, in addition to acquiring further insight into the systematic error contributions affecting each space geodetic technique. In this study, we compare elastic deformation derived from water load estimates taken from the CNES, CSR, GFZ and JPL time variable GRACE fields. We compare these surface displacements with those derived at a global network of GPS sites that have been homogeneously reprocessed in the GAMIT/GLOBK suite. We extend our comparison to include a series of different GPS solutions, with each solution only subtly different based on the methodology used to down weight the height component in realizing site coordinates on the terrestrial reference frame. Each of the GPS solutions incorporate modeling of atmospheric loading and utilization of the VMF1 and a priori zenith hydrostatic delays derived via ray tracing through ECMWF meteorological fields. The agreement between GRACE and GPS derived deformations is not limited to the vertical component, with excellent agreement in the horizontal component across areas where large hydrologic signals occur over broad spatial scales (with correlation in horizontal components as high as 0.9). Agreement is also observed at smaller scales, including across Europe. These comparisons assist in understanding the magnitude of current error contributions within both space geodetic techniques. With the emergence of homogeneously reprocessed GPS time series spanning the GRACE mission, this technique offers one possible means of validating the amplitude and phase of quasi-periodic signals present in GPS time series.

Ice cap melting and low viscosity crustal root explain narrow geodetic uplift of the Western Alps

NASA Astrophysics Data System (ADS)

Chery, Jean; Genti, Manon; Vernant, Philippe

2016-04-01

More than 10 years of geodetic measurements demonstrate an uplift rate of 1-3 mm/yr of the high topography region of the Western Alps. By contrast, no significant horizontal motion has been detected. Three uplift mechanisms have been proposed so far: (1) the isostatic response to denudation. However this process is responsible for only a fraction of the observed uplift and (2) the rebound induced by the Wurmian ice cap melting. This process leads to a broader uplifting region than the one evidenced by geodetic observations. (3) a deep source motion associated with slab motion or some deep isostatic unbalance. Using a numerical model accounting for crustal and mantle rheology of the Alps and its foreland, we model the response to Wurmian ice cap melting. We show that a crustal viscosity contrast between the foreland and the central part of the Alps, the later being weaker with a viscosity of 1021 Pa.s, is needed to produce a narrow uplift. The vertical rates are enhanced if the strong uppermost mantle beneath the Moho is interrupted across the Alps, therefore allowing a weak vertical rheological anomaly thanks to the continuity between the low viscosity parts of the crust and mantle. References: Champagnac, J.-D., F. Schlunegger, K. Norton, F. von Blanckenburg, L. M. Abbühl, and M. Schwab (2009), Erosion-driven uplift of the modern Central Alps, Tectonophysics, 474(1-2), 236-249. Vernant, P., F. Hivert, J. Chéry, P. Steer, R. Cattin, and A. Rigo (2013), Erosion-induced isostatic rebound triggers extension in low convergent mountain ranges, geology, 41(4), 467-470.

Analysis of ILRS Site Ties

NASA Astrophysics Data System (ADS)

Husson, V. S.; Long, J. L.; Pearlman, M.

2001-12-01

By the end of 2000, 94% of ILRS stations had completed station and site information forms (i.e. site logs). These forms contain six types of information. These six categories include site identifiers, contact information, approximate coordinates, system configuration history, system ranging capabilities, and local survey ties. The ILRS Central Bureau, in conjunction with the ILRS Networks and Engineering Working Group, has developed procedures to quality control site log contents. Part of this verification entails data integrity checks of local site ties and is the primary focus of this paper. Local survey ties are critical to the combination of space geodetic network coordinate solutions (i.e. GPS, SLR, VLBI, DORIS) of the International Terrestrial Reference Frame (ITRF). Approximately 90% of active SLR sites are collocated with at least one other space geodetic technique. The process used to verify these SLR ties, at collocated sites, is identical to the approach used in ITRF2000. Local vectors (X, Y, Z) from each ILRS site log are differenced from its corresponding ITRF2000 position vectors (i.e. no transformations). These X, Y, and Z deltas are converted into North, East, and Up. Any deltas, in any component, larger than 5 millimeter is flagged for investigation. In the absence of ITRF2000 SLR positions, CSR positions were used. To further enhance this comparison and to fill gaps in information, local ties contained in site logs from the other space geodetic services (i.e. IGS, IVS, IDS) were used in addition to ITRF2000 ties. Case studies of two collocated sites (McDonald/Ft. Davis and Hartebeeshtoek) will be explored in-depth. Recommendations on how local site surveys should be conducted and how this information should be managed will also be presented.

The most remote point method for the site selection of the future GGOS network

NASA Astrophysics Data System (ADS)

Hase, Hayo; Pedreros, Felipe

2014-10-01

The Global Geodetic Observing System (GGOS) proposes 30-40 geodetic observatories as global infrastructure for the most accurate reference frame to monitor the global change. To reach this goal, several geodetic observatories have upgrade plans to become GGOS stations. Most initiatives are driven by national institutions following national interests. From a global perspective, the site distribution remains incomplete and the initiatives to improve this are up until now insufficient. This article is a contribution to answer the question on where to install new GGOS observatories and where to add observation techniques to existing observatories. It introduces the iterative most remote point (MRP) method for filling in the largest gaps in existing technique-specific networks. A spherical version of the Voronoi-diagram is used to pick the optimal location of the new observatory, but practical concerns determine its realistic location. Once chosen, the process is iterated. A quality and a homogeneity parameter of global networks measure the progress of improving the homogeneity of the global site distribution. This method is applied to the global networks of VGOS, and VGOS co-located with SLR to derive some clues about where additional observatory sites or additional observation techniques at existing observatories will improve the GGOS network configuration. With only six additional VGOS-stations, the homogeneity of the global VGOS-network could be significantly improved by more than . From the presented analysis, 25 known or new co-located VGOS and SLR sites are proposed as the future GGOS backbone: Colombo, Easter Island, Fairbanks, Fortaleza, Galapagos, GGAO, Hartebeesthoek, Honiara, Ibadan, Kokee Park, La Plata, Mauritius, McMurdo, Metsahövi, Ny Alesund, Riyadh, San Diego, Santa Maria, Shanghai, Syowa, Tahiti, Tristan de Cunha, Warkworth, Wettzell, and Yarragadee.

Practical Considerations before Installing Ground-Based Geodetic Infrastructure for Integrated InSAR and cGNSS Monitoring of Vertical Land Motion.

PubMed

Parker, Amy L; Featherstone, Will E; Penna, Nigel T; Filmer, Mick S; Garthwaite, Matt C

2017-07-31

Continuously operating Global Navigation Satellite Systems (cGNSS) can be used to convert relative values of vertical land motion (VLM) derived from Interferometric Synthetic Aperture Radar (InSAR) to absolute values in a global or regional reference frame. Artificial trihedral corner reflectors (CRs) provide high-intensity and temporally stable reflections in SAR time series imagery, more so than naturally occurring permanent scatterers. Therefore, it is logical to co-locate CRs with cGNSS as ground-based geodetic infrastructure for the integrated monitoring of VLM. We describe the practical considerations for such co-locations using four case-study examples from Perth, Australia. After basic initial considerations such as land access, sky visibility and security, temporary test deployments of co-located CRs with cGNSS should be analysed together to determine site suitability. Signal to clutter ratios from SAR imagery are used to determine potential sites for placement of the CR. A significant concern is whether the co-location of a deliberately designed reflecting object generates unwanted multipath (reflected signals) in the cGNSS data. To mitigate against this, we located CRs >30 m from the cGNSS with no inter-visibility. Daily RMS values of the zero-difference ionosphere-free carrier-phase residuals, and ellipsoidal heights from static precise point positioning GNSS processing at each co-located site were then used to ascertain that the CR did not generate unwanted cGNSS multipath. These steps form a set of recommendations for the installation of such geodetic ground-infrastructure, which may be of use to others wishing to establish integrated InSAR-cGNSS monitoring of VLM elsewhere.

Practical Considerations before Installing Ground-Based Geodetic Infrastructure for Integrated InSAR and cGNSS Monitoring of Vertical Land Motion

PubMed Central

Featherstone, Will E.; Filmer, Mick S.

2017-01-01

Continuously operating Global Navigation Satellite Systems (cGNSS) can be used to convert relative values of vertical land motion (VLM) derived from Interferometric Synthetic Aperture Radar (InSAR) to absolute values in a global or regional reference frame. Artificial trihedral corner reflectors (CRs) provide high-intensity and temporally stable reflections in SAR time series imagery, more so than naturally occurring permanent scatterers. Therefore, it is logical to co-locate CRs with cGNSS as ground-based geodetic infrastructure for the integrated monitoring of VLM. We describe the practical considerations for such co-locations using four case-study examples from Perth, Australia. After basic initial considerations such as land access, sky visibility and security, temporary test deployments of co-located CRs with cGNSS should be analysed together to determine site suitability. Signal to clutter ratios from SAR imagery are used to determine potential sites for placement of the CR. A significant concern is whether the co-location of a deliberately designed reflecting object generates unwanted multipath (reflected signals) in the cGNSS data. To mitigate against this, we located CRs >30 m from the cGNSS with no inter-visibility. Daily RMS values of the zero-difference ionosphere-free carrier-phase residuals, and ellipsoidal heights from static precise point positioning GNSS processing at each co-located site were then used to ascertain that the CR did not generate unwanted cGNSS multipath. These steps form a set of recommendations for the installation of such geodetic ground-infrastructure, which may be of use to others wishing to establish integrated InSAR-cGNSS monitoring of VLM elsewhere. PMID:28758970

Remote sensing of the coastal ocean with standard geodetic GNSS-equipment

NASA Astrophysics Data System (ADS)

Löfgren, J. S.; Haas, R.; Larson, K. M.; Scherneck, H.-G.

2012-04-01

We use standard geodetic Global Navigation Satellite System (GNSS) equipment to perform remote sensing measurements of the coastal ocean. This is done by a so-called GNSS-based tide gauge that uses both direct GNSS-signals and GNSS-signals that are reflected off the sea surface. Our installation is located at the Onsala Space Observatory (OSO) at the west coast of Sweden and consists of a zenith-looking Right Hand Circularly Polarized (RHCP) and a nadir-looking Left Hand Circularly Polarized (LHCP) antenna. Each antenna is connected to a standard geodetic-type GNSS-receiver. We applied two different analysis strategies to our GNSS data set. The first strategy is based on a traditional geodetic differential analysis [Löfgren et al., 2011] and makes use of the data from both receivers; connected to the zenith and the nadir looking antennae. This approach results in local sea level that is automatically corrected for land motion, meaning that the GNSS-based tide gauge can provide reliable sea-level estimates even in tectonic active regions. The second strategy focuses on the Signal-to-Noise Ratio (SNR) recorded with the receiver connected to the zenith-looking antenna [Larson et al., 2011]. The SNR is affected by multipath originating from the sea surface reflections. Analysis of the SNR data allows to determine the distance between the antenna and the reflecting surface, and thus to measure sea surface height. Results from both analysis strategies are compared to independently observed sea-level data from two stilling-well gauges operated by the Swedish Meteorological and Hydrological Institute (SMHI), which lie in a distance of several km from OSO. The root-mean-square agreement between the different time series of several month's length is on the order of 5 cm and better. These results indicate the large potential for using coastal GNSS-sites for the monitoring of the coastal ocean.

Reconciling geodetic and geologic slip rates along the Carboneras fault in the Betics: work in progress

NASA Astrophysics Data System (ADS)

Khazaradze, Giorgi; López, Robert; Pallàs, Raimon; Bordonau, Jaume; Masana, Eulàlia

2017-04-01

As part of the recently initiated research project we are in the process of studying in detail the geodynamic behavior of the Carboneras fault in the SE Betics in Spain. Specifically, we plan to quantify the geodetic and geologic slip rates for the onland section of the fault, as well as getting some insight on the state of locking of the fault. As a result of our previous GPS observations, we have been able to illustrate the continuing tectonic activity of the Carboneras fault, expressed mainly as a left-lateral strike slip motion of 1.3±0.2 mm/yr (Echeverria et al., 2015). To reveal how the deformation is partitioned between different structures, 3 new continuous GPS points are being established along fault-perpendicular profile. In addition, since summer 2016, we have conducted surveys of the nearby CuaTeNeo and IGN Regente points. We have also established and measured several new geodetic points in the vicinity of the fault, with the aim of increasing the spatial coverage around it. The above-mentioned geodetic, short-term, slip rates are in surprisingly good agreement with the estimates of geologic slip rates based on paleoseismic studies, which indicate a minimum strike-slip rate of 1.31 mm/yr and a dip-slip rate of 0.05 mm/yr since 110.3 ka (Moreno et al. 2015). In order to increase the paleoseismic event database, 6 new sites have been identified along the fault, where further paleoseismic trenching surveys will be conducted within the coming years. These new data, combined with the findings of the recent geomorphological study of river offsets (Ferrater, 2016) and new GPS observations, should significantly improve the reliability of the existent deformation data and as a consequence, contribute to better understanding the seismic hazard posed by the Carbonears fault in the SE Betics. This work is funded by the project PREVENT (CGL2015-66263-R), financed by the Ministry of Economy, Industry and Competitiveness.

Comparison of hydrological signal in polar motion excitation with those based on the FGOALS-g2 climate model

NASA Astrophysics Data System (ADS)

Wińska, Małgorzata; Nastula, Jolanta; Salstein, David

2016-04-01

Our investigations are focused on the influence of different land hydrosphere surface parameters (precipitation, evaporation, total runoff, soil moisture, accumulated snow) on polar motion excitation functions at seasonal and nonseasonal timescales. Here these different variables are obtained from the Flexible Global Ocean-Atmosphere-Land System Model, Grid point Version 2 (FGOALS-g2), which is a climate model from the fifth phase of the Coupled Model Intercomparison Project (CMIP5); with CMIP5 being composed of separate component models of the atmosphere, ocean, sea ice, and land surface. In this study Terrestrial Water Storage TWS changes were determined as: differences between the precipitation, evaporation and total surface runoff content, and as the total soil moisture content being a sum of soil moisture and snowfall flux changes. We compare the model-based data with those from estimates of the Equivalent Water Thickness determined by GRACE satellite observations from the Center for Space Research (CSR). The transfer of angular momentum from global geophysical fluids to the solid Earth is described by the equatorial components χ1 and χ2 of the polar motion excitation functions. Observationally, these so-called geodetic excitation functions of polar motion can be determined on the basis of the equations of motion by using observed x, y components of the pole. The second-degree, first-order coefficients of the Earth gravity field are proportional to variations of the equatorial component χ1, χ2 of the series of the gravimetric excitation function of polar motion. This gravimetric function can be compared with the mass term of geodetic excitation of polar motion. Our analysis comprises (1) determinations and comparisons of regional patterns of hydrological excitation functions of polar motion, and (2) comparison of the global hydrological function determined from the FGOALS-g2 and GRACE data with a hydrological signal in the geodetic excitation function of polar motion, determined as a residual geodetic and atmospheric plus oceanic excitations.

Astro-geodetic platform for high accuracy geoid determinat ion

NASA Astrophysics Data System (ADS)

Bǎdescu, Octavian; Nedelcu, Dan Alin; Cǎlin, Alexandru; Dumitru, Paul Daniel; Cǎlin, Lavinia A.; Popescu, Marcel

The paper presents first technical realizations of a mobile platform for vertical deviation determination at a satisfactory precision and low cost. The conception of the platform was made in the framework of a project regarding CCD astro-geodetic vertical deviation for geoid determination or geoid modeling. The project with the acronym A-GEO represents a collaboration between Technical University of Civil Engineering Bucharest - Faculty of Geodesy, (TUCEB-FG), Astronomical Institute of the Romanian academy (AIRA), and a private partner GeoGIS Proiect S.R.L. The paper presents some hardware and software aspects regarding design, development, and automation of the platform, based on an electro-optical geodetic instrument, CCD observations and satellite time synchronization for astro-geodetic measurements.

Testing impact of the strategy of VLBI data analysis on the estimation of Earth Orientation Parameters and station coordinates

NASA Astrophysics Data System (ADS)

Wielgosz, Agata; Tercjak, Monika; Brzeziński, Aleksander

2016-06-01

Very Long Baseline Interferometry (VLBI) is the only space geodetic technique capable to realise the Celestial Reference Frame and tie it with the Terrestrial Reference Frame. It is also the only technique, which measures all the Earth Orientation Parameters (EOP) on a regular basis, thus the role of VLBI in determination of the universal time, nutation and polar motion and station coordinates is invaluable. Although geodetic VLBI has been providing observations for more than 30 years, there are no clear guidelines how to deal with the stations or baselines having significantly bigger post-fit residuals than the other ones. In our work we compare the common weighting strategy, using squared formal errors, with strategies involving exclusion or down-weighting of stations or baselines. For that purpose we apply the Vienna VLBI Software VieVS with necessary additional procedures. In our analysis we focus on statistical indicators that might be the criterion of excluding or down-weighting the inferior stations or baselines, as well as on the influence of adopted strategy on the EOP and station coordinates estimation. Our analysis shows that in about 99% of 24-hour VLBI sessions there is no need to exclude any data as the down-weighting procedure is sufficiently efficient. Although results presented here do not clearly indicate the best algorithm, they show strengths and weaknesses of the applied methods and point some limitations of automatic analysis of VLBI data. Moreover, it is also shown that the influence of the adopted weighting strategy is not always clearly reflected in the results of analysis.

LOD estimation from DORIS observations

NASA Astrophysics Data System (ADS)

Stepanek, Petr; Filler, Vratislav; Buday, Michal; Hugentobler, Urs

2016-04-01

The difference between astronomically determined duration of the day and 86400 seconds is called length of day (LOD). The LOD could be also understood as the daily rate of the difference between the Universal Time UT1, based on the Earth rotation, and the International Atomic Time TAI. The LOD is estimated using various Satellite Geodesy techniques as GNSS and SLR, while absolute UT1-TAI difference is precisely determined by VLBI. Contrary to other IERS techniques, the LOD estimation using DORIS (Doppler Orbitography and Radiopositioning Integrated by satellite) measurement did not achieve a geodetic accuracy in the past, reaching the precision at the level of several ms per day. However, recent experiments performed by IDS (International DORIS Service) analysis centre at Geodetic Observatory Pecny show a possibility to reach accuracy around 0.1 ms per day, when not adjusting the cross-track harmonics in the Satellite orbit model. The paper presents the long term LOD series determined from the DORIS solutions. The series are compared with C04 as the reference. Results are discussed in the context of accuracy achieved with GNSS and SLR. Besides the multi-satellite DORIS solutions, also the LOD series from the individual DORIS satellite solutions are analysed.

Puzzling features of western Mediterranean tectonics explained by slab dragging

NASA Astrophysics Data System (ADS)

Spakman, Wim; Chertova, Maria V.; van den Berg, Arie.; van Hinsbergen, Douwe J. J.

2018-03-01

The recent tectonic evolution of the western Mediterranean region is enigmatic. The causes for the closure of the Moroccan marine gateway prior to the Messinian salinity crisis, for the ongoing shortening of the Moroccan Rif and for the origin of the seismogenic Trans-Alboran shear zone and eastern Betics extension are unclear. These puzzling tectonic features cannot be fully explained by subduction of the east-dipping Gibraltar slab in the context of the regional relative plate motion frame. Here we use a combination of geological and geodetic data, as well as three-dimensional numerical modelling of subduction, to show that these unusual tectonic features could be the consequence of slab dragging—the north to north-eastward dragging of the Gibraltar slab by the absolute motion of the African Plate. Comparison of our model results to patterns of deformation in the western Mediterranean constrained by geological and geodetic data confirm that slab dragging provides a plausible mechanism for the observed deformation. Our results imply that the impact of absolute plate motion on subduction is identifiable from crustal observations. Identifying such signatures elsewhere may improve the mantle reference frame and provide insights on subduction evolution and associated crustal deformation.

Time series of low-degree geopotential coefficients from SLR data: estimation of Earth's figure axis and LOD variations

NASA Astrophysics Data System (ADS)

Luceri, V.; Sciarretta, C.; Bianco, G.

2012-12-01

The redistribution of the mass within the earth system induces changes in the Earth's gravity field. In particular, the second-degree geopotential coefficients reflect the behaviour of the Earth's inertia tensor of order 2, describing the main mass variations of our planet impacting the EOPs. Thanks to the long record of accurate and continuous laser ranging observations to Lageos and other geodetic satellites, SLR is the only current space technique capable to monitor the long time variability of the Earth's gravity field with adequate accuracy. Time series of low-degree geopotential coefficients are estimated with our analysis of SLR data (spanning more than 25 years) from several geodetic satellites in order to detect trends and periodic variations related to tidal effects and atmospheric/oceanic mass variations. This study is focused on the variations of the second-degree Stokes coefficients related to the Earth's principal figure axis and oblateness: C21, S21 and C20. On the other hand, surface mass load variations induce excitations in the EOPs that are proportional to the same second-degree coefficients. The time series of direct estimates of low degree geopotential and those derived from the EOP excitation functions are compared and presented together with their time and frequency analysis.

Effect of wet tropospheric path delays on estimation of geodetic baselines in the Gulf of California using the Global Positioning System

NASA Technical Reports Server (NTRS)

Tralli, David M.; Dixon, Timothy H.; Stephens, Scott A.

1988-01-01

Surface Meteorological (SM) and Water Vapor Radiometer (WVR) measurements are used to provide an independent means of calibrating the GPS signal for the wet tropospheric path delay in a study of geodetic baseline measurements in the Gulf of California using GPS in which high tropospheric water vapor content yielded wet path delays in excess of 20 cm at zenith. Residual wet delays at zenith are estimated as constants and as first-order exponentially correlated stochastic processes. Calibration with WVR data is found to yield the best repeatabilities, with improved results possible if combined carrier phase and pseudorange data are used. Although SM measurements can introduce significant errors in baseline solutions if used with a simple atmospheric model and estimation of residual zenith delays as constants, SM calibration and stochastic estimation for residual zenith wet delays may be adequate for precise estimation of GPS baselines. For dry locations, WVRs may not be required to accurately model tropospheric effects on GPS baselines.

Measurement of Dam Deformations: Case Study of Obruk Dam (Turkey)

NASA Astrophysics Data System (ADS)

Gulal, V. Engin; Alkan, R. Metin; Alkan, M. Nurullah; İlci, Veli; Ozulu, I. Murat; Tombus, F. Engin; Kose, Zafer; Aladogan, Kayhan; Sahin, Murat; Yavasoglu, Hakan; Oku, Guldane

2016-04-01

In the literature, there is information regarding the first deformation and displacement measurements in dams that were conducted in 1920s Switzerland. Todays, deformation measurements in the dams have gained very different functions with improvements in both measurement equipment and evaluation of measurements. Deformation measurements and analysis are among the main topics studied by scientists who take interest in the engineering measurement sciences. The Working group of Deformation Measurements and Analysis, which was established under the International Federation of Surveyors (FIG), carries out its studies and activities with regard to this subject. At the end of the 1970s, the subject of the determination of fixed points in the deformation monitoring network was one of the main subjects extensively studied. Many theories arose from this inquiry, as different institutes came to differing conclusions. In 1978, a special commission with representatives of universities has been established within the FIG 6.1 working group; this commission worked on the issue of determining a general approach to geometric deformation analysis. The results gleaned from the commission were discussed at symposiums organized by the FIG. In accordance with these studies, scientists interested in the subject have begun to work on models that investigate cause and effect relations between the effects that cause deformation and deformation. As of the scientist who interest with the issue focused on different deformation methods, another special commission was established within the FIG engineering measurements commission in order to classify deformation models and study terminology. After studying this material for a long time, the official commission report was published in 2001. In this prepared report, studies have been carried out by considering the FIG Engineering Surveying Commission's report entitled, 'MODELS AND TERMINOLOGY FOR THE ANALYSIS OF GEODETIC MONITORING OBSERVATIONS'. In October of 2015, geodetic deformation measurements were conducted by considering FIG reports related to deformation measurements and German DIN 18710 Engineering Measurements norms in the Çorum province of Turkey. The main purpose of the study is to determine optimum measurement and evaluation methods that will be used to specify movements in the horizontal and vertical directions for the fill dam. For this purpose; • In reference networks consisting of 8 points, measurements were performed by using long-term dual-frequency GNSS receivers for duration of 8 hours. • GNSS measurements were conducted in varying times between 30 minutes and 120 minutes at the 44 units object points on the body of the dam. • Two repetitive measurements of real time kinematic (RTK) GNSS were conducted at the object points on dam. • Geometric leveling measurements were performed between reference and object points. • Trigonometric leveling measurements were performed between reference and object points. • Polar measurements were performed between references and object points. GNSS measurements performed at reference points of the monitoring network for 8 hours have been evaluated by using GAMIT software in accordance with the IGS points in the region. In this manner, regional and local movements in the network can be determined. It is aimed to determine measurement period which will provide 1-2mm accuracy that expected in local GNSS network by evaluating GNSS measurements performed on body of dam. Results will be compared by offsetting GNSS and terrestrial measurements. This study will investigate whether or not there is increased accuracy provided by GNSS measurements carried out among reference points without the possibility of vision.

5 CFR 831.301 - Military service.

Code of Federal Regulations, 2013 CFR

2013-01-01

... Administration (formerly Coast and Geodetic Survey and Environmental Science Services Administration), performed... (formerly Coast and Geodetic Survey and Environmental Science Services Administration), performed before the...

5 CFR 831.301 - Military service.

Code of Federal Regulations, 2014 CFR

2014-01-01

... Administration (formerly Coast and Geodetic Survey and Environmental Science Services Administration), performed... (formerly Coast and Geodetic Survey and Environmental Science Services Administration), performed before the...

5 CFR 831.301 - Military service.

Code of Federal Regulations, 2012 CFR

2012-01-01

... Administration (formerly Coast and Geodetic Survey and Environmental Science Services Administration), performed... (formerly Coast and Geodetic Survey and Environmental Science Services Administration), performed before the...

5 CFR 831.301 - Military service.

Code of Federal Regulations, 2011 CFR

2011-01-01

... Administration (formerly Coast and Geodetic Survey and Environmental Science Services Administration), performed... (formerly Coast and Geodetic Survey and Environmental Science Services Administration), performed before the...

Impact of Glacial Isostatic Adjustment on North America Plate Specific Terrestrial Reference Frame

NASA Astrophysics Data System (ADS)

Herring, Thomas; Melbourne, Tim; Murray, Mark; Floyd, Mike; Szeliga, Walter; King, Robert; Phillips, David; Puskas, Christine

2017-04-01

We examine the impact of incorporating glacial isostatic adjustment (GIA) models in determining the Euler poles for plate specific terrestrial reference frames. We will specifically examine the impact of GIA models on the realization of a North America Reference frame. We use a combination of the velocity fields determined by the Geodesy Advancing Geosciences and EarthScope (GAGE) Facility which analyzes GPS data from the Plate Boundary Observatory (PBO) and other geodetic quality GPS sites in North America, and from the ITRF2014 re-analysis. Initial analysis of the GAGE velocity field shows reduced root-mean-square (RMS) scatter of velocity estimate residuals when the North America Euler pole is estimated including the ICE-6G GIA mode. The reduction in the north-south direction is from 0.69 mm/yr to 0.52 mm/yr, in the east-west direction from 0.34 mm/yr to 0.30 mm/yr and in height from 0.93 mm/yr to 0.72 mm/yr. The reduction in the height RMS is not surprising since the contemporary geodetic height velocity estimates are used in the developing the ICE-6G model. Contemporary horizontal motions are not used the GIA model development, and the reduction in horizontal RMS provides a partial validation of the model. There is no reduction in the horizontal velocity residual when the ICE-5G model is used. Although removing the ICE-6G model before fitting an Euler pole for the North American plate reduces the RMS of the residuals, the pattern of residuals is still systematic suggesting possibly that a spherically symmetric viscosity model might not be adequate for accurate modeling of the horizontal motions associated with GIA in North America. This presentation in focus on the prospects and impacts of incorporating GIA models in plate-specific Euler poles with emphasis on North America.

Geodetic glacier mass balances at the push of a button: application of Structure from Motion technology on aerial images in mountain regions

NASA Astrophysics Data System (ADS)

Bolch, T.; Mölg, N.

2017-12-01

The application of Structure-from-Motion (SfM) to generate digital terrain models (DTMs) derived out of images from various kinds of sources has strongly increased in recent years. The major reason for this is its easy-to-use handling in comparison to conventional photogrammetry. In glaciology, DTMs are intensely used, among others, to calculate the geodetic mass balances. Few studies investigated the application of SfM to aerial images in mountainous terrain and results look promising. We tested this technique in a demanding environment in the Swiss Alps including very steep slopes, snow and ice covered terrain. SfM (using the commercial software packages of Agisoft Photoscan and Pix4DMapper) and conventional photogrammetry (ERDAS Photogrammetry) were applied on archival aerial images for nine dates between 1946 and 2005 the results were compared regarding bundle adjustment and final DTM quality. The overall precision of the DTMs could be defined with the use of a modern, high-quality reference DTM by Swisstopo. Results suggest a high performance of SfM to produce DTMs of similar quality as conventional photogrammetry. A ground resolution of high quality (little noise and artefacts) can be up to 50% higher, with 3-6 times less user effort. However, the controls on the commercial SfM software packages are limited in comparison to ERDAS Photogrammetry. SfM performs less reliably when few images with little overlap are processed. Overall, the uncertainty of DTMs from the different software are comparable and mostly within the uncertainty range of the reference DTM, making them highly valuable for glaciological purposes. Even though SfM facilitates the largely automated production of high quality DTMs, the user is not exempt from a thorough quality check, at best with reference data where available.

GNSS-SLR satellite co-location for the estimate of local ties

NASA Astrophysics Data System (ADS)

Bruni, Sara; Zerbini, Susanna; Errico, Maddalena; Santi, Efisio

2013-04-01

The current realization of the International Terrestrial Reference Frame (ITRF) is based on four different space-geodetic techniques, so that the benefits brought by each observing system to the definition of the frame can compensate for the drawbacks of the others and technique-specific systematic errors might be identified. The strategy used to combine the observations from the different techniques is then of prominent importance for the realization of a precise and stable reference frame. This study concentrates, in particular, on the combination of Satellite Laser Ranging (SLR) and Global Navigation Satellite System (GNSS) observations by exploiting satellite co-locations. This innovative approach is based on the fact that laser tracking of GNSS satellites, carrying on board laser reflector arrays, allows for the combination of optical and microwave signals in the determination of the spacecraft orbit. Besides, the use of satellite co-locations differs quite significantly from the traditional combination method in which each single technique solution is carried out autonomously and is interrelated in a second step. One of the benefits of the approach adopted in this study is that it allows for an independent validation of the local tie, i.e. of the vector connecting the SLR and GNSS reference points in a multi-techniques station. Typically, local ties are expressed by a single value, measured with ground-based geodetic techniques and taken as constant. In principle, however, local ties might show time variations likely caused by the different monumentation characteristics of the GNSS antennas with respect to those of a SLR system. This study evaluates the possibility of using the satellite co-location approach to generate local-ties time series by means of observations available for a selected network of ILRS stations. The data analyzed in this study were acquired as part of the NASA's Earth Science Data Systems and are archived and distributed by the Crustal Dynamics Data Information System (CDDIS).

Implementation of CGPS at Estartit, Ibiza and Barcelona harbours for sea level monitoring

NASA Astrophysics Data System (ADS)

Martinez-Benjamin, J. J.; Ortiz Castellon, M.; Martinez-Garcia, M.; Perez, B.; Bosch, E.; Termens, A.; Martinez de Oses, X.

2009-12-01

The determination of global and regional mean sea level variations with accura-cies better than 1 mm/yr is a critical problem, the resolution of which is central to the current debate on climate change and its impact on the environment. Highly accurate time series from both satellite altimetry and tide gauges are needed. Measuring the sea surface height with in-situ tide gauges and GPS receivers pro-vides an efficient way to control the long term stability of the radar altimeters and other applications as the vertical land motion and studies of sea level change. L’Estartit tide gauge is a classical floating tide gauge set up in l’Estartit harbour (NE Spain) in 1990. Data are taken in graphics registers from which each two hours the mean value is recorded in an electronic support and delivered to the Permanent Service for Mean Sea level (PSMSL). Periodic surveying campaigns along the year are carried out for monitoring possible vertical movement of the geodetic benchmark adjacent to the tide gauge. Puertos del Estado (Spanish Harbours) installed the tide gauge station at Ibiza har-bour in January 2003 and a near GPS reference station. The station belongs to the REDMAR network, composed at this moment by 21 stations distributed along the whole Spanish waters, including also the Canary islands (http://www.puertos.es). The tide gauge also belongs to the ESEAS (European Sea Level) network. A description of the actual infrastructure at Ibiza, Barcelona and l’Estartit har-bours is presented.The main objective is the implementation of these harbours as a precise geodetic areas for sea level monitoring and altimeter calibration. Actually is a CGPS with a radar tide gauge from Puertos del Estado and a GPS belonging to Puerto de Barcelona. A precise levelling has been made by the Cartographic Insti-tute of Catalonia, ICC. The instrumentation of sea level measurements has been improved by providing the Barcelona site with a radar tide gauge Datamar 3000C device and a Thales Navigation Internet-Enabled GPS Continuous Geodetic Ref-erence Station (iCGRS) with a choke ring antenna, located at the EPSEB of the Technical University of Catalonia, UPC. It is intended that the overall system will constitute a CGPS Station of the ESEAS and TIGA networks.

Near real-time monitoring of UT1 with geodetic VLBI

NASA Astrophysics Data System (ADS)

Haas, R.; Hobiger, T.; Sekido, M.; Koyama, Y.; Kondo, T.; Takiguchi, H.; Kurihara, S.; Kokado, K.; Tanimoto, D.; Nozawa, K.; Wagner, J.; Ritakari, J.; Mujunen, A.; Uunila, M.

2011-07-01

Geodetic VLBI is unique among the geodetic space techniques since it provides a direct connection between the international terrestrial reference frame and the international celestial reference frame. The Earth rotation angle, usually expressed as UT1, can be determined directly from geodetic VLBI observations. Accurate information about the Earth rotation angle is necessary and important for navigation purposes, in particular for satellite missions and space navigation. A near real-time knowledge of UT1 with high accuracy is therefore highly desirable. During the last few years the advances in data transfer over high-speed optical fibre lines have made it possible to electronically send the observational data from a VLBI radio telescope on one side of the globe in real-time to a VLBI correlator on the other side of the globe. Thus, data of two telescopes on opposite sides of the Earth, forming a long east-west oriented baseline, can be correlated in near real-time. Furthermore, advances in automated processing of the correlation results have made it possible to derive the Earth rotation angle UT1 in near real-time. Since 2007, the VLBI research groups in Sweden, Finland and Japan collaborate to derive UT1 in near real-time. Several dedicated so-called ultra-rapid UT1-sessions with 1-2 hours duration were performed. It was shown that final UT1-results can be derived within a few minutes after the end of an observing session (Sekido et al., 2008; Matsuzaka et al., 2008). The quality of the UT1-results is on the same level as the so-called IERS rapid solutions, but with a much lower latency (Haas et al., 2010). Recently, the ultra-rapid approach has been applied to standard 24 hour long VLBI observing sessions that are organized by the International VLBI Service for Geodesy and Astrometry (IVS). The long east-west baseline between Onsala (Sweden) and Tsukuba (Japan) is used to derive UT1 with a sliding window approach already during the ongoing IVS-session. The data processing and analysis is performed with a fully automated analysis software (Hobiger et al., 2010). We present results from the ultra-rapid UT1-sessions, both, from dedicated one-baseline sessions, as well from 24-hour ultra-rapid sessions during standard IVS-experiments. The near real-time UT1 results are compared to corresponding post-processing results, and results from independent analyses and techniques. Refrences: Sekido et al. (2008) Ultra-rapid UT1 measurements by e-VLBI, Earth Planets and Space, Vol. 60, 865-870. Matsuzaka et al. (2008) Ultra Rapid UT1 Experiment with e-VLBI, In: Proc. 5th IVS General Meeting, 68-71. Haas R et al. (2010) Ultra-Rapid DUT1-Observations with E-VLBI. Artificial Satellites, 45, 75-79. Hobiger et al. (2010) Fully automated VLBI analysis with c5++ for ultra-rapid determination of UT1, Earth Planets Space.

The Determination of Earth Orientation by VLBI and GNSS: Principles and Results

NASA Astrophysics Data System (ADS)

Capitaine, Nicole

2017-10-01

The Earth Orientation Parameters (EOP) connect the International Terrestrial Reference System (ITRS) to the Geocentric Celestial Reference System (GCRS). These parameters, i.e., Universal Time, UT1, and pole coordinates in the ITRS and in the GCRS, describe the irregularities of the Earth's rotation. They are mainly determined by two modern astro-geodetic techniques, VLBI (Very Long Baseline Radio Interferometry) on extragalactic radio sources, which is used to realize and maintain the International Celestial Reference System (ICRS), and Global Navigation Satellite System (GNSS), especially GPS (Global Positioning System), which has an important contribution to the realization of the ITRS. The aim of this presentation is twofold: to present the modern bases for the consider- ation of Earth orientation and to discuss how the principles of VLBI and GPS give access to the measure of different components of the EOP variations, especially UT1. The accuracy that can be achieved is based on the improved concepts, definitions, and models that have been adopted by IAU/IUGG resolutions on reference systems and Earth's rotation, as well as on the refined strategy of the observations.

Expected Improvements in VLBI Measurements of the Earth's Orientation

NASA Technical Reports Server (NTRS)

Ma, Chopo

2003-01-01

Measurements of the Earth s orientation since the 1970s using space geodetic techniques have provided a continually expanding and improving data set for studies of the Earth s structure and the distribution of mass and angular momentum. The accuracy of current one-day measurements is better than 100 microarcsec for the motion of the pole with respect to the celestial and terrestrial reference frames and better than 3 microsec for the rotation around the pole. VLBI uniquely provides the three Earth orientation parameters (nutation and UTI) that relate the Earth to the extragalactic celestial reference frame. The accuracy and resolution of the VLBI Earth orientation time series can be expected to improve substantially in the near future because of refinements in the realization of the celestial reference frame, improved modeling of the troposphere and non-linear station motions, larger observing networks, optimized scheduling, deployment of disk-based Mark V recorders, full use of Mark IV capabilities, and e-VLBI. More radical future technical developments will be discussed.

First results of the Nordic and Baltic GNSS Analysis Centre

NASA Astrophysics Data System (ADS)

Lahtinen, Sonja; Pasi, Häkli; Jivall, Lotti; Kempe, Christina; Kollo, Karin; Kosenko, Ksenija; Pihlak, Priit; Prizginiene, Dalia; Tangen, Oddvar; Weber, Mette; Paršeliūnas, Eimuntas; Baniulis, Rimvydas; Galinauskas, Karolis

2018-03-01

The Nordic Geodetic Commission (NKG) has launched a joint NKG GNSS Analysis Centre that aims to routinely produce high qualityGNSS solutions for the common needs of the NKG and the Nordic and Baltic countries. A consistent and densified velocity field is needed for the constraining of the gla-cial isostatic adjustment (GIA) modelling that is a key component of maintaining the national reference frame realisations in the area. We described the methods of the NKG GNSS Analysis Centre including the defined processing setup for the local analysis centres (LAC) and for the combination centres.We analysed the results of the first 2.5 years (2014.5-2016). The results showed that different subnets were consistent with the combined solution within 1-2 mm level. We observed the so called network effect affecting our reference frame alignment. However, the accuracy of the reference frame alignment was on a few millimetre level in the area of the main interest (Nordic and Baltic Countries). TheNKGGNSS AC was declared fully operational in April 2017.

Marine geodetic control for geoidal profile mapping across the Puerto Rican Trench

NASA Technical Reports Server (NTRS)

Fubara, D. M.; Mourad, A. G.

1975-01-01

A marine geodetic control was established for the northern end of the geoidal profile mapping experiment across the Puerto Rican Trench by determining the three-dimensional geodetic coordinates of the four ocean-bottom mounted acoustic transponders. The data reduction techniques employed and analytical processes involved are described. Before applying the analytical techniques to the field data, they were tested with simulated data and proven to be effective in theory as well as in practice.

Global Geodesy Using GPS Without Fiducial Sites

NASA Technical Reports Server (NTRS)

Heflin, Michael B.; Blewitt, Geoffrey

1994-01-01

Global Positioning System, GPS, used to make global geodetic measurements without use of fiducial site coordinates. Baseline lengths and geocentric radii for each site determined without having to fix any site coordinates. Given n globally distributed sites, n baseline lengths and n geocentric radii form polyhedron with each site at vertex and with geocenter at intersection of all radii. Geodetic information derived from structure of polyhedron and its change with time. Approach applied to any global geodetic technique.

Large Scale Deformation of the Western U.S. Cordillera

NASA Technical Reports Server (NTRS)

Bennett, Richard A.

2002-01-01

Over the past couple of years, with support from NASA, we used a large collection of data from GPS, VLBI, SLR, and DORIS networks which span the Western U.S. Cordillera (WUSC) to precisely quantify present-day large-scale crustal deformations in a single uniform reference frame. Our work was roughly divided into an analysis of these space geodetic observations to infer the deformation field across and within the entire plate boundary zone, and an investigation of the implications of this deformation field regarding plate boundary dynamics. Following the determination of the first generation WUSC velocity solution, we placed high priority on the dissemination of the velocity estimates. With in-kind support from the Smithsonian Astrophysical Observatory, we constructed a web-site which allows anyone to access the data, and to determine their own velocity reference frame.

Large Scale Deformation of the Western U.S. Cordillera

NASA Technical Reports Server (NTRS)

Bennett, Richard A.

2002-01-01

Over the past couple of years, with support from NASA, we used a large collection of data from GPS, VLBI, SLR, and DORIS networks which span the Westem U.S. Cordillera (WUSC) to precisely quantify present-day large-scale crustal deformations in a single uniform reference frame. Our work was roughly divided into an analysis of these space geodetic observations to infer the deformation field across and within the entire plate boundary zone, and an investigation of the implications of this deformation field regarding plate boundary dynamics. Following the determination of the first generation WUSC velocity solution, we placed high priority on the dissemination of the velocity estimates. With in-kind support from the Smithsonian Astrophysical Observatory, we constructed a web-site which allows anyone to access the data, and to determine their own velocity reference frame.

Dislocation model for aseismic fault slip in the transverse ranges of Southern California

NASA Technical Reports Server (NTRS)

Cheng, A.; Jackson, D. D.; Matsuura, M.

1985-01-01

Geodetic data at a plate boundary can reveal the pattern of subsurface displacements that accompany plate motion. These displacements are modelled as the sum of rigid block motion and the elastic effects of frictional interaction between blocks. The frictional interactions are represented by uniform dislocation on each of several rectangular fault patches. The block velocities and fault parameters are then estimated from geodetic data. Bayesian inversion procedure employs prior estimates based on geological and seismological data. The method is applied to the Transverse Ranges, using prior geological and seismological data and geodetic data from the USGS trilateration networks. Geodetic data imply a displacement rate of about 20 mm/yr across the San Andreas Fault, while the geologic estimates exceed 30 mm/yr. The prior model and the final estimates both imply about 10 mm/yr crustal shortening normal to the trend of the San Andreas Fault. Aseismic fault motion is a major contributor to plate motion. The geodetic data can help to identify faults that are suffering rapid stress accumulation; in the Transverse Ranges those faults are the San Andreas and the Santa Susana.

A new unified approach to determine geocentre motion using space geodetic and GRACE gravity data

NASA Astrophysics Data System (ADS)

Wu, Xiaoping; Kusche, Jürgen; Landerer, Felix W.

2017-06-01

Geocentre motion between the centre-of-mass of the Earth system and the centre-of-figure of the solid Earth surface is a critical signature of degree-1 components of global surface mass transport process that includes sea level rise, ice mass imbalance and continental-scale hydrological change. To complement GRACE data for complete-spectrum mass transport monitoring, geocentre motion needs to be measured accurately. However, current methods of geodetic translational approach and global inversions of various combinations of geodetic deformation, simulated ocean bottom pressure and GRACE data contain substantial biases and systematic errors. Here, we demonstrate a new and more reliable unified approach to geocentre motion determination using a recently formed satellite laser ranging based geocentric displacement time-series of an expanded geodetic network of all four space geodetic techniques and GRACE gravity data. The unified approach exploits both translational and deformational signatures of the displacement data, while the addition of GRACE's near global coverage significantly reduces biases found in the translational approach and spectral aliasing errors in the inversion.

EGNOS Tran Solutions for River Information Services

NASA Astrophysics Data System (ADS)

Jandrisits, Marko; de Mateo Garcia, Juan Carlos; Abwerzger, Gunther

2005-03-01

Within the ESA Advanced Research Telecommunications program ARTES-5, the project GALEWAT (Galileo and EGNOS for Waterway Transport) aims at introducing EGNOS into River Information Systems (RIS) through the Automatic Identification System (AIS).The GALEWAT project is carried out by a consortium composed by via donau (Austria), responsible for the overall project coordination and the operations in Vienna; Kongsberg Seatex AS (Norway), mainly responsible for the ship and shore equipment provision and installation; TeleConsult Austria (Austria), responsible for the geodetic reference system and performance evaluation of the tests, and INOV (Portugal), responsible for software development, i.e. performance monitor software and web interface for the external segment.During the definition phase, the system architecture and user equipment have been defined, in line with standards and international recommendations. The activity is currently in its implementation phase. Three demo sites are targeted: Vienna (Austria), Lisbon (Portugal) and Constanta (Romania) in order to illustrate the system in different environments (river navigation, harbour approach, open sea). The objective of this paper is to present the results of the tests and demo trials that took place based on the EGNOS signals during the last quarter of 2004 in Vienna.

Mobile radio interferometric geodetic systems

NASA Technical Reports Server (NTRS)

Macdoran, P. F.; Niell, A. E.; Ong, K. M.; Resch, G. M.; Morabito, D. D.; Claflin, E. S.; Lockhart, T. G.

1978-01-01

Operation of the Astronomical Radio Interferometric Earth Surveying (ARIES) in a proof of concept mode is discussed. Accuracy demonstrations over a short baseline, a 180 km baseline, and a 380 km baseline are documented. Use of ARIES in the Sea Slope Experiment of the National Geodetic Survey to study the apparent differences between oceanographic and geodetic leveling determinations of the sea surface along the Pacific Coast is described. Intergration of the NAVSTAR Global Positioning System and a concept called SERIES (Satellite Emission Radio Interferometric Earth Surveying) is briefly reviewed.

Global satellite triangulation and trilateration for the National Geodetic Satellite Program (solutions WN 12, 14 and 16). [study and analysis of data from artificial satellites

NASA Technical Reports Server (NTRS)

Mueller, I. I.; Kumar, M.; Reilly, J. P.; Saxena, N.; Soler, T.

1973-01-01

A multi-year study and analysis of data from satellites launched specifically for geodetic purposes and from other satellites useful in geodetic studies was conducted. The program of work included theoretical studies and analysis for the geometric determination of station positions derived from photographic observations of both passive and active satellites and from range observations. The current status of data analysis, processing and results are examined.

Active NE-SW Compressional Strain Within the Arabian Plate

NASA Astrophysics Data System (ADS)

Floyd, M. A.; ArRajehi, A.; King, R. W.; McClusky, S.; Reilinger, R. E.; Douad, M.; Sholan, J.; Bou-Rabee, F.

2012-12-01

Motion of the Arabian plate with respect to Eurasia has been remarkably steady over more than 25 Myr as revealed by comparison of geodetic and plate tectonic reconstructions (e.g., McQuarrie et al., 2003, GRL; ArRajehi et al., 2010, Tectonics). While internal plate deformation is small in comparison to the rate of Arabia-Eurasia convergence, the improved resolution of GPS observations indicate ~ NE-SW compressional strain that appears to affect much of the plate south of latitude ~ 30°N. Seven ~ NE-SW oriented inter-station baselines all indicated shortening at rates in the range of 0.5-2 mm/yr, for the most part with 1-sigma velocity uncertainties < 0.4 mm/yr. Plate-scale strain rates exceed 2×10-9/yr. The spatial distribution of strain can not be resolved from the sparse available data, but strain appears to extend at least to Riyadh, KSA, ~ 600 km west of the Zagros Fold and Thrust Belt that forms the eastern, collisional boundary of the Arabian plate with Eurasia (Iran). Geodetic velocities in the plate tectonic reference frame for Arabia, derived from magnetic anomalies in the Red Sea (Chu and Gordon, 1998, GJI), show no significant E-W motion for GPS stations located along the Red Sea coast (i.e., geodetic and plate tectonic spreading rates across the Red Sea agree within their resolution), in contrast to sites in the plate interior and along the east side of the plate that indicate east-directed motions. In addition, NE-SW contraction is roughly normal to ~ N-S striking major structural folds in the sedimentary rocks within the Arabian Platform. These relationships suggest that geodetically observed contraction has characterized the plate for at least the past ~ 3 Myr. Broad-scale contraction of the Arabian plate seems intuitively reasonable given that the east and north sides of the plate are dominated by active continental collision (Zagros, E Turkey/Caucasus) while the west and south sides are bordered by mid-ocean ridge spreading (Red Sea and Gulf of Aden). While the dynamic processes responsible for the observed strain remain speculative, we are investigating models involving long-range effects of the Arabia-Eurasia collision, ridge-push along the Red Sea and Gulf of Aden, and gravitational spreading of the higher elevation Arabian Shield towards the lower elevation platform.

Challenges of Replacing NAD 83, NAVD 88, and IGLD 85: Exploiting the Characteristics of 3-D Digital Spatial Data

NASA Astrophysics Data System (ADS)

Burkholder, E. F.

2016-12-01

One way to address challenges of replacing NAD 83, NGVD 88 and IGLD 85 is to exploit the characteristics of 3-D digital spatial data. This presentation describes the 3-D global spatial data model (GSDM) which accommodates rigorous scientific endeavors while simultaneously supporting a local flat-earth view of the world. The GSDM is based upon the assumption of a single origin for 3-D spatial data and uses rules of solid geometry for manipulating spatial data components. This approach exploits the characteristics of 3-D digital spatial data and preserves the quality of geodetic measurements while providing spatial data users the option of working with rectangular flat-earth components and computational procedures for local applications. This flexibility is provided by using a bidirectional rotation matrix that allows any 3-D vector to be used in a geodetic reference frame for high-end applications and/or the local frame for flat-earth users. The GSDM is viewed as compatible with the datum products being developed by NGS and provides for unambiguous exchange of 3-D spatial data between disciplines and users worldwide. Three geometrical models will be summarized - geodetic, map projection, and 3-D. Geodetic computations are performed on an ellipsoid and are without equal in providing rigorous coordinate values for latitude, longitude, and ellipsoid height. Members of the user community have, for generations, sought ways to "flatten the world" to accommodate a flat-earth view and to avoid the complexity of working on an ellipsoid. Map projections have been defined for a wide variety of applications and remain very useful for visualizing spatial data. But, the GSDM supports computations based on 3-D components that have not been distorted in a 2-D map projection. The GSDM does not invalidate either geodesy or cartographic computational processes but provides a geometrically correct view of any point cloud from any point selected by the user. As a bonus, the GSDM also defines spatial data accuracy and includes procedures for establishing, tracking and using spatial data accuracy - increasingly important in many applications but especially relevant given development of procedures for tracking drones (primarily absolute) and intelligent vehicles (primarily relative).

Detailed comparison of the geodetic and direct glaciological mass balances on an annual time scale at Hintereisferner, Austria

NASA Astrophysics Data System (ADS)

Klug, Christoph; Bollmann, Erik; Galos, Stephan; Kaser, Georg; Prinz, Rainer; Rieg, Lorenzo; Sailer, Rudolf

2016-04-01

The quantification of glacier mass changes is fundamental for glacier monitoring and provides important information for climate change assessments, hydrological applications and sea-level changes. On Alpine glaciers two methods of measuring glacier mass changes are widely applied: the direct glaciological method and the geodetic method. Over the last decades several studies compared the mass balance estimates obtained by both methods to identify and correct stochastic and systematic errors. In almost all of these studies, the time span for comparison between the two methods is about one decade or longer. On Hintereisferner (HEF; Ötztal Alps, Austria) mass balance measurements were initiated in the glaciological year 1952/53, resulting in a consistent mass balance data set with an estimated accuracy of ±0.2 m w.e. a-1. Furthermore, 11 airborne laser scanning (ALS) campaigns were conducted between 2001 and 2011 at HEF, all consistent in accuracy as well as in precision (± 0.04 to 0.10 m for slopes ≤ 50°). This is a world-wide unique ALS dataset of a glacierized alpine catchment. Flight campaigns were performed close to the end of the hydrological year (30th September). Resulting data provide high quality topographic information to derive glacier mass changes by applying the geodetic method. On sub-decadal time-scales such method comparisons are rare, or reveal unexplainable large discrepancies between both mass balance methods. In this study we estimate stochastic and systematic uncertainties of the ALS data for processing volume changes, and quantify methodological differences, such as density assumptions, unequal measurement dates, crevasses and glacier dynamics. Hence, we present a method to compare direct glaciological and geodetic mass balances on an annual basis. In a first step, we calculate the annual geodetic mass balance of HEF between 2001 and 2011, resulting in a thickness change map of the glacier. In a second step, the snow cover, which has eventually built up before the ALS acquisition, is corrected. As snow cover biases are particular uncertain, a statistical approach has been applied to assess combined DTM errors by using the population of DTM differences over stable terrain. This method incorporates all known and unknown error sources from the surface difference in stable areas and uses its median thickness for correction in all altitudinal belts. In addition, intensity data of the ALS surveys are used to classify the optical surface properties into ice and firn zones. The resulting grids with according conversion factors (900 and 700 kg/m³ for ice and firn, respectively) are combined to calculate mass changes. In a last step, the survey dates are adjusted, using numerous field observations. On an annual time scale, the geodetic mass balances of HEF corrected using this approach, correlate well with the results from the homogenized direct glaciological method. Significant deviations occur in years with few measurements in the uppermost areas applying the direct glaciological method, due to strong melt in areas not equipped with ablation stakes (cf. Figure 2 for 2002/03) or inaccessibility due to weather conditions. On the basis of these results, the conventional error risk (e.g. confidence levels), was adopted in order to test the null hypothesis and to check if unexplained discrepancies suggest reanalyses of glaciological mass balances. Regarding the cumulative mass balance, the deviations between the two methods tend to become smaller the longer the period of comparison extends. Averaged between 2001 and 2011 the largest sources of differences are snow cover and density assumptions having high uncertainties in their estimates and/or leading to higher error ranges in the geodetic mass balances. Some errors were found to have a minor impact and are not treated explicitly, such as uncertainties in different glacier outlines used in both methods or the influence of snow covered and snow free crevasses in successive years on the geodetic mass balance.

VANDENBERG AFB, CALIF. - In the NASA spacecraft processing facility on North Vandenberg Air Force Base, a balloon gently lifts the solar array panel to be installed on the Gravity Probe B spacecraft. Installing each array is a 3-day process and includes a functional deployment test. The Gravity Probe B mission is a relativity experiment developed by NASA’s Marshall Space Flight Center, Stanford University and Lockheed Martin. The spacecraft will test two extraordinary predictions of Albert Einstein’s general theory of relativity that he advanced in 1916: the geodetic effect (how space and time are warped by the presence of the Earth) and frame dragging (how Earth’s rotation drags space and time around with it). Gravity Probe B consists of four sophisticated gyroscopes that will provide an almost perfect space-time reference system. The mission will look in a precision manner for tiny changes in the direction of spin.

NASA Image and Video Library

2003-11-04

VANDENBERG AFB, CALIF. - In the NASA spacecraft processing facility on North Vandenberg Air Force Base, a balloon gently lifts the solar array panel to be installed on the Gravity Probe B spacecraft. Installing each array is a 3-day process and includes a functional deployment test. The Gravity Probe B mission is a relativity experiment developed by NASA’s Marshall Space Flight Center, Stanford University and Lockheed Martin. The spacecraft will test two extraordinary predictions of Albert Einstein’s general theory of relativity that he advanced in 1916: the geodetic effect (how space and time are warped by the presence of the Earth) and frame dragging (how Earth’s rotation drags space and time around with it). Gravity Probe B consists of four sophisticated gyroscopes that will provide an almost perfect space-time reference system. The mission will look in a precision manner for tiny changes in the direction of spin.

VANDENBERG AFB, CALIF. - In the NASA spacecraft processing facility on North Vandenberg Air Force Base, the Gravity Probe B spacecraft is seen with all four solar array panels installed. Installing each array is a 3-day process and includes a functional deployment test. The Gravity Probe B mission is a relativity experiment developed by NASA’s Marshall Space Flight Center, Stanford University and Lockheed Martin. The spacecraft will test two extraordinary predictions of Albert Einstein’s general theory of relativity that he advanced in 1916: the geodetic effect (how space and time are warped by the presence of the Earth) and frame dragging (how Earth’s rotation drags space and time around with it). Gravity Probe B consists of four sophisticated gyroscopes that will provide an almost perfect space-time reference system. The mission will look in a precision manner for tiny changes in the direction of spin.

NASA Image and Video Library

2003-11-04

VANDENBERG AFB, CALIF. - In the NASA spacecraft processing facility on North Vandenberg Air Force Base, the Gravity Probe B spacecraft is seen with all four solar array panels installed. Installing each array is a 3-day process and includes a functional deployment test. The Gravity Probe B mission is a relativity experiment developed by NASA’s Marshall Space Flight Center, Stanford University and Lockheed Martin. The spacecraft will test two extraordinary predictions of Albert Einstein’s general theory of relativity that he advanced in 1916: the geodetic effect (how space and time are warped by the presence of the Earth) and frame dragging (how Earth’s rotation drags space and time around with it). Gravity Probe B consists of four sophisticated gyroscopes that will provide an almost perfect space-time reference system. The mission will look in a precision manner for tiny changes in the direction of spin.

VANDENBERG AFB, CALIF. - A worker in the NASA spacecraft processing facility on North Vandenberg Air Force Base adjust the supports on a solar array panel to be lifted and installed on the Gravity Probe B spacecraft. Installing each array is a 3-day process and includes a functional deployment test. The Gravity Probe B mission is a relativity experiment developed by NASA’s Marshall Space Flight Center, Stanford University and Lockheed Martin. The spacecraft will test two extraordinary predictions of Albert Einstein’s general theory of relativity that he advanced in 1916: the geodetic effect (how space and time are warped by the presence of the Earth) and frame dragging (how Earth’s rotation drags space and time around with it). Gravity Probe B consists of four sophisticated gyroscopes that will provide an almost perfect space-time reference system. The mission will look in a precision manner for tiny changes in the direction of spin.

NASA Image and Video Library

2003-11-03

VANDENBERG AFB, CALIF. - A worker in the NASA spacecraft processing facility on North Vandenberg Air Force Base adjust the supports on a solar array panel to be lifted and installed on the Gravity Probe B spacecraft. Installing each array is a 3-day process and includes a functional deployment test. The Gravity Probe B mission is a relativity experiment developed by NASA’s Marshall Space Flight Center, Stanford University and Lockheed Martin. The spacecraft will test two extraordinary predictions of Albert Einstein’s general theory of relativity that he advanced in 1916: the geodetic effect (how space and time are warped by the presence of the Earth) and frame dragging (how Earth’s rotation drags space and time around with it). Gravity Probe B consists of four sophisticated gyroscopes that will provide an almost perfect space-time reference system. The mission will look in a precision manner for tiny changes in the direction of spin.

VANDENBERG AFB, CALIF. - In the NASA spacecraft processing facility on North Vandenberg Air Force Base, the Gravity Probe B spacecraft is seen with two solar array panels installed. Installing each array is a 3-day process and includes a functional deployment test. The Gravity Probe B mission is a relativity experiment developed by NASA’s Marshall Space Flight Center, Stanford University and Lockheed Martin. The spacecraft will test two extraordinary predictions of Albert Einstein’s general theory of relativity that he advanced in 1916: the geodetic effect (how space and time are warped by the presence of the Earth) and frame dragging (how Earth’s rotation drags space and time around with it). Gravity Probe B consists of four sophisticated gyroscopes that will provide an almost perfect space-time reference system. The mission will look in a precision manner for tiny changes in the direction of spin.

NASA Image and Video Library

2003-11-04

VANDENBERG AFB, CALIF. - In the NASA spacecraft processing facility on North Vandenberg Air Force Base, the Gravity Probe B spacecraft is seen with two solar array panels installed. Installing each array is a 3-day process and includes a functional deployment test. The Gravity Probe B mission is a relativity experiment developed by NASA’s Marshall Space Flight Center, Stanford University and Lockheed Martin. The spacecraft will test two extraordinary predictions of Albert Einstein’s general theory of relativity that he advanced in 1916: the geodetic effect (how space and time are warped by the presence of the Earth) and frame dragging (how Earth’s rotation drags space and time around with it). Gravity Probe B consists of four sophisticated gyroscopes that will provide an almost perfect space-time reference system. The mission will look in a precision manner for tiny changes in the direction of spin.

VANDENBERG AFB, CALIF. - In the NASA spacecraft processing facility on North Vandenberg Air Force Base, Dr. Francis Everitt, principal investigator, and Brad Parkinson, co-principal investigator, both from Stanford University, hold one of the small gyroscopes used in the Gravity Probe B spacecraft. The GP-B towers behind them. The Gravity Probe B mission is a relativity experiment developed by NASA’s Marshall Space Flight Center, Stanford University and Lockheed Martin. The spacecraft will test two extraordinary predictions of Albert Einstein’s general theory of relativity that he advanced in 1916: the geodetic effect (how space and time are warped by the presence of the Earth) and frame dragging (how Earth’s rotation drags space and time around with it). Gravity Probe B consists of four sophisticated gyroscopes that will provide an almost perfect space-time reference system. The mission will look in a precision manner for tiny changes in the direction of spin.

NASA Image and Video Library

2003-11-10

VANDENBERG AFB, CALIF. - In the NASA spacecraft processing facility on North Vandenberg Air Force Base, Dr. Francis Everitt, principal investigator, and Brad Parkinson, co-principal investigator, both from Stanford University, hold one of the small gyroscopes used in the Gravity Probe B spacecraft. The GP-B towers behind them. The Gravity Probe B mission is a relativity experiment developed by NASA’s Marshall Space Flight Center, Stanford University and Lockheed Martin. The spacecraft will test two extraordinary predictions of Albert Einstein’s general theory of relativity that he advanced in 1916: the geodetic effect (how space and time are warped by the presence of the Earth) and frame dragging (how Earth’s rotation drags space and time around with it). Gravity Probe B consists of four sophisticated gyroscopes that will provide an almost perfect space-time reference system. The mission will look in a precision manner for tiny changes in the direction of spin.

VANDENBERG AFB, CALIF. - In the NASA spacecraft processing facility on North Vandenberg Air Force Base, a worker checks the installation of a solar array panel onto the Gravity Probe B spacecraft. Installing each array is a 3-day process and includes a functional deployment test. The Gravity Probe B mission is a relativity experiment developed by NASA’s Marshall Space Flight Center, Stanford University and Lockheed Martin. The spacecraft will test two extraordinary predictions of Albert Einstein’s general theory of relativity that he advanced in 1916: the geodetic effect (how space and time are warped by the presence of the Earth) and frame dragging (how Earth’s rotation drags space and time around with it). Gravity Probe B consists of four sophisticated gyroscopes that will provide an almost perfect space-time reference system. The mission will look in a precision manner for tiny changes in the direction of spin.

NASA Image and Video Library

2003-11-04

VANDENBERG AFB, CALIF. - In the NASA spacecraft processing facility on North Vandenberg Air Force Base, a worker checks the installation of a solar array panel onto the Gravity Probe B spacecraft. Installing each array is a 3-day process and includes a functional deployment test. The Gravity Probe B mission is a relativity experiment developed by NASA’s Marshall Space Flight Center, Stanford University and Lockheed Martin. The spacecraft will test two extraordinary predictions of Albert Einstein’s general theory of relativity that he advanced in 1916: the geodetic effect (how space and time are warped by the presence of the Earth) and frame dragging (how Earth’s rotation drags space and time around with it). Gravity Probe B consists of four sophisticated gyroscopes that will provide an almost perfect space-time reference system. The mission will look in a precision manner for tiny changes in the direction of spin.

VANDENBERG AFB, CALIF. - Workers in the NASA spacecraft processing facility on North Vandenberg Air Force Base prepare for the installation of solar array panel 3 on the Gravity Probe B spacecraft. Installing each array is a 3-day process and includes a functional deployment test. The Gravity Probe B mission is a relativity experiment developed by NASA’s Marshall Space Flight Center, Stanford University and Lockheed Martin. The spacecraft will test two extraordinary predictions of Albert Einstein’s general theory of relativity that he advanced in 1916: the geodetic effect (how space and time are warped by the presence of the Earth) and frame dragging (how Earth’s rotation drags space and time around with it). Gravity Probe B consists of four sophisticated gyroscopes that will provide an almost perfect space-time reference system. The mission will look in a precision manner for tiny changes in the direction of spin.

NASA Image and Video Library

2003-11-03

VANDENBERG AFB, CALIF. - Workers in the NASA spacecraft processing facility on North Vandenberg Air Force Base prepare for the installation of solar array panel 3 on the Gravity Probe B spacecraft. Installing each array is a 3-day process and includes a functional deployment test. The Gravity Probe B mission is a relativity experiment developed by NASA’s Marshall Space Flight Center, Stanford University and Lockheed Martin. The spacecraft will test two extraordinary predictions of Albert Einstein’s general theory of relativity that he advanced in 1916: the geodetic effect (how space and time are warped by the presence of the Earth) and frame dragging (how Earth’s rotation drags space and time around with it). Gravity Probe B consists of four sophisticated gyroscopes that will provide an almost perfect space-time reference system. The mission will look in a precision manner for tiny changes in the direction of spin.

VANDENBERG AFB, CALIF. - Workers in the NASA spacecraft processing facility on North Vandenberg Air Force Base prepare to rotate the framework containing one of four solar panels to be installed on the Gravity Probe B spacecraft. Installing each array is a 3-day process and includes a functional deployment test. The Gravity Probe B mission is a relativity experiment developed by NASA’s Marshall Space Flight Center, Stanford University and Lockheed Martin. The spacecraft will test two extraordinary predictions of Albert Einstein’s general theory of relativity that he advanced in 1916: the geodetic effect (how space and time are warped by the presence of the Earth) and frame dragging (how Earth’s rotation drags space and time around with it). Gravity Probe B consists of four sophisticated gyroscopes that will provide an almost perfect space-time reference system. The mission will look in a precision manner for tiny changes in the direction of spin.

NASA Image and Video Library

2003-11-03

VANDENBERG AFB, CALIF. - Workers in the NASA spacecraft processing facility on North Vandenberg Air Force Base prepare to rotate the framework containing one of four solar panels to be installed on the Gravity Probe B spacecraft. Installing each array is a 3-day process and includes a functional deployment test. The Gravity Probe B mission is a relativity experiment developed by NASA’s Marshall Space Flight Center, Stanford University and Lockheed Martin. The spacecraft will test two extraordinary predictions of Albert Einstein’s general theory of relativity that he advanced in 1916: the geodetic effect (how space and time are warped by the presence of the Earth) and frame dragging (how Earth’s rotation drags space and time around with it). Gravity Probe B consists of four sophisticated gyroscopes that will provide an almost perfect space-time reference system. The mission will look in a precision manner for tiny changes in the direction of spin.

VANDENBERG AFB, CALIF. - Workers in the NASA spacecraft processing facility on North Vandenberg Air Force Base work on a solar array panel to be installed on the Gravity Probe B spacecraft. Installing each array is a 3-day process and includes a functional deployment test. The Gravity Probe B mission is a relativity experiment developed by NASA’s Marshall Space Flight Center, Stanford University and Lockheed Martin. The spacecraft will test two extraordinary predictions of Albert Einstein’s general theory of relativity that he advanced in 1916: the geodetic effect (how space and time are warped by the presence of the Earth) and frame dragging (how Earth’s rotation drags space and time around with it). Gravity Probe B consists of four sophisticated gyroscopes that will provide an almost perfect space-time reference system. The mission will look in a precision manner for tiny changes in the direction of spin.

NASA Image and Video Library

2003-11-03

VANDENBERG AFB, CALIF. - Workers in the NASA spacecraft processing facility on North Vandenberg Air Force Base work on a solar array panel to be installed on the Gravity Probe B spacecraft. Installing each array is a 3-day process and includes a functional deployment test. The Gravity Probe B mission is a relativity experiment developed by NASA’s Marshall Space Flight Center, Stanford University and Lockheed Martin. The spacecraft will test two extraordinary predictions of Albert Einstein’s general theory of relativity that he advanced in 1916: the geodetic effect (how space and time are warped by the presence of the Earth) and frame dragging (how Earth’s rotation drags space and time around with it). Gravity Probe B consists of four sophisticated gyroscopes that will provide an almost perfect space-time reference system. The mission will look in a precision manner for tiny changes in the direction of spin.

VANDENBERG AFB, CALIF. - In the NASA spacecraft processing facility on North Vandenberg Air Force Base, workers prepare to attach the top of a solar array panel onto the Gravity Probe B spacecraft. Installing each array is a 3-day process and includes a functional deployment test. The Gravity Probe B mission is a relativity experiment developed by NASA’s Marshall Space Flight Center, Stanford University and Lockheed Martin. The spacecraft will test two extraordinary predictions of Albert Einstein’s general theory of relativity that he advanced in 1916: the geodetic effect (how space and time are warped by the presence of the Earth) and frame dragging (how Earth’s rotation drags space and time around with it). Gravity Probe B consists of four sophisticated gyroscopes that will provide an almost perfect space-time reference system. The mission will look in a precision manner for tiny changes in the direction of spin.

NASA Image and Video Library

2003-11-04

VANDENBERG AFB, CALIF. - In the NASA spacecraft processing facility on North Vandenberg Air Force Base, workers prepare to attach the top of a solar array panel onto the Gravity Probe B spacecraft. Installing each array is a 3-day process and includes a functional deployment test. The Gravity Probe B mission is a relativity experiment developed by NASA’s Marshall Space Flight Center, Stanford University and Lockheed Martin. The spacecraft will test two extraordinary predictions of Albert Einstein’s general theory of relativity that he advanced in 1916: the geodetic effect (how space and time are warped by the presence of the Earth) and frame dragging (how Earth’s rotation drags space and time around with it). Gravity Probe B consists of four sophisticated gyroscopes that will provide an almost perfect space-time reference system. The mission will look in a precision manner for tiny changes in the direction of spin.

VANDENBERG AFB, CALIF. - Workers in the NASA spacecraft processing facility on North Vandenberg Air Force Base attach a solar array panel on the Gravity Probe B spacecraft. Installing each array is a 3-day process and includes a functional deployment test. The Gravity Probe B mission is a relativity experiment developed by NASA’s Marshall Space Flight Center, Stanford University and Lockheed Martin. The spacecraft will test two extraordinary predictions of Albert Einstein’s general theory of relativity that he advanced in 1916: the geodetic effect (how space and time are warped by the presence of the Earth) and frame dragging (how Earth’s rotation drags space and time around with it). Gravity Probe B consists of four sophisticated gyroscopes that will provide an almost perfect space-time reference system. The mission will look in a precision manner for tiny changes in the direction of spin.

NASA Image and Video Library

2003-11-03

VANDENBERG AFB, CALIF. - Workers in the NASA spacecraft processing facility on North Vandenberg Air Force Base attach a solar array panel on the Gravity Probe B spacecraft. Installing each array is a 3-day process and includes a functional deployment test. The Gravity Probe B mission is a relativity experiment developed by NASA’s Marshall Space Flight Center, Stanford University and Lockheed Martin. The spacecraft will test two extraordinary predictions of Albert Einstein’s general theory of relativity that he advanced in 1916: the geodetic effect (how space and time are warped by the presence of the Earth) and frame dragging (how Earth’s rotation drags space and time around with it). Gravity Probe B consists of four sophisticated gyroscopes that will provide an almost perfect space-time reference system. The mission will look in a precision manner for tiny changes in the direction of spin.

VANDENBERG AFB, CALIF. - Workers in the NASA spacecraft processing facility on North Vandenberg Air Force Base attach supports to a solar array panel to be lifted and installed on the Gravity Probe B spacecraft. Installing each array is a 3-day process and includes a functional deployment test. The Gravity Probe B mission is a relativity experiment developed by NASA’s Marshall Space Flight Center, Stanford University and Lockheed Martin. The spacecraft will test two extraordinary predictions of Albert Einstein’s general theory of relativity that he advanced in 1916: the geodetic effect (how space and time are warped by the presence of the Earth) and frame dragging (how Earth’s rotation drags space and time around with it). Gravity Probe B consists of four sophisticated gyroscopes that will provide an almost perfect space-time reference system. The mission will look in a precision manner for tiny changes in the direction of spin.

NASA Image and Video Library

2003-11-03

VANDENBERG AFB, CALIF. - Workers in the NASA spacecraft processing facility on North Vandenberg Air Force Base attach supports to a solar array panel to be lifted and installed on the Gravity Probe B spacecraft. Installing each array is a 3-day process and includes a functional deployment test. The Gravity Probe B mission is a relativity experiment developed by NASA’s Marshall Space Flight Center, Stanford University and Lockheed Martin. The spacecraft will test two extraordinary predictions of Albert Einstein’s general theory of relativity that he advanced in 1916: the geodetic effect (how space and time are warped by the presence of the Earth) and frame dragging (how Earth’s rotation drags space and time around with it). Gravity Probe B consists of four sophisticated gyroscopes that will provide an almost perfect space-time reference system. The mission will look in a precision manner for tiny changes in the direction of spin.

Mobile Laser Scanning Systems for Measuring the Clearance Gauge of Railways: State of Play, Testing and Outlook

PubMed Central

Mikrut, Sławomir; Kohut, Piotr; Pyka, Krystian; Tokarczyk, Regina; Barszcz, Tomasz; Uhl, Tadeusz

2016-01-01

The paper contains a survey of mobile scanning systems for measuring the railway clearance gauge. The research was completed as part of the project carried out for the PKP (PKP Polish Railway Lines S.A., Warsaw, Poland) in 2011–2013. The authors conducted experiments, including a search for the latest solutions relating to mobile measurement systems that meet the basic requirement. At the very least, these solutions needed to be accurate and have the ability for quick retrieval of data. In the paper, specifications and the characteristics of the component devices of the scanning systems are described. Based on experiments, the authors did some examination of the selected mobile systems to be applied for measuring the clearance gauge. The Riegl (VMX-250) and Z+F (Zoller + Fröhlich) Solution were tested. Additional test measurements were carried out within a 30-kilometer section of the Warsaw-Kraków route. These measurements were designed so as to provide various elements of the railway infrastructure, the track geometry and the installed geodetic control network. This ultimately made it possible to reduce the time for the preparation of geodetic reference measurements for the testing of the accuracy of the selected systems. Reference measurements included the use of the polar method to select profiles perpendicular to the axis of the track. In addition, the coordinates selected were well defined as measuring points of the objects of the infrastructure of the clearance gauge. All of the tested systems meet the accuracy requirements initially established (within the range of 2 cm as required by the PKP). The tested systems have shown their advantages and disadvantages. PMID:27187400

DAM Safety and Deformation Monitoring in Dams

NASA Astrophysics Data System (ADS)

Kalkan, Y.; Bilgi, S.; Potts, L.; Miiama, J.; Mahgoub, M.; Rahman, S.

2013-12-01

Water is the life and necessity to water is increasing day by day with respect to the World population, rising of living standards and destruction of nature. Thus, the importance of water and water structures have been increasing gradually. Dams are among the most important engineering structures used for water supplies, flood controls, agricultural purposes as well as drinking and hydroelectric power. There are about 150.000 large size dams in the World. Especially after the Second World War, higher and larger capacity dams have been constructed. Dams create certain risks like the other manmade structures. No one knows precisely how many dam failures have occurred in the World, whereas hundreds of dam failures have occurred throughout the U.S. history. Some basic physical data are very important for assessing the safety and performance of dams. These are movement, water pressure, seepage, reservoir and tail-water elevations, local seismic activities, total pressure, stress and strain, internal concrete temperature, ambient temperature and precipitation. These physical data are measured and monitored by the instruments and equipment. Dams and their surroundings have to be monitored by using essential methods at periodic time intervals in order to determine the possible changes that may occur over the time. Monitoring programs typically consist of; surveillance or visual observation. These programs on dams provide information for evaluating the dam's performance related to the design intent and expected changes that could affect the safety performance of the dam. Additionally, these programs are used for investigating and evaluating the abnormal or degrading performance where any remedial action is necessary. Geodetic and non-geodetic methods are used for monitoring. Monitoring the performance of the dams is critical for producing and maintaining the safe dams. This study provides some information, safety and the techniques about the deformation monitoring of the dams. Therefore, this study gives essential information about the dam safety and related analysis. Monitoring of dams is crucial since deformation might have occurred as a result of erosion, water load, hydraulic gradients, and water saturation. The case study is the deformation measurements of Ataturk Dam. This dam was constructed on Firat River and it has importance for providing drinking water, hydroelectric power and especially irrigation. In addition, brief information is given about this dam and the methods of geodetic and non-geodetic monitoring measurements applied by various disciplines. Geodetic monitoring methods are emphasized in this study. Some results have been obtained from this method for nearly seven years are presented in this work. In addition, some deformation predictions have been made especially for the cross sections where the maximum deformations took place.

Geodetic Space Weather Monitoring by means of Ionosphere Modelling

NASA Astrophysics Data System (ADS)

Schmidt, Michael

2017-04-01

The term space weather indicates physical processes and phenomena in space caused by radiation of energy mainly from the Sun. Manifestations of space weather are (1) variations of the Earth's magnetic field, (2) the polar lights in the northern and southern hemisphere, (3) variations within the ionosphere as part of the upper atmosphere characterized by the existence of free electrons and ions, (4) the solar wind, i.e. the permanent emission of electrons and photons, (5) the interplanetary magnetic field, and (6) electric currents, e.g. the van Allen radiation belt. It can be stated that ionosphere disturbances are often caused by so-called solar storms. A solar storm comprises solar events such as solar flares and coronal mass ejections (CMEs) which have different effects on the Earth. Solar flares may cause disturbances in positioning, navigation and communication. CMEs can effect severe disturbances and in extreme cases damages or even destructions of modern infrastructure. Examples are interruptions to satellite services including the global navigation satellite systems (GNSS), communication systems, Earth observation and imaging systems or a potential failure of power networks. Currently the measurements of solar satellite missions such as STEREO and SOHO are used to forecast solar events. Besides these measurements the Earth's ionosphere plays another key role in monitoring the space weather, because it responses to solar storms with an increase of the electron density. Space-geodetic observation techniques, such as terrestrial GNSS, satellite altimetry, space-borne GPS (radio occultation), DORIS and VLBI provide valuable global information about the state of the ionosphere. Additionally geodesy has a long history and large experience in developing and using sophisticated analysis and combination techniques as well as empirical and physical modelling approaches. Consequently, geodesy is predestinated for strongly supporting space weather monitoring via modelling the ionosphere and detecting and forecasting its disturbances. At present a couple of nations, such as the US, UK, Japan, Canada and China, are taken the threats from extreme space weather events seriously and support the development of observing strategies and fundamental research. However, (extreme) space weather events are in all their consequences on the modern highly technologized society, causative global problems which have to be treated globally and not regionally or even nationally. Consequently, space weather monitoring must include (1) all space-geodetic observation techniques and (2) geodetic evaluation methods such as data combination, real-time modelling and forecast. In other words, geodetic space weather monitoring comprises the basic ideas of GGOS and will provide products such as forecasts of severe solar events in order to initiate necessary activities to protect the infrastructure of modern society.

Wavelet based comparison of high frequency oscillations in the geodetic and fluid excitation functions of polar motion

NASA Astrophysics Data System (ADS)

Kosek, W.; Popinski, W.; Niedzielski, T.

2011-10-01

It has been already shown that short period oscillations in polar motion, with periods less than 100 days, are very chaotic and are responsible for increase in short-term prediction errors of pole coordinates data. The wavelet technique enables to compare the geodetic and fluid excitation functions in the high frequency band in many different ways, e.g. by looking at the semblance function. The waveletbased semblance filtering enables determination the common signal in both geodetic and fluid excitation time series. In this paper the considered fluid excitation functions consist of the atmospheric, oceanic and land hydrology excitation functions from ECMWF atmospheric data produced by IERS Associated Product Centre Deutsches GeoForschungsZentrum, Potsdam. The geodetic excitation functions have been computed from the combined IERS pole coordinates data.

Geodetic observations of ice flow velocities over the southern part of subglacial Lake Vostok, Antarctica, and their glaciological implications

NASA Astrophysics Data System (ADS)

Wendt, Jens; Dietrich, Reinhard; Fritsche, Mathias; Wendt, Anja; Yuskevich, Alexander; Kokhanov, Andrey; Senatorov, Anton; Lukin, Valery; Shibuya, Kazuo; Doi, Koichiro

2006-09-01

In the austral summer seasons 2001/02 and 2002/03, Global Positioning System (GPS) data were collected in the vicinity of Vostok Station to determine ice flow velocities over Lake Vostok. Ten GPS sites are located within a radius of 30km around Vostok Station on floating ice as well as on grounded ice to the east and to the west of the lake. Additionally, a local deformation network around the ice core drilling site 5G-1 was installed. The derived ice flow velocity for Vostok Station is 2.00ma-1 +/- 0.01ma-1. Along the flowline of Vostok Station an extension rate of about 10-5a-1 (equivalent to 1cm km-1 a-1) was determined. This significant velocity gradient results in a new estimate of 28700 years for the transit time of an ice particle along the Vostok flowline from the bedrock ridge in the southwest of the lake to the eastern shoreline. With these lower velocities compared to earlier studies and, hence, larger transit times the basal accretion rate is estimated to be 4mma-1 along a portion of the Vostok flowline. An assessment of the local accretion rate at Vostok Station using the observed geodetic quantities yields an accretion rate in the same order of magnitude. Furthermore, the comparison of our geodetic observations with results inferred from ice-penetrating radar data indicates that the ice flow may not have changed significantly for several thousand years.

Variation Scenarios in System Deployments for the GGOS2020 Space Geodesy Network

NASA Astrophysics Data System (ADS)

Pavlis, Erricos C.; Kuzmicz-Cieslak, Magdalena; MacMillan, Daniel S.

2017-04-01

Simulation studies have so far determined an approximate size and station density for the Space Geodetic Network that will meet the requirements recommended by the U.S. National Research Council report "Precise Geodetic Infrastructure: National Requirements for a Shared Resource" (2010). A network of about 30 globally distributed "core" observatories with state of the art equipment needs to be deployed over the next decade. Subsequently, GGOS—the Global Geodetic Observing System issued a "Call for Proposals for the expansion and update of the network, to which several countries committed to contribute. The renewal process will not happen instantly and for a long time, the network will comprise legacy and next generation equipment. We conducted a new batch of simulation studies using the proposed site locations and the proposed equipment at each site, to gauge the contribution of specific systems and locations to the global results. The majority of the examined sites are well-established future sites, some of which are even close to completion. Despite the good intentions of the contributing agencies/countries, in some cases we have identified regional gaps in coverage with either SLR or VLBI systems. We have characterized the effect of these gaps on the quality of the final TRF. We present the results of these simulation studies and rank the examined cases according to the likelihood that the designed network will successfully meet the GGOS goals of 1 mm accuracy (decadal scale) and a temporal stability on the order of 0.1 mm/y, with similar numbers for the scale and orientation components of the TRF.

GGOS2020 Space Geodesy Network: Variations in System Deployment Scenarios

NASA Astrophysics Data System (ADS)

Pavlis, E. C.; Koenig, D.; Kuzmicz-Cieslak, M.; MacMillan, D. S.

2016-12-01

Simulation studies have so far determined an approximate size and station density for the Space Geodetic Network that will meet the requirements recommended by the U.S. National Research Council report "Precise Geodetic Infrastructure: National Requirements for a Shared Resource" (2010). A network of about 30 globally distributed "core" observatories with state of the art equipment needs to be deployed over the next decade. Subsequently, GGOS—the Global Geodetic Observing System issued a "Call for Proposals for the expansion and update of the network, to which several countries committed to contribute. The renewal process will not happen instantly and for a long time, the network will comprise legacy and next generation equipment. We conducted a new batch of simulation studies using the proposed site locations and the proposed equipment at each site, to gauge the contribution of specific systems and locations to the global results. The majority of the examined sites are well-established future sites, some of which are even close to completion. Despite the good intentions of the contributing agencies/countries, in some cases we have identified regional gaps in coverage with either SLR or VLBI systems. We have characterized the effect of these gaps on the quality of the final TRF. We present the results of these simulation studies and rank the examined cases according to the likelihood that the designed network will successfully meet the GGOS goals of 1 mm accuracy (decadal scale) and a temporal stability on the order of 0.1 mm/y, with similar numbers for the scale and orientation components of the TRF.

Separation of atmospheric, oceanic and hydrological polar motion excitation mechanisms based on a combination of geometric and gravimetric space observations

NASA Astrophysics Data System (ADS)

Göttl, F.; Schmidt, M.; Seitz, F.; Bloßfeld, M.

2015-04-01

The goal of our study is to determine accurate time series of geophysical Earth rotation excitations to learn more about global dynamic processes in the Earth system. For this purpose, we developed an adjustment model which allows to combine precise observations from space geodetic observation systems, such as Satellite Laser Ranging (SLR), Global Navigation Satellite Systems, Very Long Baseline Interferometry, Doppler Orbit determination and Radiopositioning Integrated on Satellite, satellite altimetry and satellite gravimetry in order to separate geophysical excitation mechanisms of Earth rotation. Three polar motion time series are applied to derive the polar motion excitation functions (integral effect). Furthermore we use five time variable gravity field solutions from Gravity Recovery and Climate Experiment to determine not only the integral mass effect but also the oceanic and hydrological mass effects by applying suitable filter techniques and a land-ocean mask. For comparison the integral mass effect is also derived from degree 2 potential coefficients that are estimated from SLR observations. The oceanic mass effect is also determined from sea level anomalies observed by satellite altimetry by reducing the steric sea level anomalies derived from temperature and salinity fields of the oceans. Due to the combination of all geodetic estimated excitations the weaknesses of the individual processing strategies can be reduced and the technique-specific strengths can be accounted for. The formal errors of the adjusted geodetic solutions are smaller than the RMS differences of the geophysical model solutions. The improved excitation time series can be used to improve the geophysical modeling.

Characterizing the Effects of Low Order Perturbations on Geodetic Satellite Precision Orbit Determination

DTIC Science & Technology

2015-08-07

Journal of Geodesy , Vol. 72, No. 6, 1998, pp. 333–342. [19] “Etalon-1, and -2,” http://ilrs.gsfc.nasa.gov/missions/satellite_missions...current_missions/g129_general.html, 2012. [24] L. Kanner and Associates, “Translation of ’Le satellite de geodesie ’Starlette’,’ Groupe de Recherches...de Geodesie Spatiale, Centre National d’Etudes Spatiales, Bretigny-sur-Orge, France, Report, 1974, 25 pp,” National Aeronautics and Space

Beyond plate tectonics - Looking at plate deformation with space geodesy

NASA Technical Reports Server (NTRS)

Jordan, Thomas H.; Minster, J. Bernard

1988-01-01

The requirements that must be met by space-geodetic systems in order to constrain the horizontal secular motions associated with the geological deformation of the earth's surface are explored. It is suggested that in order to improve existing plate-motion models, the tangential components of relative velocities on interplate baselines must be resolved to an accuracy of less than 3 mm/yr. Results indicate that measuring the velocities between crustal blocks to + or - 5 mm/yr on 100-km to 1000-km scales can produce geologically significant constraints on the integrated deformation rates across continental plate-boundary zones such as the western United States.

Demonstration of the Cascadia G‐FAST geodetic earthquake early warning system for the Nisqually, Washington, earthquake

USGS Publications Warehouse

Crowell, Brendan; Schmidt, David; Bodin, Paul; Vidale, John; Gomberg, Joan S.; Hartog, Renate; Kress, Victor; Melbourne, Tim; Santillian, Marcelo; Minson, Sarah E.; Jamison, Dylan

2016-01-01

A prototype earthquake early warning (EEW) system is currently in development in the Pacific Northwest. We have taken a two‐stage approach to EEW: (1) detection and initial characterization using strong‐motion data with the Earthquake Alarm Systems (ElarmS) seismic early warning package and (2) the triggering of geodetic modeling modules using Global Navigation Satellite Systems data that help provide robust estimates of large‐magnitude earthquakes. In this article we demonstrate the performance of the latter, the Geodetic First Approximation of Size and Time (G‐FAST) geodetic early warning system, using simulated displacements for the 2001Mw 6.8 Nisqually earthquake. We test the timing and performance of the two G‐FAST source characterization modules, peak ground displacement scaling, and Centroid Moment Tensor‐driven finite‐fault‐slip modeling under ideal, latent, noisy, and incomplete data conditions. We show good agreement between source parameters computed by G‐FAST with previously published and postprocessed seismic and geodetic results for all test cases and modeling modules, and we discuss the challenges with integration into the U.S. Geological Survey’s ShakeAlert EEW system.

Integration of space geodesy: a US National Geodetic Observatory

NASA Technical Reports Server (NTRS)

Yunck, Thomas P.; Neilan, Ruth

2003-01-01

In the interest of improving the performance and efficiency of space geodesy a diverse group in the U.S., in collaboration with IGGOS, has begun to establish a unified National Geodetic Observatory (NGO).

New VLBI2010 scheduling strategies and implications on the terrestrial reference frames.

PubMed

Sun, Jing; Böhm, Johannes; Nilsson, Tobias; Krásná, Hana; Böhm, Sigrid; Schuh, Harald

In connection with the work for the next generation VLBI2010 Global Observing System (VGOS) of the International VLBI Service for Geodesy and Astrometry, a new scheduling package (Vie_Sched) has been developed at the Vienna University of Technology as a part of the Vienna VLBI Software. In addition to the classical station-based approach it is equipped with a new scheduling strategy based on the radio sources to be observed. We introduce different configurations of source-based scheduling options and investigate the implications on present and future VLBI2010 geodetic schedules. By comparison to existing VLBI schedules of the continuous campaign CONT11, we find that the source-based approach with two sources has a performance similar to the station-based approach in terms of number of observations, sky coverage, and geodetic parameters. For an artificial 16 station VLBI2010 network, the source-based approach with four sources provides an improved distribution of source observations on the celestial sphere. Monte Carlo simulations yield slightly better repeatabilities of station coordinates with the source-based approach with two sources or four sources than the classical strategy. The new VLBI scheduling software with its alternative scheduling strategy offers a promising option with respect to applications of the VGOS.

DIORAMA Location Type User's Guide

DOE Office of Scientific and Technical Information (OSTI.GOV)

Terry, James Russell

2015-01-29

The purpose of this report is to present the current design and implementation of the DIORAMA location type object (LocationType) and to provide examples and use cases. The LocationType object is included in the diorama-app package in the diorama::types namespace. Abstractly, the object is intended to capture the full time history of the location of an object or reference point. For example, a location may be speci ed as a near-Earth orbit in terms of a two-line element set, in which case the location type is capable of propagating the orbit both forward and backward in time to provide amore » location for any given time. Alternatively, the location may be speci ed as a xed set of geodetic coordinates (latitude, longitude, and altitude), in which case the geodetic location of the object is expected to remain constant for all time. From an implementation perspective, the location type is de ned as a union of multiple independent objects defi ned in the DIORAMA tle library. Types presently included in the union are listed and described in subsections below, and all conversions or transformation between these location types are handled by utilities provided by the tle library with the exception of the \\special-values" location type.« less

New VLBI2010 scheduling strategies and implications on the terrestrial reference frames

NASA Astrophysics Data System (ADS)

Sun, Jing; Böhm, Johannes; Nilsson, Tobias; Krásná, Hana; Böhm, Sigrid; Schuh, Harald

2014-05-01

In connection with the work for the next generation VLBI2010 Global Observing System (VGOS) of the International VLBI Service for Geodesy and Astrometry, a new scheduling package (Vie_Sched) has been developed at the Vienna University of Technology as a part of the Vienna VLBI Software. In addition to the classical station-based approach it is equipped with a new scheduling strategy based on the radio sources to be observed. We introduce different configurations of source-based scheduling options and investigate the implications on present and future VLBI2010 geodetic schedules. By comparison to existing VLBI schedules of the continuous campaign CONT11, we find that the source-based approach with two sources has a performance similar to the station-based approach in terms of number of observations, sky coverage, and geodetic parameters. For an artificial 16 station VLBI2010 network, the source-based approach with four sources provides an improved distribution of source observations on the celestial sphere. Monte Carlo simulations yield slightly better repeatabilities of station coordinates with the source-based approach with two sources or four sources than the classical strategy. The new VLBI scheduling software with its alternative scheduling strategy offers a promising option with respect to applications of the VGOS.

Normal gravity field in relativistic geodesy

NASA Astrophysics Data System (ADS)

Kopeikin, Sergei; Vlasov, Igor; Han, Wen-Biao

2018-02-01

Modern geodesy is subject to a dramatic change from the Newtonian paradigm to Einstein's theory of general relativity. This is motivated by the ongoing advance in development of quantum sensors for applications in geodesy including quantum gravimeters and gradientometers, atomic clocks and fiber optics for making ultra-precise measurements of the geoid and multipolar structure of the Earth's gravitational field. At the same time, very long baseline interferometry, satellite laser ranging, and global navigation satellite systems have achieved an unprecedented level of accuracy in measuring 3-d coordinates of the reference points of the International Terrestrial Reference Frame and the world height system. The main geodetic reference standard to which gravimetric measurements of the of Earth's gravitational field are referred is a normal gravity field represented in the Newtonian gravity by the field of a uniformly rotating, homogeneous Maclaurin ellipsoid of which mass and quadrupole momentum are equal to the total mass and (tide-free) quadrupole moment of Earth's gravitational field. The present paper extends the concept of the normal gravity field from the Newtonian theory to the realm of general relativity. We focus our attention on the calculation of the post-Newtonian approximation of the normal field that is sufficient for current and near-future practical applications. We show that in general relativity the level surface of homogeneous and uniformly rotating fluid is no longer described by the Maclaurin ellipsoid in the most general case but represents an axisymmetric spheroid of the fourth order with respect to the geodetic Cartesian coordinates. At the same time, admitting a post-Newtonian inhomogeneity of the mass density in the form of concentric elliptical shells allows one to preserve the level surface of the fluid as an exact ellipsoid of rotation. We parametrize the mass density distribution and the level surface with two parameters which are intrinsically connected to the existence of the residual gauge freedom, and derive the post-Newtonian normal gravity field of the rotating spheroid both inside and outside of the rotating fluid body. The normal gravity field is given, similarly to the Newtonian gravity, in a closed form by a finite number of the ellipsoidal harmonics. We employ transformation from the ellipsoidal to spherical coordinates to deduce a more conventional post-Newtonian multipolar expansion of scalar and vector gravitational potentials of the rotating spheroid. We compare these expansions with that of the normal gravity field generated by the Kerr metric and demonstrate that the Kerr metric has a fairly limited application in relativistic geodesy as it does not match the normal gravity field of the Maclaurin ellipsoid already in the Newtonian limit. We derive the post-Newtonian generalization of the Somigliana formula for the normal gravity field measured on the surface of the rotating spheroid and employed in practical work for measuring Earth's gravitational field anomalies. Finally, we discuss the possible choice of the gauge-dependent parameters of the normal gravity field model for practical applications and compare it with the existing EGM2008 model of a gravitational field.

A Non-linear Geodetic Data Inversion Using ABIC for Slip Distribution on a Fault With an Unknown dip Angle

NASA Astrophysics Data System (ADS)

Fukahata, Y.; Wright, T. J.

2006-12-01

We developed a method of geodetic data inversion for slip distribution on a fault with an unknown dip angle. When fault geometry is unknown, the problem of geodetic data inversion is non-linear. A common strategy for obtaining slip distribution is to first determine the fault geometry by minimizing the square misfit under the assumption of a uniform slip on a rectangular fault, and then apply the usual linear inversion technique to estimate a slip distribution on the determined fault. It is not guaranteed, however, that the fault determined under the assumption of a uniform slip gives the best fault geometry for a spatially variable slip distribution. In addition, in obtaining a uniform slip fault model, we have to simultaneously determine the values of the nine mutually dependent parameters, which is a highly non-linear, complicated process. Although the inverse problem is non-linear for cases with unknown fault geometries, the non-linearity of the problems is actually weak, when we can assume the fault surface to be flat. In particular, when a clear fault trace is observed on the EarthOs surface after an earthquake, we can precisely estimate the strike and the location of the fault. In this case only the dip angle has large ambiguity. In geodetic data inversion we usually need to introduce smoothness constraints in order to compromise reciprocal requirements for model resolution and estimation errors in a natural way. Strictly speaking, the inverse problem with smoothness constraints is also non-linear, even if the fault geometry is known. The non-linearity has been dissolved by introducing AkaikeOs Bayesian Information Criterion (ABIC), with which the optimal value of the relative weight of observed data to smoothness constraints is objectively determined. In this study, using ABIC in determining the optimal dip angle, we dissolved the non-linearity of the inverse problem. We applied the method to the InSAR data of the 1995 Dinar, Turkey earthquake and obtained a much shallower dip angle than before.

Single-baseline RTK GNSS Positioning for Hydrographic Surveying

NASA Astrophysics Data System (ADS)

Metin Alkan, Reha; Murat Ozulu, I.; Ilçi, Veli; Kahveci, Muzaffer

2015-04-01

Positioning with GNSS technique can be carried out in two ways, absolute and relative. It has been possible to reach a few meters absolute point positioning accuracies in real time after disabling SA permanently in May 2000. Today, accuracies obtainable from absolute point positioning using code observations are not sufficient for most surveying applications. Thus to meet higher accuracy requirements, differential methods using single or dual frequency geodetic-grade GNSS receivers that measure carrier phase have to be used. However, this method requires time-cost field and office works and if the measurement is not carried out with conventional RTK method, user needs a GNSS data processing software to estimate the coordinates. If RTK is used, at least two or more GNSS receivers are required, one as a reference and the other as a rover. Moreover, the distance between the receivers must not exceed 15-20 km in order to be able to rapidly and reliably resolve the carrier phase ambiguities. On the other hand, based on the innovations and improvements in satellite geodesy and GNSS modernization studies occurred within the last decade, many new positioning methods and new approaches have been developed. One of them is Network-RTK (or commonly known as CORS) and the other is Single-baseline RTK. These methods are widely used for many surveying applications in many countries. The user of the system can obtain his/her position within a few cm level of accuracy in real-time with only a single GNSS receiver that has Network RTK (CORS) capability. When compared with the conventional differential and RTK methods, this technique has several significant advantages as it is easy to use and it produces accurate, cost-effective and rapid solutions. In Turkey, establishment of a multi-base RTK network was completed and opened for civilian use in 2009. This network is called CORS-TR and consists of 146 reference stations having about 80-100 km interstation distances. It is possible for a user to determine his/her position with a few cm accuracy in real time in Turkey. Besides, there are some province municipalities in Turkey which have established their own local CORS networks such as Istanbul (with 9 reference stations) and Ankara (with 10 reference stations). There is also a local RTK base station which disseminates real time position corrections for surveyors in Çorum province and is operated by Çorum Municipality. This is the first step of establishing a complete local CORS network in Çorum (the municipality has plans to increase this number and establish a CORS network within a few years). At the time of this study, unfortunately, national CORS-TR stations in Çorum Province were under maintenance and thus we could not receive corrections from our national CORS network. Instead, Çorum Province's local RTK reference station's corrections were used during the study. The main purpose of this study is to investigate the accuracy performance of the Single-baseline RTK GNSS system operated by Çorum Municipality in marine environment. For this purpose, a kinematic test measurement was carried out at Obruk Dam, Çorum, Turkey. During the test measurement, a small vessel equipped with a dual-frequency geodetic-grade GNSS receiver, Spectra Precision ProMark 500, was used. The coordinates of the vessel were obtained from the Single-baseline RTK system in ITRF datum in real-time with fix solutions. At the same time, the raw kinematic GNSS data were also recorded to the receiver in order to estimate the known coordinates of the vessel with post-processed differential kinematic technique. In this way, GPS data were collected under the same conditions, which allowed precise assessment of the used system. The measurements were carried out along the survey profiles for about 1 hour. During the kinematic test, another receiver was set up on a geodetic point at the shore and data were collected in static mode to calculate the coordinates of the vessel for each epoch. As mentioned above, the vessel coordinates were estimated very accurately by using data collected on shore and vessel by using differential GNSS technique. The Single-baseline RTK-derived coordinates were compared with those obtained from the post-processing of the GNSS data for each epoch. Computed differences show that the coordinates agree with the relative solutions at 7 cm and below in position. Some marine applications like precise hydrographic surveying, monitoring silt accretion and erosion in rivers, lakes, estuaries, coastal waters and harbor areas; marine geodynamics; automatic docking; dredging; construction work; attitude control of ships, buoys and floating platforms, require high accuracy better than 0.1 m in position and height. Results obtained from this application show that Single-baseline RTK and/or CORS systems can reliably be utilized for the above mentioned marine applications and some others especially for positioning as a strong alternative to the conventional differential methods.

Three decades of harnessing the GPS data explosion for geophysics (Vening Meinesz Medal Lecture)

NASA Astrophysics Data System (ADS)

Blewitt, Geoffrey

2015-04-01

In this presentation, I attempt to convey the immensity of the task that faced the geodesy community three decades ago, and continues to challenge us, to harness all potentially valuable GPS data available in the world for geophysical science. It would be fair to see that three decades ago, we were struggling with controlled tests just to get GPS geodesy working, and had little time to imagine the flood of data today. Yet the geodesy community has succeeded in meeting this challenge. Today, for example, the Nevada Geodetic Laboratory produces and makes publicly available coordinate time series for over 12,000 geodetic GPS station around the globe with various data intervals, latencies, and reference frames. About 8,000 stations have their daily time series updated every week, with 4,000 being updated the next day with coordinates at daily and 5 minute intervals. About 2,000 stations have their time series updated every hour with coordinates at 5 minute intervals. I will show examples of how these time series are being used by NGL and many other scientists to study a wide variety of geophysical topics, including plate tectonics, earthquake modeling, seismic and tsunami hazard, volcanic deformation, water resources, mountain growth, terrestrial reference frame realization, glacial isostatic adjustment, ice sheet melting, sea level rise and coastal subsidence, and even fundamental physics, using GPS atomic clocks to probe the nature of dark matter in the universe. The explosion in GPS data has challenged us to invent new data processing algorithms and develop robust automation in order to keep up with the flood. This explosion has been exponential, and therefore it can be said that it is not a recent phenomena, but rather that it began in the earliest years of GPS geodesy, and has always posed a challenge to us. Over the course of my post-doctoral career starting in late 1985, I have had the good fortune to witness the key developments that have taken place since the early years of geodetic GPS and over the course of three decades. These developments continue today as strongly as ever. Essential innovations have included, for example, automation of GPS cycle slip detection and mitigation, carrier phase ambiguity resolution, the birth and operation of the IGS for reliable orbit and clock estimation, the invention of algorithms that scale linearly with the number of stations, and the deep integration of GPS solutions into the ITRF, providing measures of accuracy, precision, and stability. As a recent example of automation, I show a new non-parametric algorithm to estimate station velocities quickly and robustly, without need to detect and correct for outliers, seasonal signals, and discontinuities in the time series steps that commonly occur due to equipment changes. The complete automation from data collection to production of station velocities (and, now, velocity time series) allows us to process all potentially valuable data, and to focus more on discovery and analysis of the results for geophysical applications, often with great redundancy in the data leading to high statistical significance and more robust scientific conclusions. I show by example that another benefit of this capability to process all data in a robust turn-key fashion is to enhance the opportunity for making discoveries, without necessarily planning all of the steps that can lead us to discovery's door.

Kinematics, seismotectonics and seismic potential of the eastern sector of the European Alps from GPS and seismic deformation data

NASA Astrophysics Data System (ADS)

Serpelloni, E.; Vannucci, G.; Anderlini, L.; Bennett, R. A.

2016-10-01

We present a first synoptic view of the seismotectonics and kinematics of the eastern sector of the European Alps using geodetic and seismological data. The study area marks the boundary between the Adriatic and the Eurasian plates, through a wide zone of deformation including a variety of tectonic styles within a complex network of crustal and lithospheric faults. A new dense GPS velocity field, new focal mechanisms and seismic catalogues, with uniformly re-calibrated magnitudes (from 1005), are used to estimate geodetic and seismic deformation rates and to develop interseismic kinematic and fault locking models. Kinematic indicators from seismological and geodetic data are remarkably consistent at different spatial scales. In addition to large-scale surface motion, GPS velocities highlight more localized deformation features revealing a complex configuration of interacting tectonic blocks, for which new constraints are provided in this work accounting for elastic strain build up at faults bonding rotating blocks. The geodetic and seismological data highlight two belts of higher deformation rates running WSW-ENE along the Eastern Southern Alps (ESA) in Italy and E-W in Slovenia, where deformation is more distributed. The highest geodetic strain-rates are observed in the Montello-Cansiglio segment of the ESA thrust front, for which the higher density of the GPS network provides indications of limited interseismic locking. Most of the dextral shear between the Eastern Southern Alps and the Eastern Alps blocks is accommodated along the Fella-Sava fault rather than the Periadriatic fault. In northern Croatia and Slovenia geodetic and seismological data allow constraining the kinematics of the active structures bounding the triangular-shaped region encompassing the Sava folds, which plays a major role in accommodating the transition from Adria- to Pannonian-like motion trends. The analysis of the seismic and geodetic moment rates provides new insights into the seismic potential along the ESA front.

International VLBI Service for Geodesy and Astrometry: 1999 Annual Report

NASA Technical Reports Server (NTRS)

Vandenberg, Nancy R. (Editor)

1999-01-01

This volume of reports is the 1999 Annual Report of the International VLBI Service for Geodesy and Astrometry -IVS. The individual reports were contributed by VLBI groups in the international geodetic community who constitute the components of IVS. The 1999 Annual Report documents the work of the IVS components for the year ending March 1, 1999, the official inauguration date of IVS. As the newest of the space technique services, IVS decided to publish this Annual Report as a reference to our organization and its components. The entire contents of this Annual Report also appear on the IVS website at: http://ivscc.gsfc.nasa.gov/pub/arl999. The IVS 1999 Annual Report will be a valuable reference for information about IVS and its components. This Annual Report will serve as a baseline from which we can measure the anticipated progress of IVS in coming years.

3D displacements maps of the L'Aquila earthquake by applying SISTEM method to GPS and ENVISAT and ALOS DInSAR data

NASA Astrophysics Data System (ADS)

Guglielmino, Francesco; Anzidei, Marco; Briole, Pierre; de Michele, Marcello; Elias, Panagiotis; Nunnari, Giuseppe; Puglisi, Giuseppe; Spata, Alessandro

2010-05-01

We present an application of the novel SISTEM (Simultaneous and Integrated Strain Tensor Estimation from geodetic and satellite deformation Measurements) approach [Guglielmino et al., 2009] to obtain a 3D estimation of the ground deformation pattern produced by the April 6, 2009, Mw 6.3 L'Aquila earthquake, the most destructive in the Abruzzo region since the huge 1703 earthquake [Boschi et al., 2000; Chiarabba et al., 2005]. The focal mechanism of the main shock is of normal faulting with NE-SW oriented T-axis [INGV, 2009]. Most of the aftershocks, located by the INGV seismic network, are in the depth range 5÷15 km, depicting a SW dipping fault plane [INGV, 2009]. Field observations [EMERGEO working group, 2009] have identified surface ground cracks with centimeter to decimeters throws over a wide belt running along the Paganica Fault. A closely spaced GPS (Global Positioning System) network was set up in this sector of the Apennines after 1999 [Anzidei et al., 2005] and more than 10 Continuous GPS (CGPS) stations have been operating in this region over the last years. On March 30 2008, INGV installed five GPS receivers on selected benchmarks of the Central Apennine Geodetic Network (CaGeoNet) bordering the L'Aquila basin in order to detect the eventual ground movements during the seismic sequence. These stations were crucial to resolve the near-field co-seismic deformation pattern properly, allowing direct observation of the details of co-seismic displacement related to the main shock. Thanks to the ESA Earth Watching project, which made Envisat data quickly available after their acquisition, we performed a DInSAR (Differential Interferometric Synthetic Aperture Radar) analysis of ascending and descending images sampling the date of the earthquake. In particular, we analyze the descending pair for the interval 27/04/2008 - 12/04/2009 (tbline = 350 days; Bperp = 44m) and the ascending pair for the interval 11/03/2009 - 15/04/2009 (tbline = 35 days; Bperp = 227m). We also analyzed ALOS PALSAR interferograms produced with images acquired along two different ascending tracks and relevant to the 3/7/2008 - 21/5/2009 time interval (track 638; tbline = 322 days; Bperp = 665 m ) and 2/3/2007 - 22/4/2009 time interval (track 639; tbline = 782 days; Bperp = 466 m ). In order to derive 3D surface motion maps, we apply the SISTEM method to the available geodetic dataset (both GPS and DInSAR). The SISTEM method performs an integration of GPS and DInSAR data for computing displacements on each point of the studied area. The SISTEM is based on elastic theory, and provides the complete 3D strain and the rigid body rotation tensors in the same solution. To achieve higher accuracy and get better the constraint of the 3D components of the displacements, we improved the standard formulation of SISTEM approach, based on a single DInSAR data, in order to take into account both ascending and descending interferograms and the DInSAR data acquired by different sensors(ALOS and ENVISAT). The SISTEM integration results show a complex kinematics, where the main movements (max westward movement of 165 mm associated with a max lowering of 260 mm) are recorded in the area between the surface evidence of the Paganica fault and Monticchio-fossa fault. These results, which provide both accurate and fine spatial characterization of ground deformation, are hence promising for future studies aimed at improving the knowledge of the kinematic of the Paganica fault and identification of additional faults responsible of the seismic sequence and that have contributed to the observed ground deformation. References. Anzidei, M., P. Baldi, A. Pesci, A. Esposito, A. Galvani, F. Loddo, P. Cristofoletti, A. Massucci, and S. Del Mese (2005), Geodetic deformation across the Central Apennines from GPS data in the time span 1999-2003, Ann. Geophys., 48(2), 259-271. Boschi, E., E. Guidoboni, G. Ferrrari, D. Mariotti, G. Valensise, and P. Gasperini (2000), Catalogue of strong Italian earthquakes from 461 B.C. to 1997, Ann. Geofis., 43, 609- 868. Chiarabba, C., L. Jovane, and R. Di Stefano (2005), A new view of Italian seismicity using 20 years of instrumental recordings, Tectonophysics, 395, 251-268, doi:10.1016/j.tecto.2004.09.013. EMERGEO Working Group (2009), Field geological survey in the epicentral area of the Abruzzi (central Italy) seismic sequence of April 6th, 2009, in Quaderni di Geofisica, vol. 70, Ist. Naz. Di Geofis. e Vulcanol., Rome. Guglielmino F., Nunnari G., Puglisi G., Spata A. (2009), Simultaneous and Integrated Strain Tensor Estimation from geodetic and satellite deformation Measurements (SISTEM) to obtain threedimensional displacements maps. Submitted to IEEE Transactions on Geoscience and Remote Sensing. Istituto Nazionale di Geofisica e Vulcanologia (INGV) (2009), The L'Aquila seismic sequence— April 2009, Ist. Naz. di Geofis. e Vulcanol., Rome. (Available at http://portale.ingv.it/).

The Wettzell System Monitoring Concept and First Realizations

NASA Technical Reports Server (NTRS)

Ettl, Martin; Neidhardt, Alexander; Muehlbauer, Matthias; Ploetz, Christian; Beaudoin, Christopher

2010-01-01

Automated monitoring of operational system parameters for the geodetic space techniques is becoming more important in order to improve the geodetic data and to ensure the safety and stability of automatic and remote-controlled observations. Therefore, the Wettzell group has developed the system monitoring software, SysMon, which is based on a reliable, remotely-controllable hardware/software realization. A multi-layered data logging system based on a fanless, robust industrial PC with an internal database system is used to collect data from several external, serial, bus, or PCI-based sensors. The internal communication is realized with Remote Procedure Calls (RPC) and uses generative programming with the interface software generator idl2rpc.pl developed at Wettzell. Each data monitoring stream can be configured individually via configuration files to define the logging rates or analog-digital-conversion parameters. First realizations are currently installed at the new laser ranging system at Wettzell to address safety issues and at the VLBI station O Higgins as a meteorological data logger. The system monitoring concept should be realized for the Wettzell radio telescope in the near future.

Linear homotopy solution of nonlinear systems of equations in geodesy

NASA Astrophysics Data System (ADS)

Paláncz, Béla; Awange, Joseph L.; Zaletnyik, Piroska; Lewis, Robert H.

2010-01-01

A fundamental task in geodesy is solving systems of equations. Many geodetic problems are represented as systems of multivariate polynomials. A common problem in solving such systems is improper initial starting values for iterative methods, leading to convergence to solutions with no physical meaning, or to convergence that requires global methods. Though symbolic methods such as Groebner bases or resultants have been shown to be very efficient, i.e., providing solutions for determined systems such as 3-point problem of 3D affine transformation, the symbolic algebra can be very time consuming, even with special Computer Algebra Systems (CAS). This study proposes the Linear Homotopy method that can be implemented easily in high-level computer languages like C++ and Fortran that are faster than CAS by at least two orders of magnitude. Using Mathematica, the power of Homotopy is demonstrated in solving three nonlinear geodetic problems: resection, GPS positioning, and affine transformation. The method enlarging the domain of convergence is found to be efficient, less sensitive to rounding of numbers, and has lower complexity compared to other local methods like Newton-Raphson.

Combined Exact-Repeat and Geodetic Mission Altimetry for High-Resolution Empirical Tide Mapping

NASA Astrophysics Data System (ADS)

Zaron, E. D.

2014-12-01

The configuration of present and historical exact-repeat mission (ERM) altimeter ground tracks determines the maximum resolution of empirical tidal maps obtained with ERM data. Although the mode-1 baroclinic tide is resolvable at mid-latitudes in the open ocean, the ability to detect baroclinic and barotropic tides near islands and complex coastlines is limited, in part, by ERM track density. In order to obtain higher resolution maps, the possibility of combining ERM and geodetic mission (GM) altimetry is considered, using a combination of spatial thin-plate splines and temporal harmonic analysis. Given the present spatial and temporal distribution of GM missions, it is found that GM data can contribute to resolving tidal features smaller than 75 km, provided the signal amplitude is greater than about 1 cm. Uncertainties in the mean sea surface and environmental corrections are significant components of the GM error budget, and methods to optimize data selection and along-track filtering are still being optimized. Application to two regions, Monterey Bay and Luzon Strait, finds evidence for complex tidal fields in agreement with independent observations and modeling studies.

The Earth isn't flat: The (large) influence of topography on geodetic fault slip imaging.

NASA Astrophysics Data System (ADS)

Thompson, T. B.; Meade, B. J.

2017-12-01

While earthquakes both occur near and generate steep topography, most geodetic slip inversions assume that the Earth's surface is flat. We have developed a new boundary element tool, Tectosaur, with the capability to study fault and earthquake problems including complex fault system geometries, topography, material property contrasts, and millions of elements. Using Tectosaur, we study the model error induced by neglecting topography in both idealized synthetic fault models and for the cases of the MW=7.3 Landers and MW=8.0 Wenchuan earthquakes. Near the steepest topography, we find the use of flat Earth dislocation models may induce errors of more than 100% in the inferred slip magnitude and rake. In particular, neglecting topographic effects leads to an inferred shallow slip deficit. Thus, we propose that the shallow slip deficit observed in several earthquakes may be an artefact resulting from the systematic use of elastic dislocation models assuming a flat Earth. Finally, using this study as an example, we emphasize the dangerous potential for forward model errors to be amplified by an order of magnitude in inverse problems.

Modern Geodetic Measurement Techniques in Gravimetric Studies on the Example of Gypsum Karst in the Siesławice Region

NASA Astrophysics Data System (ADS)

Porzucek, Sławomir; Łój, Monika; Matwij, Karolina; Matwij, Wojciech

2018-03-01

In the region of Siesławice (near Busko-Zdrój, Poland) there are unique phenomena of gypsum karst. Atmospheric factors caused numerous gypsum outcrops, canals and underground voids. The article presents the possibility of using non-invasive gravimetric surveys supplemented with geodetic measurements to illustrate karst changes occurring around the void. The use of modern geodetic measurement techniques including terrestrial and airborne laser scanning enables to generate a digital terrain model and a three-dimensional model of voids. Gravimetric field studies allowed to map the anomalies of the gravitational field of the near-surface zone. Geodetic measurement results have made it possible to accurately determine the terrain correction that supplemented the gravimetric anomaly information. Geophysical interpretation indicate the presence of weathered rocks in the near surface zone and fractures and loosened zones located surround the karst cave.

Ice cap melting and low-viscosity crustal root explain the narrow geodetic uplift of the Western Alps

NASA Astrophysics Data System (ADS)

Chéry, J.; Genti, M.; Vernant, P.

2016-04-01

More than 10 years of geodetic measurements demonstrate an uplift rate of 1-3 mm/yr of the high topography region of the Western Alps. By contrast, no significant horizontal motion has been detected. Two uplift mechanisms have been proposed: (1) the isostatic response to denudation responsible for only a fraction of the observed uplift and (2) the rebound induced by the Wurmian ice cap melting which predicts a broader uplifting region than the one evidenced by geodetic observations. Using a numerical model to fit the geodetic data, we show that a crustal viscosity contrast between the foreland and the central part of the Alps, the latter being weaker with a viscosity of 1021 Pa s, is needed. The vertical rates are enhanced if the strong uppermost mantle beneath the Moho is interrupted across the Alps, therefore allowing a weak vertical rheological anomaly over the entire lithosphere.

Delay estimation in digital correlation interferometers with special consideration of the MK 2 system of the Max-Planck Institute of Radio Astronomy

NASA Astrophysics Data System (ADS)

Beyer, W. K. G.

The estimation accuracy of the group delay measured in a single video frequency band was analyzed as a function of the system bandwidth and the signal to noise ratio. Very long base interferometry (VLBI) measurements from geodetic experiments were used to check the geodetic applicability of the Mark 2 evaluation system. The geodetic observation quantities and the correlation geometry are introduced. The data flow in the VLBI experiment, the correlation analysis, the analyses and evaluation in the MK2 system, and the delay estimation procedure following the least squares method are presented. It is shown that the MK2 system is no longer up to date for geodetic applications. The superiority of the developed estimation method with respect to the interpolation algorithm is demonstrated. The numerical investigations show the deleterious influence of the distorting bit shift effects.

Integrating Analysis Goals for EOP, CRF and TRF

NASA Technical Reports Server (NTRS)

Ma, Chopo; MacMillan, D.; Petrov, L.; Smith, David E. (Technical Monitor)

2001-01-01

In a simplified, idealized way the TRF can be considered a set of positions at epoch and corresponding linear rates of change while the CRF is a set of fixed directions in space. VLBI analysis can be optimized for CRF and TRF separately while handling some of the complexity of geodetic and astrometric reality. For EOP time series both CRF and TRF should be accurate at the epoch of interest and well defined over time. The optimal integral EOP, TRF and CRF in a single VLBI solution configuration requires a detailed consideration of the data set and the possibly conflicting nature of reference frames.

Geodetic positioning of the Aerospace Electronics Research Lab (ERL) Osborne Time Transfer Receiver (TTR) using the GPS NAVSTAR Block I satellites

NASA Technical Reports Server (NTRS)

Liu, Anthony S.

1990-01-01

Aerospace has routinely processed the Osborne Time Transfer Receiver (TTR) data for the purpose of monitoring the performance of ground and GPS atomic clocks in near real-time with on-line residual displays and characterizing clock stability with Allan Variance calculations. Recently, Aerospace added the ability to estimate the TTR's location by differentially correcting the TTR's location in the WGS84 reference system. This new feature is exercised on a set of TTR clock phase data and Sub-meter accurate station location estimates of the TTR at the Aerospace Electronic Research Lab (ERL) are obtained.

A strawman SLR program plan for the 1990s

NASA Technical Reports Server (NTRS)

Degnan, John J.

1994-01-01

A series of programmatic and technical goals for the satellite laser ranging (SLR) network are presented. They are: (1) standardize the performance of the global SLR network; (2) improve the geographic distribution of stations; (3) reduce costs of field operations and data processing; (4) expand the 24 hour temporal coverage to better serve the growing constellation of satellites; (5) improve absolute range accuracy to 2 mm at key stations; (6) improve satellite force, radiative propagation, and station motion models and investigate alternative geodetic analysis techniques; (7) support technical intercomparison and the Terrestrial Reference Frame through global collocations; (8) investigate potential synergisms between GPS and SLR.

Geodetic measurement of deformation in the Loma Prieta, California earthquake with very long baseline interferometry

NASA Technical Reports Server (NTRS)

Clark, T. A.; Ma, C.; Sauber, J. M.; Ryan, J. W.; Gordon, D.; Shaffer, D. B.; Carprette, D. S.; Vandenberg, N. R.

1990-01-01

VLBI measurements were conducted immediately after the Loma Prieta earthquake and compared with VLBI gathered at Monterey, San Francisco, and Point Reyes since 1983 to obtain preearthquake deformation rates with respect to a North American reference frame. The estimated displacements at Monterey and San Francisco are consistent with the static displacements predicted on the basis of a coseismic slip model in which slip on the southern segment is shallower than slip on the northern segment of the fault rupture. Cartesian positions are presented at epoch 1990.0 of a set of VLBI fiducial stations and the three mobile sites in the earthquake's vicinity.

Geodetic Strain Analysis Tool

NASA Technical Reports Server (NTRS)

Kedar, Sharon; Baxter, Sean C.; Parker, Jay W.; Webb, Frank H.; Owen, Susan E.; Sibthorpe, Anthony J.; Dong, Danan

2011-01-01

A geodetic software analysis tool enables the user to analyze 2D crustal strain from geodetic ground motion, and create models of crustal deformation using a graphical interface. Users can use any geodetic measurements of ground motion and derive the 2D crustal strain interactively. This software also provides a forward-modeling tool that calculates a geodetic velocity and strain field for a given fault model, and lets the user compare the modeled strain field with the strain field obtained from the user s data. Users may change parameters on-the-fly and obtain a real-time recalculation of the resulting strain field. Four data products are computed: maximum shear, dilatation, shear angle, and principal components. The current view and data dependencies are processed first. The remaining data products and views are then computed in a round-robin fashion to anticipate view changes. When an analysis or display parameter is changed, the affected data products and views are invalidated and progressively re-displayed as available. This software is designed to facilitate the derivation of the strain fields from the GPS and strain meter data that sample it to facilitate the understanding of the strengths and weaknesses of the strain field derivation from continuous GPS (CGPS) and other geodetic data from a variety of tectonic settings, to converge on the "best practices" strain derivation strategy for the Solid Earth Science ESDR System (SESES) project given the CGPS station distribution in the western U.S., and to provide SESES users with a scientific and educational tool to explore the strain field on their own with user-defined parameters.

Update on High-Resolution Geodetically Controlled LROC Polar Mosaics

NASA Astrophysics Data System (ADS)

Archinal, B.; Lee, E.; Weller, L.; Richie, J.; Edmundson, K.; Laura, J.; Robinson, M.; Speyerer, E.; Boyd, A.; Bowman-Cisneros, E.; Wagner, R.; Nefian, A.

2015-10-01

We describe progress on high-resolution (1 m/pixel) geodetically controlled LROC mosaics of the lunar poles, which can be used for locating illumination resources (for solar power or cold traps) or landing site and surface operations planning.

Off Shore Geodetic Measurements Simulations in the Context of Seismic and Tsunami Hazard Evaluation in the Lesser Antilles

NASA Astrophysics Data System (ADS)

Sakic, P.; Ballu, V.; Piete, H.; Royer, J. Y.; de Chabalier, J. B.

2015-12-01

Based on the current state of knowledge, the megathrust/tsunami hazard estimation in the Lesser Antilles forearc remains uncertain. Some major events have been reported (e.g. the 1843 earthquake estimated with a IX intensity), however no associated mega-tsunami has been recorded, maybe because of the nature of the event (slab locked up to the trench or not) or the too short observation period. GNSS monitoring networks are deployed on all Caribbean Islands (Guadeloupe and Martinique in particular). However, land areas are far from the trench, and their configuration is not optimal for the strain measurement related to a possible locking between the two plates up to the seafloor.The GPS/Acoustics (GPS/A) technique aims to overcome this limitation. It consists of a surface platform used as a relay between aerial and underwater media. The position is obtained in a global reference frame by GNSS kinematic processing and is transferred to the seafloor by acoustic ranging to a set of transponders permanently installed on the seabed. Repeated measurements over the years will allow to compute the velocity of the study area in a global reference frame. We present a case study for a future deployment of this kind of submarine network off the French Caribbean Islands. Numerical simulations of GPS/A are performed in order to evaluate the accuracy achievable in the Antilles context, using water variability information from past oceanographic campaigns and MOVE buoys. The kinematic GNSS treatments are carried out on test cruises data by different methods (real-time differential, differential post treatment and Precise Point Positioning) to assess the performances in different conditions. In order to characterize the geophysical context, we also present a reprocessing of the GNSS stations of the Guadeloupe and Martinique Islands using a PPP approach with the CNES GINS software, along with a finite element model of the subduction zone.

Rigorous Combination of GNSS and VLBI: How it Improves Earth Orientation and Reference Frames

NASA Astrophysics Data System (ADS)

Lambert, S. B.; Richard, J. Y.; Bizouard, C.; Becker, O.

2017-12-01

Current reference series (C04) of the International Earth Rotation and Reference Systems Service (IERS) are produced by a weighted combination of Earth orientation parameters (EOP) time series built up by combination centers of each technique (VLBI, GNSS, Laser ranging, DORIS). In the future, we plan to derive EOP from a rigorous combination of the normal equation systems of the four techniques.We present here the results of a rigorous combination of VLBI and GNSS pre-reduced, constraint-free, normal equations with the DYNAMO geodetic analysis software package developed and maintained by the French GRGS (Groupe de Recherche en GeÌodeÌsie Spatiale). The used normal equations are those produced separately by the IVS and IGS combination centers to which we apply our own minimal constraints.We address the usefulness of such a method with respect to the classical, a posteriori, combination method, and we show whether EOP determinations are improved.Especially, we implement external validations of the EOP series based on comparison with geophysical excitation and examination of the covariance matrices. Finally, we address the potential of the technique for the next generation celestial reference frames, which are currently determined by VLBI only.

South American regional ionospheric maps computed by GESA: A pilot service in the framework of SIRGAS

NASA Astrophysics Data System (ADS)

Brunini, C.; Meza, A.; Gende, M.; Azpilicueta, F.

2008-08-01

SIRGAS (Geocentric Reference Frame for the Americas) is an international enterprise of the geodetic community that aims to realize the Terrestrial Reference Frame in the America's countries. In order to fulfill this commitment, SIRGAS manages a network of continuously operational GNSS receivers totalling around one hundred sites in the Caribbean, Central, and South American region. Although the network was not planed for ionospheric studies, its potential to be used for such a purpose was recently recognized and SIRGAS started a pilot experiment devoted to establish a regular service for computing and releasing regional vertical TEC (vTEC) maps based on GNSS data. Since July, 2005, the GESA (Geodesia Espacial y Aeronomía) laboratory belonging to the Facultad de Ciencias Astronómicas y Geofísicas of the Universidad Nacional de La Plata computes hourly maps of vertical Total Electron Content (vTEC) in the framework of the SIRGAS pilot experiment. These maps exploit all the GNSS data available in the South American region and are computed with the LPIM (La Plata Ionospheric Model). LPIM implements a de-biasing procedure that improves data calibration in relation to other procedures commonly used for such purposes. After calibration, slant TEC measurements are converted to vertical and mapped using local-time and modip latitude. The use of modip latitude smoothed the spatial variability of vTEC, especially in the South American low latitude region and hence allows for a better vTEC interpolation. This contribution summarizes the results obtained by GESA in the framework of the SIRGAS pilot experiment.

The International Gravity Field Service (IGFS): Present Day Activities And Future Plans

NASA Astrophysics Data System (ADS)

Barzaghi, R.; Vergos, G. S.

2016-12-01

IGFS is a unified "umbrella" IAG service that coordinates the servicing of the geodetic and geophysical community with gravity field related data, software and information. The combined data of the IGFS entities will include global geopotential models, terrestrial, airborne, satellite and marine gravity observations, Earth tide data, GPS/levelling data, digital models of terrain and bathymetry, as well as ocean gravity field and geoid from satellite altimetry. The IGFS structure is based on the Gravity Services, the "operating arms" of IGFS. These Services related to IGFS are: BGI (Bureau Gravimetrique International), Toulouse, France ISG (International Service for the Geoid), Politecnico di Milano, Milano, Italy IGETS (International Geodynamics and Earth Tides Service), EOST, Strasbourg, France ICGEM (International Center for Global Earth Models), GFZ, Potsdam, Germany IDEMS (International Digital Elevation Model Service), ESRI, Redlands, CA, USA The Central Bureau, hosted at the Aristotle Thessaloniki University, is in charge for all the interactions among the services and the other IAG bodies, particularly GGOS. In this respect, connections with the GGOS Bureaus of Products and Standards and of Networks and Observations have been recently strengthened in order to align the Gravity services to the GGOS standards. IGFS is also strongly involved in the most relevant projects related to the gravity field such as the establishment of the new Global Absolute Gravity Reference System and of the International Height Reference System. These projects, along with the organization of Geoid Schools devoted to methods for gravity and geoid estimate, will play a central role in the IGFS future actions in the framework of GGOS.

A compensated multi-pole linear ion trap mercury frequency standard for ultra-stable timekeeping.

PubMed

Burt, Eric A; Diener, William A; Tjoelker, Robert L

2008-12-01

The multi-pole linear ion trap frequency standard (LITS) being developed at the Jet Propulsion Laboratory (JPL) has demonstrated excellent short- and long-term stability. The technology has now demonstrated long-term field operation providing a new capability for timekeeping standards. Recently implemented enhancements have resulted in a record line Q of 5 x 10(12) for a room temperature microwave atomic transition and a short-term fractional frequency stability of 5 x 10(-14)/tau(1/2). A scheme for compensating the second order Doppler shift has led to a reduction of the combined sensitivity to the primary LITS systematic effects below 5 x 10(-17) fractional frequency. Initial comparisons to JPL's cesium fountain clock show a systematic floor of less than 2 x 10(-16). The compensated multi-pole LITS at JPL was operated continuously and unattended for a 9-mo period from October 2006 to July 2007. During that time it was used as the frequency reference for the JPL geodetic receiver known as JPLT, enabling comparisons to any clock used as a reference for an International GNSS Service (IGS) site. Comparisons with the laser-cooled primary frequency standards that reported to the Bureau International des Poids et Mesures (BIPM) over this period show a frequency deviation less than 2.7 x 10(-17)/day. In the capacity of a stand-alone ultra-stable flywheel, such a standard could be invaluable for long-term timekeeping applications in metrology labs while its methodology and robustness make it ideal for space applications as well.

An accuracy assessment of realtime GNSS time series toward semi- real time seafloor geodetic observation

NASA Astrophysics Data System (ADS)

Osada, Y.; Ohta, Y.; Demachi, T.; Kido, M.; Fujimoto, H.; Azuma, R.; Hino, R.

2013-12-01

Large interplate earthquake repeatedly occurred in Japan Trench. Recently, the detail crustal deformation revealed by the nation-wide inland GPS network called as GEONET by GSI. However, the maximum displacement region for interplate earthquake is mainly located offshore region. GPS/Acoustic seafloor geodetic observation (hereafter GPS/A) is quite important and useful for understanding of shallower part of the interplate coupling between subducting and overriding plates. We typically conduct GPS/A in specific ocean area based on repeated campaign style using research vessel or buoy. Therefore, we cannot monitor the temporal variation of seafloor crustal deformation in real time. The one of technical issue on real time observation is kinematic GPS analysis because kinematic GPS analysis based on reference and rover data. If the precise kinematic GPS analysis will be possible in the offshore region, it should be promising method for real time GPS/A with USV (Unmanned Surface Vehicle) and a moored buoy. We assessed stability, precision and accuracy of StarFireTM global satellites based augmentation system. We primarily tested for StarFire in the static condition. In order to assess coordinate precision and accuracy, we compared 1Hz StarFire time series and post-processed precise point positioning (PPP) 1Hz time series by GIPSY-OASIS II processing software Ver. 6.1.2 with three difference product types (ultra-rapid, rapid, and final orbits). We also used difference interval clock information (30 and 300 seconds) for the post-processed PPP processing. The standard deviation of real time StarFire time series is less than 30 mm (horizontal components) and 60 mm (vertical component) based on 1 month continuous processing. We also assessed noise spectrum of the estimated time series by StarFire and post-processed GIPSY PPP results. We found that the noise spectrum of StarFire time series is similar pattern with GIPSY-OASIS II processing result based on JPL rapid orbit products with 300 seconds interval clock information. And we report stability, precision and accuracy of StarFire in the moving conditon.

Satellite laser ranging as a tool for the recovery of tropospheric gradients

NASA Astrophysics Data System (ADS)

Drożdżewski, M.; Sośnica, K.

2018-11-01

Space geodetic techniques, such as Global Navigation Satellite Systems (GNSS) and Very Long Baseline Interferometry (VLBI) have been extensively used for the recovery of the tropospheric parameters. Both techniques employ microwave observations, for which the troposphere is a non-dispersive medium and which are very sensitive to the water vapor content. Satellite laser ranging (SLR) is the only space geodetic technique used for the definition of the terrestrial reference frames which employs optical - laser observations. The SLR sensitivity to the hydrostatic part of the troposphere delay is similar to that of microwave observations, whereas the sensitivity of laser observations to non-hydrostatic part of the delay is about two orders of magnitude smaller than in the case of microwave observations. Troposphere is a dispersive medium for optical wavelengths, which means that the SLR tropospheric delay depends on the laser wavelength. This paper presents the sensitivity and capability of the SLR observations for the recovery of azimuthal asymmetry over the SLR stations, which can be described as horizontal gradients of the troposphere delay. For the first time, the horizontal gradients are estimated, together with other parameters typically estimated from the SLR observations to spherical LAGEOS satellites, i.e., station coordinates, earth rotation parameters, and satellite orbits. Most of the SLR stations are co-located with GNSS receivers, thus, a cross-correlation between both techniques is possible. We compare our SLR horizontal gradients to GNSS results and to the horizontal gradients derived from the numerical weather models (NWM). Due to a small number of the SLR observations, SLR is not capable of reconstructing short-period phenomena occurring in the atmosphere. However, the long-term analysis allows for the recovery of the atmosphere asymmetry using SLR. As a result, the mean offsets of the SLR-derived horizontal gradients agree to the level of 47%, 74%, 54% with GNSS, hydrostatic delay, and total delay from NWM, respectively. SLR can be thus employed as a tool for the recovery of the atmospheric parameters with a major sensitivity to the hydrostatic part of the delay.

GGOS Focus Area 3: Understanding and Forecasting Sea-Level Rise and Variability

NASA Astrophysics Data System (ADS)

Schöne, Tilo; Shum, Ck; Tamisiea, Mark; Woodworth, Philip

2017-04-01

Sea level and its change have been measured for more than a century. Especially for coastal nations, deltaic regions, and coastal-oriented industries, observations of tides, tidal extremes, storm surges, and sea level rise at the interannual or longer scales have substantial impacts on coastal vulnerability towards resilience and sustainability of world's coastal regions. To date, the observed global sea level rise is largely associated with climate related changes. To find the patterns and fingerprints of those changes, and to e.g., separate the land motion from sea level signals, different monitoring techniques have been developed. Some of them are local, e.g., tide gauges, while others are global, e.g., satellite altimetry. It is well known that sea level change and land vertical motion varies regionally, and both signals need to be measured in order to quantify relative sea level at the local scale. The Global Geodetic Observing System (GGOS) and its services contribute in many ways to the monitoring of the sea level. These includes tide gauge observations, estimation of gravity changes, satellite altimetry, InSAR/Lidar, GNSS-control of tide gauges, providing ground truth sites for satellite altimetry, and importantly the maintenance of the International Reference Frame. Focus Area 3 (Understanding and Forecasting Sea-Level Rise and Variability) of GGOS establishes a platform and a forum for researchers and authorities dealing with estimating global and local sea level changes in a 10- to 30-year time span, and its project to the next century or beyond. It presents an excellent opportunity to emphasize the global, through to regional and local, importance of GGOS to a wide range of sea-level related science and practical applications. Focus Area 3 works trough demonstration projects to highlight the value of geodetic techniques to sea level science and applications. Contributions under a call for participation (http://www.ggos.org/Applications/theme3_SL.html) are welcome. The present status of GGOS Focus Area 3 will be highlighted. http://www.ggos-portal.org/lang_en/GGOS-Portal/EN/Themes/SeaLevel/seaLevel.html

Future global SLR network evolution and its impact on the terrestrial reference frame

NASA Astrophysics Data System (ADS)

Kehm, Alexander; Bloßfeld, Mathis; Pavlis, Erricos C.; Seitz, Florian

2018-06-01

Satellite laser ranging (SLR) is an important technique that contributes to the determination of terrestrial geodetic reference frames, especially to the realization of the origin and the scale of global networks. One of the major limiting factors of SLR-derived reference frame realizations is the datum accuracy which significantly suffers from the current global SLR station distribution. In this paper, the impact of a potential future development of the SLR network on the estimated datum parameters is investigated. The current status of the SLR network is compared to a simulated potential future network featuring additional stations improving the global network geometry. In addition, possible technical advancements resulting in a higher amount of observations are taken into account as well. As a result, we find that the network improvement causes a decrease in the scatter of the network translation parameters of up to 24%, and up to 20% for the scale, whereas the technological improvement causes a reduction in the scatter of up to 27% for the translations and up to 49% for the scale. The Earth orientation parameters benefit by up to 15% from both effects.

77 FR 26959 - Final Flood Elevation Determinations

Federal Register 2010, 2011, 2012, 2013, 2014

2012-05-08

... Creek confluence. * National Geodetic Vertical Datum. + North American Vertical Datum. Depth in feet... County, Indiana, and Incorporated Areas Docket No.: FEMA-B-1171 Big Walnut Creek Approximately 845 feet... feet upstream +692 of Houck Road (North County Road 25 East). * National Geodetic Vertical Datum...

76 FR 1121 - Proposed Flood Elevation Determinations

Federal Register 2010, 2011, 2012, 2013, 2014

2011-01-07

... approximately 410 feet of Lewis County. upstream of U.S. Route 61 Business. * National Geodetic Vertical Datum... intersection of Impact Drive and FM Road 2404. * National Geodetic Vertical Datum. + North American Vertical..., Environmental Consideration. An environmental impact assessment has not been prepared. Regulatory Flexibility...

The Importance of Geodetically Controlled Data Sets: THEMIS Controlled Mosaics of Mars, a Case Study

NASA Astrophysics Data System (ADS)

Fergason, R. L.; Weller, L.

2018-04-01

Accurate image registration is necessary to answer questions that are key to addressing fundamental questions about our universe. To provide such a foundational product for Mars, we have geodetically controlled and mosaicked THEMIS IR images.

23 CFR 630.402 - Policy.

Code of Federal Regulations, 2011 CFR

2011-04-01

... 23 Highways 1 2011-04-01 2011-04-01 false Policy. 630.402 Section 630.402 Highways FEDERAL HIGHWAY ADMINISTRATION, DEPARTMENT OF TRANSPORTATION ENGINEERING AND TRAFFIC OPERATIONS PRECONSTRUCTION PROCEDURES Geodetic Markers § 630.402 Policy. (a) Geodetic surveys along Federal-aid highway routes may be programmed...

Foundational Data Products for Europa: A Planetary Spatial Data Infrastructure Example

NASA Astrophysics Data System (ADS)

Archinal, B. A.; Laura, J.; Becker, T. L.; Bland, M. T.; Kirk, R. L.

2017-12-01

Any Spatial Data Infrastructure (SDI), including a Planetary SDI (PSDI [1]), includes primary components such as "policy, access network, technical standards, people (including partnerships), and data" [2]. Data is largely categorized into critical foundational products and framework data products. Of data themes [3] previously identified for the U. S. National SDI, we identify [4] three types of products that are foundational to a PSDI: geodetic coordinate reference systems, elevation information, and orthomosaics. We previously listed examples of such products for the Moon (ibid.). Here, we list the current state of these three foundational products for Europa, a key destination in the outer Solar System. Geodetic coordinate reference systems for Europa are based on photogrammetric control networks generated from processing of Voyager and Galileo images, the most recent being that created by M. Davies and T. Colvin at The RAND Corporation in the late 1990s. The Voyager and Galileo images provide insufficient stereo coverage to derive a detailed global topographic model, but various global ellipsoidal shape models have been derived using e.g. the RAND network or limb profile data. The best-known global mosaic of Europa is a controlled orthomosaic produced by the U.S. Geological Survey [5], based on the RAND network and triaxial ellipsoid shape model. Near future needs include comparing the resolution and accuracy of these products with estimates for newer products that might supersede them, including released or unreleased regional products (such as digital terrain models or mosaics) and products that could be made by processing of extant data. Understanding these PSDI fundamental needs will also improve assessing and prioritizing products that are planned for by the upcoming NASA Europa Clipper mission. This effort is not only useful for Europa science, but is also a first step toward developing such summaries for all Solar System bodies with relevant data, which collectively will serve as a foundation of an entire PSDI. References: [1] Laura et al., ISPRS J. Geo-Info., 6, #181. [2] Rajabifard and Williamson, in Williamson and Rajabifard, eds., ISPRS-WG IV/8, Hong Kong, China, Ch. 6, 2001. [3] OMB Circular A-16 Supp. Guidance. [4] LPS XLVIII, #2286. [5] USGS map I-2757.

Modernizing the National Spatial Reference System

NASA Astrophysics Data System (ADS)

Smith, D. A.

2016-12-01

The National Spatial Reference System (NSRS) is that system of datums, reference frames, shorelines, software and standards which serve the entire federal civilian geospatial community. It is the mission of the National Geodetic Survey (NGS) to define, maintain and provide access to the NSRS. Currently the NSRS contains three geometric reference frames (NAD 83(2011), NAD 83(PA11) and NAD 83(MA11)), one dynamic height datum (IGLD 85) and 6 vertical datums (NAVD 88, PRVD02, ASVD02, NMVD03, GUVD04, VIVD09). All of these datums are built on aging technology and contain systematic errors that grow more noticeable as access to accurate positioning becomes more widespread. It was determined by NGS in 2007 that this was not sustainable and as such, all datums and reference frames are scheduled to be replaced in 2022. [At the time of this abstract, the exact names of the replacements are being finalized and are expected to be announced by the AGU fall meeting.] Replacing the official datums and reference frames requires a carefully coordinated effort of dozens of interrelated technical projects spanning years (over a decade in some cases) and involving a majority of NGS employees. This talk will cover the plans thus far, projects completed, projects underway and will summarize the NSRS as it is expected to look and be accessed in 2022 and beyond.

An Autonomous, Low Cost Platform for Seafloor Geodetic Observations

NASA Astrophysics Data System (ADS)

Ericksen, T.; Foster, J. H.; Bingham, B. S.; Oshiro, J.

2014-12-01

The Pacific GPS Facility and the Field Robotics Laboratory at the University of Hawaii have developed an approach to significantly reduce costs below ship based methods of accurately measuring short-term vertical motions of the seafloor and maintaining a continuous long-term record of seafloor pressure. Our goal has been to reduce the primary barrier preventing us from acquiring the observations we need to understand geodetic processes, and the hazards they present, at subduction zones, submarine volcanoes, and subsea landslides. To this end, we have designed a payload package for one of the University of Hawaii Wave Gliders which incorporates an acoustic telemetry package, a dual frequency geodetic-grade Global Positioning System (GPS) receiver, meteorological sensors, processing computer, and cellular communications. The Wave Glider will interrogate high accuracy pressure sensors on the seafloor to maintain a near-continuous stream of pressure and temperature data. The seafloor geodetic monument seats a sensor capable of recording pressure, temperature, and sound velocity for a deployment duration of over 5 years with an acoustic modem for communications, and an integral acoustic release for recovery and replacement of batteries. The design of the geodetic monument allows for precise repositioning of the sensor to extend the pressure record beyond a single 5+ year deployment, and includes the capability to install a mobile pressure recorder for calibration of the linear drift of the continuous pressure sensor. We will present the design of the Wave Glider payload and seafloor geodetic monument, as well as a discussion of nearshore and offshore field tests and operational procedures. An assessment of our ability to determine cm-scale vertical seafloor motions will be made by integrating the seafloor pressure measurements recovered during field testing with independent measurements of sea surface pressure and sea surface height made by the sea surface payload.

Recurrent landsliding of a high bank at Dunaszekcső, Hungary: Geodetic deformation monitoring and finite element modeling

NASA Astrophysics Data System (ADS)

Bányai, László; Mentes, Gyula; Újvári, Gábor; Kovács, Miklós; Czap, Zoltán; Gribovszki, Katalin; Papp, Gábor

2014-04-01

Five years of geodetic monitoring data at Dunaszekcső, Hungary, are processed to evaluate recurrent landsliding, which is a characteristic geomorphological process affecting the high banks of the Middle Danube valley in Hungary. The integrated geodetic observations provide accurate three dimensional coordinate time series, and these data are used to calculate the kinematic features of point movements and the rigid body behavior of point blocks. Additional datasets include borehole tiltmeter data and hydrological recordings of the Danube and soil water wells. These data, together with two dimensional final element analyses, are utilized to gain a better understanding of the physical, soil mechanical background and stability features of the high bank. Here we indicate that the main trigger of movements is changing groundwater levels, whose effect is an order of magnitude higher than that of river water level changes. Varying displacement rates of the sliding blocks are interpreted as having been caused by basal pore water pressure changes originating from shear zone volume changes, floods of the River Danube through later seepage and rain infiltration. Both data and modeling point to the complex nature of bank sliding at Dunaszekcső. Some features imply that the movements are rotational, some reveal slumping. By contrast, all available observational and modeling data point to the retrogressive development of the high bank at Dunaszekcső. Regarding mitigation, the detailed analysis of three basic parameters (the direction of displacement vectors, tilting, and the acceleration component of the kinematic function) is suggested because these parameters indicate the zone where the largest lateral displacements can be expected and point to the advent of the rapid landsliding phase that affects high banks along the River Danube.

ISSM-SESAW v1.0: mesh-based computation of gravitationally consistent sea-level and geodetic signatures caused by cryosphere and climate driven mass change

NASA Astrophysics Data System (ADS)

Adhikari, Surendra; Ivins, Erik R.; Larour, Eric

2016-03-01

A classical Green's function approach for computing gravitationally consistent sea-level variations associated with mass redistribution on the earth's surface employed in contemporary sea-level models naturally suits the spectral methods for numerical evaluation. The capability of these methods to resolve high wave number features such as small glaciers is limited by the need for large numbers of pixels and high-degree (associated Legendre) series truncation. Incorporating a spectral model into (components of) earth system models that generally operate on a mesh system also requires repetitive forward and inverse transforms. In order to overcome these limitations, we present a method that functions efficiently on an unstructured mesh, thus capturing the physics operating at kilometer scale yet capable of simulating geophysical observables that are inherently of global scale with minimal computational cost. The goal of the current version of this model is to provide high-resolution solid-earth, gravitational, sea-level and rotational responses for earth system models operating in the domain of the earth's outer fluid envelope on timescales less than about 1 century when viscous effects can largely be ignored over most of the globe. The model has numerous important geophysical applications. For example, we compute time-varying computations of global geodetic and sea-level signatures associated with recent ice-sheet changes that are derived from space gravimetry observations. We also demonstrate the capability of our model to simultaneously resolve kilometer-scale sources of the earth's time-varying surface mass transport, derived from high-resolution modeling of polar ice sheets, and predict the corresponding local and global geodetic signatures.

75 FR 59095 - Final Flood Elevation Determinations

Federal Register 2010, 2011, 2012, 2013, 2014

2010-09-27

... Mile 673........ +202 * National Geodetic Vertical Datum. + North American Vertical Datum. Depth in...,434 upstream of Northeast 24th Street. * National Geodetic Vertical Datum. + North American Vertical Datum. Depth in feet above ground. [caret] Mean Sea Level, rounded to the nearest 0.1 meter. ADDRESSES...

A study program for geodetic satellite applications

NASA Technical Reports Server (NTRS)

Pearlman, M. R.

1972-01-01

The work is reported on support of the GEOS-C Program, National Geodetic Satellite program, and the Earth Physics Program. The statement of work, and a description of the GEOS-C are presented along with the trip reports, and the Earth and Ocean Physics Application program.

LANDSAT-4 MSS Geometric Correction: Methods and Results

NASA Technical Reports Server (NTRS)

Brooks, J.; Kimmer, E.; Su, J.

1984-01-01

An automated image registration system such as that developed for LANDSAT-4 can produce all of the information needed to verify and calibrate the software and to evaluate system performance. The on-line MSS archive generation process which upgrades systematic correction data to geodetic correction data is described as well as the control point library build subsystem which generates control point chips and support data for on-line upgrade of correction data. The system performance was evaluated for both temporal and geodetic registration. For temporal registration, 90% errors were computed to be .36 IFOV (instantaneous field of view) = 82.7 meters) cross track, and .29 IFOV along track. Also, for actual production runs monitored, the 90% errors were .29 IFOV cross track and .25 IFOV along track. The system specification is .3 IFOV, 90% of the time, both cross and along track. For geodetic registration performance, the model bias was measured by designating control points in the geodetically corrected imagery.

On Similarity Transformation and Geodetic Network Distortions Based on Doppler Satellite Observations

NASA Technical Reports Server (NTRS)

Leick, Alfred; Vangelder, Boudewijn H. W.

1975-01-01

Models used in geodesy to transform two sets of coordinates are studied and distortions in geodetic networks are investigated. Commonly used transformation models are first reviewed and most of them are interpreted. Differences between various models are discussed. Pitfalls in partial solutions are then considered. It is shown that only as many chords and/or directional elements can be used in the computation as are needed to completely determine the size or shape of the polyhedron implied in the set of Cartesian coordinates. Each additional element causes the normal matrix to be singular provided that all correlations between the chords are used. A number of tables and maps indicating distortions in the NAD 27, Precise Traverse M-R '72, AUS, and SAD 69 geodetic datums are also included. The residuals of the coordinates are scanned for systematic patterns after transforming each geodetic system to the NWL9D Doppler system. Also, an attempt is made to show scale distortions in the NAD 27.

Aseismic Deformation Associated with an Earthquake Swarm in the Northern Apennines (Italy)

NASA Astrophysics Data System (ADS)

Gualandi, A.; Nichele, C.; Serpelloni, E.; Chiaraluce, L.; Anderlini, L.; Latorre, D.; Belardinelli, M. E.; Avouac, J. P.

2017-12-01

Analyzing the displacement time series from continuous GPS (cGPS) with an Independent Component Analysis (ICA) we detect a transient deformation signal that correlates both in space and time with a seismic swarm activity (maximum Mw = 3.69 ± 0.09) occurred in the hanging wall of the Altotiberina normal fault (Northern Apennines, Italy) in 2013-2014. The geodetic transient lasted ˜6 months and produced a NW-SE trending extension of ˜ 5.3 mm, consistent with the regional tectonic regime. The seismicity and the geodetic signal are consistent with slip on two splay faults in the ATF hanging wall. Comparing the seismic moment associated with the geodetic transient and the seismic events, we observe that seismicity accounts for only a fraction of the measured geodetic deformation. The combined seismic and aseismic slip decreased the Coulomb stress on the locked shallow portion of the ATF, while the transition region to the creeping section has been loaded.

An Autonomous, Low Cost Platform for Seafloor Geodetic Observations

NASA Astrophysics Data System (ADS)

Ericksen, T.; Foster, J. H.; Bingham, B. S.; Oshiro, J.

2015-12-01

The Pacific GPS Facility and the Field Robotics Laboratory at the University of Hawaii have developed an approach to significantly reduce the costs of accurately measuring short-term vertical motions of the seafloor and maintaining a continuous long-term record of seafloor pressure. Traditional ship-based methods of acquiring these measurements are often prohibitively expensive. Our goal has been to reduce the primary barrier preventing us from acquiring the observations we need to understand geodetic processes, and the hazards they present, at subduction zones, submarine volcanoes, and subsea landslides. To this end, we have designed a payload package for the University of Hawaii Wave Glider which incorporates an acoustic telemetry package, a dual frequency geodetic-grade Global Positioning System (GPS) receiver, meteorological sensors, processing computer, and cellular communications. The Wave Glider is able to interrogate high accuracy pressure sensors on the seafloor to maintain a near-continuous stream of ocean bottom pressure and temperature data. The Wave Glider also functions as an integral part of the seafloor geodetic observing system, recording accurate sea surface elevations and barometric pressure; direct measurements of two of the primary sources of seafloor pressure change. The seafloor geodetic monument seats a sensor capable of recording pressure, temperature, and sound velocity for a deployment duration of over 5 years with an acoustic modem for communications, and an integral acoustic release for recovery and replacement of batteries. The design of the geodetic monument allows for precise repositioning of the sensor to extend the pressure record beyond a single 5+ year deployment, and includes the capability to install a mobile pressure recorder for calibration of the linear drift of the continuous pressure sensor. We will present the results of our field tests and an assessment of our ability to determine cm-scale vertical seafloor motions by integrating our seafloor pressure measurements with the independent Wave Glider measurements of sea surface pressure and sea surface height. An overall summary of the performance and costs of making seafloor geodetic measurement with this system will be provided.

Near Real-Time Processing and Archiving of GPS Surveys for Crustal Motion Monitoring

NASA Astrophysics Data System (ADS)

Crowell, B. W.; Bock, Y.

2008-12-01

We present an inverse instantaneous RTK method for rapidly processing and archiving GPS data for crustal motion surveys that gives positional accuracy similar to traditional post-processing methods. We first stream 1 Hz data from GPS receivers over Bluetooth to Verizon XV6700 smartphones equipped with Geodetics, Inc. RTD Rover software. The smartphone transmits raw receiver data to a real-time server at the Scripps Orbit and Permanent Array Center (SOPAC) running RTD Pro. At the server, instantaneous positions are computed every second relative to the three closest base stations in the California Real Time Network (CRTN), using ultra-rapid orbits produced by SOPAC, the NOAATrop real-time tropospheric delay model, and ITRF2005 coordinates computed by SOPAC for the CRTN stations. The raw data are converted on-the-fly to RINEX format at the server. Data in both formats are stored on the server along with a file of instantaneous positions, computed independently at each observation epoch. The single-epoch instantaneous positions are continuously transmitted back to the field surveyor's smartphone, where RTD Rover computes a median position and interquartile range for each new epoch of observation. The best-fit solution is the last median position and is available as soon as the survey is completed. We describe how we used this method to process 1 Hz data from the February, 2008 Imperial Valley GPS survey of 38 geodetic monuments established by Imperial College, London in the 1970's, and previously measured by SOPAC using rapid-static GPS methods in 1993, 1999 and 2000, as well as 14 National Geodetic Survey (NGS) monuments. For redundancy, each monument was surveyed for about 15 minutes at least twice and at staggered intervals using two survey teams operating autonomously. Archiving of data and the overall project at SOPAC is performed using the PGM software, developed by the California Spatial Reference Center (CSRC) for the National Geodetic Survey (NGS). The importation of raw receiver data, site metadata and antenna height information is performed using PGM client software running on the same PDA running RTD Rover or laptop, and uploaded to the PGM server where the raw data are converted to RINEX format. The campaign information is then published online, where all of the campaign information can be accessed such as start and stop times, equipment information, RINEX and solution SINEX files, observer information and baseline information for network adjustments.

Implementation of Barcelona, L'estartit and Ibiza Sites for Altimeter Calibration

NASA Astrophysics Data System (ADS)

Martinez-Benjamin, J. J.; Gili, J.; Lopez, R.; Tapia, A.; Bosch, E.; Perez, B.; Pros, F.

2012-12-01

A marine campaign to compute the sea surface data along the Spanish Mediterranean coastline and Balearic Islands is being prepared for 2013. Jason-2 (period ~10 days) and Saral/AltiKa (period of 35 days and expected launch in 2012) altimetric data and on-board GPS data will be used. Many GPS Buoy sessions along the ship route will be performed.Sea height estimates (instantaneous and mean sea levels) will be compared. Recently some geodetic improvements has been made in specific coastal spanish sites in the NW Mediterranean Sea for monitoring sea level. The goal is to maintain and improve the quality of the observation of the sea level change in the three sites. The information is coming from Puertos del Estado www.puertos.es L'Estartit tide gauge has been co-located with geodetic techniques (GPS measurements of XU, Utilitary Network, and XdA, Levelling Network,) and it is tied to the SPGIC (Integrated Geodetic Positioning System of Catalonia) project of the Cartographic Institute of Catalunya (ICC). In the past three calibration campaigns for Topex/Poseidon and Jason-1 in March 1999, August 2000 and July 2002 near Cape of Begur. At Barcelona harbour there is one MIROS radar tide gauge belonging to Puertos del Estado (Spanish Harbours).The radar sensor is over the water surface, on a L-shaped structure which elevates it a few meters above the quay shelf. 1-min data are transmitted to the ENAGAS Control Center by cable and then sent each 1 min to Puertos del Estado by e-mail. The information includes wave forescast (mean period, significant wave height, sea level, etc.This sensor also measures agitation and sends wave parameters each 20 min. There is a GPS station Leica Geosystems GRX1200 GG Pro and antenna 1202. Bathymetric campaigns inside the harbour have been made. At Ibiza site new measurements and levelling between the GPS reference station and a Radar MIROS, both from Puertos del Estado, has been made recently. A calibration campaign for Jason-1 was made in June 2003 in the Ibiza area, main calibration site. The presentation is directed to the description of the actual situation of the geodetic infrastructure of Barcelona, l'Estartit sites for sea level determination and complementing Ibiza site for a new altimeter calibration campaign of Jason-2 and Saral/AltiKa satellites to be made in 2013. Specifications of the new marine calibration campaign will be presented.

Post-Correlation Processing for the VLBI2010 Proof-of-Concept System

NASA Technical Reports Server (NTRS)

Beaudoin, Christopher; Niell, Arthur

2010-01-01

For the past three years, the MIT Haystack Observatory and the broadband team have been developing a proof-of-concept broadband geodetic VLBI microwave (2-12 GHz) receiver. Also on-going at Haystack is the development of post-correlation processing needed to extract the geodetic observables. Using this processing, the first fully-phase-calibrated geodetic fringes have been produced from observations conducted with the proof-of-concept system. The results we present show that the phase-calibrated phase residuals from four 512 MHz bands spanning 2 GHz have an RMS phase variation of 8deg which corresponds to a delay uncertainty of 12 ps.

Relativistic effects in local inertial frames including parametrized-post-Newtonian effects

NASA Astrophysics Data System (ADS)

Shahid-Saless, Bahman; Ashby, Neil

1988-09-01

We use the concept of a generalized Fermi frame to describe relativistic effects, due to local and distant sources of gravitation, on a body placed in a local inertial frame of reference. In particular we have considered a model of two spherically symmetric gravitating point sources, moving in circular orbits around a common barycenter where one of the bodies is chosen to be the local and the other the distant one. This has been done using the slow-motion, weak-field approximation and including four of the parametrized-post-Newtonian (PPN) parameters. The position of the classical center of mass must be modified when the PPN parameter ζ2 is included. We show that the main relativistic effect on a local satellite is described by the Schwarzschild field of the local body and the nonlinear term corresponding to the self-interaction of the local source with itself. There are also much smaller terms that are proportional, respectively, to the product of the potentials of local and distant bodies and to the distant body's self-interactions. The spatial axes of the local frame undergo geodetic precession. In addition we have an acceleration of the order of 10-11 cm sec-2 that vanish in the case of general relativity, which is discussed in detail.

Point Cloud Generation from sUAS-Mounted iPhone Imagery: Performance Analysis

NASA Astrophysics Data System (ADS)

Ladai, A. D.; Miller, J.

2014-11-01

The rapidly growing use of sUAS technology and fast sensor developments continuously inspire mapping professionals to experiment with low-cost airborne systems. Smartphones has all the sensors used in modern airborne surveying systems, including GPS, IMU, camera, etc. Of course, the performance level of the sensors differs by orders, yet it is intriguing to assess the potential of using inexpensive sensors installed on sUAS systems for topographic applications. This paper focuses on the quality analysis of point clouds generated based on overlapping images acquired by an iPhone 5s mounted on a sUAS platform. To support the investigation, test data was acquired over an area with complex topography and varying vegetation. In addition, extensive ground control, including GCPs and transects were collected with GSP and traditional geodetic surveying methods. The statistical and visual analysis is based on a comparison of the UAS data and reference dataset. The results with the evaluation provide a realistic measure of data acquisition system performance. The paper also gives a recommendation for data processing workflow to achieve the best quality of the final products: the digital terrain model and orthophoto mosaic. After a successful data collection the main question is always the reliability and the accuracy of the georeferenced data.

The Application of Coherent Local Time for Optical Time Transfer and the Quantification of Systematic Errors in Satellite Laser Ranging

NASA Astrophysics Data System (ADS)

Schreiber, K. Ulrich; Kodet, Jan

2018-02-01

Highly precise time and stable reference frequencies are fundamental requirements for space geodesy. Satellite laser ranging (SLR) is one of these techniques, which differs from all other applications like Very Long Baseline Interferometry (VLBI), Global Navigation Satellite Systems (GNSS) and finally Doppler Orbitography and Radiopositioning Integrated by Satellite (DORIS) by the fact that it is an optical two-way measurement technique. That means that there is no need for a clock synchronization process between both ends of the distance covered by the measurement technique. Under the assumption of isotropy for the speed of light, SLR establishes the only practical realization of the Einstein Synchronization process so far. Therefore it is a powerful time transfer technique. However, in order to transfer time between two remote clocks, it is also necessary to tightly control all possible signal delays in the ranging process. This paper discusses the role of time and frequency in SLR as well as the error sources before it address the transfer of time between ground and space. The need of an improved signal delay control led to a major redesign of the local time and frequency distribution at the Geodetic Observatory Wettzell. Closure measurements can now be used to identify and remove systematic errors in SLR measurements.

Repeating aftershocks of the great 2004 Sumatra and 2005 Nias earthquakes

NASA Astrophysics Data System (ADS)

Yu, Wen-che; Song, Teh-Ru Alex; Silver, Paul G.

2013-05-01

We investigate repeating aftershocks associated with the great 2004 Sumatra-Andaman (Mw 9.2) and 2005 Nias-Simeulue (Mw 8.6) earthquakes by cross-correlating waveforms recorded by the regional seismographic station PSI and teleseismic stations. We identify 10 and 18 correlated aftershock sequences associated with the great 2004 Sumatra and 2005 Nias earthquakes, respectively. The majority of the correlated aftershock sequences are located near the down-dip end of a large afterslip patch. We determine the precise relative locations of event pairs among these sequences and estimate the source rupture areas. The correlated event pairs identified are appropriately referred to as repeating aftershocks, in that the source rupture areas are comparable and significantly overlap within a sequence. We use the repeating aftershocks to estimate afterslip based on the slip-seismic moment scaling relationship and to infer the temporal decay rate of the recurrence interval. The estimated afterslip resembles that measured from the near-field geodetic data to the first order. The decay rate of repeating aftershocks as a function of lapse time t follows a power-law decay 1/tp with the exponent p in the range 0.8-1.1. Both types of observations indicate that repeating aftershocks are governed by post-seismic afterslip.

47 CFR 24.5 - Terms and definitions.

Code of Federal Regulations, 2011 CFR

2011-10-01

... in the National Geodetic Survey (NGS) data base. (Source: National Geodetic Survey, U.S. Department... antenna site. Base Station. A land station in the land mobile service. Broadband PCS. PCS services.... Fixed Station. A station in the fixed service. Land Mobile Service. A mobile service between base...

47 CFR 24.5 - Terms and definitions.

Code of Federal Regulations, 2013 CFR

2013-10-01

... in the National Geodetic Survey (NGS) data base. (Source: National Geodetic Survey, U.S. Department... antenna site. Base Station. A land station in the land mobile service. Broadband PCS. PCS services.... Fixed Station. A station in the fixed service. Land Mobile Service. A mobile service between base...

47 CFR 24.5 - Terms and definitions.

Code of Federal Regulations, 2014 CFR

2014-10-01

... in the National Geodetic Survey (NGS) data base. (Source: National Geodetic Survey, U.S. Department... antenna site. Base Station. A land station in the land mobile service. Broadband PCS. PCS services.... Fixed Station. A station in the fixed service. Land Mobile Service. A mobile service between base...

47 CFR 24.5 - Terms and definitions.

Code of Federal Regulations, 2012 CFR

2012-10-01

... in the National Geodetic Survey (NGS) data base. (Source: National Geodetic Survey, U.S. Department... antenna site. Base Station. A land station in the land mobile service. Broadband PCS. PCS services.... Fixed Station. A station in the fixed service. Land Mobile Service. A mobile service between base...

76 FR 43923 - Final Flood Elevation Determinations

Federal Register 2010, 2011, 2012, 2013, 2014

2011-07-22

... downstream of Big Bethel +9 Road. Approximately 20 feet upstream of the confluence +22 with Newmarket Creek... Approximately 30 feet downstream of I-64 +22 *National Geodetic Vertical Datum. +North American Vertical Datum... Center Street. * National Geodetic Vertical Datum. + North American Vertical Datum. Depth in feet above...

Geodesy: A look to the future

NASA Technical Reports Server (NTRS)

1985-01-01

The report deals with the current and future uses of contemporary geodetic data and poses some questions and possibilities for the future. It is anticipated that the document will generate interest in present and future geodetic data for the solution of problems in Earth, ocean, and atmospheric sciences.

Fault geometry inversion and slip distribution of the 2010 Mw 7.2 El Mayor-Cucapah earthquake from geodetic data

NASA Astrophysics Data System (ADS)

Huang, Mong-Han; Fielding, Eric J.; Dickinson, Haylee; Sun, Jianbao; Gonzalez-Ortega, J. Alejandro; Freed, Andrew M.; Bürgmann, Roland

2017-01-01

The 4 April 2010 Mw 7.2 El Mayor-Cucapah (EMC) earthquake in Baja, California, and Sonora, Mexico, had primarily right-lateral strike-slip motion and a minor normal-slip component. The surface rupture extended about 120 km in a NW-SE direction, west of the Cerro Prieto fault. Here we use geodetic measurements including near- to far-field GPS, interferometric synthetic aperture radar (InSAR), and subpixel offset measurements of radar and optical images to characterize the fault slip during the EMC event. We use dislocation inversion methods and determine an optimal nine-segment fault geometry, as well as a subfault slip distribution from the geodetic measurements. With systematic perturbation of the fault dip angles, randomly removing one geodetic data constraint, or different data combinations, we are able to explore the robustness of the inferred slip distribution along fault strike and depth. The model fitting residuals imply contributions of early postseismic deformation to the InSAR measurements as well as lateral heterogeneity in the crustal elastic structure between the Peninsular Ranges and the Salton Trough. We also find that with incorporation of near-field geodetic data and finer fault patch size, the shallow slip deficit is reduced in the EMC event by reductions in the level of smoothing. These results show that the outcomes of coseismic inversions can vary greatly depending on model parameterization and methodology.

First Local Ties from Data of the Wettzell Triple Radio Telescope Array

NASA Astrophysics Data System (ADS)

Schüler, T.; Plötz, C.; Mähler, S.; Klügel, T.; Neidhardt, A.; Bertarini, A.; Halsig, S.; Nothnagel, A.; Lösler, M.; Eschelbach, C.; Anderson, J.

2016-12-01

The Geodetic Observatory Wettzell features three radio telescopes. Local ties between the reference points are available from terrestrial precision surveying with an expected accuracy below 0.7 mm. In addition, local VLBI data analysis is currently investigated to provide independent vectors and to provide quality feedback to the engineers. The preliminary results presented in this paper show a deviation from the local survey at the level of one millimeter with a clear systematic component. Sub-millimeter precision is reached after removal of this bias. This systematic effect is likely caused by omission of thermal expansion and gravity deformation, which is not yet implemented in our local VLBI analysis software.

GGOS working group on ground networks and communications

NASA Technical Reports Server (NTRS)

Pearlman, M.; Altamimi, Z.; Beck, N.; Forsberg, R.; Gurtner, W.; Kenyon, S.; Behrend, D.; Lemoine, F. G.; Ma, C.; Noll, C. E.;

Aspects of ICRF-3

NASA Astrophysics Data System (ADS)

Ma, Chopo; MacMillan, Daniel; Le Bail, Karine; Gordon, David

2016-12-01

The Second Realization of the International Celestial Reference Frame (ICRF2) used dual-frequency VLBI data acquired for geodetic and astrometric purposes from 1979-2009 by organizations coordinated by the IVS and various precursor networks. Since 2009 the data set has been significantly broadened, especially by observations in the southern hemisphere. While the new southern data have ameliorated the north/south imbalance of observations, they appear to produce a systematic zonal declination change in the catalog positions. Over the 35 years of the ICRF data set the effect of galactic aberration may be significant. Geophysical and tropospheric models also may affect the source positions. All these effects need to be addressed in preparation for ICRF-3.

Korea Geodetic VLBI Station, Sejong

NASA Technical Reports Server (NTRS)

Donghyun, Baek; Sangoh, Yi; Hongjong, Oh; Sangchul, Han

2013-01-01

The Sejong VLBI station officially joined the IVS as a new Network Station in 2012. This report summarizes the activities of the Sejong station during 2012. The following are the activities at the station: 1) VLBI test observations were carried out with the Tsukuba 34-m antenna of the GSI in Japan. As a result, the Sejong antenna needs to improve its efficiency, which is currently in progress, 2) A survey to connect the VLBI reference point to GNSS and ground marks was conducted, and 3) To see the indirect effects of RFI (Radio Frequency Interference) at this place, we checked the omni-direction (AZ 0? to 360?, EL fixed at 7?) for RFI influence.

Uplift of the Western Transverse Ranges and Ventura Area of Southern California: A Four-Technique Geodetic Study Combining GPS, InSAR, Leveling, and Tide Gauges

NASA Astrophysics Data System (ADS)

Hammond, William C.; Burgette, Reed J.; Johnson, Kaj M.; Blewitt, Geoffrey

2018-01-01

We estimate the rate of vertical land motion (VLM) in the region around the Western Transverse Ranges (WTR), Ventura, and Big Bend of the San Andreas Fault (SAF) of southern California using data from four geodetic techniques: GPS, interferometric synthetic aperture radar (InSAR), leveling, and tide gauges. We use a new analysis technique called GPS Imaging to combine the techniques and leverage the synergy between (1) high geographic resolution of InSAR, (2) precision, stability, and geocentric reference frame of GPS, (3) decades long observation of VLM with respect to the sea surface from tide gauges, and (4) relative VLM along dense leveling lines. The uncertainty in the overall rate field is 1 mm/yr, though some individual techniques have uncertainties as small as 0.2 mm/yr. The most rapid signals are attributable to subsidence in aquifers and groundwater changes. Uplift of the WTR is geographically continuous, adjacent to the SAF and appears related to active crustal contraction across Pacific/North America plate boundary fault system. Uplift of the WTR and San Gabriel Mountains is 2 mm/yr and is asymmetrically focused west of the SAF, consistent with interseismic strain accumulation across thrust faults in the Ventura area and Santa Barbara channel that accommodate contraction against the near vertical SAF.

A Railway Track Geometry Measuring Trolley System Based on Aided INS

PubMed Central

Chen, Qijin; Niu, Xiaoji; Zuo, Lili; Zhang, Tisheng; Xiao, Fuqin; Liu, Yi; Liu, Jingnan

2018-01-01

Accurate measurement of the railway track geometry is a task of fundamental importance to ensure the track quality in both the construction phase and the regular maintenance stage. Conventional track geometry measuring trolleys (TGMTs) in combination with classical geodetic surveying apparatus such as total stations alone cannot meet the requirements of measurement accuracy and surveying efficiency at the same time. Accurate and fast track geometry surveying applications call for an innovative surveying method that can measure all or most of the track geometric parameters in short time without interrupting the railway traffic. We provide a novel solution to this problem by integrating an inertial navigation system (INS) with a geodetic surveying apparatus, and design a modular TGMT system based on aided INS, which can be configured according to different surveying tasks including precise adjustment of slab track, providing tamping measurements, measuring track deformation and irregularities, and determination of the track axis. TGMT based on aided INS can operate in mobile surveying mode to significantly improve the surveying efficiency. Key points in the design of the TGMT’s architecture and the data processing concept and workflow are introduced in details, which should benefit subsequent research and provide a reference for the implementation of this kind of TGMT. The surveying performance of proposed TGMT with different configurations is assessed in the track geometry surveying experiments and actual projects. PMID:29439423

Northward migration of the Cascadia forearc in the northwestern U.S. and implications for subduction deformation

USGS Publications Warehouse

Wells, R.E.; Simpson, R.W.

2001-01-01

Geologic and paleomagnetic data from the Cascadia forearc indicate long-term northward migration and clockwise rotation of an Oregon coastal block with respect to North America. Paleomagnetic rotation of coastal Oregon is linked by a Klamath Mountains pole to geodetically and geologically determined motion of the Sierra Nevada block to derive a new Oregon Coast-North America (OC-NA) pole of rotation and velocity field. This long-term velocity field, which is independent of Pacific Northwest GPS data, is interpreted to be the result of Basin-Range extension and Pacific-North America dextral shear. The resulting Oregon Coast pole compares favorably to those derived solely from GPS data, although uncertainties are large. Subtracting the long-term motion from forearc GPS velocities reveals ENE motion with respect to an OC reference frame that is parallel to the direction of Juan de Fuca-OC convergence and decreases inland. We interpret this to be largely the result of subduction-related deformation. The adjusted mean GPS velocities are generally subparallel to those predicted from elastic dislocation models for Cascadia, but more definitive interpretations await refinement of the present large uncertainty in the Sierra Nevada block motion. Copyright ?? The Society of Geomagnetism and Earth, Planetary and Space Sciences (SGEPSS); The Seismological Society of Japan; The Volcanological Society of Japan; The Geodetic Society of Japan; The Japanese Society for Planetary Sciences.

National Geodetic Satellite Program, Part 1

NASA Technical Reports Server (NTRS)

Henriksen, S. W. (Editor)

1977-01-01

The work performed by individual contributors to the National Geodetic Satellite Program is presented. The purpose of the organization, the instruments used in obtaining the data, a description of the data itself, the theory used in processing the data, and evaluation of the results are detailed for the participating organizations.

Measuring Crustal Deformation in the American West.

ERIC Educational Resources Information Center

Jordan, Thomas H.; Minster, J. Bernard

1988-01-01

Suggests that there is a close relationship between deformation in the western United States and the large-scale motions of tectonic plates. Introduces very-long-baseline interferometry (VLBI) as one of the space-geodetic techniques, vector addition of the VLBI data and geological data, and a new geodetic network. (YP)

Millimeter accuracy satellites for two color ranging

NASA Technical Reports Server (NTRS)

Degnan, John J.

1993-01-01

The principal technical challenge in designing a millimeter accuracy satellite to support two color observations at high altitudes is to provide high optical cross-section simultaneously with minimal pulse spreading. In order to address this issue, we provide, a brief review of some fundamental properties of optical retroreflectors when used in spacecraft target arrays, develop a simple model for a spherical geodetic satellite, and use the model to determine some basic design criteria for a new generation of geodetic satellites capable of supporting millimeter accuracy two color laser ranging. We find that increasing the satellite diameter provides: a larger surface area for additional cube mounting thereby leading to higher cross-sections; and makes the satellite surface a better match for the incoming planar phasefront of the laser beam. Restricting the retroreflector field of view (e.g. by recessing it in its holder) limits the target response to the fraction of the satellite surface which best matches the optical phasefront thereby controlling the amount of pulse spreading. In surveying the arrays carried by existing satellites, we find that European STARLETTE and ERS-1 satellites appear to be the best candidates for supporting near term two color experiments in space.

Earth rotation excitation mechanisms derived from geodetic space observations

NASA Astrophysics Data System (ADS)

Göttl, F.; Schmidt, M.

2009-04-01

Earth rotation variations are caused by mass displacements and motions in the subsystems of the Earth. Via the satellite Gravity and Climate Experiment (GRACE) gravity field variations can be identified which are caused by mass redistribution in the Earth system. Therefore time variable gravity field models (GFZ RL04, CSR RL04, JPL RL04, ITG-Grace03, GRGS, ...) can be used to derive different impacts on Earth rotation. Furthermore satellite altimetry provides accurate information on sea level anomalies (AVISO, DGFI) which are caused by mass and volume changes of seawater. Since Earth rotation is solely affected by mass variations and motions the volume (steric) effect has to be reduced from the altimetric observations in order to infer oceanic contributions to Earth rotation variations. Therefore the steric effect is estimated from physical ocean parameters such as temperature and salinity changes in the oceans (WOA05, Ishii). In this study specific individual geophysical contributions to Earth rotation variations are identified by means of a multitude of accurate geodetic space observations in combination with a realistic error propagation. It will be shown that due to adjustment of altimetric and/or gravimetric solutions the results for polar motion excitations can be improved.

Estimability of geodetic parameters from space VLBI observables

NASA Technical Reports Server (NTRS)

Adam, Jozsef

1990-01-01

The feasibility of space very long base interferometry (VLBI) observables for geodesy and geodynamics is investigated. A brief review of space VLBI systems from the point of view of potential geodetic application is given. A selected notational convention is used to jointly treat the VLBI observables of different types of baselines within a combined ground/space VLBI network. The basic equations of the space VLBI observables appropriate for convariance analysis are derived and included. The corresponding equations for the ground-to-ground baseline VLBI observables are also given for a comparison. The simplified expression of the mathematical models for both space VLBI observables (time delay and delay rate) include the ground station coordinates, the satellite orbital elements, the earth rotation parameters, the radio source coordinates, and clock parameters. The observation equations with these parameters were examined in order to determine which of them are separable or nonseparable. Singularity problems arising from coordinate system definition and critical configuration are studied. Linear dependencies between partials are analytically derived. The mathematical models for ground-space baseline VLBI observables were tested with simulation data in the frame of some numerical experiments. Singularity due to datum defect is confirmed.

A revised estimate of Pacific-North America motion and implications for Western North America plate boundary zone tectonics

NASA Technical Reports Server (NTRS)

Demets, Charles; Gordon, Richard G.; Stein, Seth; Argus, Donald F.

1987-01-01

Marine magnetic profiles from the Gulf of Californa are studied in order to revise the estimate of Pacific-North America motion. It is found that since 3 Ma spreading has averaged 48 mm/yr, consistent with a new global plate motion model derived without any data. The present data suggest that strike-slip motion on faults west of the San Andreas is less than previously thought, reducing the San Andreas discrepancy with geodetic, seismological, and other geologic observations.

Options for developing modernized geodetic datum for Nepal following the April 25, 2015 Mw7.8 Gorkha earthquake

NASA Astrophysics Data System (ADS)

Pearson, Chris; Manandhar, Niraj; Denys, Paul

2017-09-01

Along with the damage to buildings and infrastructure, the April 25, 2015 Mw7.8 Gorkha earthquake caused significant deformation over a large area of eastern Nepal with displacements of over 2 m recorded in the vicinity of Kathmandu. Nepal currently uses a classical datum developed in 1984 by the Royal (UK) Engineers in collaboration with the Nepal Survey Department. It has served Nepal well; however, the recent earthquakes have provided an impetus for developing a semi-dynamic datum that will be based on ITRF2014 and have the capacity to correct for tectonic deformation. In the scenario we present here, the datum would be based on ITRF2014 with a reference epoch set some time after the end of the current sequence of earthquakes. The deformation model contains a grid of the secular velocity field combined with models of the Gorkha Earthquake and the May 12 Mw7.3 aftershock. We have developed a preliminary velocity field by collating GPS derived crustal velocities from four previous studies for Nepal and adjacent parts of China and India and aligning them to the ITRF. Patches for the co-seismic part of the deformation for the Gorkha earthquake and the May 12, 2015 Mw 7.2 aftershock are based on published dislocation models. High order control would be a CORS network based around the existing Nepal GPS Array. Coordinates for existing lower order control would be determined by readjusting existing survey measurements and these would be combined with a series of new control stations spread throughout Nepal.

Point Cloud Storage and Access on a Global Scale

DTIC Science & Technology

2015-01-01

coordinates. These Geodetic values are appended to the list of parameters and are re-projected into WGS84 Geocentric (ECEF X,Y,Z), replacing the original...Append Lon,Lat,Alt to point parameters Re-project point with Proj.4 from Geodetic (Lon,Lat,Alt) -> Geocentric (X,Y,Z) Insert point into

Satellite-tracking and earth-dynamics research programs. [geodetic and geophysical investigations and atmospheric research using satellite drag data

NASA Technical Reports Server (NTRS)

1972-01-01

Satellite tracking and earth dynamics research programs are discussed. Geodetic and geophysical investigations are reported along with atmospheric research using satellite drag data. Satellite tracking network functions and support groups which are discussed include: network operations, communications, data-services division, moonwatch, and programming group.

Statistical description of tectonic motions

NASA Technical Reports Server (NTRS)

Agnew, Duncan Carr

1993-01-01

This report summarizes investigations regarding tectonic motions. The topics discussed include statistics of crustal deformation, Earth rotation studies, using multitaper spectrum analysis techniques applied to both space-geodetic data and conventional astrometric estimates of the Earth's polar motion, and the development, design, and installation of high-stability geodetic monuments for use with the global positioning system.

Effects of non-tidal atmospheric loading on a Kalman filter-based terrestrial reference frame

NASA Astrophysics Data System (ADS)

Abbondanza, C.; Altamimi, Z.; Chin, T. M.; Collilieux, X.; Dach, R.; Heflin, M. B.; Gross, R. S.; König, R.; Lemoine, F. G.; MacMillan, D. S.; Parker, J. W.; van Dam, T. M.; Wu, X.

2013-12-01

The International Terrestrial Reference Frame (ITRF) adopts a piece-wise linear model to parameterize regularized station positions and velocities. The space-geodetic (SG) solutions from VLBI, SLR, GPS and DORIS global networks used as input in the ITRF combination process account for tidal loading deformations, but ignore the non-tidal part. As a result, the non-linear signal observed in the time series of SG-derived station positions in part reflects non-tidal loading displacements not introduced in the SG data reduction. In this analysis, the effect of non-tidal atmospheric loading (NTAL) corrections on the TRF is assessed adopting a Remove/Restore approach: (i) Focusing on the a-posteriori approach, the NTAL model derived from the National Center for Environmental Prediction (NCEP) surface pressure is removed from the SINEX files of the SG solutions used as inputs to the TRF determinations. (ii) Adopting a Kalman-filter based approach, a linear TRF is estimated combining the 4 SG solutions free from NTAL displacements. (iii) Linear fits to the NTAL displacements removed at step (i) are restored to the linear reference frame estimated at (ii). The velocity fields of the (standard) linear reference frame in which the NTAL model has not been removed and the one in which the model has been removed/restored are compared and discussed.

Plate motions and deformations from geologic and geodetic data

NASA Technical Reports Server (NTRS)

Jordan, Thomas H.

1989-01-01

The very long baseline interferometry (VLBI) measurements made in the western U.S. since 1979 provide discrete samples of the temporal and spatial deformation field. The interpretation of the VLBI derived rates of deformation requires an examination of geologic information and more densely sampled ground based geodetic data. Triangulation and trilateration data measured on two regional networks, one in the central Mojave Desert and one in the Coast Ranges east of the San Andreas fault, were processed. At the spatial scales spanned by these local geodetic networks, auxiliary geologic and geophysical data were utilized to examine the relation between measured incremental strain and the accommodation of strain seen in local geologic structures, strain release in earthquakes, and principal stress directions inferred from in situ measurements. VLBI data was also processed from stations distributed across the Pacific-North America plate boundary zone in the western U.S. The VLBI data were used to constrain the integrated rate of deformation across portions of the continental plate boundary in California and to provide a tectonic framework to interpret regional geodetic and geologic studies.

COLD MAGICS - Continuous Local Deformation Monitoring of an Arctic Geodetic Fundamental Station

NASA Technical Reports Server (NTRS)

Haas, Ruediger; Bergstrand, Sten

2010-01-01

We describe the experience gained in a project to continuously monitor the local tie at the Geodetic Observatory Ny-Alesund. A PC-controlled robotic total station was used to monitor survey prisms that were attached to survey pillars of the local network and the monuments used for geodetic VLBI and GNSS measurements. The monitoring lasted for seven days and had a temporal resolution of six minutes. The raw angle and distance measurements show clear sinusoidal signatures with a daily period, most strongly for a four-day period with 24 hours of sunshine. The derived topocentric coordinates of the survey prisms attached to the GNSS monument and the VLBI radio telescope act as approximation for the local tie. We detect clear signatures at the mm-level. With the current approach we cannot distinguish between real motion of the prisms and potential thermal influences on the instrument used for the observations. However, the project shows that continuous local tie monitoring is feasible today and in the future can and should be used for all geodetic co-location stations.

Geodetic monitoring of subrosion-induced subsidence processes in urban areas

NASA Astrophysics Data System (ADS)

Kersten, Tobias; Kobe, Martin; Gabriel, Gerald; Timmen, Ludger; Schön, Steffen; Vogel, Detlef

2017-03-01

The research project SIMULTAN applies an advanced combination of geophysical, geodetic, and modelling techniques to gain a better understanding of the evolution and characteristics of sinkholes. Sinkholes are inherently related to surface deformation and, thus, of increasing societal relevance, especially in dense populated urban areas. One work package of SIMULTAN investigates an integrated approach to monitor sinkhole-related mass translations and surface deformations induced by salt dissolution. Datasets from identical and adjacent points are used for a consistent combination of geodetic and geophysical techniques. Monitoring networks are established in Hamburg and Bad Frankenhausen (Thuringia). Levelling surveys indicate subsidence rates of about 4-5 mm per year in the main subsidence areas of Bad Frankenhausen with a local maximum of 10 mm per year around the leaning church tower. Here, the concept of combining geodetic and gravimetric techniques to monitor and characterise geological processes on and below the Earth's surface is exemplary discussed for the focus area Bad Frankenhausen. For the different methods (levelling, GNSS, relative/absolute gravimetry) stable network results at identical points are obtained by the first campaigns, i.e., the results are generally in agreement.

Geodynamical behavior of some active area in Egypt, as deduced from geodetic and gravity data

NASA Astrophysics Data System (ADS)

Issawy, E.; Mrlina, J.; Radwan, A.; Mahmoud, S.; Rayan, A.

2009-04-01

Temporal gravity variation in parallel with the space geodetic technique (GPS) had been started in Egypt for real campaigns in 1997. The geodetic networks around the High Dam, Aswan area was the first net to be measured. More than five measurement epochs were performed. The results had a considerable limit of coincidence between gravity and GPS observations. The trend of gravity changes indicated a positive stress and had the vertical displacement observed for leveling points. The lowest gravity changes along Kalabsha fault reflect extensional and/or strike component of the stress field. Also, the areas around Cairo (Greater Cairo) and due to the occurrence of an earthquake of 1992, such type of measurements were useful for monitoring the recent activity. The data of the geodetic network around Cairo after 5 campaigns showed that, the estimated horizontal velocities for almost all points are 5.5± mm/year in approximately NW-SE direction. The non-tidal changes can explain the dynamic process within the upper crust related to the development of local stress conditions. The trends of gravity changes are more or less coincident with that deduced from GPS deformation analysis and the occurrence of the main shocks in the area. In additions, in 2005 the geodetic network around the southern part of Sinai and the Gulf of Suez were established. One campaign of measurements had been performed and the gravity values were obtained.

Isostatic gravity map of the Monterey 30 x 60 minute quadrangle and adjacent areas, California

USGS Publications Warehouse

Langenheim, V.E.; Stiles, S.R.; Jachens, R.C.

2002-01-01

The digital dataset consists of one file (monterey_100k.iso) containing 2,385 gravity stations. The file, monterey_100k.iso, contains the principal facts of the gravity stations, with one point coded per line. The format of the data is described below. Each gravity station has a station name, location (latitude and longitude, NAD27 projection), elevation, and an observed gravity reading. The data are on the IGSN71 datum and the reference ellipsoid is the Geodetic Reference System 1967 (GRS67). The free-air gravity anomalies were calculated using standard formulas (Telford and others, 1976). The Bouguer, curvature, and terrain corrections were applied to the free-air anomaly at each station to determine the complete Bouguer gravity anomalies at a reduction density of 2.67 g/cc. An isostatic correction was then applied to remove the long-wavelength effect of deep crustal and/or upper mantle masses that isostatically support regional topography.

Co-location satellite GPS and SLR geodetic techniques at the Felix Aguilar Astronomical Observatory of San Juan, Argentina

NASA Astrophysics Data System (ADS)

Podestá, R.; Pacheco, A. M.; Alvis Rojas, H.; Quinteros, J.; Podestá, F.; Albornoz, E.; Navarro, A.; Luna, M.

2018-01-01

This work shows the strategy followed for the co-location of the Satellite Laser Ranging (SLR) ILRS 7406 telescope and the antenna of the permanent Global Positioning System (GPS) station, located at the Félix Aguilar Astronomical Observatory (OAFA) in San Juan, Argentina. The accomplishment of the co-location consisted in the design, construction, measurement, adjustment and compensation of a geodesic net between the stations SLR and GPS, securing support points solidly built in the soil. The co-location allows the coordinates of the station to be obtained by combining the data of both SLR and GPS techniques, achieving a greater degree of accuracy than individually. The International Earth Rotation and Reference Systems Service (IERS) considers the co-located stations as the most valuable and important points for the maintenance of terrestrial reference systems and their connection with the celestial ones. The 3 mm precision required by the IERS has been successfully achieved.

Standard Observing Bands: Is Now the Time to Replace S/X with X/Ka?

NASA Technical Reports Server (NTRS)

Jacobs, C. S.; Lanyi, G. E.; Naudet, C. J.

2004-01-01

In this paper we will argue that the VLBI community should be developing a road map to transition from S/X to simultaneous X and Ka-band (32 GHz) observations. There are both negative and positive reasons for planning such a transition. On the negative side, we will outline concerns that S-band observations may be headed toward obsolescence. On the positive side, we will refer to evidence that X/Ka has potential for providing a more stable reference frame than S/X. We will propose timetables for a transition to X/Ka observing starting from the current status of X/Ka and plans that are now taking shape. First X/Ka fringes were obtained in 2001 with the Deep Space Network. Future plans will be discussed including a proposed X/Ka-band upgrade to the VLBA. Lastly, we will consider the need for a period of overlap between S/X and X/Ka so that the long and rich history of astrometric and geodetic VLBI is not compromised.

Verification of the Usefulness of the Trimble Rtx Extended Satellite Technology with the Xfill Function in the Local Network Implementing Rtk Measurements

NASA Astrophysics Data System (ADS)

Siejka, Zbigniew

2014-12-01

The paper presents the method of satellite measurements, which gives users the ability of GNSS continuous precise positioning in real time, even in the case of short interruptions in receiving the correction of the local ground system of measurements support. The proposed method is a combination of two satellite positioning technologies RTN GNSS and RTX Extended. In technology RTX Extended the xFill function was used for precise positioning in real time and in the local reference system. This function provides the ability to perform measurement without the need for constant communication with the ground support satellite system. Test measurements were performed on a test basis located in Krakow, and RTN GNSS positioning was done based on the national network of reference stations of the ASGEUPOS. The solution allows for short (up to 5 minutes) interruptions in radio or internet communication. When the primary stream of RTN correction is not available, then the global corrections Trimble xFill broadcasted by satellite are used. The new technology uses in the real-time data from the global network of tracking stations and contributes significantly to improving the quality and efficiency of surveying works. At present according to the authors, technology Trimble CenterPoint RTX can guarantee repeatability of measurements not worse than 3.8 cm (Trimble Survey Division, 2012). In the paper the comparative analysis of measurement results between the two technologies was performed: RTN carried out in the classic way, which was based on the corrections of the terrestrial local network of the Polish system of active geodetic network (ASG-EUPOS) and RTK xFill technology. The results were related to the data of test network, established as error free. The research gave satisfactory results and confirmed the great potential of the use of the new technology in the geodetic work realization. By combining these two technologies of GNSS surveying the user can greatly improve the overall performance of real-time positioning.

VANDENBERG AFB, CALIF. - In the NASA spacecraft processing facility on North Vandenberg Air Force Base, workers stand by as the balloon at right is released to lift the solar array panel into position for installation on the Gravity Probe B spacecraft. Installing each array is a 3-day process and includes a functional deployment test. The Gravity Probe B mission is a relativity experiment developed by NASA’s Marshall Space Flight Center, Stanford University and Lockheed Martin. The spacecraft will test two extraordinary predictions of Albert Einstein’s general theory of relativity that he advanced in 1916: the geodetic effect (how space and time are warped by the presence of the Earth) and frame dragging (how Earth’s rotation drags space and time around with it). Gravity Probe B consists of four sophisticated gyroscopes that will provide an almost perfect space-time reference system. The mission will look in a precision manner for tiny changes in the direction of spin.

NASA Image and Video Library

2003-11-04

VANDENBERG AFB, CALIF. - In the NASA spacecraft processing facility on North Vandenberg Air Force Base, workers stand by as the balloon at right is released to lift the solar array panel into position for installation on the Gravity Probe B spacecraft. Installing each array is a 3-day process and includes a functional deployment test. The Gravity Probe B mission is a relativity experiment developed by NASA’s Marshall Space Flight Center, Stanford University and Lockheed Martin. The spacecraft will test two extraordinary predictions of Albert Einstein’s general theory of relativity that he advanced in 1916: the geodetic effect (how space and time are warped by the presence of the Earth) and frame dragging (how Earth’s rotation drags space and time around with it). Gravity Probe B consists of four sophisticated gyroscopes that will provide an almost perfect space-time reference system. The mission will look in a precision manner for tiny changes in the direction of spin.

SLR in the framework of the EGSIEM project

NASA Astrophysics Data System (ADS)

Maier, Andrea; Sušnik, Andreja; Meyer, Ulrich; Arnold, Daniel; Dach, Rolf; Jäggi, Adrian; Sośnica, Krzysztof; Thaller, Daniela

2016-04-01

This contribution describes the three roles Satellite Laser Ranging (SLR) is playing within the European Gravity Service for the Improved Emergency Management (EGSIEM). The purpose of this Horizon 2020 project is to combine monthly gravity field solutions from the Gravity Recovery and Climate Experiment (GRACE) mission that are derived by different institutions. The combined gravity field product will provide complementary information to traditional products for flood and drought monitoring and forecasting. First, SLR is used to validate Global Navigational Satellite System (GNSS) orbits, which are computed at the Astronomical Institute of the University of Bern. To ensure a consistent set of GNSS products (orbits, Earth rotation parameters, and clocks) a reprocessing campaign was initiated. The reprocessed products are based on the new Empirical CODE Orbit Model, which is used for all orbit products generated at the Center for Orbit Determination in Europe (CODE) from January 4, 2015 onwards. Since the kinematic orbits of GRACE will be based on these orbits, we present an in-depth validation of the GNSS orbits using SLR. Second, SLR to geodetic satellites is crucial for the estimation of the dynamical Earth's flattening term (C20) since this coefficient is degraded by aliasing when derived from GRACE data. We will compare the temporal variation of C20 with external solutions and demonstrate the benefit of involving a larger number of geodetic satellites. The third aspect is based on the fact that the gravity field product delivered by EGSIEM will include GRACE and SLR data. It is thus desirable to establish a reference frame based on both GNSS data and SLR observations. For this purpose it is planned to analyze SLR measurements to GNSS satellites equipped with a retroreflector array and to estimate common parameters such as station coordinates and geocenter coordinates from a combined set of SLR and GNSS data. We will present a workflow how to derive a common reference frame.

Imaging Cascadia coupling: optimal design for an offshore seafloor geodetic network

NASA Astrophysics Data System (ADS)

Evans, E. L.; Minson, S. E.

2017-12-01

The Cascadia subduction zone in the Pacific Northwest of the United States is known to produce MW≈9.2 earthquakes, and accompanying tsunamis every 600 years. An outstanding question in this region (as in most offshore subduction zones) is the degree to which the megathrust is locked (i.e., the coupling rate), and whether the locked zone extends to the trench, where onshore geodetic measurements cannot uniquely resolve strain accumulation. Seafloor geodetic techniques, such as acoustic ranging combined with GNSS positioning, are capable of providing unique observations of strain accumulation near the offshore trench of subduction zones. These observations may be used to constrain megathrust coupling rate and spatial distribution, and ultimately forecast the potential size and rupture pattern of a future subduction zone earthquake, with resolution beyond the capability of onshore observations alone. However, the high cost of seafloor geodesy limits the number of stations that may be deployed and monitored. Therefore, it is essential that deployed stations be positioned in such a way to provide the most informative data for resolving subduction zone coupling. We identify optimal seafloor observation locations by minimizing the Shannon Information Entropy of potential geodetic observation locations, given the current onshore geodetic network. Because coupling rate on the Cascadia megathrust depends on the relative convergence rate between the Juan de Fuca and North American plates, the most valuable location for a single seafloor geodetic station is west of the Juan de Fuca trench, on the Juan de Fuca plate itself. Subsequent optimal locations are also identified offshore, on the hanging wall near the trench. This approach provides a quantitative assessment of the value of seafloor observations: a single offshore observation provides 30 times the information gain of an additional onshore observation, and adding many (>50) onshore observations cannot provide the information gain of a single offshore observation.

Misbheaving Faults: The Expanding Role of Geodetic Imaging in Unraveling Unexpected Fault Slip Behavior

NASA Astrophysics Data System (ADS)

Barnhart, W. D.; Briggs, R.

2015-12-01

Geodetic imaging techniques enable researchers to "see" details of fault rupture that cannot be captured by complementary tools such as seismology and field studies, thus providing increasingly detailed information about surface strain, slip kinematics, and how an earthquake may be transcribed into the geological record. For example, the recent Haiti, Sierra El Mayor, and Nepal earthquakes illustrate the fundamental role of geodetic observations in recording blind ruptures where purely geological and seismological studies provided incomplete views of rupture kinematics. Traditional earthquake hazard analyses typically rely on sparse paleoseismic observations and incomplete mapping, simple assumptions of slip kinematics from Andersonian faulting, and earthquake analogs to characterize the probabilities of forthcoming ruptures and the severity of ground accelerations. Spatially dense geodetic observations in turn help to identify where these prevailing assumptions regarding fault behavior break down and highlight new and unexpected kinematic slip behavior. Here, we focus on three key contributions of space geodetic observations to the analysis of co-seismic deformation: identifying near-surface co-seismic slip where no easily recognized fault rupture exists; discerning non-Andersonian faulting styles; and quantifying distributed, off-fault deformation. The 2013 Balochistan strike slip earthquake in Pakistan illuminates how space geodesy precisely images non-Andersonian behavior and off-fault deformation. Through analysis of high-resolution optical imagery and DEMs, evidence emerges that a single fault map slip as both a strike slip and dip slip fault across multiple seismic cycles. These observations likewise enable us to quantify on-fault deformation, which account for ~72% of the displacements in this earthquake. Nonetheless, the spatial distribution of on- and off-fault deformation in this event is highly spatially variable- a complicating factor for comparisons of geologic and geodetic slip rates. As such, detailed studies such as this will play a continuing vital role in the accurate assessment of short- and long-term fault slip kinematics.

Debris flow cartography using differential GNSS and Theodolite measurements

NASA Astrophysics Data System (ADS)

Khazaradze, Giorgi; Guinau, Marta; Calvet, Jaume; Furdada, Gloria; Victoriano, Ane; Génova, Mar; Suriñach, Emma

2016-04-01

The presented results form part of a CHARMA project, which pursues a broad objective of reducing damage caused by uncontrolled mass movements, such as rockfalls, snow avalanches and debris flows. Ultimate goal of the project is to contribute towards the establishment of new scientific knowledge and tools that can help in the design and creation of early warning systems. Here we present the specific results that deal with the application of differential GNSS and classical geodetic (e.g. theodolite) methods for mapping debris and torrential flows. Specifically, we investigate the Portainé stream located in the Pallars Sobirà region of Catalonia (Spain), in the eastern Pyrenees. In the last decade more than ten debris-flow type phenomena have affected the region, causing considerable economic losses. Since early 2014, we have conducted several field campaigns within the study area, where we have employed a multi-disciplinary approach, consisting of geomorphological, dendro-chronological and geodetic methods, in order to map the river bed and reconstruct the history of the extreme flooding and debris flow events. Geodetic studies included several approaches, using the classical and satellite based methods. The former consisted of angle and distance measurements between the Geodolite 502 total station and the reflecting prisms placed on top of the control points located within the riverbed. These type of measurements are precise, although present several disadvantages such as the lack of absolute coordinates that makes the geo-referencing difficult, as well as a relatively time-consuming process that involves two persons. For this reason, we have also measured the same control points using the differential GNSS system, in order to evaluate the feasibility of replacing the total station measurements with the GNSS. The latter measuring method is fast and can be conducted by one person. However, the fact that the study area is within the riverbed, often below the trees, limits the visibility of the satellites and thus, can result in meter-level errors while estimating the positions. We have conducted 2 measurements using various differential GNSS systems in March and in September of 2015. During these measurements we used Leica Viva GS14 receiver as a rover station, which was equipped with a GSM card to establish an internet connection in order to receive differential corrections from continuous GNSS networks. During the first campaign we have used the RTK positioning method using the SmartNet network (http://es.smartnet-eu.com) operated by Leica. This system had the advantage of transmitting differential corrections for GPS and GLONASS systems. During the second campaign, we have had an access to the ICGC (http://www.icc.cat) CatNet permanent GPS network, which only provides GPS satellite corrections. Here we present the analysis of the obtained precisions from these two RTK systems. Additionally, we have analyzed the geodetic data in a post-processing mode using the Leica Geo Office 8.4 software with IGS estimated final orbits. For this procedure, in addition to using the data from nearby CatNet CGPS stations, we have also used data from the base station(s) specifically setup near the study area during the campaign period. The work has been supported by the Spanish Ministry of Science and Innovation project CHARMA: CHAracterization and ContRol of MAss Movements. A Challenge for Geohazard Mitigation (CGL2013-40828-R) and RISKNAT group (2014GR/1243).

Campaign-Style Measurements of Vertical Seafloor Deformation in the Cascadia Subduction Zone Using an Absolute Self-Calibrating Pressure Recorder

NASA Astrophysics Data System (ADS)

Cook, M. J.; Sasagawa, G. S.; Roland, E. C.; Schmidt, D. A.; Wilcock, W. S. D.; Zumberge, M. A.

2017-12-01

Seawater pressure can be used to measure vertical seafloor deformation since small seafloor height changes produce measurable pressure changes. However, resolving secular vertical deformation near subduction zones can be difficult due to pressure gauge drift. A typical gauge drift rate of about 10 cm/year exceeds the expected secular rate of 1 cm/year or less in Cascadia. The absolute self-calibrating pressure recorder (ASCPR) was developed to solve the issue of gauge drift by using a deadweight calibrator to make campaign-style measurements of the absolute seawater pressure. Pressure gauges alternate between observing the ambient seawater pressure and the deadweight calibrator pressure, which is an accurately known reference value, every 10-20 minutes for several hours. The difference between the known reference pressure and the observed seafloor pressure allows offsets and transients to be corrected to determine the true, absolute seafloor pressure. Absolute seafloor pressure measurements provide a great utility for geodetic deformation studies. The measurements provide instrument-independent, benchmark values that can be used far into the future as epoch points in long-term time series or as important calibration points for other continuous pressure records. The ASCPR was first deployed in Cascadia in 2014 and 2015, when seven concrete seafloor benchmarks were placed along a trench-perpendicular profile extending from 20 km to 105 km off the central Oregon coast. Two benchmarks have ASCPR measurements that span three years, one benchmark spans two years, and four benchmarks span one year. Measurement repeatability is currently 3 to 4 cm, but we anticipate accuracy on the order of 1 cm with improvements to the instrument metrology and processing tidal and non-tidal oceanographic signals.

Strategic planning of INA-CORS development for public service and tectonic deformation study

NASA Astrophysics Data System (ADS)

Syetiawan, Agung; Gaol, Yustisi Ardhitasari Lumban; Safi'i, Ayu Nur

2017-07-01

GPS technology can be applied for surveying, mapping and research purposes. The simplicity of GPS technology for positioning make it become the first choice for survey compared with another positioning method. GPS can measure a position with various accuracy level based on the measurement method. In order to facilitate the GPS positioning, many organizations are establishing permanent GPS station. National Geodetic Survey (NGS) called it as Continuously Operating Reference Stations (CORS). Those devices continuously collect and record GPS data to be used by users. CORS has been built by several government agencies for particular purposes and scattered throughout Indonesia. Geospatial Information Agency (BIG) as a geospatial information providers begin to compile a grand design of Indonesia CORS (INA-CORS) that can be used for public service such as Real Time Kinematic (RTK), RINEX data request, or post-processing service and for tectonic deformation study to determine the deformation models of Indonesia and to evaluate the national geospatial reference system. This study aims to review the ideal location to develop CORS network distribution. The method was used is to perform spatial analysis on the data distribution of BIG and BPN CORS overlayed with Seismotectonic Map of Indonesia and land cover. The ideal condition to be achieved is that CORS will be available on each radius of 50 km. The result showed that CORS distribution in Java and Nusa Tenggara are already tight while on Sumatra, Celebes and Moluccas are still need to be more tighten. Meanwhile, the development of CORS in Papua will encounter obstacles toward road access and networking. This analysis result can be used as consideration for determining the priorities of CORS development in Indonesia.

A precise vertical network: Establishing new orthometric heights with static surveys in Florida tidal marshes

USGS Publications Warehouse

Raabe, E.A.; Stumpf, R.P.; Marth, N.J.; Shrestha, R.L.

1996-01-01

Elevation differences on the order of 10 cm within Florida's marsh system influence major variations in tidal flooding and in the associated plant communities. This low elevation gradient combined with sea level fluctuation of 5-to-10 cm over decadel and longer periods can generate significant alteration and erosion of marsh habitats along the Gulf Coast. Knowledge of precise and accurate elevations in the marsh is critical to the efficient monitoring and management of these habitats. Global positioning system (GPS) technology was employed to establish six new orthometric heights along the Gulf Coast from which kinematic surveys into the marsh interior are conducted. The vertical accuracy achieved using GPS technology was evaluated using two networks with 16 vertical and nine horizontal NGS published high accuracy positions. New positions were occupied near St. Marks National Wildlife Refuge and along the coastline of Levy County and Citrus County. Static surveys were conducted using four Ashtech dual frequency P-code receivers for 45-minute sessions and a data logging rate of 10 seconds. Network vector lengths ranged from 4 to 64 km and, including redundant baselines, totaled over 100 vectors. Analysis includes use of the GEOID93 model with a least squares network adjustment and reference to the National Geodetic Reference System (NGRS). The static surveys show high internal consistency and the desired centimeter-level accuracy is achieved for the local network. Uncertainties for the newly established vertical positions range from 0.8 cm to 1.8 cm at the 95% confidence level. These new positions provide sufficient vertical accuracy to achieve the project objectives of tying marsh surface elevations to long-term water level gauges recording sea level fluctuations along the coast.

JTRF2014, the JPL Kalman filter and smoother realization of the International Terrestrial Reference System

NASA Astrophysics Data System (ADS)

Abbondanza, Claudio; Chin, Toshio M.; Gross, Richard S.; Heflin, Michael B.; Parker, Jay W.; Soja, Benedikt S.; van Dam, Tonie; Wu, Xiaoping

2017-10-01

We present and discuss JTRF2014, the Terrestrial Reference Frame (TRF) the Jet Propulsion Laboratory constructed by combining space-geodetic inputs from very long baseline interferometry (VLBI), satellite laser ranging (SLR), Global Navigation Satellite Systems (GNSS), and Doppler orbitography and radiopositioning integrated by satellite submitted for the realization of ITRF2014. Determined through a Kalman filter and Rauch-Tung-Striebel smoother assimilating position observations, Earth orientation parameters, and local ties, JTRF2014 is a subsecular, time series-based TRF whose origin is at the quasi-instantaneous center of mass (CM) as sensed by SLR and whose scale is determined by the quasi-instantaneous VLBI and SLR scales. The dynamical evolution of the positions accounts for a secular motion term, annual, and semiannual periodic modes. Site-dependent variances based on the analysis of loading displacements induced by mass redistributions of terrestrial fluids have been used to control the extent of random walk adopted in the combination. With differences in the amplitude of the annual signal within the range 0.5-0.8 mm, JTRF2014-derived center of network-to-center of mass (CM-CN) is in remarkable agreement with the geocenter motion obtained via spectral inversion of GNSS, Gravity Recovery and Climate Experiment (GRACE) observations and modeled ocean bottom pressure from Estimating the Circulation and Climate of the Ocean (ECCO). Comparisons of JTRF2014 to ITRF2014 suggest high-level consistency with time derivatives of the Helmert transformation parameters connecting the two frames below 0.18 mm/yr and weighted root-mean-square differences of the polar motion (polar motion rate) in the order of 30 μas (17 μas/d).

Transformation formulas relating geodetic coordinates to a tangent to Earth, plane coordinate system

NASA Technical Reports Server (NTRS)

Credeur, L.

1981-01-01

Formulas and their approximation were developed to map geodetic position to an Earth tangent plane with an airport centered rectangular coordinate system. The transformations were developed for use in a terminal area air traffic model with deterministic aircraft traffic. The exact configured vehicle's approximation equations used in their precision microwave landing system navigation experiments.

VLBI2010: The Astro-Geo Connection

NASA Technical Reports Server (NTRS)

Porcas, Richard

2010-01-01

VLBI2010 holds out promise for greatly increased precision in measuring geodetic and Earth rotation parameters. As a by-product there will be a wealth of interesting new astronomical data. At the same time, astronomical knowledge may be needed to disentangle the astronomical and geodetic contributions to the measured delays and phases. This presentation explores this astro-geo link.

The Reference Elevation Model of Antarctica (REMA): A High Resolution, Time-Stamped Digital Elevation Model for the Antarctic Ice Sheet

NASA Astrophysics Data System (ADS)

Howat, I.; Noh, M. J.; Porter, C. C.; Smith, B. E.; Morin, P. J.

2017-12-01

We are creating the Reference Elevation Model of Antarctica (REMA), a continuous, high resolution (2-8 m), high precision (accuracy better than 1 m) reference surface for a wide range of glaciological and geodetic applications. REMA will be constructed from stereo-photogrammetric Digital Surface Models (DSM) extracted from pairs of submeter resolution DigitalGlobe satellite imagery and vertically registred to precise elevations from near-coincident airborne LiDAR, ground-based GPS surveys and Cryosat-2 radar altimetry. Both a seamless mosaic and individual, time-stamped DSM strips, collected primarily between 2012 and 2016, will be distributed to enable change measurement. These data will be used for mapping bed topography from ice thickness, measuring ice thickness changes, constraining ice flow and geodynamic models, mapping glacial geomorphology, terrain corrections and filtering of remote sensing observations, and many other science tasks. Is will also be critical for mapping ice traverse routes, landing sites and other field logistics planning. REMA will also provide a critical elevation benchmark for future satellite altimetry missions including ICESat-2. Here we report on REMA production progress, initial accuracy assessment and data availability.

Space Geodesy, VLBI, and the Fourth Pillar of Geodesy - Spacetime Curvature

NASA Astrophysics Data System (ADS)

Combrinck, Ludwig

2014-12-01

Typically geodesy is described as having ``three pillars'': the variations in Earth's shape, gravity field, and rotation. These pillars form the conceptual and observational basis for the celestial and terrestrial reference frames required for Earth and space observations. However, it is no longer adequate to base the conceptual and observational basis on only three pillars. Spacetime curvature as described by the General Theory of Relativity (GTR) is an integral component of all space geodesy techniques and influences all measurements, techniques, and data reduction. Spacetime curvature is therefore the fourth pillar. It is the measurement of the shape of spacetime and its variations. Due to accuracies of Very Long Baseline Interferometry (VLBI) and optical celestial reference frame measurements reaching the tens of micro-arcsecond level in the near future, it is essential to recognize the impact of spacetime seeing on the accuracy objectives of the Global Geodetic Observing System. Spacetime seeing (resulting from spacetime curvature) is analogous to astronomical seeing (resulting from atmospheric conditions), as all of spacetime is affected by microlensing/weak lensing to some extent as a result of mass (normal baryonic and darkmatter) distribution, placing a limit on the realization of the celestial reference frame.

High Performance Clocks and Gravity Field Determination

NASA Astrophysics Data System (ADS)

Müller, J.; Dirkx, D.; Kopeikin, S. M.; Lion, G.; Panet, I.; Petit, G.; Visser, P. N. A. M.

2018-02-01

Time measured by an ideal clock crucially depends on the gravitational potential and velocity of the clock according to general relativity. Technological advances in manufacturing high-precision atomic clocks have rapidly improved their accuracy and stability over the last decade that approached the level of 10^{-18}. This notable achievement along with the direct sensitivity of clocks to the strength of the gravitational field make them practically important for various geodetic applications that are addressed in the present paper. Based on a fully relativistic description of the background gravitational physics, we discuss the impact of those highly-precise clocks on the realization of reference frames and time scales used in geodesy. We discuss the current definitions of basic geodetic concepts and come to the conclusion that the advances in clocks and other metrological technologies will soon require the re-definition of time scales or, at least, clarification to ensure their continuity and consistent use in practice. The relative frequency shift between two clocks is directly related to the difference in the values of the gravity potential at the points of clock's localization. According to general relativity the relative accuracy of clocks in 10^{-18} is equivalent to measuring the gravitational red shift effect between two clocks with the height difference amounting to 1 cm. This makes the clocks an indispensable tool in high-precision geodesy in addition to laser ranging and space geodetic techniques. We show how clock measurements can provide geopotential numbers for the realization of gravity-field-related height systems and can resolve discrepancies in classically-determined height systems as well as between national height systems. Another application of clocks is the direct use of observed potential differences for the improved recovery of regional gravity field solutions. Finally, clock measurements for space-borne gravimetry are analyzed along with closely-related deficiencies of this method like an extra-ordinary knowledge of the spacecraft velocity, etc. For all these applications besides the near-future prospects, we also discuss the challenges that are related to using those novel clock data in geodesy.

Geocenter Motion Derived from the JTRF2014 Combination

NASA Astrophysics Data System (ADS)

Abbondanza, C.; Chin, T. M.; Gross, R. S.; Heflin, M. B.; Parker, J. W.; van Dam, T. M.; Wu, X.

2016-12-01

JTRF2014 represents the JPL Terrestrial Reference Frame (TRF) recently obtained as a result of the combination of the space-geodetic reprocessed inputs to the ITRF2014. Based upon a Kalman filter and smoother approach, JTRF2014 assimilates station positions and Earth-Orientation Parameters (EOPs) from GNSS, VLBI, SLR and DORIS and combine them through local tie measurements. JTRF is in its essence a time-series based TRF. In the JTRF2014 the dynamical evolution of the station positions is formulated by introducing linear and seasonal terms (annual and semi-annual periodic modes). Non-secular and non-seasonal motions of the geodetic sites are included in the smoothed time series by properly defining the station position process noise whose variance is characterized by analyzing station displacements induced by temporal changes of planetary fluid masses (atmosphere, oceans and continental surface water). With its station position time series output at a weekly resolution, JTRF2014 materializes a sub-secular frame whose origin is at the quasi-instantaneous Center of Mass (CM) as sensed by SLR. Both SLR and VLBI contribute to the scale of the combined frame. The sub-secular nature of the frame allows the users to directly access the quasi-instantaneous geocenter and scale information. Unlike standard combined TRF products which only give access to the secular component of the CM-CN motions, JTRF2014 is able to preserve -in addition to the long-term- the seasonal, non-seasonal and non-secular components of the geocenter motion. In the JTRF2014 assimilation scheme, local tie measurements are used to transfer the geocenter information from SLR to the space-geodetic techniques which are either insensitive to CM (VLBI) or whose geocenter motion is poorly determined (GNSS and DORIS). Properly tied to the CM frame through local ties and co-motion constraints, GNSS, VLBI and DORIS contribute to improve the SLR network geometry. In this paper, the determination of the weekly (CM-CN) time series as inferred from the JTRF2014 combination will be presented. Comparisons with geocenter time series derived from global inversions of GPS, GRACE and ocean bottom pressure models show the JTRF2014-derived geocenter favourably compares to the results of the inversion.

Stress coupling in the seismic cycle indicated from geodetic measurements

NASA Astrophysics Data System (ADS)

Wang, L.; Hainzl, S.; Zoeller, G.; Holschneider, M.

2012-12-01

The seismic cycle includes several phases, the interseismic, coseismic and postseismic phase. In the interseismic phase, strain gradually builds up around the overall locked fault in tens to thousands of years, while it is coseismically released in seconds. In the postseismic interval, stress relaxation lasts months to years, indicated by evident aseismic deformations which have been indicated to release comparable or even higher strain energy than the main shocks themselves. Benefiting from the development of geodetic observatory, e.g., Global Positioning System (GPS) and Interferometric Synthetic Aperture Radar (InSAR) in the last two decades, the measurements of surface deformation have been significantly improved and become valuable information for understanding the stress evolution on the large fault plane. In this study, we utilize the GPS/InSAR data to investigate the slip deficit during the interseismic phase, the coseismic slip and the early postseismic creep on the fault plane. However, it is already well-known that slip inversions based only on the surface measurements are typically non-unique and subject to large uncertainties. To reduce the ambiguity, we utilize the assumption of stress coupling between interseismic and coseismic phases, and between coseismic and postseismic phases. We use a stress constrained joint inversion in Bayesian approach (Wang et al., 2012) to invert simultaneously for (1) interseismic slip deficit and coseismic slip, and (2) coseismic slip and postseismic creep. As case studies, we analyze earthquakes occurred in well-instrumented regions such as the 2004 M6.0 Parkfield earthquake, the 2010 M8.7 earthquake and the 2011 M9.1 Tohoku-Oki earthquake. We show that the inversion with the stress-coupling constraint leads to better constrained slip distributions. Meanwhile, the results also indicate that the assumed stress coupling is reasonable and can be well reflected from the available geodetic measurements. Reference: Lifeng Wang, Sebastian Hainzl, Gert Zöller, Matthias Holschneider, M., 2012. Stress- and aftershock- constrained joint inversions for co- and post- seismic slip applied to the 2004 M6.0 Parkfield earthquake. J. Geophys. Res. doi:10.1029/2011JB009017.

The Space Geodesy Project and Radio Frequency Interference Characterization and Mitigation

NASA Technical Reports Server (NTRS)

Lawrence, Hilliard M.; Beaudoin, C.; Corey, B. E.; Tourain, C. L.; Petrachenko, B.; Dickey, John

2013-01-01

The Space Geodesy Project (SGP) development by NASA is an effort to co-locate the four international geodetic techniques Satellite Laser Ranging (SLR) and Lunar Laser Ranging (LLR), Very Long Baseline Interferometry (VLBI), Global Navigation Satellite System (GNSS), and Doppler Orbitography and Radiopositioning Integrated by Satellite (DORIS) into one tightly referenced campus and coordinated reference frame analysis. The SGP requirement locates these stations within a small area to maintain line-of-sight and frequent automated survey known as the vector tie system. This causes a direct conflict with the new broadband VLBI technique. Broadband means 2-14 GHz, and RFI susceptibility at -80 dBW or higher due to sensitive RF components in the front end of the radio receiver.

Accuracy Analysis of a Wireless Indoor Positioning System Using Geodetic Methods

NASA Astrophysics Data System (ADS)

Wagner, Przemysław; Woźniak, Marek; Odziemczyk, Waldemar; Pakuła, Dariusz

2017-12-01

Ubisense RTLS is one of the Indoor positioning systems using an Ultra Wide Band. AOA and TDOA methods are used as a principle of positioning. The accuracy of positioning depends primarily on the accuracy of determined angles and distance differences. The paper presents the results of accuracy research which includes a theoretical accuracy prediction and a practical test. Theoretical accuracy was calculated for two variants of system components geometry, assuming the parameters declared by the system manufacturer. Total station measurements were taken as a reference during the practical test. The results of the analysis are presented in a graphical form. A sample implementation (MagMaster) developed by Globema is presented in the final part of the paper.

Data catalog series for space science and applications flight missions. Volume 4A: Descriptions of meteorological and terrestrial applications spacecraft and investigations

NASA Technical Reports Server (NTRS)

Ng, C. Y. (Editor); Sheu, Y. T. P. (Editor)

1985-01-01

The National Space Science Data Center (NSSDC) provides data from and information about space science and applications flight investigations in support of additional studies beyond those performed as the principal part of any flight mission. The Earth-orbiting spacecraft for investigations of the earth and its atmosphere is discussed. Geodetic tracking data are included in this category. The principal subject areas presented are meteorology and earth resources survey, and the spacecraft selection is made according to those subjects. All experiments on board the spacecraft are described. No attempt is made to reference investigations that are related to the above disciplines, but that are described in other volumes of this series.

The New IERS Special Bureau for Loading (SBL)

NASA Technical Reports Server (NTRS)

vanDam, Tonie; Plag, Hans-Peter; Blewitt, Geoffrey; Boy, Jean-Paul; Francis, Olivier; Gegout, Pascal; Kierulf, Halfdan Pascal; Sato, Tadahiro; Scherneck, Hans-Georg; Wahr, John

2002-01-01

Currently, the establishment of the International Earth Rotation Service (IERS) Special Bureau for Loading (SBL) is in progress as part of the IERS Global Geophysical Fluids Center (GGFC). The main purpose of the SBL is to provide reliable, consistent model predictions of loading signals that have been thoroughly tested and validated. The products will describe at least the surface deformation, gravity signal and geo-center variations due to the various surface loading processes in reference frames relevant for direct comparison with existing geodetic observing techniques. To achieve these goals, major scientific advances are required with respect to the Earth model, the theory and algorithms used to model deformations of the Earth as well as improvements in the observational data related to surface loading.

Resolution testing and limitations of geodetic and tsunami datasets for finite fault inversions along subduction zones

NASA Astrophysics Data System (ADS)

Williamson, A.; Newman, A. V.

2017-12-01

Finite fault inversions utilizing multiple datasets have become commonplace for large earthquakes pending data availability. The mixture of geodetic datasets such as Global Navigational Satellite Systems (GNSS) and InSAR, seismic waveforms, and when applicable, tsunami waveforms from Deep-Ocean Assessment and Reporting of Tsunami (DART) gauges, provide slightly different observations that when incorporated together lead to a more robust model of fault slip distribution. The merging of different datasets is of particular importance along subduction zones where direct observations of seafloor deformation over the rupture area are extremely limited. Instead, instrumentation measures related ground motion from tens to hundreds of kilometers away. The distance from the event and dataset type can lead to a variable degree of resolution, affecting the ability to accurately model the spatial distribution of slip. This study analyzes the spatial resolution attained individually from geodetic and tsunami datasets as well as in a combined dataset. We constrain the importance of distance between estimated parameters and observed data and how that varies between land-based and open ocean datasets. Analysis focuses on accurately scaled subduction zone synthetic models as well as analysis of the relationship between slip and data in recent large subduction zone earthquakes. This study shows that seafloor deformation sensitive datasets, like open-ocean tsunami waveforms or seafloor geodetic instrumentation, can provide unique offshore resolution for understanding most large and particularly tsunamigenic megathrust earthquake activity. In most environments, we simply lack the capability to resolve static displacements using land-based geodetic observations.

The Impact of Sea Level Rise on Geodetic Vertical Datum of Peninsular Malaysia

NASA Astrophysics Data System (ADS)

Din, A. H. M.; Abazu, I. C.; Pa'suya, M. F.; Omar, K. M.; Hamid, A. I. A.

2016-09-01

Sea level rise is rapidly turning into major issues among our community and all levels of the government are working to develop responses to ensure these matters are given the uttermost attention in all facets of planning. It is more interesting to understand and investigate the present day sea level variation due its potential impact, particularly on our national geodetic vertical datum. To determine present day sea level variation, it is vital to consider both in-situ tide gauge and remote sensing measurements. This study presents an effort to quantify the sea level rise rate and magnitude over Peninsular Malaysia using tide gauge and multi-mission satellite altimeter. The time periods taken for both techniques are 32 years (from 1984 to 2015) for tidal data and 23 years (from 1993 to 2015) for altimetry data. Subsequently, the impact of sea level rise on Peninsular Malaysia Geodetic Vertical Datum (PMGVD) is evaluated in this study. the difference between MSL computed from 10 years (1984 - 1993) and 32 years (1984 - 2015) tidal data at Port Kelang showed that the increment of sea level is about 27mm. The computed magnitude showed an estimate of the long-term effect a change in MSL has on the geodetic vertical datum of Port Kelang tide gauge station. This will help give a new insight on the establishment of national geodetic vertical datum based on mean sea level data. Besides, this information can be used for a wide variety of climatic applications to study environmental issues related to flood and global warming in Malaysia.

A Solution to Bring the National Astronomical-Geodetic Network from S/42 System to WGS-84 System

NASA Astrophysics Data System (ADS)

Radu, Ion

In the framework of a Romanian-Bulgarian cooperation, the Military Astronomical Observatory Bucharest integrated GPS measurements with points in the Southern zone of the national geodetic network. Molodensky's, Zhogolovich's and Ihde's relations were used to pass from S/42 system to WGS-84 system. Six variants for the choice of common points were considered.

Geodetic monitoring of tectonic deformation: Toward a strategy

NASA Technical Reports Server (NTRS)

1981-01-01

Issues of interest and importance to society and science are presented. The problems considered are of national concern; their solutions may contribute to a better understanding of tectonic deformation and earthquake hazards. The need for additional field data, the role of geodetic measurements, the importance of both ground and space techniques, and the need for advanced instrumentation development are discussed.

Global Digital Image Mosaics of Mars: Assessment of Geodetic Accuracy

NASA Technical Reports Server (NTRS)

Kirk, R.; Archinal, B. A.; Lee, E. M.; Davies, M. E.; Colvin, T. R.; Duxbury, T. C.

2001-01-01

A revised global image mosaic of Mars (MDIM 2.0) was recently completed by USGS. Comparison with high-resolution gridded Mars Orbiter Laser Altimeter (MOLA) digital image mosaics will allow us to quantify its geodetic errors; linking the next MDIM to the MOLA data will help eliminate those errors. Additional information is contained in the original extended abstract.

An Overview of Geodetic Volcano Research in the Canary Islands

NASA Astrophysics Data System (ADS)

Fernández, José; González, Pablo J.; Camacho, Antonio G.; Prieto, Juan F.; Brú, Guadalupe

2015-11-01

The Canary Islands are mostly characterized by diffuse and scattered volcanism affecting a large area, with only one active stratovolcano, the Teide-Pico Viejo complex (Tenerife). More than 2 million people live and work in the 7,447 km2 of the archipelago, resulting in an average population density three times greater than the rest of Spain. This fact, together with the growth of exposure during the past 40 years, increases volcanic risk with respect previous eruptions, as witnessed during the recent 2011-2012 El Hierro submarine eruption. Therefore, in addition to purely scientific reasons there are economic and population-security reasons for developing and maintaining an efficient volcano monitoring system. In this scenario geodetic monitoring represents an important part of the monitoring system. We describe volcano geodetic monitoring research carried out in the Canary Islands and the results obtained. We consider for each epoch the two main existing constraints: the level of volcanic activity in the archipelago, and the limitations of the techniques available at the time. Theoretical and observational aspects are considered, as well as the implications for operational volcano surveillance. Current challenges of and future perspectives in geodetic volcano monitoring in the Canaries are also presented.

Geodetic measurement of deformation in California. Ph.D. Thesis

NASA Technical Reports Server (NTRS)

Sauber, Jeanne Marie

1988-01-01

The very long baseline interferometry (VLBI) measurements made in the western U.S. since 1979 as part of the NASA Crustal Dynamics Project provide discrete samples of the temporal and spatial deformation field. The interpretation of the VLBI-derived rates of deformation requires an examination of geologic information and more densely sampled ground-based geodetic data. In the first two of three related studies embodying this thesis triangulation and trilateration data measured on two regional networks are processed, one in the central Mojave Desert and one in the Coast Ranges east of the San Andreas fault. At the spatial scales spanned by these local geodetic networks, auxiliary geologic and geophysical data have been utilized to examine the relation between measured incremental strain and the accommodation of strain seen in local geological structures, strain release in earthquakes, and principal stress directions inferred from in situ measurements. In the third study, VLBI data from stations distributed across the Pacific - North American plate boundary zone in the western United States are processed. The VLBI data have been used to constrain the integrated rate of deformation across portions of the continental plate boundary in California and to provide a tectonic framework to interpret regional geodetic and geologic studies.

CDDIS: NASA's Archive of Space Geodesy Data and Products Supporting GGOS

NASA Technical Reports Server (NTRS)

Noll, Carey; Michael, Patrick

2016-01-01

The Crustal Dynamics Data Information System (CDDIS) supports data archiving and distribution activities for the space geodesy and geodynamics community. The main objectives of the system are to store space geodesy and geodynamics related data and products in a central archive, to maintain information about the archival of these data,to disseminate these data and information in a timely manner to a global scientific research community, and provide user based tools for the exploration and use of the archive. The CDDIS data system and its archive is a key component in several of the geometric services within the International Association of Geodesy (IAG) and its observing systemthe Global Geodetic Observing System (GGOS), including the IGS, the International DORIS Service (IDS), the International Laser Ranging Service (ILRS), the International VLBI Service for Geodesy and Astrometry (IVS), and the International Earth Rotation and Reference Systems Service (IERS). The CDDIS provides on-line access to over 17 Tbytes of dataand derived products in support of the IAG services and GGOS. The systems archive continues to grow and improve as new activities are supported and enhancements are implemented. Recently, the CDDIS has established a real-time streaming capability for GNSS data and products. Furthermore, enhancements to metadata describing the contents ofthe archive have been developed to facilitate data discovery. This poster will provide a review of the improvements in the system infrastructure that CDDIS has made over the past year for the geodetic community and describe future plans for the system.

ERP-Variations on Time Scales Between Hours and Months Derived From GNSS Observations

NASA Astrophysics Data System (ADS)

Weber, R.; Englich, S.; Mendes Cerveira, P.

2007-05-01

Current observations gained by the space geodetic techniques, especially VLBI, GPS and SLR, allow for the determination of Earth Rotation Parameters (ERPs - polar motion, UT1/LOD) with unprecedented accuracy and temporal resolution. This presentation focuses on contributions to the ERP recovery provided by satellite navigation systems (primarily GPS). The IGS (International GNSS Service), for example, currently provides daily polar motion with an accuracy of less than 0.1mas and LOD estimates with an accuracy of a few microseconds. To study more rapid variations in polar motion and LOD we established in a first step a high resolution (hourly resolution) ERP-time series from GPS observation data of the IGS network covering the year 2005. The calculations were carried out by means of the Bernese GPS Software V5.0 considering observations from a subset of 113 fairly stable stations out of the IGS05 reference frame sites. From these ERP time series the amplitudes of the major diurnal and semidiurnal variations caused by ocean tides are estimated. After correcting the series for ocean tides the remaining geodetic observed excitation is compared with variations of atmospheric excitation (AAM). To study the sensitivity of the estimates with respect to the applied mapping function we applied both the widely used NMF (Niell Mapping Function) and the VMF1 (Vienna Mapping Function 1). In addition, based on computations covering two months in 2005, the potential improvement due to the use of additional GLONASS data will be discussed.

Star Scheduling Mode—A New Observing Strategy for Monitoring Weak Southern Radio Sources with the AuScope VLBI Array

NASA Astrophysics Data System (ADS)

McCallum, Lucia; Mayer, David; Le Bail, Karine; Schartner, Matthias; McCallum, Jamie; Lovell, Jim; Titov, Oleg; Shu, Fengchun; Gulyaev, Sergei

2017-11-01

The International Celestial Reference Frame suffers from significantly less observations in the southern hemisphere compared to the northern one. One reason for this is the historically low number of very long baseline interferometry radio telescopes in the south. The AuScope very long baseline interferometry array with three new telescopes on the Australian continent and an identical antenna in New Zealand were built to address this issue. While the overall number of observations in the south has greatly improved since then, a closer look reveals that this improvement is only true for strong radio sources (source flux densities >0.6 Jy). The new array of small very long baseline interferometry antennas has a relatively low baseline sensitivity so that only strong sources can be observed within a short integration time. A new observing strategy, the star scheduling mode, was developed to enable efficient observations of weak sources during geodetic sessions, through the addition of a single more sensitive antenna to the network. This scheduling mode was implemented in the Vienna very long baseline interferometry Software and applied in four 24-h sessions in 2016. These observations provide updated positions and source flux densities for 42 weak southern radio sources and significantly reduce the formal uncertainties for these sources. The star scheduling mode now allows the AuScope very long baseline interferometry array to undertake greater responsibility in monitoring sources in the southern sky, without significantly weakening the session for geodetic purposes.

Geodetic measurement of deformation in the Loma Prieta, California earthquake with Very Long Baseline Interferometry (VLBI)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Clark, T.A.; Ma, C.; Sauber, J.M.

Following the Loma Prieta earthquake, two mobile Very Long Baseline Interferometry (VLBI) systems operated by the NASA Crustal Dynamics Project and the NOAA National Geodetic Survey were deployed at three previously established VLBI sites in the earthquake area: Fort Ord (near Monterey), the Presidio (in San Francisco) and Point Reyes. From repeated VLBI occupations of these sites since 1983, the pre-earthquake rates of deformation have been determined with respect to a North American reference frame with 1{sigma} formal standard errors of {approximately}1 mm/yr. The VLBI measurements immediately following the earthquake showed that the Fort Ord site was displaced 49 {plusmore » minus} 4 mm at an azimuth of 11 {plus minus} 4{degree} and that the Presidio site was displaced 12 {plus minus} 5 mm at an azimuth of 148 {plus minus} 13{degree}. No anomalous change was detected at Point Reyes with 1{sigma} uncertainty of 4 mm. The estimated displacements at Fort Ord and the Presidio are consistent with the static displacements predicted on the basis of a coseismic slip model in which slip on the southern segment is shallower than slip on the more northern segment is shallower than slip on the more northern segment of the fault rupture. The authors also give the Cartesian positions at epoch 1990.0 of a set of VLBI fiducial stations and the three mobile sites in the vicinity of the earthquake.« less

Predicting present-day rates of glacial isostatic adjustment using a smoothed GPS velocity field for the reconciliation of NAD83 reference frames in Canada

NASA Astrophysics Data System (ADS)

Craymer, M. R.; Henton, J. A.; Piraszewski, M.

2008-12-01

Glacial isostatic adjustment following the last glacial period is the dominant source of crustal deformation in Canada east of the Rocky Mountains. The present-day vertical component of motion associated with this process may exceed 1 cm/y and is being directly measured with the Global Positioning System (GPS). A consequence of this steady deformation is that high accuracy coordinates at one epoch may not be compatible with those at another epoch. For example, modern precise point positioning (PPP) methods provide coordinates at the epoch of observation while NAD83, the officially adopted reference frame in Canada and the U.S., is expressed at some past reference epoch. The PPP positions are therefore incompatible with coordinates in such a realization of the reference frame and need to be propagated back to the frame's reference epoch. Moreover, the realizations of NAD83 adopted by the provincial geodetic agencies in Canada are referenced to different coordinate epochs; either 1997.0 or 2002.0. Proper comparison of coordinates between provinces therefore requires propagating them from one reference epoch to another. In an effort to reconcile PPP results and different realizations of NAD83, we empirically represent crustal deformation throughout Canada using a velocity field based solely on high accuracy continuous and episodic GPS observations. The continuous observations from 2001 to 2007 were obtained from nearly 100 permanent GPS stations, predominately operated by Natural Resources Canada (NRCan) and provincial geodetic agencies. Many of these sites are part of the International GNSS Service (IGS) global network. Episodic observations from 1994 to 2006 were obtained from repeated occupations of the Canadian Base Network (CBN), which consists of approximately 160 stable pillar-type monuments across the entire country. The CBN enables a much denser spatial sampling of crustal motions although coverage in the far north is still rather sparse. NRCan solutions of the continuous GPS data were combined with those from other agencies as part of the North American Reference Frame (NAREF) effort to improve the reliability of the results. This NAREF solution has then been combined with our CBN results to obtain a denser velocity sampling for fitting different types of surfaces in a first attempt to determine a continuous GPS velocity field for the entire country. Expressing this velocity field as a grid enables users to interpolate to any location in Canada, allowing for the propagation of coordinates to any desired reference epoch. We examine the accuracy and limitations of this GPS velocity field by comparing it to other published GPS velocity solutions (which are all based on less data) as well as to GIA models, including versions of ICE-3G, ICE-5G and the recent Stable North America Reference Frame (SNARF) model. Of course, the accuracy of the GPS velocity field depends directly on the density of the GPS coverage. Consequently, the GPS velocity field is unable to fully represent the actual GIA motion in the far north and tends to smooth out the signal due to the spatially sparse coverage. On the other hand, the model performs quite well in the southern parts of the country where there is a much greater spatial density of GPS measurements.

Field Installation and Real-Time Data Processing of the New Integrated SeismoGeodetic System with Real-Time Acceleration and Displacement Measurements for Earthquake Characterization Based on High-Rate Seismic and GPS Data

NASA Astrophysics Data System (ADS)

Zimakov, Leonid; Jackson, Michael; Passmore, Paul; Raczka, Jared; Alvarez, Marcos; Barrientos, Sergio

2015-04-01

We will discuss and show the results obtained from an integrated SeismoGeodetic System, model SG160-09, installed in the Chilean National Network. The SG160-09 provides the user high rate GNSS and accelerometer data, full epoch-by-epoch measurement integrity and, using the Trimble Pivot™ SeismoGeodetic App, the ability to create combined GNSS and accelerometer high-rate (200Hz) displacement time series in real-time. The SG160-09 combines seismic recording with GNSS geodetic measurement in a single compact, ruggedized package. The system includes a low-power, 220-channel GNSS receiver powered by the latest Trimble-precise Maxwell™6 technology and supports tracking GPS, GLONASS and Galileo signals. The receiver incorporates on-board GNSS point positioning using Real-Time Precise Point Positioning (PPP) technology with satellite clock and orbit corrections delivered over IP networks. The seismic recording element includes an ANSS Class A, force balance triaxial accelerometer with the latest, low power, 24-bit A/D converter, which produces high-resolution seismic data. The SG160-09 processor acquires and packetizes both seismic and geodetic data and transmits it to the central station using an advanced, error-correction protocol with back fill capability providing data integrity between the field and the processing center. The SG160-09 has been installed in the seismic station close to the area of the Iquique earthquake of April 1, 2014, in northern Chile, a seismically prone area at the current time. The hardware includes the SG160-09 system, external Zephyr Geodetic-2 GNSS antenna, and high-speed Internet communication media. Both acceleration and displacement data was transmitted in real-time to the National Seismological Center in Santiago for real-time data processing using Earthworm / Early Bird software. Command/Control of the field station and real-time GNSS position correction are provided via the Pivot software suite. Data from the SG160-09 system was used for seismic event characterization along with data from traditional stand-alone broadband seismic and geodetic stations installed in the network. Our presentation will focus on the key improvements of the network installation with the SG160-09 system, rapid data transmission, and real-time data processing for strong seismic events and aftershock characterization as well as advanced features of the SG160-09 for Earthquake and Tsunami Early Warning system.

Geodetic slip rate estimates for the Alhama de Murcia and Carboneras faults in the SE Betics, Spain

NASA Astrophysics Data System (ADS)

Khazaradze, Giorgi; Echeverria, Anna; Masana, Eulàlia

2016-04-01

The Alhama de Murcia and the Carboneras faults are the most prominent geologic structures within the Eastern Betic Shear Zone (EBSZ), located in SE Spain. Using continuous and campaign GPS observations conducted during the last decade, we were able to confirm the continuing tectonic activity of these faults by quantifying their geodetic slip-rates and comparing the estimated values with the geological (including paleoseismological) observations. We find that the bulk of the observed deformation is concentrated around the Alhama de Murcia (AMF) and the Palomares (PF) faults. The geodetic horizontal slip rate (reverse-sinistral) of 1.5±0.3 mm/yr calculated for the AMF and PF fault system is in good agreement with geological observations at the AMF, as well as, the focal mechanism of the 2011 Lorca earthquake, suggesting a main role of the AMF. We also find that the geodetic slip rate of the Carboneras fault zone (CFZ) is almost purely sinistral strike-slip with a rate of 1.3±0.2 mm/yr along N48° direction, very similar to 1.1 mm/yr geologic slip-rate, estimated from recent onshore and offshore paleoseismic and geomorphologic studies. The fact the geodetic and the geologic slip-rates are similar at the AMF and CF faults, suggests that both faults have been tectonically active since Quaternary, slipping at approximately at constant rate of 1.1 to 1.8 mm/yr. Since the existing GPS data cannot discern whether the CFZ is slipping seismically or aseismically, we have intended to relate the on-going seismic activity to the slip-rates estimated using GPS. For this reason we compared seismic and geodetic strain rates, where the latter are larger than seismic strain rates, suggesting the presence of aseismic processes in the area. Nevertheless, due to the large earthquake recurrence intervals, we may be underestimating the seismic strain rates. The direction of the P and T average stress axes are in good agreement with geodetic principal strain rate axes. To summarize, in eastern Betics, Alhama de Murcia and Carboneras left-lateral faults are the most active faults and they play an important role in the regional plate convergence kinematics. The work has been supported by the Spanish Ministry of Science and Innovation projects: SHAKE (CGL2011-30005-C02-01), CHARMA (CGL2013-40828-R) and EVENT (CGL2006-12861-C02-01).

A new global plate velocity model using space geodetic data, REVEL

NASA Astrophysics Data System (ADS)

Sella, G. F.; Dixon, T. H.; Mao, A.; Stein, S.

2001-12-01

Our model describes the relative velocities of 19 plates and continental blocks, and is derived from publicly available space geodetic (primarily GPS) data for the period 1993-2000. We include an independent and rigorous estimate for GPS velocity uncertainties in order to assess plate rigidity, and propagate these uncertainties to the velocity predictions. By excluding sites that may be influenced by seismic cycle effects within the plate boundary zone as well sites affected by glacial isostatic adjustment, we believe the plate velocity model is representative of geologically Recent motions (last ~10,000 years) and have termed it REVEL, for Recent velocity. Departures from short term rigid plate behaviour due to glacial isostatic adjustment are clearly observed for North America and Eurasia. Australia shows possible differences from rigid plate behavior in a manner consistent with its mapped intraplate stress field. We see statistically significant differences between the velocity predictions of REVEL-2000 and those of the NUVEL-1A geologic model for about one third of tested plate pairs. Pacific-North America motion and motion of the Caribbean plate with respect to North and South America are significantly faster than NUVEL-1A, presumably reflecting systematic errors in the geological model because the relevant rate data do not reflect the full plate rate. Many other differences between the geodetic and geological models appear to reflect real velocity changes over the last few million years. Nubia-Arabia and Arabia-Eurasia appear to be slowing, perhaps related to the collision of Arabia with Eurasia and consequent increased resistance to Arabia's northward motion Several other plate pairs, including Nazca-Pacific, Nazca-South America and Nubia-South America, are experiencing gradual slowing that dates back to about 25 Ma. This is the time of the initiation of the modern Andes mountains, and we speculate that associated crustal thickening on the leading edge of South America may play a role in this deceleration by affecting the balance of plate driving forces.