The International GPS Service: A Global Resource for GPS Applications and Research

NASA Technical Reports Server (NTRS)

Neilan, Ruth E.; Zumberge, James F.; Beutler, Gerhard; Kouba, Jan

1997-01-01

Since June, 1992, the International GPS service has been coordinating a global civilian GPS infrastructure in order to support numerous GPS applications and research activities. A key aspect of the IGS is the reliability and quality of the analysis products that have been made available over the past five years through the IGS Analysis Centers and the Analysis Center Coordinator.

New approach for processing data provided by an INS/GPS system onboard a vehicle

NASA Astrophysics Data System (ADS)

Dumitrascu, Ana; Serbanescu, Ionut; Tamas, Razvan D.; Danisor, Alin; Caruntu, George; Ticu, Ionela

2016-12-01

Due to the technology development, navigation systems are widely used in ground vehicle applications such as position prediction, safety of life, etc. It is known that a hybrid navigation system consisting of a GPS and inertial navigation system (INS) can provide a more accurate position prediction. By applying a Method of Moments (MoM) approach on the acquired data with INS/GPS we can extract both the coordinate and important information concerning safety of life. This kind of system will be cost effective and can also be used as a black box on boats, cars, submersible ships and even on small aircrafts.

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.

Fast mapping algorithm of lighting spectrum and GPS coordinates for a large area

NASA Astrophysics Data System (ADS)

Lin, Chih-Wei; Hsu, Ke-Fang; Hwang, Jung-Min

2016-09-01

In this study, we propose a fast rebuild technology for evaluating light quality in large areas. Outdoor light quality, which is measured by illuminance uniformity and the color rendering index, is difficult to conform after improvement. We develop an algorithm for a lighting quality mapping system and coordinates using a micro spectrometer and GPS tracker integrated with a quadcopter or unmanned aerial vehicle. After cruising at a constant altitude, lighting quality data is transmitted and immediately mapped to evaluate the light quality in a large area.

Study of the global positioning system for maritime concepts/applications: Study of the feasibility of replacing maritime shipborne navigation systems with NAVSTAR

NASA Technical Reports Server (NTRS)

Winn, C. B.; Huston, W.

1981-01-01

A geostationary reference satellite (REFSAT) that broadcasts every four seconds updated GPS satellite coordinates was developed. This procedure reduces the complexity of the GPS receiver. The economic and performance payoffs associated with replacing maritime stripborne navigation systems with NAVSTAR was quantified and the use of NAVSTAR for measurements of ocean currents in the broad ocean areas of the world was evaluated.

Performance analysis of an integrated GPS/inertial attitude determination system. M.S. Thesis - MIT

NASA Technical Reports Server (NTRS)

Sullivan, Wendy I.

1994-01-01

The performance of an integrated GPS/inertial attitude determination system is investigated using a linear covariance analysis. The principles of GPS interferometry are reviewed, and the major error sources of both interferometers and gyroscopes are discussed and modeled. A new figure of merit, attitude dilution of precision (ADOP), is defined for two possible GPS attitude determination methods, namely single difference and double difference interferometry. Based on this figure of merit, a satellite selection scheme is proposed. The performance of the integrated GPS/inertial attitude determination system is determined using a linear covariance analysis. Based on this analysis, it is concluded that the baseline errors (i.e., knowledge of the GPS interferometer baseline relative to the vehicle coordinate system) are the limiting factor in system performance. By reducing baseline errors, it should be possible to use lower quality gyroscopes without significantly reducing performance. For the cases considered, single difference interferometry is only marginally better than double difference interferometry. Finally, the performance of the system is found to be relatively insensitive to the satellite selection technique.

Global Positioning System Time Transfer Receiver (GPS/TTR) prototype design and initial test evaluation

NASA Technical Reports Server (NTRS)

Oaks, J.; Frank, A.; Falvey, S.; Lister, M.; Buisson, J.; Wardrip, C.; Warren, H.

1982-01-01

Time transfer equipment and techniques used with the Navigation Technology Satellites were modified and extended for use with the Global Positioning System (GPS) satellites. A prototype receiver was built and field tested. The receiver uses the GPS L1 link at 1575 MHz with C/A code only to resolve a measured range to the satellite. A theoretical range is computed from the satellite ephemeris transmitted in the data message and the user's coordinates. Results of user offset from GPS time are obtained by differencing the measured and theoretical ranges and applying calibration corrections. Results of the first field test evaluation of the receiver are presented.

Geocenter variations derived from a combined processing of LEO- and ground-based GPS observations

NASA Astrophysics Data System (ADS)

Männel, Benjamin; Rothacher, Markus

2017-08-01

GNSS observations provided by the global tracking network of the International GNSS Service (IGS, Dow et al. in J Geod 83(3):191-198, 2009) play an important role in the realization of a unique terrestrial reference frame that is accurate enough to allow a detailed monitoring of the Earth's system. Combining these ground-based data with GPS observations tracked by high-quality dual-frequency receivers on-board low earth orbiters (LEOs) is a promising way to further improve the realization of the terrestrial reference frame and the estimation of geocenter coordinates, GPS satellite orbits and Earth rotation parameters. To assess the scope of the improvement on the geocenter coordinates, we processed a network of 53 globally distributed and stable IGS stations together with four LEOs (GRACE-A, GRACE-B, OSTM/Jason-2 and GOCE) over a time interval of 3 years (2010-2012). To ensure fully consistent solutions, the zero-difference phase observations of the ground stations and LEOs were processed in a common least-squares adjustment, estimating all the relevant parameters such as GPS and LEO orbits, station coordinates, Earth rotation parameters and geocenter motion. We present the significant impact of the individual LEO and a combination of all four LEOs on the geocenter coordinates. The formal errors are reduced by around 20% due to the inclusion of one LEO into the ground-only solution, while in a solution with four LEOs LEO-specific characteristics are significantly reduced. We compare the derived geocenter coordinates w.r.t. LAGEOS results and external solutions based on GPS and SLR data. We found good agreement in the amplitudes of all components; however, the phases in x- and z-direction do not agree well.

Indoor/Outdoor Seamless Positioning Using Lighting Tags and GPS Cellular Phones for Personal Navigation

NASA Astrophysics Data System (ADS)

Namie, Hiromune; Morishita, Hisashi

The authors focused on the development of an indoor positioning system which is easy to use, portable and available for everyone. This system is capable of providing the correct position anywhere indoors, including onboard ships, and was invented in order to evaluate the availability of GPS indoors. Although the performance of GPS is superior outdoors, there has been considerable research regarding indoor GPS involving sensitive GPS, pseudolites (GPS pseudo satellite), RFID (Radio Frequency IDentification) tags, and wireless LAN .However, the positioning rate and the precision are not high enough for general use, which is the reason why these technologies have not yet spread to personal navigation systems. In this regard, the authors attempted to implement an indoor positioning system using cellular phones with built-in GPS and infrared light data communication functionality, which are widely used in Japan. GPS is becoming increasingly popular, where GPGGS sentences of the NMEA outputted from the GPS receiver provide spatiotemporal information including latitude, longitude, altitude, and time or ECEF xyz coordinates. As GPS applications grow rapidly, spatiotemporal data becomes key to the ubiquitous outdoor and indoor seamless positioning services at least for the entire area of Japan, as well as to becoming familiar with satellite positioning systems (e.g. GPS). Furthermore, the authors are also working on the idea of using PDAs (Personal Digital Assistants), as cellular phones with built-in GPS and PDA functionality are also becoming increasingly popular.

Integrating GPS, GYRO, vehicle speed sensor, and digital map to provide accurate and real-time position in an intelligent navigation system

NASA Astrophysics Data System (ADS)

Li, Qingquan; Fang, Zhixiang; Li, Hanwu; Xiao, Hui

2005-10-01

The global positioning system (GPS) has become the most extensively used positioning and navigation tool in the world. Applications of GPS abound in surveying, mapping, transportation, agriculture, military planning, GIS, and the geosciences. However, the positional and elevation accuracy of any given GPS location is prone to error, due to a number of factors. The applications of Global Positioning System (GPS) positioning is more and more popular, especially the intelligent navigation system which relies on GPS and Dead Reckoning technology is developing quickly for future huge market in China. In this paper a practical combined positioning model of GPS/DR/MM is put forward, which integrates GPS, Gyro, Vehicle Speed Sensor (VSS) and digital navigation maps to provide accurate and real-time position for intelligent navigation system. This model is designed for automotive navigation system making use of Kalman filter to improve position and map matching veracity by means of filtering raw GPS and DR signals, and then map-matching technology is used to provide map coordinates for map displaying. In practical examples, for illustrating the validity of the model, several experiments and their results of integrated GPS/DR positioning in intelligent navigation system will be shown for the conclusion that Kalman Filter based GPS/DR integrating position approach is necessary, feasible and efficient for intelligent navigation application. Certainly, this combined positioning model, similar to other model, can not resolve all situation issues. Finally, some suggestions are given for further improving integrated GPS/DR/MM application.

GPS Auto-Navigation Design for Unmanned Air Vehicles

NASA Technical Reports Server (NTRS)

Nilsson, Caroline C. A.; Heinzen, Stearns N.; Hall, Charles E., Jr.; Chokani, Ndaona

2003-01-01

A GPS auto-navigation system is designed for Unmanned Air Vehicles. The objective is to enable the air vehicle to be used as a test-bed for novel flow control concepts. The navigation system uses pre-programmed GPS waypoints. The actual GPS position, heading, and velocity are collected by the flight computer, a PC104 system running in Real-Time Linux, and compared with the desired waypoint. The navigator then determines the necessity of a heading correction and outputs the correction in the form of a commanded bank angle, for a level coordinated turn, to the controller system. This controller system consists of 5 controller! (pitch rate PID, yaw damper, bank angle PID, velocity hold, and altitude hold) designed for a closed loop non-linear aircraft model with linear aerodynamic coefficients. The ability and accuracy of using GPS data, is validated by a GPS flight. The autopilots are also validated in flight. The autopilot unit flight validations show that the designed autopilots function as designed. The aircraft model, generated on Matlab SIMULINK is also enhanced by the flight data to accurately represent the actual aircraft.

A method for remote sounding of a bottom relief of water objects with using GPS

NASA Astrophysics Data System (ADS)

Mamontova, L. S.

2014-12-01

The no-fly automated system of small rivers' depth's measurement which is based on a combination of a differential method GPS-definition of the pro-measured vessel's coordinates both the method of depth's measurement with sonic depth finder and the method of the vessel's management was examined in this article.On the central station the digital card with a relief for a pro-measured zone of the reservoir is formed and the position of a pro-measured vessel on the tacks is controlled thanks to the coordinates of a pro-measured vessel and depth's measurements with sonic depth finder.The offered system allows to raise the level of depth's pro-measured works.

Evaluation of the Horizontal and Vertical Accuracy of GNSS Survey Observations from a Real-Time Network

NASA Astrophysics Data System (ADS)

Allahyari, M.; Olsen, M. J.; Gillins, D. T.; Dennis, M. L.

2016-12-01

Many current surveying standards in the United States require several long-duration, static Global Navigation Satellite System (GNSS) observations to derive high-accuracy geodetic coordinates. However, over the past decade, many entities have established real-time GNSS networks (RTNs), which could reduce the field time for establishing geodetic control from hours to minutes. To evaluate the accuracy of RTN GNSS observations, data collected from two National Geodetic Survey (NGS) surveys in South Carolina and Oregon were studied. The objectives were to: 1) determine the accuracy of a real-time observation as a function of duration; 2) examine the influence of including GLONASS (Russia's version of GPS); 3) compare results using a single base to the full RTN network solution; and 4) assess the effect of baseline length on accuracy. In South Carolina, 360 observations ranging from 5 to 600 seconds were collected on 20 passive marks using RTN and single-base solutions, both with GPS+GLONASS and GPS-only. In Oregon, 18 passive marks were observed from 5 to 900 seconds using GPS-only with the RTN, and with GPS+GLONASS and GPS-only from a single-base. To develop "truth" coordinates, at least 30 hours of static GPS data were also collected on all marks. Each static survey session was post-processed in OPUS-Projects, and the resulting vectors were used to build survey networks that were least-squares adjusted using the NGS software ADJUST. The resulting coordinates provided the basis for evaluating the accuracy of the real-time observations. Results from this study indicate great potential in the use of RTNs for accurate derivation of geodetic coordinates. Both case studies showed an optimal observation duration of 180 seconds. RTN data tended to be more accurate and consistent than single-base data, and GLONASS slightly improved accuracy. A key benefit of GLONASS was the ability to obtain more fixed solutions at longer baseline lengths than single-base solutions.

A Kalman Filter Implementation for Precision Improvement in Low-Cost GPS Positioning of Tractors

PubMed Central

Gomez-Gil, Jaime; Ruiz-Gonzalez, Ruben; Alonso-Garcia, Sergio; Gomez-Gil, Francisco Javier

2013-01-01

Low-cost GPS receivers provide geodetic positioning information using the NMEA protocol, usually with eight digits for latitude and nine digits for longitude. When these geodetic coordinates are converted into Cartesian coordinates, the positions fit in a quantization grid of some decimeters in size, the dimensions of which vary depending on the point of the terrestrial surface. The aim of this study is to reduce the quantization errors of some low-cost GPS receivers by using a Kalman filter. Kinematic tractor model equations were employed to particularize the filter, which was tuned by applying Monte Carlo techniques to eighteen straight trajectories, to select the covariance matrices that produced the lowest Root Mean Square Error in these trajectories. Filter performance was tested by using straight tractor paths, which were either simulated or real trajectories acquired by a GPS receiver. The results show that the filter can reduce the quantization error in distance by around 43%. Moreover, it reduces the standard deviation of the heading by 75%. Data suggest that the proposed filter can satisfactorily preprocess the low-cost GPS receiver data when used in an assistance guidance GPS system for tractors. It could also be useful to smooth tractor GPS trajectories that are sharpened when the tractor moves over rough terrain. PMID:24217355

GPS Modeling and Analysis. Summary of Research: GPS Satellite Axial Ratio Predictions

NASA Technical Reports Server (NTRS)

Axelrad, Penina; Reeh, Lisa

2002-01-01

This report outlines the algorithms developed at the Colorado Center for Astrodynamics Research to model yaw and predict the axial ratio as measured from a ground station. The algorithms are implemented in a collection of Matlab functions and scripts that read certain user input, such as ground station coordinates, the UTC time, and the desired GPS (Global Positioning System) satellites, and compute the above-mentioned parameters. The position information for the GPS satellites is obtained from Yuma almanac files corresponding to the prescribed date. The results are displayed graphically through time histories and azimuth-elevation plots.

Design of Deformation Monitoring System for Volcano Mitigation

NASA Astrophysics Data System (ADS)

Islamy, M. R. F.; Salam, R. A.; Munir, M. M.; Irsyam, M.; Khairurrijal

2016-08-01

Indonesia has many active volcanoes that are potentially disastrous. It needs good mitigation systems to prevent victims and to reduce casualties from potential disaster caused by volcanoes eruption. Therefore, the system to monitor the deformation of volcano was built. This system employed telemetry with the combination of Radio Frequency (RF) communications of XBEE and General Packet Radio Service (GPRS) communication of SIM900. There are two types of modules in this system, first is the coordinator as a parent and second is the node as a child. Each node was connected to coordinator forming a Wireless Sensor Network (WSN) with a star topology and it has an inclinometer based sensor, a Global Positioning System (GPS), and an XBEE module. The coordinator collects data to each node, one a time, to prevent collision data between nodes, save data to SD Card and transmit data to web server via GPRS. Inclinometer was calibrated with self-built in calibrator and tested in high temperature environment to check the durability. The GPS was tested by displaying its position in web server via Google Map Application Protocol Interface (API v.3). It was shown that the coordinator can receive and transmit data from every node to web server very well and the system works well in a high temperature environment.

The Spring 1985 high precision baseline test of the JPL GPS-based geodetic system

NASA Technical Reports Server (NTRS)

Davidson, John M.; Thornton, Catherine L.; Stephens, Scott A.; Blewitt, Geoffrey; Lichten, Stephen M.; Sovers, Ojars J.; Kroger, Peter M.; Skrumeda, Lisa L.; Border, James S.; Neilan, Ruth E.

1987-01-01

The Spring 1985 High Precision Baseline Test (HPBT) was conducted. The HPBT was designed to meet a number of objectives. Foremost among these was the demonstration of a level of accuracy of 1 to 2:10 to the 7th power, or better, for baselines ranging in length up to several hundred kilometers. These objectives were all met with a high degree of success, with respect to the demonstration of system accuracy in particular. The results from six baselines ranging in length from 70 to 729 km were examined for repeatability and, in the case of three baselines, were compared to results from colocated VLBI systems. Repeatability was found to be 5:10 to the 8th power (RMS) for the north baseline coordinate, independent of baseline length, while for the east coordinate RMS repeatability was found to be larger than this by factors of 2 to 4. The GPS-based results were found to be in agreement with those from colocated VLBI measurements, when corrected for the physical separations of the VLBI and CPG antennas, at the level of 1 to 2:10 to the 7th power in all coordinates, independent of baseline length. The results for baseline repeatability are consistent with the current GPA error budget, but the GPS-VLBI intercomparisons disagree at a somewhat larger level than expected. It is hypothesized that these differences may result from errors in the local survey measurements used to correct for the separations of the GPS and VLBI antenna reference centers.

A design proposal of a certain missile tactical command system based on Beidou satellite communication and GPS positioning techniques

NASA Astrophysics Data System (ADS)

Ma, Jian; Hao, Yongsheng; Miao, Jian; Zhang, Jianmao

2007-11-01

This paper introduced a design proposal of tactical command system that applied to a kind of anti-tank missile carriers. The tactical command system was made up of embedded computer system based on PC104 bus, Linux operating system, digital military map, Beidou satellite communication equipments and GPS positioning equipments. The geographic coordinates was measured by the GPS receiver, the positioning data, commands and information were transmitted real-time between tactical command systems, tactical command systems and command center, by the Beidou satellite communication systems. The Beidou satellite communication equipments and GPS positioning equipments were integrated to an independent module, exchanging data with embedded computer through RS232 serial ports and USB ports. The decision support system software based on information fusion, calculates positioning data, geography information and battle field information synthetically, shows the position of allies and the position of enemy on the military map, and assesses the various threats of different enemy objects, educes a situation assessment and threat assessment.

Recovery of a geocentric reference frame using the present-day GPS system

NASA Technical Reports Server (NTRS)

Malla, Rajendra P.; Wu, Sien-Chong

1990-01-01

A geocentric reference frame adopts the center of mass of the earth as the origin of the coordinate axes. The center of mass of the earth is the natural and unambiguous origin of a geocentric satellite dynamical system. But in practice a kinematically obtained terrestrial reference frame may assume an origin other than the geocenter. The establishment of a geocentric reference frame, to which all relevant observations and results can be referred and in which geodynamic theories or models for the dynamic behavior of earth can be formulated, requires the ability to accurately recover a given coordinate frame origin offset from the geocenter. GPS measurements, because of their abundance and broad distribution, provide a powerful tool to obtain this origin offset in a short period of time. Two effective strategies have been devised. Data from the First Central And South America (Casa Uno) geodynamics experiment has been studied, in order to demonstrate the ability of recovering the geocenter location with present day GPS satellites and receivers.

Arduino based radioactive tracking system

NASA Astrophysics Data System (ADS)

Rahman, Nur Aira Abd; Rashid, Mohd Fazlie Bin Abdul; Rahman, Anwar Bin Abdul; Ramlan, Atikah

2017-01-01

There is a clear need to strengthen security measures to prevent any malevolent use or accidental misuse of radioactive sources. Some of these radioactive sources are regularly transported outside of office or laboratory premises for work and consultation purposes. This paper present the initial development of radioactive source tracking system, which combined Arduino microcontroller, Global Positioning System (GPS) and Global System for Mobile communication (GSM) technologies. The tracking system will help the owner to monitor the movement of the radioactive sources. Currently, the system is capable of tracking the movement of radioactive source through the GPS satellite signals. The GPS co-ordinate could either be transmitted to headquarters at fixed interval via Short Messaging Service (SMS) to enable real time monitoring, or stored in a memory card for offline monitoring and data logging.

Improved treatment of global positioning system force parameters in precise orbit determination applications

NASA Technical Reports Server (NTRS)

Vigue, Y.; Lichten, S. M.; Muellerschoen, R. J.; Blewitt, G.; Heflin, M. B.

1993-01-01

Data collected from a worldwide 1992 experiment were processed at JPL to determine precise orbits for the satellites of the Global Positioning System (GPS). A filtering technique was tested to improve modeling of solar-radiation pressure force parameters for GPS satellites. The new approach improves orbit quality for eclipsing satellites by a factor of two, with typical results in the 25- to 50-cm range. The resultant GPS-based estimates for geocentric coordinates of the tracking sites, which include the three DSN sites, are accurate to 2 to 8 cm, roughly equivalent to 3 to 10 nrad of angular measure.

High precision applications of the global positioning system

NASA Technical Reports Server (NTRS)

Lichten, Stephen M.

1991-01-01

The Global Positioning System (GPS) is a constellation of U.S. defense navigation satellites which can be used for military and civilian positioning applications. A wide variety of GPS scientific applications were identified and precise positioning capabilities with GPS were already demonstrated with data available from the present partial satellite constellation. Expected applications include: measurements of Earth crustal motion, particularly in seismically active regions; measurements of the Earth's rotation rate and pole orientation; high-precision Earth orbiter tracking; surveying; measurements of media propagation delays for calibration of deep space radiometric data in support of NASA planetary missions; determination of precise ground station coordinates; and precise time transfer worldwide.

Positional and Dimensional Accuracy Assessment of Drone Images Geo-referenced with Three Different GPSs

NASA Astrophysics Data System (ADS)

Cao, C.; Lee, X.; Xu, J.

2017-12-01

Unmanned Aerial Vehicles (UAVs) or drones have been widely used in environmental, ecological and engineering applications in recent years. These applications require assessment of positional and dimensional accuracy. In this study, positional accuracy refers to the accuracy of the latitudinal and longitudinal coordinates of locations on the mosaicked image in reference to the coordinates of the same locations measured by a Global Positioning System (GPS) in a ground survey, and dimensional accuracy refers to length and height of a ground target. Here, we investigate the effects of the number of Ground Control Points (GCPs) and the accuracy of the GPS used to measure the GCPs on positional and dimensional accuracy of a drone 3D model. Results show that using on-board GPS and a hand-held GPS produce a positional accuracy on the order of 2-9 meters. In comparison, using a differential GPS with high accuracy (30 cm) improves the positional accuracy of the drone model by about 40 %. Increasing the number of GCPs can compensate for the uncertainty brought by the GPS equipment with low accuracy. In terms of the dimensional accuracy of the drone model, even with the use of a low resolution GPS onboard the vehicle, the mean absolute errors are only 0.04 m for height and 0.10 m for length, which are well suited for some applications in precision agriculture and in land survey studies.

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.

Improved Navigational Technology and Air Traffic Control: A Description of Controller Coordination and Workload

DOT National Transportation Integrated Search

1995-04-01

Improved navigational technology, such as microwave landing systems (MLS) or : global positioning systems (GPS), installed in today's commercial aircraft : enable the air traffic control (ATC) system to better utilize its airspace. : This increased e...

Ideas for Future GPS Timing Improvements

NASA Technical Reports Server (NTRS)

Hutsell, Steven T.

1996-01-01

Having recently met stringent criteria for full operational capability (FOC) certification, the Global Positioning System (GPS) now has higher customer expectations than ever before. In order to maintain customer satisfaction, and the meet the even high customer demands of the future, the GPS Master Control Station (MCS) must play a critical role in the process of carefully refining the performance and integrity of the GPS constellation, particularly in the area of timing. This paper will present an operational perspective on several ideas for improving timing in GPS. These ideas include the desire for improving MCS - US Naval Observatory (USNO) data connectivity, an improved GPS-Coordinated Universal Time (UTC) prediction algorithm, a more robust Kalman Filter, and more features in the GPS reference time algorithm (the GPS composite clock), including frequency step resolution, a more explicit use of the basic time scale equation, and dynamic clock weighting. Current MCS software meets the exceptional challenge of managing an extremely complex constellation of 24 navigation satellites. The GPS community will, however, always seek to improve upon this performance and integrity.

GNSS-derived Geocenter Coordinates Viewed by Perturbation Theory

NASA Astrophysics Data System (ADS)

Meindl, Michael; Beutler, Gerhard; Thaller, Daniela; Dach, Rolf; Jäggi, Adrian; Rothacher, Markus

2013-04-01

Time series of geocenter coordinates were determined with data of the two global navigation satellite systems (GNSS) GPS and GLONASS. The data was recorded in the years 2008-2011 by a global network of 92 combined GPS/GLONASS receivers. Two types of solutions were generated for each system, one including the estimation of geocenter coordinates and one without these parameters. A fair agreement for GPS and GLONASS estimates was found in the x- and y-coordinate series of the geocenter. Artifacts do, however, clearly show up in the z-coordinate. Large periodic variations in the GLONASS geocenter z-coordinates of about 40 cm peak-to-peak are related to the maximum elevation angles of the Sun above/below the orbital planes of the satellite system. A detailed analysis revealed that these artifacts are almost uniquely governed by the differences of the estimates of direct solar radiation pressure (SRP) in the two solution series (with and without geocenter estimation). This effect can be explained by first-order perturbation theory of celestial mechanics. The relation between the geocenter z-coordinate and the corresponding SRP parameters will be presented. Our theory is applicable to all satellite observing techniques. In addition to GNSS, we applied it to satellite laser ranging (SLR) solutions based on LAGEOS observations. The correlation between geocenter and SRP parameters is not a critical issue for SLR, because these parameters do not have to be estimated. This basic difference between SLR and GNSS analyses explains why SLR is an excellent tool to determine geodetic datum parameters like the geocenter coordinates. The correlation between orbit parameters and the z-component of the geocenter is not limited to a particular orbit model, e.g., that of CODE. The issue should be studied for alternative (e.g., box-wing) models: As soon as non-zero mean values (over one revolution) of the out-of-plane force component exist, one has to expect biased geocenter estimates. The insights gained here should be seriously taken into account in the orbit modeling discussion currently taking place within the IGS.

IGS 1996 Analysis Center Workshop

NASA Technical Reports Server (NTRS)

Neilan, R. E. (Editor); VanScoy, P. A. (Editor); Zumberge, J. F. (Editor)

1996-01-01

Components of the IGS[International GPS (Global Positioning System) Service for geodynamics], have operated a GPS tracking system for several years. The network now contains more than 100 stations and has produced a combined GPS ephemeris that has become the standard for geodesists and geophysicists worldwide. IGS data and products are freely available to all thanks to the cooperation and participation of all the IGS members. The IGS has initiated development of several new products, and technical issues permitting greater accuracy of IGS products have been identified. The IGS convened a workshop on March 1996 in Silver Spring, Maryland, USA, to coordinate these developments and to examine technical problems and solutions. The following topics were addressed: orbit/clock combination; Earth orientation; antenna calibration; SINEX and densification of the International Terrestrial Reference Frame (ITRF) using the GPS; receiver standards and performance; and atmospheric topics.

Global Positioning System (GPS) survey of Augustine Volcano, Alaska, August 3-8, 2000: data processing, geodetic coordinates and comparison with prior geodetic surveys

USGS Publications Warehouse

Pauk, Benjamin A.; Power, John A.; Lisowski, Mike; Dzurisin, Daniel; Iwatsubo, Eugene Y.; Melbourne, Tim

2001-01-01

Between August 3 and 8,2000,the Alaska Volcano Observatory completed a Global Positioning System (GPS) survey at Augustine Volcano, Alaska. Augustine is a frequently active calcalkaline volcano located in the lower portion of Cook Inlet (fig. 1), with reported eruptions in 1812, 1882, 1909?, 1935, 1964, 1976, and 1986 (Miller et al., 1998). Geodetic measurements using electronic and optical surveying techniques (EDM and theodolite) were begun at Augustine Volcano in 1986. In 1988 and 1989, an island-wide trilateration network comprising 19 benchmarks was completed and measured in its entirety (Power and Iwatsubo, 1998). Partial GPS surveys of the Augustine Island geodetic network were completed in 1992 and 1995; however, neither of these surveys included all marks on the island.Additional GPS measurements of benchmarks A5 and A15 (fig. 2) were made during the summers of 1992, 1993, 1994, and 1996. The goals of the 2000 GPS survey were to:1) re-measure all existing benchmarks on Augustine Island using a homogeneous set of GPS equipment operated in a consistent manner, 2) add measurements at benchmarks on the western shore of Cook Inlet at distances of 15 to 25 km, 3) add measurements at an existing benchmark (BURR) on Augustine Island that was not previously surveyed, and 4) add additional marks in areas of the island thought to be actively deforming. The entire survey resulted in collection of GPS data at a total of 24 sites (fig. 1 and 2). In this report we describe the methods of GPS data collection and processing used at Augustine during the 2000 survey. We use this data to calculate coordinates and elevations for all 24 sites surveyed. Data from the 2000 survey is then compared toelectronic and optical measurements made in 1988 and 1989. This report also contains a general description of all marks surveyed in 2000 and photographs of all new marks established during the 2000 survey (Appendix A).

Geospatial Technology

ERIC Educational Resources Information Center

Reed, Philip A.; Ritz, John

2004-01-01

Geospatial technology refers to a system that is used to acquire, store, analyze, and output data in two or three dimensions. This data is referenced to the earth by some type of coordinate system, such as a map projection. Geospatial systems include thematic mapping, the Global Positioning System (GPS), remote sensing (RS), telemetry, and…

D Coordinate Transformation Using Artificial Neural Networks

NASA Astrophysics Data System (ADS)

Konakoglu, B.; Cakır, L.; Gökalp, E.

2016-10-01

Two coordinate systems used in Turkey, namely the ED50 (European Datum 1950) and ITRF96 (International Terrestrial Reference Frame 1996) coordinate systems. In most cases, it is necessary to conduct transformation from one coordinate system to another. The artificial neural network (ANN) is a new method for coordinate transformation. One of the biggest advantages of the ANN is that it can determine the relationship between two coordinate systems without a mathematical model. The aim of this study was to investigate the performances of three different ANN models (Feed Forward Back Propagation (FFBP), Cascade Forward Back Propagation (CFBP) and Radial Basis Function Neural Network (RBFNN)) with regard to 2D coordinate transformation. To do this, three data sets were used for the same study area, the city of Trabzon. The coordinates of data sets were measured in the ED50 and ITRF96 coordinate systems by using RTK-GPS technique. Performance of each transformation method was investigated by using the coordinate differences between the known and estimated coordinates. The results showed that the ANN algorithms can be used for 2D coordinate transformation in cases where optimum model parameters are selected.

The first geocenter estimation results using GPS measurements

NASA Technical Reports Server (NTRS)

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

1990-01-01

The center of mass of the Earth is the natural and unambiguous origin of a geocentric satellite dynamical system. A geocentric reference frame assumes that the origin of its coordinate axes is at the geocenter, in which all relevant observations and results can be referred and in which geodynamic theories or models for the dynamic behavior of Earth can be formulated. In practice, however, a kinematically obtained terrestrial reference frame may assume an origin other than the geocenter. A fast and accurate method of determining origin offset from the geocenter is highly desirable. Global Positioning System (GPS) measurements, because of their abundance and broad distribution, provide a powerful tool to obtain this origin offset in a short period of time. Two effective strategies have been devised. Data from the first Central and South America (Casa Uno) global GPS experiment were studied to demonstrate the ability of recovering the geocenter location with present-day GPS satellites and receivers.

GPS-Free Localization Algorithm for Wireless Sensor Networks

PubMed Central

Wang, Lei; Xu, Qingzheng

2010-01-01

Localization is one of the most fundamental problems in wireless sensor networks, since the locations of the sensor nodes are critical to both network operations and most application level tasks. A GPS-free localization scheme for wireless sensor networks is presented in this paper. First, we develop a standardized clustering-based approach for the local coordinate system formation wherein a multiplication factor is introduced to regulate the number of master and slave nodes and the degree of connectivity among master nodes. Second, using homogeneous coordinates, we derive a transformation matrix between two Cartesian coordinate systems to efficiently merge them into a global coordinate system and effectively overcome the flip ambiguity problem. The algorithm operates asynchronously without a centralized controller; and does not require that the location of the sensors be known a priori. A set of parameter-setting guidelines for the proposed algorithm is derived based on a probability model and the energy requirements are also investigated. A simulation analysis on a specific numerical example is conducted to validate the mathematical analytical results. We also compare the performance of the proposed algorithm under a variety multiplication factor, node density and node communication radius scenario. Experiments show that our algorithm outperforms existing mechanisms in terms of accuracy and convergence time. PMID:22219694

Maintenance of Time and Frequency in the DSN Using the Global Positioning System

NASA Technical Reports Server (NTRS)

Clements, P. A.; Kirk, A.; Borutzki, S. E.

1985-01-01

The Deep Space Network must maintain time and frequency within specified limits in order to accurately track the spacecraft engaged in deep space exploration. The DSN has three tracking complexes, located approximately equidistantly around the Earth. Various methods are used to coordinate the clocks among the three complexes. These methods include Loran-C, TV Line 10, very long baseline interferometry (VLBI), and the Global Positioning System (GPS). The GPS is becoming increasingly important because of the accuracy, precision, and rapid availability of the data; GPS receivers have been installed at each of the DSN complexes and are used to obtain daily time offsets between the master clock at each site and UTC(USNO/NBS). Calculations are made to obtain frequency offsets and Allan variances. These data are analyzed and used to monitor the performance of the hydrogen masers that provide the reference frequencies for the DSN frequency and timing system (DFT). A brief history of the GPS timing receivers in the DSN, a description of the data and information flow, data on the performance of the DSN master clocks and GPS measurement system, and a description of hydrogen maser frequency steering using these data are presented.

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.

Improving the Quality of Low-Cost GPS Receiver Data for Monitoring Using Spatial Correlations

NASA Astrophysics Data System (ADS)

Zhang, Li; Schwieger, Volker

2016-06-01

The investigations on low-cost single frequency GPS receivers at the Institute of Engineering Geodesy (IIGS) show that u-blox LEA-6T GPS receivers combined with Trimble Bullet III GPS antennas containing self-constructed L1-optimized choke rings can already obtain an accuracy in the range of millimeters which meets the requirements of geodetic precise monitoring applications (see [27]). However, the quality (accuracy and reliability) of low-cost GPS receiver data, particularly in shadowing environment, should still be improved, since the multipath effects are the major error for the short baselines. For this purpose, several adjoined stations with low-cost GPS receivers and antennas were set up next to the metal wall on the roof of the IIGS building and measured statically for several days. The time series of three-dimensional coordinates of the GPS receivers were analyzed. Spatial correlations between the adjoined stations, possibly caused by multipath effect, will be taken into account. The coordinates of one station can be corrected using the spatial correlations of the adjoined stations, so that the quality of the GPS measurements is improved. The developed algorithms are based on the coordinates and the results will be delivered in near-real-time (in about 30 minutes), so that they are suitable for structural health monitoring applications.

Office of Positioning, Navigation and Timing (PNT) and Spectrum Management Program Overview.

DOT National Transportation Integrated Search

2017-01-01

Civil Global Positioning System (GPS)/PNT Leadership : Coordinate the development of departmental positions on PNT and : spectrum policy and protection from harmful radio frequency : interference and operational degradation of capabilities : ...

Combination of GPS and GLONASS IN PPP algorithms and its effect on site coordinates determination

NASA Astrophysics Data System (ADS)

Hefty, J.; Gerhatova, L.; Burgan, J.

2011-10-01

Precise Point Positioning (PPP) approach using the un-differenced code and phase GPS observations, precise orbits and satellite clocks is an important alternative to the analyses based on double differences. We examine the extension of the PPP method by introducing the GLONASS satellites into the processing algorithms. The procedures are demonstrated on the software package ABSOLUTE developed at the Slovak University of Technology. Partial results, like ambiguities and receiver clocks obtained from separate solutions of the two GNSS are mutually compared. Finally, the coordinate time series from combination of GPS and GLONASS observations are compared with GPS-only solutions.

Analysis of Vlbi, Slr and GPS Site Position Time Series

NASA Astrophysics Data System (ADS)

Angermann, D.; Krügel, M.; Meisel, B.; Müller, H.; Tesmer, V.

Conventionally the IERS terrestrial reference frame (ITRF) is realized by the adoption of a set of epoch coordinates and linear velocities for a set of global tracking stations. Due to the remarkable progress of the space geodetic observation techniques (e.g. VLBI, SLR, GPS) the accuracy and consistency of the ITRF increased continuously. The accuracy achieved today is mainly limited by technique-related systematic errors, which are often poorly characterized or quantified. Therefore it is essential to analyze the individual techniques' solutions with respect to systematic differences, models, parameters, datum definition, etc. Main subject of this presentation is the analysis of GPS, SLR and VLBI time series of site positions. The investigations are based on SLR and VLBI solutions computed at DGFI with the software systems DOGS (SLR) and OCCAM (VLBI). The GPS time series are based on weekly IGS station coordinates solutions. We analyze the time series with respect to the issues mentioned above. In particular we characterize the noise in the time series, identify periodic signals, and investigate non-linear effects that complicate the assignment of linear velocities for global tracking sites. One important aspect is the comparison of results obtained by different techniques at colocation sites.

UTC Dissemination to the Real-Time User: The Role of USNO

NASA Technical Reports Server (NTRS)

Miranian, Mihran

1996-01-01

Coordinated Universal Time (UTC) is available worldwide via the Global Positioning System (GPS). The UTC disseminated by GPS is referenced to the US Naval Observatory Master Clock UTC(USNO) which is regularly steered and maintained as close as possible to UTC Bureau International des Poids et Mesures (BIPM), the international time scale. This paper will describe the role of the USNO in monitoring the time disseminated by the GPS and the steps involved to ensure its accuracy to the user. The paper will also discuss the other sources of UTC(USNO) and the process by which UTC(USNO) is steered to UTC(BIPM).

Absolute GPS Positioning Using Genetic Algorithms

NASA Astrophysics Data System (ADS)

Ramillien, G.

A new inverse approach for restoring the absolute coordinates of a ground -based station from three or four observed GPS pseudo-ranges is proposed. This stochastic method is based on simulations of natural evolution named genetic algorithms (GA). These iterative procedures provide fairly good and robust estimates of the absolute positions in the Earth's geocentric reference system. For comparison/validation, GA results are compared to the ones obtained using the classical linearized least-square scheme for the determination of the XYZ location proposed by Bancroft (1985) which is strongly limited by the number of available observations (i.e. here, the number of input pseudo-ranges must be four). The r.m.s. accuracy of the non -linear cost function reached by this latter method is typically ~10-4 m2 corresponding to ~300-500-m accuracies for each geocentric coordinate. However, GA can provide more acceptable solutions (r.m.s. errors < 10-5 m2), even when only three instantaneous pseudo-ranges are used, such as a lost of lock during a GPS survey. Tuned GA parameters used in different simulations are N=1000 starting individuals, as well as Pc=60-70% and Pm=30-40% for the crossover probability and mutation rate, respectively. Statistical tests on the ability of GA to recover acceptable coordinates in presence of important levels of noise are made simulating nearly 3000 random samples of erroneous pseudo-ranges. Here, two main sources of measurement errors are considered in the inversion: (1) typical satellite-clock errors and/or 300-metre variance atmospheric delays, and (2) Geometrical Dilution of Precision (GDOP) due to the particular GPS satellite configuration at the time of acquisition. Extracting valuable information and even from low-quality starting range observations, GA offer an interesting alternative for high -precision GPS positioning.

Coordinated path-following and direct yaw-moment control of autonomous electric vehicles with sideslip angle estimation

NASA Astrophysics Data System (ADS)

Guo, Jinghua; Luo, Yugong; Li, Keqiang; Dai, Yifan

2018-05-01

This paper presents a novel coordinated path following system (PFS) and direct yaw-moment control (DYC) of autonomous electric vehicles via hierarchical control technique. In the high-level control law design, a new fuzzy factor is introduced based on the magnitude of longitudinal velocity of vehicle, a linear time varying (LTV)-based model predictive controller (MPC) is proposed to acquire the wheel steering angle and external yaw moment. Then, a pseudo inverse (PI) low-level control allocation law is designed to realize the tracking of desired external moment torque and management of the redundant tire actuators. Furthermore, the vehicle sideslip angle is estimated by the data fusion of low-cost GPS and INS, which can be obtained by the integral of modified INS signals with GPS signals as initial value. Finally, the effectiveness of the proposed control system is validated by the simulation and experimental tests.

An integrated GPS-FID system for airborne gas detection of pipeline right-of-ways

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

Gehue, H.L.; Sommer, P.

1996-12-31

Pipeline integrity, safety and environmental concerns are of prime importance in the Canadian natural gas industry. Terramatic Technology Inc. (TTI) has developed an integrated GPS/FID gas detection system known as TTI-AirTrac{trademark} for use in airborne gas detection (AGD) along pipeline right-of-ways. The Flame Ionization Detector (FID), which has traditionally been used to monitor air quality for gas plants and refineries, has been integrated with the Global Positioning System (GPS) via a 486 DX2-50 computer and specialized open architecture data acquisition software. The purpose of this technology marriage is to be able to continuously monitor air quality during airborne pipeline inspection.more » Event tagging from visual surveillance is used to determine an explanation of any delta line deviations (DLD). These deviations are an indication of hydrocarbon gases present in the plume that the aircraft has passed through. The role of the GPS system is to provide mapping information and coordinate data for ground inspections. The ground based inspection using a handheld multi gas detector will confirm whether or not a leak exists.« less

The March 1985 demonstration of the fiducial network concept for GPS geodesy: A preliminary report

NASA Technical Reports Server (NTRS)

Davidson, J. M.; Thornton, C. L.; Dixon, T. H.; Vegos, C. J.; Young, L. E.; Yunck, T. P.

1986-01-01

The first field tests in preparation for the NASA Global Positioning System (GPS) Caribbean Initiative were conducted in late March and Early April of 1985. The GPS receivers were located at the POLARIS Very Long Base Interferometry (VLBI) stations at Westford, Massachusetts; Richmond, Florida; and Ft. Davis, Texas; and at the Mojave, Owens Valley, and Hat Creek VLBI stations in California. Other mobile receivers were placed near Mammoth Lakes, California; Pt. Mugu, California; Austin, Texas; and Dahlgren, Virginia. These sites were equipped with a combination of GPS receiver types, including SERIES-X, TI-4100 and AFGL dual frequency receivers. The principal objectives of these tests were the demonstration of the fiducial network concept for precise GPS geodesy, the performance assessment of the participating GPS receiver types, and to conduct the first in a series of experiments to monitor ground deformation in the Mammoth Lakes-Long Valley caldera region in California. Other objectives included the testing of the water vapor radiometers for the calibration of GPS data, the development of efficient procedures for planning and coordinating GPS field exercise, the establishment of institutional interfaces for future cooperating ventures, the testing of the GPS Data Analysis Software (GIPSY, for GPS Inferred Positioning SYstem), and the establishment of a set of calibration baselines in California. Preliminary reports of the success of the field tests, including receiver performance and data quality, and on the status of the data analysis software are given.

Geographical Information Systems (GIS) Mapping of Environmental Samples across College Campuses

ERIC Educational Resources Information Center

Purvis-Roberts, Kathleen L.; Moeur, Harriet P.; Zanella, Andrew

2007-01-01

In this laboratory experiment, students take environmental samples at various locations around the college campuses, take geospatial coordinates with a global position systems (GPS) unit, and map their results on a geo-referenced campus map with geographical information systems (GIS) software. Nitrogen dioxide air pollution sampling is used as an…

Determination of Exterior Orientation Parameters Through Direct Geo-Referencing in a Real-Time Aerial Monitoring System

NASA Astrophysics Data System (ADS)

Kim, H.; Lee, J.; Choi, K.; Lee, I.

2012-07-01

Rapid responses for emergency situations such as natural disasters or accidents often require geo-spatial information describing the on-going status of the affected area. Such geo-spatial information can be promptly acquired by a manned or unmanned aerial vehicle based multi-sensor system that can monitor the emergent situations in near real-time from the air using several kinds of sensors. Thus, we are in progress of developing such a real-time aerial monitoring system (RAMS) consisting of both aerial and ground segments. The aerial segment acquires the sensory data about the target areas by a low-altitude helicopter system equipped with sensors such as a digital camera and a GPS/IMU system and transmits them to the ground segment through a RF link in real-time. The ground segment, which is a deployable ground station installed on a truck, receives the sensory data and rapidly processes them to generate ortho-images, DEMs, etc. In order to generate geo-spatial information, in this system, exterior orientation parameters (EOP) of the acquired images are obtained through direct geo-referencing because it is difficult to acquire coordinates of ground points in disaster area. The main process, since the data acquisition stage until the measurement of EOP, is discussed as follows. First, at the time of data acquisition, image acquisition time synchronized by GPS time is recorded as part of image file name. Second, the acquired data are then transmitted to the ground segment in real-time. Third, by processing software for ground segment, positions/attitudes of acquired images are calculated through a linear interpolation using the GPS time of the received position/attitude data and images. Finally, the EOPs of images are obtained from position/attitude data by deriving the relationships between a camera coordinate system and a GPS/IMU coordinate system. In this study, we evaluated the accuracy of the EOP decided by direct geo-referencing in our system. To perform this, we used the precisely calculated EOP through the digital photogrammetry workstation (DPW) as reference data. The results of the evaluation indicate that the accuracy of the EOP acquired by our system is reasonable in comparison with the performance of GPS/IMU system. Also our system can acquire precise multi-sensory data to generate the geo-spatial information in emergency situations. In the near future, we plan to complete the development of the rapid generation system of the ground segment. Our system is expected to be able to acquire the ortho-image and DEM on the damaged area in near real-time. Its performance along with the accuracy of the generated geo-spatial information will also be evaluated and reported in the future work.

Geocenter coordinates estimated from GNSS data as viewed by perturbation theory

NASA Astrophysics Data System (ADS)

Meindl, Michael; Beutler, Gerhard; Thaller, Daniela; Dach, Rolf; Jäggi, Adrian

2013-04-01

Time series of geocenter coordinates were determined with data of two global navigation satellite systems (GNSSs), namely the U.S. GPS (Global Positioning System) and the Russian GLONASS (Global'naya Nawigatsionnaya Sputnikowaya Sistema). The data was recorded in the years 2008-2011 by a global network of 92 permanently observing GPS/GLONASS receivers. Two types of daily solutions were generated independently for each GNSS, one including the estimation of geocenter coordinates and one without these parameters.A fair agreement for GPS and GLONASS was found in the geocenter x- and y-coordinate series. Our tests, however, clearly reveal artifacts in the z-component determined with the GLONASS data. Large periodic excursions in the GLONASS geocenter z-coordinates of about 40 cm peak-to-peak are related to the maximum elevation angles of the Sun above/below the orbital planes of the satellite system and thus have a period of about 4 months (third of a year). A detailed analysis revealed that the artifacts are almost uniquely governed by the differences of the estimates of direct solar radiation pressure (SRP) in the two solution series (with and without geocenter estimation). A simple formula is derived, describing the relation between the geocenter z-coordinate and the corresponding parameter of the SRP. The effect can be explained by first-order perturbation theory of celestial mechanics. The theory also predicts a heavy impact on the GNSS-derived geocenter if once-per-revolution SRP parameters are estimated in the direction of the satellite's solar panel axis. Specific experiments using GPS observations revealed that this is indeed the case.Although the main focus of this article is on GNSS, the theory developed is applicable to all satellite observing techniques. We applied the theory to satellite laser ranging (SLR) solutions using LAGEOS. It turns out that the correlation between geocenter and SRP parameters is not a critical issue for the SLR solutions. The reasons are threefold: The direct SRP is about a factor of 30-40 smaller for typical geodetic SLR satellites than for GNSS satellites, allowing it in most cases to not solve for SRP parameters (ruling out the correlation between these parameters and the geocenter coordinates); the orbital arc length of 7 days (which is typically used in SLR analysis) contains more than 50 revolutions of the LAGEOS satellites as compared to about two revolutions of GNSS satellites for the daily arcs used in GNSS analysis; the orbit geometry is not as critical for LAGEOS as for GNSS satellites, because the elevation angle of the Sun w.r.t. the orbital plane is usually significantly changing over 7 days.

Comparison of GPS-TEC variation during quiet and disturbed period using the Holt-Winter method and IRI-2012 model over Malaysia

NASA Astrophysics Data System (ADS)

Ahmed Ismail, Nouf Abd Emunim; Abdullah, Mardina; Hasbi, Alina Marie

2016-07-01

Total Electron Content (TEC) is the main parameter in the ionosphere that has significant effects on radio wave; it changes the speed and direction of the signal propagation, causing the delay of the Global Positioning System (GPS) signals. Therefore, it is crucial to validate the performance of the ionospheric model to reveal the variety of ionospheric behaviour during quiet and disturbed period. This research presents the performance evaluation of the statistical Holt-Winter method and IRI-2012 model using three topside electron density options: IRI-2001, IRI01-corr and NeQuick with the observed GPS-TEC during quiet and disturbed period. The GPS-TEC data were derived from the dual frequency GPS receiver at JUPEM (Department of Survey and Mapping Malaysia), from the UUMK station (north Peninsular Malaysia) at geographic coordinates of 6.46°N-100.50°E and geomagnetic coordinates of 3.32°S-172.99°E and TGPG station (south Peninsular Malaysia) at geographic coordinates of 1.36°N-104.10°E and geomagnetic coordinates of 8.43°S -176.53°E, during March of 2013. The maximum value of the GPS-TEC was at the post noon time at 17:00 LT and the minimum was in the early morning from 6:00-7:00 LT. During the quiet period, the maximum GPS-TEC at the UUMK station was 52 TECU while at the TGPG station, it was 60 TECU. During the disturbed period, when intense geomagnetic storm occurred on 17 March 2013, the maximum GPS-TEC recorded was 58 TECU and 65 TECU in UUMK and TGPG station, respectively. The diurnal hourly variation during the quiet period indicated that IRI-2001, IRI01-corr, and NeQuick had overestimation agreement during the day hours except for the time between 11:00-19:00 LT when IRI01-corr and NeQuick showed underestimation, while during 13:00-20:00 LT, IRI-2001 showed slight underestimation whereas the Holt-Winter method showed good agreement with GPS-TEC. During the disturbed period, IRI-2001 showed overestimation agreement for all hours, while the IRI01-corr and NeQuick model did not show any changes during the geomagnetic storm event. The Holt-Winter method showed better agreement with the GPS-TEC for both the UUMK and TGPG stations. The correlation between the observed and modeled GPS-TEC during the quiet and disturbed period for the UUMK station showed a slightly better correlation compared to the TGPG station. The Holt-Winter method showed good correlation of around 0.98 during the quiet period and 0.95 during the disturbed period, while IRI-2001, IRI01-corr, and NeQuick had comparatively lower correlation of around ≈ 0.8 during the quiet period and ≈ 0.7 during the disturbed period. Overall, this research concludes that the Holt-Winter method effectively the GPS-TEC with good correlation during the quiet and disturbed period in the equatorial region over Malaysia.

75 FR 59934 - Amendment to Class E Airspace; Smithfield, NC

Federal Register 2010, 2011, 2012, 2013, 2014

2010-09-29

... Class E airspace at Johnston County Airport, Smithfield, NC, by correcting an omission of the geographic coordinates of the Area Navigation (RNAV) Global Positioning System (GPS) Special Standard Instrument Approach... System. DATES: Effective 0901 UTC, January 13, 2011. The Director of the Federal Register approves this...

Milestones Since Last Workshop [Global Positioning System Adjacent Band Compatibility Assessment Workshop V, 10/14/2016

DOT National Transportation Integrated Search

2016-10-14

Milestones Since Last Workshop - Finalized GPS/GNSS receiver test plan and test procedures - Coordinated government and manufacturer participation and executed Non-Disclosure Agreements (NDAs) - Developed/validated radiated RF test environment - Carr...

GPS common-view time transfer

NASA Technical Reports Server (NTRS)

Lewandowski, W.

1994-01-01

The introduction of the GPS common-view method at the beginning of the 1980's led to an immediate and dramatic improvement of international time comparisons. Since then, further progress brought the precision and accuracy of GPS common-view intercontinental time transfer from tens of nanoseconds to a few nanoseconds, even with SA activated. This achievement was made possible by the use of the following: ultra-precise ground antenna coordinates, post-processed precise ephemerides, double-frequency measurements of ionosphere, and appropriate international coordination and standardization. This paper reviews developments and applications of the GPS common-view method during the last decade and comments on possible future improvements whose objective is to attain sub-nanosecond uncertainty.

An Investigation on the Contribution of GLONASS to the Precise Point Positioning for Short Time Observations

NASA Astrophysics Data System (ADS)

Ulug, R.; Ozludemir, M. T.

2016-12-01

After 2011, through the modernization process of GLONASS, the number of satellites increased rapidly. This progress has made the GLONASS the only fully operational system alternative to GPS in point positioning. So far, many researches have been conducted to investigate the contribution of GLONASS to point positioning considering different methods such as Real Time Kinematic (RTK) and Precise Point Positioning (PPP). The latter one, PPP, is a method that performs precise position determination using a single GNSS receiver. PPP method has become very attractive since the early 2000s and it provided great advantages for engineering and scientific applications. However, PPP method needs at least 2 hours observation time and the required observation length may be longer depending on several factors, such as the number of satellites, satellite configuration etc. The more satellites, the less observation time. Nevertheless the impact of the number of satellites included must be known very well. In this study, to determine the contribution of GLONASS on PPP, GLONASS satellite observations were added one by one from 1 to 5 satellite in 2, 4 and 6 hours of observations. For this purpose, the data collected at the IGS site ISTA was used. Data processing has been done for Day of Year (DOY) 197 in 2016. 24 hours GPS observations have been processed by Bernese 5.2 PPP module and the output was selected as the reference while 2, 4 and 6 hours GPS and GPS/GLONASS observations have been processed by magic GNSS PPP module. The results clearly showed that GPS/GLONASS observations improved positional accuracy, precision, dilution of precision and convergence to the reference coordinates. In this context, coordinate differences between 24 hours GPS observations and 6 hours GPS/GLONASS observations have been obtained as less than 2 cm.

Assessment of Hybrid Coordinate Model Velocity Fields During Agulhas Return Current 2012 Cruise

DTIC Science & Technology

2013-06-01

Forecasts GDEM Generalized Digital Environmental Model GPS Global Positioning System HYCOM HYbrid Coordinate Ocean Model MICOM Miami Isopycnal...speed profiles was climatology from the Generalized Digital Environmental Model ( GDEM ; Teague et al. 1990). Made operational in 1999, the Modular... GDEM was the only tool a naval oceanographer had at his or her disposal to characterize ocean conditions where in-situ observations could not be

International GPS Service for Geodynamics

NASA Technical Reports Server (NTRS)

Zumberge, J. F. (Editor); Urban, M. P. (Editor); Liu, R. (Editor); Neilan, R. E. (Editor)

1996-01-01

This 1995 annual report of the IGS International GPS (Global Positioning System) Service for Geodynamics - describes the second operational year of the service. It provides the many IGS contributing agencies and the rapidly growing user community with essential information on current organizational and technical matters promoting the IGS standards and products (including organizational framework, data processing strategies, and statistics showing the remarkable expansion of the GPS monitoring network, the improvement of IGS performance, and product quality). It also introduces important practical concepts for network densification by integration of regional stations and the combination of station coordinate solutions. There are groups of articles describing general aspects of the IGS, the Associate Analysis Centers (AACs), Data Centers, and IGS stations.

Collaboration between general practitioners and mental health care professionals: a qualitative study.

PubMed

Fredheim, Terje; Danbolt, Lars J; Haavet, Ole R; Kjønsberg, Kari; Lien, Lars

2011-05-23

Collaboration between general practice and mental health care has been recognised as necessary to provide good quality healthcare services to people with mental health problems. Several studies indicate that collaboration often is poor, with the result that patient' needs for coordinated services are not sufficiently met, and that resources are inefficiently used. An increasing number of mental health care workers should improve mental health services, but may complicate collaboration and coordination between mental health workers and other professionals in the treatment chain. The aim of this qualitative study is to investigate strengths and weaknesses in today's collaboration, and to suggest improvements in the interaction between General Practitioners (GPs) and specialised mental health service. This paper presents a qualitative focus group study with data drawn from six groups and eight group sessions with 28 health professionals (10 GPs, 12 nurses, and 6 physicians doing post-doctoral training in psychiatry), all working in the same region and assumed to make professional contact with each other. GPs and mental health professionals shared each others expressions of strengths, weaknesses and suggestions for improvement in today's collaboration. Strengths in today's collaboration were related to common consultations between GPs and mental health professionals, and when GPs were able to receive advice about diagnostic treatment dilemmas. Weaknesses were related to the GPs' possibility to meet mental health professionals, and lack of mutual knowledge in mental health services. The results describe experiences and importance of interpersonal knowledge, mutual accessibility and familiarity with existing systems and resources. There is an agreement between GPs and mental health professionals that services will improve with shared knowledge about patients through systematic collaborative services, direct cell-phone lines to mental health professionals and allocated times for telephone consultation. GPs and mental health professionals experience collaboration as important. GPs are the gate-keepers to specialised health care, and lack of collaboration seems to create problems for GPs, mental health professionals, and for the patients. Suggestions for improvement included identification of situations that could increase mutual knowledge, and make it easier for GPs to reach the right mental health care professional when needed.

Automating the process for locating no-passing zones using georeferencing data.

DOT National Transportation Integrated Search

2012-08-01

This research created a method of using global positioning system (GPS) coordinates to identify the location of no-passing zones in two-lane highways. Analytical algorithms were developed for analyzing the availability of sight distance along the ali...

Measuring levee elevation heights in North Louisiana.

DOT National Transportation Integrated Search

2010-01-01

The primary goals of this research are to measure the elevation and centerline coordinates of the top of federal and local levees and also to ensure that the resulting global positioning system (GPS) measurement data is within a precision interval of...

Management of behavioural change in patients presenting with a diagnosis of dementia: a video vignette study with Australian general practitioners.

PubMed

Jiwa, Moyez; Nichols, Pam; Magin, Parker; Pagey, Georgina; Meng, Xingqiong; Parsons, Richard; Pillai, Vinita

2014-09-25

To test the impact of feedback on the proposed management of standardised patients presenting with behavioural change with a diagnosis of dementia in Australian primary care. A video vignette study was performed with Australian general practitioners (GPs) in 2013. Participants viewed six pairs of matched videos depicting people presenting changed behaviour in the context of a dementia diagnosis in two phases. In both phases GPs indicated their diagnosis and management. After phase 1, GPs were offered feedback on management strategies for the patients depicted. Analyses focused on identification of change in management between the two phases of the study. Factors impacting on the intention to coordinate care for such patients were tested in a questionnaire based on the Theory of Planned Behaviour. Forty-five GPs completed the study. There was significant improvement in the proposed management of three of the six scenarios after the intervention. Older GPs were more likely to refer appropriately (OR=1.11 (1.01 to 1.23), p=0.04.). Overall referral to support agencies was more likely after the intervention (OR=2.52 (1.53 to 4.14), p<0.001). Older GPs were less likely to intend to coordinate care for such patients (OR=0.89 (0.81 to 0.98) p=0.02). Participants who felt confident about their ability to coordinate care were more likely to do so (OR=3.79 (1.08 to 13.32) p=0.04). The intervention described in this study promoted multidisciplinary management of patients with behavioural problems with a diagnosis of dementia. Increasing practitioner confidence in their ability to coordinate care may increase the proportion of GPs who will respond to patients and carers in this context. Older GPs may benefit in particular. Published by the BMJ Publishing Group Limited. For permission to use (where not already granted under a licence) please go to http://group.bmj.com/group/rights-licensing/permissions.

Management of behavioural change in patients presenting with a diagnosis of dementia: a video vignette study with Australian general practitioners

PubMed Central

Jiwa, Moyez; Nichols, Pam; Magin, Parker; Pagey, Georgina; Meng, Xingqiong; Parsons, Richard; Pillai, Vinita

2014-01-01

Objective To test the impact of feedback on the proposed management of standardised patients presenting with behavioural change with a diagnosis of dementia in Australian primary care. Materials and methods A video vignette study was performed with Australian general practitioners (GPs) in 2013. Participants viewed six pairs of matched videos depicting people presenting changed behaviour in the context of a dementia diagnosis in two phases. In both phases GPs indicated their diagnosis and management. After phase 1, GPs were offered feedback on management strategies for the patients depicted. Analyses focused on identification of change in management between the two phases of the study. Factors impacting on the intention to coordinate care for such patients were tested in a questionnaire based on the Theory of Planned Behaviour. Results Forty-five GPs completed the study. There was significant improvement in the proposed management of three of the six scenarios after the intervention. Older GPs were more likely to refer appropriately (OR=1.11 (1.01 to 1.23), p=0.04.). Overall referral to support agencies was more likely after the intervention (OR=2.52 (1.53 to 4.14), p<0.001). Older GPs were less likely to intend to coordinate care for such patients (OR=0.89 (0.81 to 0.98) p=0.02). Participants who felt confident about their ability to coordinate care were more likely to do so (OR=3.79 (1.08 to 13.32) p=0.04). Conclusions The intervention described in this study promoted multidisciplinary management of patients with behavioural problems with a diagnosis of dementia. Increasing practitioner confidence in their ability to coordinate care may increase the proportion of GPs who will respond to patients and carers in this context. Older GPs may benefit in particular. PMID:25256189

Accuracy of Single Frequency GPS Observations Processing In Near Real-time With Use of Code Predicted Products

NASA Astrophysics Data System (ADS)

Wielgosz, P. A.

In this year, the system of active geodetic GPS permanent stations is going to be estab- lished in Poland. This system should provide GPS observations for a wide spectrum of users, especially it will be a great opportunity for surveyors. Many of surveyors still use cheaper, single frequency receivers. This paper focuses on processing of single frequency GPS observations only. During processing of such observations the iono- sphere plays an important role, so we concentrated on the influence of the ionosphere on the positional coordinates. Twenty consecutive days of GPS data from 2001 year were processed to analyze the accuracy of a derived three-dimensional relative vec- tor position between GPS stations. Observations from two Polish EPN/IGS stations: BOGO and JOZE were used. In addition to, a new test station - IGIK was created. In this paper, the results of single frequency GPS observations processing in near real- time are presented. Baselines of 15, 27 and 42 kilometers and sessions of 1, 2, 3, 4, and 6 hours long were processed. While processing we used CODE (Centre for Orbit De- termination in Europe, Bern, Switzerland) predicted products: orbits and ionosphere info. These products are available in real-time and enable near real-time processing. Software Bernese v. 4.2 for Linux and BPE (Bernese Processing Engine) mode were used. These results are shown with a reference to dual frequency weekly solution (the best solution). Obtained GPS positional time and GPS baseline length dependency accuracy is presented for single frequency GPS observations.

Measuring Magnetic Declination With Compass, GPS and Virtual Globes

NASA Astrophysics Data System (ADS)

O'Brien, W. P.

2006-12-01

Using virtual globe (VG) imagery to determine geographic bearing and a compass to determine magnetic bearing yielded acceptable experimental magnetic declination values for large linear physical features at 13 sites in the western continental United States. The geographic bearing of each feature was determined from measurements involving the latitude/longitude coordinate system associated with the VG image (from World Wind or Google Earth). The corresponding magnetic bearing was measured on the ground at the feature with a hand-bearing compass calibrated in 1-degree subdivisions. A sequence of GPS trackpoints, recorded while traveling along the feature either in an automobile or on foot, unambiguously identified the pertinent portion of the feature (a straight segment of a road, for example) when plotted on the VG image. For each physical feature located on a VG image, its geographic bearing was determined directly using on-screen measurement tools available with the VG program or by hand using ruler/protractor methods with printed copies of the VG image. An independent (no use of VG) geographic bearing was also extracted from the slope of a straight-line fit to a latitude/longitude plot of each feature's GPS coordinates, a value that was the same (to within the inherent uncertainty of the data) as the VG-determined bearing, thus validating this procedure for finding geographic bearings. Differences between the VG bearings and the magnetic bearings yielded experimental magnetic declination values within one degree (8 within 0.5 degree) of expected values. From the point of view of physics and geophysics pedagogy, this project affords students a simple magnetism/geodesy field experiment requiring only a good compass and a GPS receiver with memory and a data port. The novel and straightforward data analysis with VG software yields reliable experimental values for an important abstract geophysical quantity, magnetic declination. Just as the compass has long provided easy access to Magnetic North, the coordinate systems inherent in recently-developed VG and GPS satellite technologies now provide easy access (i.e., no astronomical measurements involving Polaris or the Sun) to Geographic North for this and future applications.

Assessment of second- and third-order ionospheric effects on regional networks: case study in China with longer CMONOC GPS coordinate time series

NASA Astrophysics Data System (ADS)

Deng, Liansheng; Jiang, Weiping; Li, Zhao; Chen, Hua; Wang, Kaihua; Ma, Yifang

2017-02-01

Higher-order ionospheric (HOI) delays are one of the principal technique-specific error sources in precise global positioning system analysis and have been proposed to become a standard part of precise GPS data processing. In this research, we apply HOI delay corrections to the Crustal Movement Observation Network of China's (CMONOC) data processing (from January 2000 to December 2013) and furnish quantitative results for the effects of HOI on CMONOC coordinate time series. The results for both a regional reference frame and global reference frame are analyzed and compared to clarify the HOI effects on the CMONOC network. We find that HOI corrections can effectively reduce the semi-annual signals in the northern and vertical components. For sites with lower semi-annual amplitudes, the average decrease in magnitude can reach 30 and 10 % for the northern and vertical components, respectively. The noise amplitudes with HOI corrections and those without HOI corrections are not significantly different. Generally, the HOI effects on CMONOC networks in a global reference frame are less obvious than the results in the regional reference frame, probably because the HOI-induced errors are smaller in comparison to the higher noise levels seen when using a global reference frame. Furthermore, we investigate the combined contributions of environmental loading and HOI effects on the CMONOC stations. The largest loading effects on the vertical displacement are found in the mid- to high-latitude areas. The weighted root mean square differences between the corrected and original weekly GPS height time series of the loading model indicate that the mass loading adequately reduced the scatter on the CMONOC height time series, whereas the results in the global reference frame showed better agreements between the GPS coordinate time series and the environmental loading. When combining the effects of environmental loading and HOI corrections, the results with the HOI corrections reduced the scatter on the observed GPS height coordinates better than the height when estimated without HOI corrections, and the combined solutions in the regional reference frame indicate more preferred improvements. Therefore, regional reference frames are recommended to investigate the HOI effects on regional networks.

GPS Software Packages Deliver Positioning Solutions

NASA Technical Reports Server (NTRS)

2010-01-01

"To determine a spacecraft s position, the Jet Propulsion Laboratory (JPL) developed an innovative software program called the GPS (global positioning system)-Inferred Positioning System and Orbit Analysis Simulation Software, abbreviated as GIPSY-OASIS, and also developed Real-Time GIPSY (RTG) for certain time-critical applications. First featured in Spinoff 1999, JPL has released hundreds of licenses for GIPSY and RTG, including to Longmont, Colorado-based DigitalGlobe. Using the technology, DigitalGlobe produces satellite imagery with highly precise latitude and longitude coordinates and then supplies it for uses within defense and intelligence, civil agencies, mapping and analysis, environmental monitoring, oil and gas exploration, infrastructure management, Internet portals, and navigation technology."

Maintenance of time and frequency in the Jet Propulsion Laboratory's Deep Space Network using the Global Positioning System

NASA Technical Reports Server (NTRS)

Clements, P. A.; Borutzki, S. E.; Kirk, A.

1984-01-01

The Deep Space Network (DSN), managed by the Jet Propulsion Laboratory for NASA, must maintain time and frequency within specified limits in order to accurately track the spacecraft engaged in deep space exploration. Various methods are used to coordinate the clocks among the three tracking complexes. These methods include Loran-C, TV Line 10, Very Long Baseline Interferometry (VLBI), and the Global Positioning System (GPS). Calculations are made to obtain frequency offsets and Allan variances. These data are analyzed and used to monitor the performance of the hydrogen masers that provide the reference frequencies for the DSN Frequency and Timing System (DFT). Areas of discussion are: (1) a brief history of the GPS timing receivers in the DSN, (2) a description of the data and information flow, (3) data on the performance of the DSN master clocks and GPS measurement system, and (4) a description of hydrogen maser frequency steering using these data.

Patient-centeredness to anticipate and organize an end-of-life project for patients receiving at-home palliative care: a phenomenological study.

PubMed

Oude Engberink, Agnès; Badin, Mélanie; Serayet, Philippe; Pavageau, Sylvain; Lucas, François; Bourrel, Gérard; Norton, Joanna; Ninot, Grégory; Senesse, Pierre

2017-02-23

The development of end-of-life primary care is a socio-medical and ethical challenge. However, general practitioners (GPs) face many difficulties when initiating appropriate discussion on proactive shared palliative care. Anticipating palliative care is increasingly important given the ageing population and is an aim shared by many countries. We aimed to examine how French GPs approached and provided at-home palliative care. We inquired about their strategy for delivering care, and the skills and resources they used to devise new care strategies. Twenty-one GPs from the South of France recruited by phone according to their various experiences of palliative care agreed to participate. Semi-structured interview transcripts were examined using a phenomenological approach inspired by Grounded theory, and further studied with semiopragmatic analysis. Offering palliative care was perceived by GPs as a moral obligation. They felt vindicated in a process rooted in the paradigm values of their profession. This study results in two key findings: firstly, their patient-centred approach facilitated the anticipatory discussions of any potential event or intervention, which the GPs openly discussed with patients and their relatives; secondly, this approach contributed to build an "end-of-life project" meeting patients' wishes and needs. The GPs all shared the idea that the end-of-life process required human presence and recommended that at-home care be coordinated and shared by multi-professional referring teams. The main tenets of palliative care as provided by GPs are a patient-centred approach in the anticipatory discussion of potential events, personalized follow-up with referring multi-professional teams, and the collaborative design of an end-of-life project meeting the aspirations of the patient and his or her family. Consequently, coordination strategies involving specialized teams, GPs and families should be modelled according to the specificities of each care system.

Centroid-moment tensor inversions using high-rate GPS waveforms

NASA Astrophysics Data System (ADS)

O'Toole, Thomas B.; Valentine, Andrew P.; Woodhouse, John H.

2012-10-01

Displacement time-series recorded by Global Positioning System (GPS) receivers are a new type of near-field waveform observation of the seismic source. We have developed an inversion method which enables the recovery of an earthquake's mechanism and centroid coordinates from such data. Our approach is identical to that of the 'classical' Centroid-Moment Tensor (CMT) algorithm, except that we forward model the seismic wavefield using a method that is amenable to the efficient computation of synthetic GPS seismograms and their partial derivatives. We demonstrate the validity of our approach by calculating CMT solutions using 1 Hz GPS data for two recent earthquakes in Japan. These results are in good agreement with independently determined source models of these events. With wider availability of data, we envisage the CMT algorithm providing a tool for the systematic inversion of GPS waveforms, as is already the case for teleseismic data. Furthermore, this general inversion method could equally be applied to other near-field earthquake observations such as those made using accelerometers.

Continuous monitoring of surface deformation at Long Valley Caldera, California, with GPS

USGS Publications Warehouse

Dixon, T.H.; Mao, A.; Bursik, M.; Heflin, M.; Langbein, J.; Stein, R.; Webb, F.

1997-01-01

Continuous Global Positioning System (GPS) measurements at Long Valley Caldera, an active volcanic region in east central California, have been made on the south side of the resurgent dome since early 1993. A site on the north side of the dome was added in late 1994. Special adaptations for autonomous operation in remote regions and enhanced vertical precision were made. The data record ongoing volcanic deformation consistent with uplift and expansion of the surface above a shallow magma chamber. Measurement precisions (1 standard error) for "absolute" position coordinates, i.e., relative to a global reference frame, are 3-4 mm (north), 5-6 mm (east), and 10-12 mm (vertical) using 24 hour solutions. Corresponding velocity uncertainties for a 12 month period are about 2 mm/yr in the horizontal components and 3-4 mm/yr in the vertical component. High precision can also be achieved for relative position coordinates on short (<10 km) baselines using broadcast ephemerides and observing times as short as 3 hours, even when data are processed rapidly on site. Comparison of baseline length changes across the resurgent dome between the two GPS sites and corresponding two-color electronic distance measurements indicates similar extension rates within error (???2 mm/yr) once we account for a random walk noise component in both systems that may reflect spurious monument motion. Both data sets suggest a pause in deformation for a 3.5 month period in mid-1995, when the extension rate across the dome decreased essentially to zero. Three dimensional positioning data from the two GPS stations suggest a depth (5.8??1.6 km) and location (west side of the resurgent dome) of a major inflation center, in agreement with other geodetic techniques, near the top of a magma chamber inferred from seismic data. GPS systems similar to those installed at Long Valley can provide a practical method for near real-time monitoring and hazard assessment on many active volcanoes.

The status of accurately locating forest inventory and analysis plots using the Global Positioning System

Treesearch

Michael Hoppus; Andrew Lister

2007-01-01

Historically, field crews used Global Positioning System (GPS) coordinates to establish and relocate plots, as well as document their general location. During the past 5 years, the increase in Geographic Information System (GIS) capabilities and in customer requests to use the spatial relationships between Forest Inventory and Analysis (FIA) plot data and other GIS...

78 FR 67024 - Modification of Class E Airspace; Prineville, OR

Federal Register 2010, 2011, 2012, 2013, 2014

2013-11-08

... Prineville, OR, to accommodate Area Navigation (RNAV) Global Positioning System (GPS) standard instrument approach procedures at Prineville Airport. This improves the safety and management of Instrument Flight Rules (IFR) operations at the airport. This action also adjusts the geographic coordinates of the...

A Report on GPS and Galileo Time Offset Coordination Efforts

DTIC Science & Technology

2007-01-01

broadcast as part of the GPS and Galileo navigation message and determined by: Two-way Satellite Time and Frequency Transfer ( TWSTFT ); Common...navigation message • use of TWSTFT and GPS Common View The overall goal is to verify the GGTO performance budget for the IOV Phase (detailed budget

Global point signature for shape analysis of carpal bones

NASA Astrophysics Data System (ADS)

Chaudhari, Abhijit J.; Leahy, Richard M.; Wise, Barton L.; Lane, Nancy E.; Badawi, Ramsey D.; Joshi, Anand A.

2014-02-01

We present a method based on spectral theory for the shape analysis of carpal bones of the human wrist. We represent the cortical surface of the carpal bone in a coordinate system based on the eigensystem of the two-dimensional Helmholtz equation. We employ a metric—global point signature (GPS)—that exploits the scale and isometric invariance of eigenfunctions to quantify overall bone shape. We use a fast finite-element-method to compute the GPS metric. We capitalize upon the properties of GPS representation—such as stability, a standard Euclidean (ℓ2) metric definition, and invariance to scaling, translation and rotation—to perform shape analysis of the carpal bones of ten women and ten men from a publicly-available database. We demonstrate the utility of the proposed GPS representation to provide a means for comparing shapes of the carpal bones across populations.

Horizontal Displacement Vector Analysis in Ujong Muloh GPS Station (UMLH) Sumatra Island on March 27 – April 25, 2012

NASA Astrophysics Data System (ADS)

Pamungkas, S. S.; Koesuma, S.; Legowo, Budi

2018-03-01

Sumatra Island is an area that has high tectonic activities. This is because the island of Sumatra is located in two major plates of the world, the Indo-Australian plate and the Eurasia plate. The subduction zone causes Sumatra to deform from time to time. The deformation of Sumatra Island can be observed by continuous recording coordinates using the GPS Station. Continous-GPS (C-GPS) in Sumatra Island is named Sumatran GPS Array (SuGAr), one of them named UMLH. The UMLH GPS station used to observe the displacement in the Aceh City of Sumatra Island, is located in Ujung Muloh. The changes of GPS coordinate recording data can represent the deformation pattern that occurred in Sumatra. On April 11, 2012, according to USGS data, there had been an earthquake in the city of Aceh about 8.6 at coordinates of 2.433°N, 93.072°E. The purpose of this research is to analyze the horizontal displacement due to the occurrence of the earthquake. Data processing is carried out using software GAMIT/GLOBK. The magnitude of the displacement of Sumatra Island before the earthquake, during the earthquake, and after the quake on component X were respectively: 0.04 mm/day, 56.63 mm/day, and 8.28 mm/day; while on component Y were respectively: 0.03 mm/day, 23.78 mm/day, and 1.22 mm/day. The direction of displacement was 253.8° towards Southwest with the assumption that 0° was in the North.

76 FR 69608 - Modification of Class E Airspace; Blythe, CA

Federal Register 2010, 2011, 2012, 2013, 2014

2011-11-09

... Blythe, CA, to accommodate aircraft using Area Navigation (RNAV) Global Positioning System (GPS) standard instrument approach procedures at Blythe Airport. This action also corrects geographic coordinates in the regulatory text. This improves the safety and management of Instrument Flight Rules (IFR) operations at the...

Airborne Antenna System for Minimum-Cycle-Slip GPS Reception

NASA Technical Reports Server (NTRS)

Wright, C. Wayne

2009-01-01

A system that includes a Global Positioning System (GPS) antenna and associated apparatus for keeping the antenna aimed upward has been developed for use aboard a remote-sensing-survey airplane. The purpose served by the system is to enable minimum- cycle-slip reception of GPS signals used in precise computation of the trajectory of the airplane, without having to restrict the airplane to maneuvers that increase the flight time needed to perform a survey. Cycle slip signifies loss of continuous track of the phase of a signal. Minimum-cycle-slip reception is desirable because maintaining constant track of the phase of the carrier signal from each available GPS satellite is necessary for surveying to centimeter or subcentimeter precision. Even a loss of signal for as short a time as a nanosecond can cause cycle slip. Cycle slips degrade the quality and precision of survey data acquired during a flight. The two principal causes of cycle slip are weakness of signals and multipath propagation. Heretofore, it has been standard practice to mount a GPS antenna rigidly on top of an airplane, and the radiation pattern of the antenna is typically hemispherical, so that all GPS satellites above the horizon are viewed by the antenna during level flight. When the airplane must be banked for a turn or other maneuver, the reception hemisphere becomes correspondingly tilted; hence, the antenna no longer views satellites that may still be above the Earth horizon but are now below the equatorial plane of the tilted reception hemisphere. Moreover, part of the reception hemisphere (typically, on the inside of a turn) becomes pointed toward ground, with a consequent increase in received noise and, therefore, degradation of GPS measurements. To minimize the likelihood of loss of signal and cycle slip, bank angles of remote-sensing survey airplanes have generally been limited to 10 or less, resulting in skidding or slipping uncoordinated turns. An airplane must be banked in order to make a coordinated turn. For small-radius, short-time coordinated turns, it is necessary to employ banks as steep as 45 , and turns involving such banks are times and for confining airplanes as closely as possible to areas to be surveyed. The idea underlying the design is that if the antenna can be kept properly aimed, then the incidence of cycle slips caused by loss or weakness of signals can be minimized. The system includes an articulating GPS antenna and associated electronic circuitry mounted under a radome atop an airplane. The electronic circuitry includes a microprocessor-based interface-circuit-and-data-translation module. The system receives data on the current attitude of the airplane from the inertial navigation system of the airplane. The microprocessor decodes the attitude data and uses them to compute commands for the GPS-antenna-articulating mechanism to tilt the antenna, relative to the airplane, in opposition to the roll or bank of the airplane to keep the antenna pointed toward the zenith. The system was tested aboard the hurricane- hunting airplane of the National Oceanic and Atmospheric Administration (NOAA) [see figure] during an 11-hour flight to observe the landfall of Hurricane Bret in late summer of 1999. No bank-angle restrictions were imposed during the flight. Post-flight analysis of the GPS trajectory data revealed that no cycle slip had occurred.considered normal maneuvers. These steep banks are highly desirable for minimizing flight

Time determination for spacecraft users of the Navstar Global Positioning System /GPS/

NASA Technical Reports Server (NTRS)

Grenchik, T. J.; Fang, B. T.

1977-01-01

Global Positioning System (GPS) navigation is performed by time measurements. A description is presented of a two body model of spacecraft motion. Orbit determination is the process of inferring the position, velocity, and clock offset of the user from measurements made of the user motion in the Newtonian coordinate system. To illustrate the effect of clock errors and the accuracy with which the user spacecraft time and orbit may be determined, a low-earth-orbit spacecraft (Seasat) as tracked by six Phase I GPS space vehicles is considered. The obtained results indicate that in the absence of unmodeled dynamic parameter errors clock biases may be determined to the nanosecond level. There is, however, a high correlation between the clock bias and the uncertainty in the gravitational parameter GM, i.e., the product of the universal gravitational constant and the total mass of the earth. It is, therefore, not possible to determine clock bias to better than 25 nanosecond accuracy in the presence of a gravitational error of one part per million.

GPS-Only Terrestrial Reference Frame Based on a Global Reprocessing

NASA Astrophysics Data System (ADS)

Dietrich, R.; Rothacher, M.; Ruelke, A.; Fritsche, M.; Steigenberger, P.

2007-12-01

The realization of the International Terrestrial Reference System (ITRS) with highest accuracy and stability is fundamental and crucial for applications in geodesy, geodynamics, geophysics and global change. In a joint effort TU Dresden and TU Munich/GFZ Potsdam reprocessed a global GPS network of more than 200 stations. As a contribution to an ITRS realization daily normal equations from 1994 to 2005 were rigorously combined in order to determine a global GPS-only reference frame (PDR05/Potsdam-Dresden-Reprocessing Reference Frame). We present a realization of the global terrestrial reference system which follows the center of mass approach in consideration of the load-induced deformation of the Earth's crust due to the redistribution of surface masses. The stability of our reference frame will be evaluated based on the obtained long-term trends of station coordinates, the load-induced deformation estimates and the homogeneous time series of station positions. We will compare our solution with other recent terrestrial reference system realizations and give some conclusions for future realizations of the ITRS.

Coordinate alignment of combined measurement systems using a modified common points method

NASA Astrophysics Data System (ADS)

Zhao, G.; Zhang, P.; Xiao, W.

2018-03-01

The co-ordinate metrology has been extensively researched for its outstanding advantages in measurement range and accuracy. The alignment of different measurement systems is usually achieved by integrating local coordinates via common points before measurement. The alignment errors would accumulate and significantly reduce the global accuracy, thus need to be minimized. In this thesis, a modified common points method (MCPM) is proposed to combine different traceable system errors of the cooperating machines, and optimize the global accuracy by introducing mutual geometric constraints. The geometric constraints, obtained by measuring the common points in individual local coordinate systems, provide the possibility to reduce the local measuring uncertainty whereby enhance the global measuring certainty. A simulation system is developed in Matlab to analyze the feature of MCPM using the Monto-Carlo method. An exemplary setup is constructed to verify the feasibility and efficiency of the proposed method associated with laser tracker and indoor iGPS systems. Experimental results show that MCPM could significantly improve the alignment accuracy.

Is the role as gatekeeper still feasible? A survey among Dutch general practitioners.

PubMed

Wammes, Joost Johan Godert; Jeurissen, Patrick Paulus Theodoor; Verhoef, Lise Maria; Assendelft, Willem J J; Westert, Gert P; Faber, Marjan J

2014-10-01

In the 2012 International Health Policy Survey by the Commonwealth Fund, 57% of Dutch GPs indicated that Dutch patients receive too much health care. This is an unexpected finding, given the clear gatekeeper role of Dutch GPs and recent efforts strengthening this role. The study aims to explore where perceived overuse of care prevails and to identify factors associated with too much care at the entry point of Dutch health care. An American survey exploring perceptions of the amount of care among primary care providers was modified for relevance to the Dutch health system. We further included additional factors possibly related to overuse based on 12 interviews with Dutch GPs. The survey was sent to a random sample of 600 GPs. Dutch GPs (N = 157; response rate 26.2%) indicated that patients receive (much) too much care in general hospitals, primary care, GP cooperatives as well as private clinics. The Dutch responding GPs showed a relatively demand-satisfying attitude, which contributed to the delivery of too much care, often leading to deviation from guidelines and professional norms. The increasing availability of diagnostic facilities was identified as an additional factor contributing to the provision of unnecessary care. Finally, funding gaps between primary care and hospitals impede cooperation and coordination, provoking unnecessary care. Our results--most notably regarding the demand-satisfying attitude of responding GPs--call into question the classical view of the guidance and gatekeeper role of GPs in the Dutch health care system. © The Author 2014. Published by Oxford University Press. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.

GPS/GLONASS Combined Precise Point Positioning with Receiver Clock Modeling

PubMed Central

Wang, Fuhong; Chen, Xinghan; Guo, Fei

2015-01-01

Research has demonstrated that receiver clock modeling can reduce the correlation coefficients among the parameters of receiver clock bias, station height and zenith tropospheric delay. This paper introduces the receiver clock modeling to GPS/GLONASS combined precise point positioning (PPP), aiming to better separate the receiver clock bias and station coordinates and therefore improve positioning accuracy. Firstly, the basic mathematic models including the GPS/GLONASS observation equations, stochastic model, and receiver clock model are briefly introduced. Then datasets from several IGS stations equipped with high-stability atomic clocks are used for kinematic PPP tests. To investigate the performance of PPP, including the positioning accuracy and convergence time, a week of (1–7 January 2014) GPS/GLONASS data retrieved from these IGS stations are processed with different schemes. The results indicate that the positioning accuracy as well as convergence time can benefit from the receiver clock modeling. This is particularly pronounced for the vertical component. Statistic RMSs show that the average improvement of three-dimensional positioning accuracy reaches up to 30%–40%. Sometimes, it even reaches over 60% for specific stations. Compared to the GPS-only PPP, solutions of the GPS/GLONASS combined PPP are much better no matter if the receiver clock offsets are modeled or not, indicating that the positioning accuracy and reliability are significantly improved with the additional GLONASS satellites in the case of insufficient number of GPS satellites or poor geometry conditions. In addition to the receiver clock modeling, the impacts of different inter-system timing bias (ISB) models are investigated. For the case of a sufficient number of satellites with fairly good geometry, the PPP performances are not seriously affected by the ISB model due to the low correlation between the ISB and the other parameters. However, the refinement of ISB model weakens the correlation between coordinates and ISB estimates and finally enhance the PPP performance in the case of poor observation conditions. PMID:26134106

Coroners' recommendations for prevention of resident deaths in aged care: The role of primary care providers

PubMed

Aitken, Georgia; Demosthenous, Athena; Bugeja, Lyndal; Willoughby, Melissa; Young, Carmel; E Ibrahim, Joseph

2018-05-01

Currently, very little is known about how coroners consider a role for general practitioners (GPs) and registered nurses (RNs) in recommendations for the prevention of premature death. Involving these professions in recommendations generally directed towards government organisations or residential aged care providers and management may contribute to more successful broader policy changes. The aim of this article was to examine whether coroners' recommendations describe a specific role for GPs and RNs in the prevention of premature death in residential aged care settings and, if so, what domains of practice were considered. This study was part of a larger retrospective cohort study. The National Coronial Information System (NCIS) was used to extract coroners' reports that included recommendations directed towards GPs and RNs. The following information was extracted: mechanism of death, incident location, text of coroners' recommendations. Of 162 unique recommendations, 14 (8.6%) were relevant to GPs and 10 (6.2%) were relevant to RNs. Most recommendations were made in the domains of 'applied professional knowledge and skills', 'organisations and legal dimensions' and 'provision and coordination of care'. Recommendations were primarily made in response to natural cause deaths and complications of clinical care. Coroners' recommendations have a limited focus directed towards GPs and RNs, and recommendations focus on their roles in application of skills and knowledge, legal domains, and provision and coordination of care. Recommendations were mainly made in response to deaths due to suboptimal care or from 'complications of clinical care'. Formulating recommendations for these health professions may increase accountability and the likelihood of a recommendation being effectively implemented.

IGS Network Coordinator Report - 2002

NASA Technical Reports Server (NTRS)

Moore, Angelyn

2004-01-01

The IGS network is a set of permanent, continuously-operating, dual-frequency GPS stations operated by over 100 worldwide agencies. The dataset is pooled at IGS Data Centers for routine use by IGS Analysis Centers in creating precise IGS products, as well as free access by other analysts around the world. The IGS Central Bureau hosts the IGS Network Coordinator, who assures adherence to standards and provides information regarding the IGS network via the Central Bureau Information System website at http://igscb.jpl.nasa.gov.

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.

Laying the foundation for a digital Nova Scotia

NASA Astrophysics Data System (ADS)

Bond, J.

2016-04-01

In 2013, the Province of Nova Scotia began an effort to modernize its coordinate referencing infrastructure known as the Nova Scotia Coordinate Referencing System (NSCRS). At that time, 8, active GPS stations were installed in southwest Nova Scotia to evaluate the technology's ability to address the Province's coordinate referencing needs. The success of the test phase helped build a business case to implement the technology across the entire Province. It is anticipated that by the end of 2015, 40 active GPS stations will be in place across Nova Scotia. This infrastructure, known as the Nova Scotia Active Control Stations (NSACS) network, will allow for instantaneous, centimetre level positioning across the Province. Originally designed to address the needs of the surveying community, the technology has also proven to have applications in mapping, machine automation, agriculture, navigation, emergency response, earthquake detection and other areas. In the foreseeable future, all spatial data sets captured in Nova Scotia will be either directly or indirectly derived from the NSACS network. The technology will promote high accuracy and homogenous spatial data sets across the Province. The technology behind the NSACS and the development of the system are described. Examples of how the technology is contributing to a digital Nova Scotia are presented. Future applications of the technology are also considered.

[Improving the physician-dental surgeon relationship to improve patient care].

PubMed

Tenenbaum, Annabelle; Folliguet, Marysette; Berdougo, Brice; Hervé, Christian; Moutel, Grégoire

2008-04-01

This study had two aims: to assess the nature of the relationship between general practitioners (GPs) and dental surgeons in relation to patient care and to evaluate qualitatively their interest in the changes that health networks and shared patient medical files could bring. Questionnaires were completed by 12 GPs belonging to ASDES, a private practitioner-hospital health network that seeks to promote a partnership between physicians and dental surgeons, and by 13 private dental surgeons in the network catchment area. The GPs and dentists had quite different perceptions of their relationship. Most dentists rated their relationship with GPs as "good" to "excellent" and did not wish to modify it, while GPs rated their relationship with dentists as nonexistent and expressed a desire to change the situation. Some GPs and some dentists supported data exchange by sharing personal medical files through the network. Many obstacles hinder communication between GPs and dentists. There is insufficient coordination between professionals. Health professionals must be made aware of how changes in the health care system (health networks, personal medical files, etc) can help to provide patients with optimal care. Technical innovations in medicine will not be beneficial to patients unless medical education and training begins to include interdisciplinary and holistic approaches to health care and preventive care.

CODE's new solar radiation pressure model for GNSS orbit determination

NASA Astrophysics Data System (ADS)

Arnold, D.; Meindl, M.; Beutler, G.; Dach, R.; Schaer, S.; Lutz, S.; Prange, L.; Sośnica, K.; Mervart, L.; Jäggi, A.

2015-08-01

The Empirical CODE Orbit Model (ECOM) of the Center for Orbit Determination in Europe (CODE), which was developed in the early 1990s, is widely used in the International GNSS Service (IGS) community. For a rather long time, spurious spectral lines are known to exist in geophysical parameters, in particular in the Earth Rotation Parameters (ERPs) and in the estimated geocenter coordinates, which could recently be attributed to the ECOM. These effects grew creepingly with the increasing influence of the GLONASS system in recent years in the CODE analysis, which is based on a rigorous combination of GPS and GLONASS since May 2003. In a first step we show that the problems associated with the ECOM are to the largest extent caused by the GLONASS, which was reaching full deployment by the end of 2011. GPS-only, GLONASS-only, and combined GPS/GLONASS solutions using the observations in the years 2009-2011 of a global network of 92 combined GPS/GLONASS receivers were analyzed for this purpose. In a second step we review direct solar radiation pressure (SRP) models for GNSS satellites. We demonstrate that only even-order short-period harmonic perturbations acting along the direction Sun-satellite occur for GPS and GLONASS satellites, and only odd-order perturbations acting along the direction perpendicular to both, the vector Sun-satellite and the spacecraft's solar panel axis. Based on this insight we assess in the third step the performance of four candidate orbit models for the future ECOM. The geocenter coordinates, the ERP differences w. r. t. the IERS 08 C04 series of ERPs, the misclosures for the midnight epochs of the daily orbital arcs, and scale parameters of Helmert transformations for station coordinates serve as quality criteria. The old and updated ECOM are validated in addition with satellite laser ranging (SLR) observations and by comparing the orbits to those of the IGS and other analysis centers. Based on all tests, we present a new extended ECOM which substantially reduces the spurious signals in the geocenter coordinate (by about a factor of 2-6), reduces the orbit misclosures at the day boundaries by about 10 %, slightly improves the consistency of the estimated ERPs with those of the IERS 08 C04 Earth rotation series, and substantially reduces the systematics in the SLR validation of the GNSS orbits.

Operational GPS Imaging System at Multiple Scales for Earth Science and Monitoring of Geohazards

NASA Astrophysics Data System (ADS)

Blewitt, Geoffrey; Hammond, William; Kreemer, Corné

2016-04-01

Toward scientific targets that range from slow deep Earth processes to geohazard rapid response, our operational GPS data analysis system produces smooth, yet detailed maps of 3-dimensional land motion with respect to our Earth's center of mass at multiple spatio-temporal scales with various latencies. "GPS Imaging" is implemented operationally as a back-end processor to our GPS data processing facility, which uses JPL's GIPSY OASIS II software to produce positions from 14,000 GPS stations in ITRF every 5 minutes, with coordinate precision that gradually improves as latency increases upward from 1 hour to 2 weeks. Our GPS Imaging system then applies sophisticated signal processing and image filtering techniques to generate images of land motion covering our Earth's continents with high levels of robustness, accuracy, spatial resolution, and temporal resolution. Techniques employed by our GPS Imaging system include: (1) similarity transformation of polyhedron coordinates to ITRF with optional common-mode filtering to enhance local transient signal to noise ratio, (2) a comprehensive database of ~100,000 potential step events based on earthquake catalogs and equipment logs, (3) an automatic, robust, and accurate non-parametric estimator of station velocity that is insensitive to prevalent step discontinuities, outliers, seasonality, and heteroscedasticity; (4) a realistic estimator of velocity error bars based on subsampling statistics; (5) image processing to create a map of land motion that is based on median spatial filtering on the Delauney triangulation, which is effective at despeckling the data while faithfully preserving edge features; (6) a velocity time series estimator to assist identification of transient behavior, such as unloading caused by drought, and (7) a method of integrating InSAR and GPS for fine-scale seamless imaging in ITRF. Our system is being used to address three main scientific focus areas, including (1) deep Earth processes, (2) anthropogenic lithospheric processes, and (3) dynamic solid Earth events. Our prototype images show that the striking, first-order signal in North America and Europe is large scale uplift and subsidence from mantle flow driven by Glacial Isostatic Adjustment. At regional scales, the images reveal that anthropogenic lithospheric processes can dominate vertical land motion in extended regions, such as the rapid subsidence of California's Central Valley (CV) exacerbated by drought. The Earth's crust is observed to rebound elastically as evidenced by uplift of surrounding mountain ranges. Images also reveal natural uplift of mountains, mantle relaxation associated with earthquakes over the last century, and uplift at plate boundaries driven by interseismic locking. Using the high-rate positions at low latency, earthquake events can be rapidly imaged, modeled, and monitored for afterslip, potential aftershocks, and subsequent deeper relaxation. Thus we are imaging deep Earth processes with unprecedented scope, resolution and accuracy. In addition to supporting these scientific focus areas, the data products are also being used to support the global reference frame (ITRF), and show potential to enhance missions such as GRACE and NISAR by providing complementary information on Earth processes.

Laser-based Relative Navigation Using GPS Measurements for Spacecraft Formation Flying

NASA Astrophysics Data System (ADS)

Lee, Kwangwon; Oh, Hyungjik; Park, Han-Earl; Park, Sang-Young; Park, Chandeok

2015-12-01

This study presents a precise relative navigation algorithm using both laser and Global Positioning System (GPS) measurements in real time. The measurement model of the navigation algorithm between two spacecraft is comprised of relative distances measured by laser instruments and single differences of GPS pseudo-range measurements in spherical coordinates. Based on the measurement model, the Extended Kalman Filter (EKF) is applied to smooth the pseudo-range measurements and to obtain the relative navigation solution. While the navigation algorithm using only laser measurements might become inaccurate because of the limited accuracy of spacecraft attitude estimation when the distance between spacecraft is rather large, the proposed approach is able to provide an accurate solution even in such cases by employing the smoothed GPS pseudo-range measurements. Numerical simulations demonstrate that the errors of the proposed algorithm are reduced by more than about 12% compared to those of an algorithm using only laser measurements, as the accuracy of angular measurements is greater than 0.001° at relative distances greater than 30 km.

Assessment Study of Using Online (CSRS) GPS-PPP Service for Mapping Applications in Egypt

NASA Astrophysics Data System (ADS)

Abd-Elazeem, Mohamed; Farah, Ashraf; Farrag, Farrag

2011-09-01

Many applications in navigation, land surveying, land title definitions and mapping have been made simpler and more precise due to accessibility of Global Positioning System (GPS) data, and thus the demand for using advanced GPS techniques in surveying applications has become essential. The differential technique was the only source of accurate positioning for many years, and remained in use despite of its cost. The precise point positioning (PPP) technique is a viable alternative to the differential positioning method in which a user with a single receiver can attain positioning accuracy at the centimeter or decimeter scale. In recent years, many organizations introduced online (GPS-PPP) processing services capable of determining accurate geocentric positions using GPS observations. These services provide the user with receiver coordinates in free and unlimited access formats via the internet. This paper investigates the accuracy of the Canadian Spatial Reference System (CSRS) Precise Point Positioning (PPP) (CSRS-PPP) service supervised by the Geodetic Survey Division (GSD), Canada. Single frequency static GPS observations have been collected at three points covering time spans of 60, 90 and 120 minutes. These three observed sites form baselines of 1.6, 7, and 10 km, respectively. In order to assess the CSRS-PPP accuracy, the discrepancies between the CSRS-PPP estimates and the regular differential GPS solutions were computed. The obtained results illustrate that the PPP produces a horizontal error at the scale of a few decimeters; this is accurate enough to serve many mapping applications in developing countries with a savings in both cost and experienced labor.

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.

Non-GPS full position and angular orientation onboard sensors for moving and stationary platforms

NASA Astrophysics Data System (ADS)

Dhadwal, Harbans S.; Rastegar, Jahangir; Feng, Dake; Kwok, Philip; Pereira, Carlos M.

2016-05-01

Angular orientation of both mobile and stationary objects continues to be an ongoing topic of interest for guidance and control as well as for non-GPS based solutions for geolocations of assets in any environment. Currently available sensors, which include inertia devices such as accelerometers and gyros; magnetometers; surface mounted antennas; radars; GPS; and optical line of sight devices, do not provide an acceptable solution for many applications, particularly for gun-fired munitions and for all-weather and all environment scenarios. A robust onboard full angular orientation sensor solution, based on a scanning polarized reference source and a polarized geometrical cavity orientation sensor, is presented. The full position of the object, in the reference source coordinate system, is determined by combining range data obtained using established time-of-flight techniques, with the angular orientation information.

Energetic Particle Data From the Global Positioning System Constellation: GPS ENERGETIC PARTICLE DATA

DOE PAGES

Morley, S. K.; Sullivan, J. P.; Carver, M. R.; ...

2017-02-01

Since 2000, Los Alamos National Laboratory (LANL) Combined X-ray and Dosimeter (CXD) and Burst Detector Dosimeter for Block II-R (BDD-IIR) instruments have been fielded on Global Positioning System (GPS) satellites. Today, 21 of the 31 operational GPS satellites are equipped with a CXD detector and a further 2 carry a BDD-IIR. Each of these instruments measures a wide range of energetic electrons and protons. These data have now been publicly released under the terms of the Executive Order for Coordinating Efforts to Prepare the Nation for Space Weather Events. The specific goal of releasing space weather data from the GPSmore » satellites is to enable broad scientific community engagement in enhancing space weather model validation and improvements in space weather forecasting and situational awareness. The time period covered by this data release is approximately 16 years, which corresponds to more than 167 satellite years of data. As a result, the large number of GPS satellites, distributed over six orbital planes, will provide important context for ongoing and historical science missions, as well as enabling new types of research not previously possible.« less

Energetic Particle Data From the Global Positioning System Constellation: GPS ENERGETIC PARTICLE DATA

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

Morley, S. K.; Sullivan, J. P.; Carver, M. R.

Since 2000, Los Alamos National Laboratory (LANL) Combined X-ray and Dosimeter (CXD) and Burst Detector Dosimeter for Block II-R (BDD-IIR) instruments have been fielded on Global Positioning System (GPS) satellites. Today, 21 of the 31 operational GPS satellites are equipped with a CXD detector and a further 2 carry a BDD-IIR. Each of these instruments measures a wide range of energetic electrons and protons. These data have now been publicly released under the terms of the Executive Order for Coordinating Efforts to Prepare the Nation for Space Weather Events. The specific goal of releasing space weather data from the GPSmore » satellites is to enable broad scientific community engagement in enhancing space weather model validation and improvements in space weather forecasting and situational awareness. The time period covered by this data release is approximately 16 years, which corresponds to more than 167 satellite years of data. As a result, the large number of GPS satellites, distributed over six orbital planes, will provide important context for ongoing and historical science missions, as well as enabling new types of research not previously possible.« less

HIFiRE-5 Flight Test Preliminary Results (Postprint)

DTIC Science & Technology

2013-11-01

DMARS-R) IMU and Ashtech DG14 Global Positioning System receiver. Results show that a tripped transition occurred on the test article leading edge...Reference System (DMARS-R) IMU and Ashtech DG14 Global Positioning System receiver. Results show that a tripped transition occurred on the test...pitch angle relative to earth as measured by IMU , or flight-path elevation angle as measured by GPS or IMU , degrees  = body-fixed angular coordinate

Conical-Domain Model for Estimating GPS Ionospheric Delays

NASA Technical Reports Server (NTRS)

Sparks, Lawrence; Komjathy, Attila; Mannucci, Anthony

2009-01-01

The conical-domain model is a computational model, now undergoing development, for estimating ionospheric delays of Global Positioning System (GPS) signals. Relative to the standard ionospheric delay model described below, the conical-domain model offers improved accuracy. In the absence of selective availability, the ionosphere is the largest source of error for single-frequency users of GPS. Because ionospheric signal delays contribute to errors in GPS position and time measurements, satellite-based augmentation systems (SBASs) have been designed to estimate these delays and broadcast corrections. Several national and international SBASs are currently in various stages of development to enhance the integrity and accuracy of GPS measurements for airline navigation. In the Wide Area Augmentation System (WAAS) of the United States, slant ionospheric delay errors and confidence bounds are derived from estimates of vertical ionospheric delay modeled on a grid at regularly spaced intervals of latitude and longitude. The estimate of vertical delay at each ionospheric grid point (IGP) is calculated from a planar fit of neighboring slant delay measurements, projected to vertical using a standard, thin-shell model of the ionosphere. Interpolation on the WAAS grid enables estimation of the vertical delay at the ionospheric pierce point (IPP) corresponding to any arbitrary measurement of a user. (The IPP of a given user s measurement is the point where the GPS signal ray path intersects a reference ionospheric height.) The product of the interpolated value and the user s thin-shell obliquity factor provides an estimate of the user s ionospheric slant delay. Two types of error that restrict the accuracy of the thin-shell model are absent in the conical domain model: (1) error due to the implicit assumption that the electron density is independent of the azimuthal angle at the IPP and (2) error arising from the slant-to-vertical conversion. At low latitudes or at mid-latitudes under disturbed conditions, the accuracy of SBAS systems based upon the thin-shell model suffers due to the presence of complex ionospheric structure, high delay values, and large electron density gradients. Interpolation on the vertical delay grid serves as an additional source of delay error. The conical-domain model permits direct computation of the user s slant delay estimate without the intervening use of a vertical delay grid. The key is to restrict each fit of GPS measurements to a spatial domain encompassing signals from only one satellite. The conical domain model is so named because each fit involves a group of GPS receivers that all receive signals from the same GPS satellite (see figure); the receiver and satellite positions define a cone, the satellite position being the vertex. A user within a given cone evaluates the delay to the satellite directly, using (1) the IPP coordinates of the line of sight to the satellite and (2) broadcast fit parameters associated with the cone. The conical-domain model partly resembles the thin-shell model in that both models reduce an inherently four-dimensional problem to two dimensions. However, unlike the thin-shell model, the conical domain model does not involve any potentially erroneous simplifying assumptions about the structure of the ionosphere. In the conical domain model, the initially four-dimensional problem becomes truly two-dimensional in the sense that once a satellite location has been specified, any signal path emanating from a satellite can be identified by only two coordinates; for example, the IPP coordinates. As a consequence, a user s slant-delay estimate converges to the correct value in the limit that the receivers converge to the user s location (or, equivalently, in the limit that the measurement IPPs converge to the user s IPP).

High-precision coseismic displacement estimation with a single-frequency GPS receiver

NASA Astrophysics Data System (ADS)

Guo, Bofeng; Zhang, Xiaohong; Ren, Xiaodong; Li, Xingxing

2015-07-01

To improve the performance of Global Positioning System (GPS) in the earthquake/tsunami early warning and rapid response applications, minimizing the blind zone and increasing the stability and accuracy of both the rapid source and rupture inversion, the density of existing GPS networks must be increased in the areas at risk. For economic reasons, low-cost single-frequency receivers would be preferable to make the sparse dual-frequency GPS networks denser. When using single-frequency GPS receivers, the main problem that must be solved is the ionospheric delay, which is a critical factor when determining accurate coseismic displacements. In this study, we introduce a modified Satellite-specific Epoch-differenced Ionospheric Delay (MSEID) model to compensate for the effect of ionospheric error on single-frequency GPS receivers. In the MSEID model, the time-differenced ionospheric delays observed from a regional dual-frequency GPS network to a common satellite are fitted to a plane rather than part of a sphere, and the parameters of this plane are determined by using the coordinates of the stations. When the parameters are known, time-differenced ionospheric delays for a single-frequency GPS receiver could be derived from the observations of those dual-frequency receivers. Using these ionospheric delay corrections, coseismic displacements of a single-frequency GPS receiver can be accurately calculated based on time-differenced carrier-phase measurements in real time. The performance of the proposed approach is validated using 5 Hz GPS data collected during the 2012 Nicoya Peninsula Earthquake (Mw 7.6, 2012 September 5) in Costa Rica. This shows that the proposed approach improves the accuracy of the displacement of a single-frequency GPS station, and coseismic displacements with an accuracy of a few centimetres are achieved over a 10-min interval.

Integrity monitoring of IGS products

NASA Technical Reports Server (NTRS)

Zumberge, James F.; Plag, H. -P.

2005-01-01

The IGS has successfully produced precise GPS and GLONASS transmitter parameters, coordinates of IGS tracking stations, Earth rotation parameters, and atmospheric parameters. In this paper we discuss the concepts of integrity monitoring, system monitoring, and performance assessment, all in the context of IGS products. We report on a recent survey of IGS product users, and propose an integrity strategy for the IGS.

Tracking down a solution: exploring the acceptability and value of wearable GPS devices for older persons, individuals with a disability and their support persons.

PubMed

Williamson, Brittany; Aplin, Tammy; de Jonge, Desleigh; Goyne, Matthew

2017-11-01

To explore the acceptability and value of three wearable GPS devices for older persons and individuals with a disability and safety concerns when accessing the community. This pilot study explored six wearers' and their support persons' experience of using three different wearable GPS devices (a pendant, watch, and mini GPS phone), each for a two-week period. Participants identified safety as the main value of using a wearable GPS device. The acceptability and value of these devices was strongly influenced by device features, ease of use, cost, appearance, the reliability of the GPS coordinates, the wearer's health condition and the users familiarity with technology. Overall, participants indicated that they preferred the pendant. Wearable GPS devices are potentially useful in providing individuals who have safety concerns with reassurance and access to assistance as required. To ensure successful utilization, future device design and device selection should consider the user's familiarity with technology and their health condition. This study also revealed that not all wearable GPS devices provide continuous location tracking. It is therefore critical to ensure that the device's location tracking functions address the wearer's requirements and reason for using the device. Implications for Rehabilitation The acceptability and usability of wearable GPS devices is strongly influenced by the device features, ease of use, cost, appearance, the reliability of the device to provide accurate and timely GPS coordinates, as well as the health condition of the wearer and their familiarity with technology. Wearable GPS devices need to be simple to use and support and training is essential to ensure they are successfully utilized. Not all wearable GPS devices provide continuous location tracking and accuracy of location is impacted by line of sight to satellites. Therefore, care needs to be taken when choosing a suitable device, to ensure that the device's location tracking features are based on the wearer's requirements and value behind using the device.

Managing work-related psychological complaints by general practitioners, in coordination with occupational physicians: a pilot study.

PubMed

Buijs, Peter C; van Dijk, Frank J H; Evers, Marÿe; vd Klink, Jacques J L; Anema, Han

2007-01-01

Increasingly, workers have psychological work-related complaints, endangering their work ability and causing considerable economic losses. Many employees consult their general practitioner (GP). He, however, often pays insufficient attention to work-relatedness or to coordination with occupational physicians (OPs). Appropriate guidelines are missing. Consequently, we developed a GP guideline to handle these problems in coordination with OPs, and tested it in a pilot, using an explorative, evaluative study design. 23 GPs were trained to include employed patients and to test the guideline. Patients received questionnaires after 0, 4, 10 and 30 wk, GPs after 4 and 30 wk. The result was a new guideline, regarding problem orientation, diagnosis and advice, meant to avoid contradictory GP-OP advice and to activate patient responsibility. It included a GP-OP-patient communication form concerning information exchange and harmonization of insight/advice. Implementing GPs concluded that the guideline promotes recovery and work resumption and OP-GP contact benefits patients, prevents conflicting advice and promotes agreement on task division. They judged guideline efficiency and OP commitment less positively. Patients were positive, especially about GP-OP contact. Accordingly, an improved guideline, when tested for its effectiveness in a Randomized Controlled Trial, can help GPs to cope with a growing, complex problem, in collaboration with their occupational colleagues.

Effects on noise properties of GPS time series caused by higher-order ionospheric corrections

NASA Astrophysics Data System (ADS)

Jiang, Weiping; Deng, Liansheng; Li, Zhao; Zhou, Xiaohui; Liu, Hongfei

2014-04-01

Higher-order ionospheric (HOI) effects are one of the principal technique-specific error sources in precise global positioning system (GPS) analysis. These effects also influence the non-linear characteristics of GPS coordinate time series. In this paper, we investigate these effects on coordinate time series in terms of seasonal variations and noise amplitudes. Both power spectral techniques and maximum likelihood estimators (MLE) are used to evaluate these effects quantitatively and qualitatively. Our results show an overall improvement for the analysis of global sites if HOI effects are considered. We note that the noise spectral index that is used for the determination of the optimal noise models in our analysis ranged between -1 and 0 both with and without HOI corrections, implying that the coloured noise cannot be removed by these corrections. However, the corrections were found to have improved noise properties for global sites. After the corrections were applied, the noise amplitudes at most sites decreased, among which the white noise amplitudes decreased remarkably. The white noise amplitudes of up to 81.8% of the selected sites decreased in the up component, and the flicker noise of 67.5% of the sites decreased in the north component. Stacked periodogram results show that, no matter whether the HOI effects are considered or not, a common fundamental period of 1.04 cycles per year (cpy), together with the expected annual and semi-annual signals, can explain all peaks of the north and up components well. For the east component, however, reasonable results can be obtained only based on HOI corrections. HOI corrections are useful for better detecting the periodic signals in GPS coordinate time series. Moreover, the corrections contributed partly to the seasonal variations of the selected sites, especially for the up component. Statistically, HOI corrections reduced more than 50% and more than 65% of the annual and semi-annual amplitudes respectively at the selected sites.

Temperature anomalies in the plumes of the August, 18 and August, 29, 2000 eruptions of Miyake Jima volcano (Japan) inferred from delays of GPS waves crossing them.

NASA Astrophysics Data System (ADS)

Houlié, N.; Nercessian, A.; Briole, P.; Murakami, M.

2003-12-01

Using the GAMIT software we processed seventy days of GPS data (30s sampling rate) collected by the GSI at four sites on Miyake Jima volcanic island (Japan) between June 27, 2000 and September 5, 2000. This period includes a large seismic swarm (June 27, 2000 - July 8, 2000) followed by several major paroxysms at the volcano crater (July 9, 10, 14, 15, August 29) producing a 1 km wide caldera. The medium term velocity of the stations coordinates, already published elsewhere, is maximum during the seismic swarm and corresponds to a large dyke intrusion mostly offshore west of the volcano. No anomalies are observed in the time series of the daily GPS coordinates for the days of the paroxysms. An epoch by epoch processing of those days, using a kinematic software shows that there is no deformation during the paroxysms themselves. We then examined epoch by epoch the path delay residuals of the GPS phases at each GPS station during the events. Those delays exceed 200 mm in some cases. As they cannot be explained by a temporal change of the stations coordinates, we conclude that the cause of these delays is the presence of the hot volcanic plume not modeled by the GPS data processing which assumes a homogenous troposphere. We used a classical seismic tomography algorithm (modified to handle 3D + time) to map the path delay anomaly in the plume as a function of time. We interpret the anomalous delays as temperature anomalies in the plume, assuming a normal pressure and a plume saturated in humidity. The maximum average temperature anomaly is 20° , a low value compared to what is currently proposed in the literature. Higher temperature should exist in the inner part of the plume, but the horizontal extension of this hot zone cannot be more than 50-100 m, otherwise the GPS data would detect it.

Detecting discontinuities in GNSS coordinate time series with STARS: case study, the Bologna and Medicina GPS sites

NASA Astrophysics Data System (ADS)

Bruni, S.; Zerbini, Susanna; Raicich, F.; Errico, M.; Santi, E.

2014-12-01

Global navigation satellite systems (GNSS) data are a fundamental source of information for achieving a better understanding of geophysical and climate-related phenomena. However, discontinuities in the coordinate time series might be a severe limiting factor for the reliable estimate of long-term trends. A methodological approach has been adapted from Rodionov (Geophys Res Lett 31:L09204, 2004; Geophys Res Lett 31:L12707, 2006) and from Rodionov and Overland (J Marine Sci 62:328-332, 2005) to identify both the epoch of occurrence and the magnitude of jumps corrupting GNSS data sets without any a priori information on these quantities. The procedure is based on the Sequential t test Analysis of Regime Shifts (STARS) (Rodionov in Geophys Res Lett 31:L09204, 2004). The method has been tested against a synthetic data set characterized by typical features exhibited by real GNSS time series, such as linear trend, seasonal cycle, jumps, missing epochs and a combination of white and flicker noise. The results show that the offsets identified by the algorithm are split into 48 % of true-positive, 28 % of false-positive and 24 % of false-negative events. The procedure has then been applied to GPS coordinate time series of stations located in the southeastern Po Plain, in Italy. The series span more than 15 years and are affected by offsets of different nature. The methodology proves to be effective, as confirmed by the comparison between the corrected GPS time series and those obtained by other observation techniques.

Nighttime Medium-Scale Traveling Ionospheric Disturbances From Airglow Imager and Global Navigation Satellite Systems Observations

NASA Astrophysics Data System (ADS)

Huang, Fuqing; Lei, Jiuhou; Dou, Xiankang; Luan, Xiaoli; Zhong, Jiahao

2018-01-01

In this study, coordinated airglow imager, GPS total electron content (TEC), and Beidou geostationary orbit (GEO) TEC observations for the first time are used to investigate the characteristics of nighttime medium-scale traveling ionospheric disturbances (MSTIDs) over central China. The results indicated that the features of nighttime MSTIDs from three types of observations are generally consistent, whereas the nighttime MSTID features from the Beidou GEO TEC are in better agreement with those from airglow images as compared with the GPS TEC, given that the nighttime MSTID characteristics from GPS TEC are significantly affected by Doppler effect due to satellite movement. It is also found that there are three peaks in the seasonal variations of the occurrence rate of nighttime MSTIDs in 2016. Our study revealed that the Beidou GEO satellites provided fidelity TEC observations to study the ionospheric variability.

Carrier phase ambiguity resolution for the Global Positioning System applied to geodetic baselines up to 2000 km

NASA Technical Reports Server (NTRS)

Blewitt, Geoffrey

1989-01-01

A technique for resolving the ambiguities in the GPS carrier phase data (which are biased by an integer number of cycles) is described which can be applied to geodetic baselines up to 2000 km in length and can be used with dual-frequency P code receivers. The results of such application demonstrated that a factor of 3 improvement in baseline accuracy could be obtained, giving centimeter-level agreement with coordinates inferred by very-long-baseline interferometry in the western United States. It was found that a method using pseudorange data is more reliable than one using ionospheric constraints for baselines longer than 200 km. It is recommended that future GPS networks have a wide spectrum of baseline lengths (ranging from baselines shorter than 100 km to those longer than 1000 km) and that GPS receivers be used which can acquire dual-frequency P code data.

Unprecented syntonization and syncronization accuracy via simultaneous viewing with GPS receivers: Construction characteristics of an NBS/GPS receiver

NASA Technical Reports Server (NTRS)

Davis, D. D.; Weiss, M.; Clements, A.; Allan, D. W.

1982-01-01

The National Bureau of Standards/Global Positioning System (NBS/GPS) receiver is discussed. It is designed around the concept of obtaining high accuracy, low cost time and frequency comparisons between remote frequency standards and clocks with the intent to aid international time and frequency coordination. Preliminary tests of this comparison technique between Boulder, CO and Washington, D.C indicate the ability to do accurate time transfer to better that 10 ns, and frequency measurements to better than 1 part in 10 to the 14th power. The hardware and software of the receiver is detailed. The receiver is fully automatic with a built-in 0.1 ns resolution time interval counter. A microprocessor does data processing. Satellite signal stabilities are routinely at the 5 ns level for 15 s averages, and the internal receiver stabilities are at the 1 ns level.

An Alternative Wearable Tracking System Based on a Low-Power Wide-Area Network.

PubMed

Fernández-Garcia, Raul; Gil, Ignacio

2017-03-14

This work presents an alternative wearable tracking system based on a low-power wide area network. A complete GPS receiver was integrated with a textile substrate, and the latitude and longitude coordinates were sent to the cloud by means of the SIM-less SIGFOX network. To send the coordinates over SIGFOX protocol, a specific codification algorithm was used and a customized UHF antenna on jeans fabric was designed, simulated and tested. Moreover, to guarantee the compliance to international regulations for human body exposure to electromagnetic radiation, the electromagnetic specific absorption rate of this antenna was analyzed. A specific remote server was developed to decode the latitude and longitude coordinates. Once the coordinates have been decoded, the remote server sends this information to the open source data viewer SENTILO to show the location of the sensor node in a map. The functionality of this system has been demonstrated experimentally. The results guarantee the utility and wearability of the proposed tracking system for the development of sensor nodes and point out that it can be a low cost alternative to other commercial products based on GSM networks.

Preliminary study of GPS orbit determination accuracy achievable from worldwide tracking data

NASA Technical Reports Server (NTRS)

Larden, D. R.; Bender, P. L.

1982-01-01

The improvement in the orbit accuracy if high accuracy tracking data from a substantially larger number of ground stations is available was investigated. Observations from 20 ground stations indicate that 20 cm or better accuracy can be achieved for the horizontal coordinates of the GPS satellites. With this accuracy, the contribution to the error budget for determining 1000 km baselines by GPS geodetic receivers would be only about 1 cm.

In-field Access to Geoscientific Metadata through GPS-enabled Mobile Phones

NASA Astrophysics Data System (ADS)

Hobona, Gobe; Jackson, Mike; Jordan, Colm; Butchart, Ben

2010-05-01

Fieldwork is an integral part of much geosciences research. But whilst geoscientists have physical or online access to data collections whilst in the laboratory or at base stations, equivalent in-field access is not standard or straightforward. The increasing availability of mobile internet and GPS-supported mobile phones, however, now provides the basis for addressing this issue. The SPACER project was commissioned by the Rapid Innovation initiative of the UK Joint Information Systems Committee (JISC) to explore the potential for GPS-enabled mobile phones to access geoscientific metadata collections. Metadata collections within the geosciences and the wider geospatial domain can be disseminated through web services based on the Catalogue Service for Web(CSW) standard of the Open Geospatial Consortium (OGC) - a global grouping of over 380 private, public and academic organisations aiming to improve interoperability between geospatial technologies. CSW offers an XML-over-HTTP interface for querying and retrieval of geospatial metadata. By default, the metadata returned by CSW is based on the ISO19115 standard and encoded in XML conformant to ISO19139. The SPACER project has created a prototype application that enables mobile phones to send queries to CSW containing user-defined keywords and coordinates acquired from GPS devices built-into the phones. The prototype has been developed using the free and open source Google Android platform. The mobile application offers views for listing titles, presenting multiple metadata elements and a Google Map with an overlay of bounding coordinates of datasets. The presentation will describe the architecture and approach applied in the development of the prototype.

Accuracy of an acoustic location system for monitoring the position of duetting songbirds in tropical forest

PubMed Central

Mennill, Daniel J.; Burt, John M.; Fristrup, Kurt M.; Vehrencamp, Sandra L.

2008-01-01

A field test was conducted on the accuracy of an eight-microphone acoustic location system designed to triangulate the position of duetting rufous-and-white wrens (Thryothorus rufalbus) in Costa Rica’s humid evergreen forest. Eight microphones were set up in the breeding territories of twenty pairs of wrens, with an average inter-microphone distance of 75.2±2.6 m. The array of microphones was used to record antiphonal duets broadcast through stereo loudspeakers. The positions of the loudspeakers were then estimated by evaluating the delay with which the eight microphones recorded the broadcast sounds. Position estimates were compared to coordinates surveyed with a global-positioning system (GPS). The acoustic location system estimated the position of loudspeakers with an error of 2.82±0.26 m and calculated the distance between the “male” and “female” loudspeakers with an error of 2.12±0.42 m. Given the large range of distances between duetting birds, this relatively low level of error demonstrates that the acoustic location system is a useful tool for studying avian duets. Location error was influenced partly by the difficulties inherent in collecting high accuracy GPS coordinates of microphone positions underneath a lush tropical canopy, and partly by the complicating influence of irregular topography and thick vegetation on sound transmission. PMID:16708941

Common mode error in Antarctic GPS coordinate time series on its effect on bedrock-uplift estimates

NASA Astrophysics Data System (ADS)

Liu, Bin; King, Matt; Dai, Wujiao

2018-05-01

Spatially-correlated common mode error always exists in regional, or-larger, GPS networks. We applied independent component analysis (ICA) to GPS vertical coordinate time series in Antarctica from 2010 to 2014 and made a comparison with the principal component analysis (PCA). Using PCA/ICA, the time series can be decomposed into a set of temporal components and their spatial responses. We assume the components with common spatial responses are common mode error (CME). An average reduction of ˜40% about the RMS values was achieved in both PCA and ICA filtering. However, the common mode components obtained from the two approaches have different spatial and temporal features. ICA time series present interesting correlations with modeled atmospheric and non-tidal ocean loading displacements. A white noise (WN) plus power law noise (PL) model was adopted in the GPS velocity estimation using maximum likelihood estimation (MLE) analysis, with ˜55% reduction of the velocity uncertainties after filtering using ICA. Meanwhile, spatiotemporal filtering reduces the amplitude of PL and periodic terms in the GPS time series. Finally, we compare the GPS uplift velocities, after correction for elastic effects, with recent models of glacial isostatic adjustment (GIA). The agreements of the GPS observed velocities and four GIA models are generally improved after the spatiotemporal filtering, with a mean reduction of ˜0.9 mm/yr of the WRMS values, possibly allowing for more confident separation of various GIA model predictions.

Ground Control Point - Wireless System Network for UAV-based environmental monitoring applications

NASA Astrophysics Data System (ADS)

Mejia-Aguilar, Abraham

2016-04-01

In recent years, Unmanned Aerial Vehicles (UAV) have seen widespread civil applications including usage for survey and monitoring services in areas such as agriculture, construction and civil engineering, private surveillance and reconnaissance services and cultural heritage management. Most aerial monitoring services require the integration of information acquired during the flight (such as imagery) with ground-based information (such as GPS information or others) for improved ground truth validation. For example, to obtain an accurate 3D and Digital Elevation Model based on aerial imagery, it is necessary to include ground-based information of coordinate points, which are normally acquired with surveying methods based on Global Position Systems (GPS). However, GPS surveys are very time consuming and especially for longer time series of monitoring data repeated GPS surveys are necessary. In order to improve speed of data collection and integration, this work presents an autonomous system based on Waspmote technologies build on single nodes interlinked in a Wireless Sensor Network (WSN) star-topology for ground based information collection and later integration with surveying data obtained by UAV. Nodes are designed to be visible from the air, to resist extreme weather conditions with low-power consumption. Besides, nodes are equipped with GPS as well as Inertial Measurement Unit (IMU), accelerometer, temperature and soil moisture sensors and thus provide significant advantages in a broad range of applications for environmental monitoring. For our purpose, the WSN transmits the environmental data with 3G/GPRS to a database on a regular time basis. This project provides a detailed case study and implementation of a Ground Control Point System Network for UAV-based vegetation monitoring of dry mountain grassland in the Matsch valley, Italy.

Geodesy in Antarctica: A pilot study based on the TAMDEF GPS network, Victoria Land, Antarctica

NASA Astrophysics Data System (ADS)

Vazquez Becerra, Guadalupe Esteban

The objective of the research presented in this dissertation is a combination of practical and theoretical problems to investigate unique aspects of GPS (Global Positioning System) geodesy in Antarctica. This is derived from a complete analysis of a GPS network called TAMDEF (Trans Antarctic Mountains Deformation), located in Victoria Land, Antarctica. In order to permit access to the International Terrestrial Reference Frame (ITRF), the McMurdo (MCM4) IGS (The International GNSS Service for Geodynamics, formerly the International GPS Service) site was adopted as part of the TAMDEF network. The following scientific achievements obtained from the cited analysis will be discussed as follows: (1) The GPS data processing for the TAMDEF network relied on the PAGES (Program for Adjustment of GPS Ephemerides) software that uses the double-differenced iono-free linear combination, which helps removing a big partial of bias (mm level) in the final positioning. (2) To validate the use of different antenna types in TAMDEF, an antenna testing experiment was conducted using the National Geodetic Survey (NGS) antenna calibration data, appropriate for each antenna type. Sub-daily and daily results from the antenna testing are at the sub-millimeter level, based on the fact that 24-hour solutions were used to average any possible bias. (3) A potential contributor that might have an impact on the TAMDEF stations positioning is the pseudorange multipath effect; thus, the root mean squared variations were estimated and analyzed in order to identify the most and least affected sites. MCM4 was found to be the site with highest multipath, and this is not good at all, since MCM4 is the primary ITRF access point for this part of Antarctica. Additionally, results from the pseudorange multipath can be used for further data cleaning to improve positioning results. (4) The Ocean Tide Modeling relied on the use of two models: CATS02.01 (Circum Antarctic Tidal Simulation) and TPXO6.2 (TOPEX/Poseidon) to investigate which model suits the Antarctic conditions best and its effect on the vertical coordinate component at the TAMDEF sites. (5) The scatter for the time-series results of the coordinate components for the TAMDEF sites are smaller when processed with respect to the Antarctic tectonic plate (Case I), in comparison with the other tectonic plates outside Antarctica (Case II-IV). Also, the seasonal effect due to the time-series seen in the TAMDEF sites with longer data span are site dependent; thus, data processing is not the reason for these effects. (6) Furthermore, the results coming from a homogeneous global network with coordinates referred and transformed to the ITRF2000 at epoch 2005.5 reflect the quality of the solution, obtained when processing TAMDEF network data with respect to the Antarctic tectonic plate. (7) An optimal data reduction strategy was developed, based on three different troposphere models and mapping functions, tested and used to estimate the total wet zenith delay (TWZD) which later was transformed to precipitable water vapor (PWV). PWV was estimated from GPS measurements and validated with a numerical weather model, AMPS (Antarctic Mesoscale Prediction System) and radiosonde PWV. Additionally, to validate the TWZD estimates at the MCM4 site before their conversion into the GPS PWV, these estimates were directly compared to TWZD computed by the CDDIS (Crustal Dynamics Data Information System) analysis center. (8) The results from the Least-Squares adjustment with Stochastic Constraints (SCLESS) as performed with PAGES are very comparable (mm-level) to those obtained from the alternative adjustment approaches: MINOLESS (Minimum-Norm Least-Squares adjustment); Partial-MINOLESS (Partial Minimum-Norm Least-Squares adjustment), and BLIMPBE (Best Linear Minimum Partial-Bias Estimation). Based on the applied network adjustment models within the Antarctic tectonic plate (Case I), it can be demonstrated that the GPS data used are clean of bias after proper care has been taken of ionosphere, troposphere, multipath, and some other sources that affect GPS positioning. Overall, it can be concluded that no suspected of bias was present in the obtained results, thus, GPS is indeed capable of capturing the signal which can be used for further geophysical interpretation within Antarctica.

Photogrammetry Tool for Forensic Analysis

NASA Technical Reports Server (NTRS)

Lane, John

2012-01-01

A system allows crime scene and accident scene investigators the ability to acquire visual scene data using cameras for processing at a later time. This system uses a COTS digital camera, a photogrammetry calibration cube, and 3D photogrammetry processing software. In a previous instrument developed by NASA, the laser scaling device made use of parallel laser beams to provide a photogrammetry solution in 2D. This device and associated software work well under certain conditions. In order to make use of a full 3D photogrammetry system, a different approach was needed. When using multiple cubes, whose locations relative to each other are unknown, a procedure that would merge the data from each cube would be as follows: 1. One marks a reference point on cube 1, then marks points on cube 2 as unknowns. This locates cube 2 in cube 1 s coordinate system. 2. One marks reference points on cube 2, then marks points on cube 1 as unknowns. This locates cube 1 in cube 2 s coordinate system. 3. This procedure is continued for all combinations of cubes. 4. The coordinate of all of the found coordinate systems is then merged into a single global coordinate system. In order to achieve maximum accuracy, measurements are done in one of two ways, depending on scale: when measuring the size of objects, the coordinate system corresponding to the nearest cube is used, or when measuring the location of objects relative to a global coordinate system, a merged coordinate system is used. Presently, traffic accident analysis is time-consuming and not very accurate. Using cubes with differential GPS would give absolute positions of cubes in the accident area, so that individual cubes would provide local photogrammetry calibration to objects near a cube.

Combination of Vlbi, GPS and Slr Observations At The Observation Level For The Realization of Terrestrial and Celestial Reference Frames

NASA Astrophysics Data System (ADS)

Andersen, P. H.

Forsvarets forskningsinstitutt (FFI, the Norwegian Defence Research Establishment) has during the last 17 years developed a software system called GEOSAT, for the analysis of any type of high precision space geodetic observations. A unique feature of GEOSAT is the possibility of combining any combination of different space geode- tic data at the observation level with one consistent model and one consistent strategy. This is a much better strategy than the strategy in use today where different types of observations are processed separately using analysis software developed specifically for each technique. The results from each technique are finally combined a posteriori. In practice the models implemented in the software packages differ at the 1-cm level which is almost one order of magnitude larger than the internal precision of the most precise techniques. Another advantage of the new proposed combination method is that for example VLBI and GPS can use the same tropospheric model with common parameterization. The same is the case for the Earth orientation parameters, the geo- center coordinates and other geodetic or geophysical parameters where VLBI, GPS and SLR can have a common estimate for each of the parameters. The analysis with GEOSAT is automated for the combination of VLBI, SLR and GPS observations. The data are analyzed in batches of one day where the result from each daily arc is a SRIF array (Square Root Information Filter). A large number of SRIF arrays can be combined into a multi-year solution using the CSRIFS program (Com- bination Square Root Information Filter and Smoother). Four parameter levels are available and any parameter can, at each level, either be represented as a constant or a stochastic parameter (white noise, colored noise, or random walk). The batch length (i.e. the time interval between the addition of noise to the SRIF array) can be made time- and parameter dependent. GEOSAT and CSRIFS have been applied in the analysis of selected VLBI and SLR data (LAGEOS I &II) from the period January 1993 to July 2001. A selected number of arcs also include GPS data. Earth orientation parameters, geocenter motion, sta- tion coordinates and velocities were estimated simultaneously with the coordinates of the radio sources and satellite orbital parameters. Recent software improvements and 1 results of analyses will be presented at the meeting. 2

Preliminary study of GPS orbit determination accuracy achievable from worldwide tracking data

NASA Technical Reports Server (NTRS)

Larden, D. R.; Bender, P. L.

1983-01-01

The improvement in the orbit accuracy if high accuracy tracking data from a substantially larger number of ground stations is available was investigated. Observations from 20 ground stations indicate that 20 cm or better accuracy can be achieved for the horizontal coordinates of the GPS satellites. With this accuracy, the contribution to the error budget for determining 1000 km baselines by GPS geodetic receivers would be only about 1 cm. Previously announced in STAR as N83-14605

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.

[Epidemics and pandemics in general practice. What can we learn from the swine flu (H1N1) and EHEC outbreak?].

PubMed

Eisele, M; Hansen, H; Wagner, H-O; von Leitner, E; Pohontsch, N; Scherer, M

2014-06-01

As primary care givers with a coordinating function, general practitioners (GP) play a key role in dealing with epidemics and pandemics. As of yet, there are no studies in Germany describing the difficulties experienced by GPs in patient care during epidemics/pandemics. This study aimed at identifying the problem areas in GPs' patient care during the H1N1 and EHEC (enterohemorrhagic strain of Escherichia coli) outbreaks. With this information, recommendations for guaranteeing proper patient care during future epidemics/pandemics can be derived. In all, 12 qualitative, semi-structured, open guideline interviews with GPs in Hamburg and Lübeck were conducted, transcribed, and evaluated with qualitative content analysis. Five areas in ambulatory patient care were identified in which changes are needed from the primary care perspective: provision of information for GPs, workload, financing of epidemic-related measures, organization of the practices, care of those taken ill. The workload of GPs in particular can and should be reduced through successful, centralized information distribution during epidemics/pandemics. The GP's function as a coordinator should be supported and consolidated, in order to relieve the in-patient sector in cases of an epidemic/pandemic. Secured financing of epidemic-associated measures can help ensure patient care.

SURMODERR: A MATLAB toolbox for estimation of velocity uncertainties of a non-permanent GPS station

NASA Astrophysics Data System (ADS)

Teza, Giordano; Pesci, Arianna; Casula, Giuseppe

2010-08-01

SURMODERR is a MATLAB toolbox intended for the estimation of reliable velocity uncertainties of a non-permanent GPS station (NPS), i.e. a GPS receiver used in campaign-style measurements. The implemented method is based on the subsampling of daily coordinate time series of one or more continuous GPS stations located inside or close to the area where the NPSs are installed. The continuous time series are subsampled according to real or planned occupation tables and random errors occurring in antenna replacement on different surveys are taken into account. In order to overcome the uncertainty underestimation that typically characterizes short duration GPS time series, statistical analysis of the simulated data is performed to estimate the velocity uncertainties of this real NPS. The basic hypotheses required are: (i) the signal must be a long-term linear trend plus seasonal and colored noise for each coordinate; (ii) the standard data processing should have already been performed to provide daily data series; and (iii) if the method is applied to survey planning, the future behavior should not be significantly different from the past behavior. In order to show the strength of the approach, two case studies with real data are presented and discussed (Central Apennine and Panarea Island, Italy).

The application of GPS precise point positioning technology in aerial triangulation

NASA Astrophysics Data System (ADS)

Yuan, Xiuxiao; Fu, Jianhong; Sun, Hongxing; Toth, Charles

In traditional GPS-supported aerotriangulation, differential GPS (DGPS) positioning technology is used to determine the 3-dimensional coordinates of the perspective centers at exposure time with an accuracy of centimeter to decimeter level. This method can significantly reduce the number of ground control points (GCPs). However, the establishment of GPS reference stations for DGPS positioning is not only labor-intensive and costly, but also increases the implementation difficulty of aerial photography. This paper proposes aerial triangulation supported with GPS precise point positioning (PPP) as a way to avoid the use of the GPS reference stations and simplify the work of aerial photography. Firstly, we present the algorithm for GPS PPP in aerial triangulation applications. Secondly, the error law of the coordinate of perspective centers determined using GPS PPP is analyzed. Thirdly, based on GPS PPP and aerial triangulation software self-developed by the authors, four sets of actual aerial images taken from surveying and mapping projects, different in both terrain and photographic scale, are given as experimental models. The four sets of actual data were taken over a flat region at a scale of 1:2500, a mountainous region at a scale of 1:3000, a high mountainous region at a scale of 1:32000 and an upland region at a scale of 1:60000 respectively. In these experiments, the GPS PPP results were compared with results obtained through DGPS positioning and traditional bundle block adjustment. In this way, the empirical positioning accuracy of GPS PPP in aerial triangulation can be estimated. Finally, the results of bundle block adjustment with airborne GPS controls from GPS PPP are analyzed in detail. The empirical results show that GPS PPP applied in aerial triangulation has a systematic error of half-meter level and a stochastic error within a few decimeters. However, if a suitable adjustment solution is adopted, the systematic error can be eliminated in GPS-supported bundle block adjustment. When four full GCPs are emplaced in the corners of the adjustment block, then the systematic error is compensated using a set of independent unknown parameters for each strip, the final result of the bundle block adjustment with airborne GPS controls from PPP is the same as that of bundle block adjustment with airborne GPS controls from DGPS. Although the accuracy of the former is a little lower than that of traditional bundle block adjustment with dense GCPs, it can still satisfy the accuracy requirement of photogrammetric point determination for topographic mapping at many scales.

Radio Frequency Identification (RFID) and communication technologies for solid waste bin and truck monitoring system.

PubMed

Hannan, M A; Arebey, Maher; Begum, R A; Basri, Hassan

2011-12-01

This paper deals with a system of integration of Radio Frequency Identification (RFID) and communication technologies for solid waste bin and truck monitoring system. RFID, GPS, GPRS and GIS along with camera technologies have been integrated and developed the bin and truck intelligent monitoring system. A new kind of integrated theoretical framework, hardware architecture and interface algorithm has been introduced between the technologies for the successful implementation of the proposed system. In this system, bin and truck database have been developed such a way that the information of bin and truck ID, date and time of waste collection, bin status, amount of waste and bin and truck GPS coordinates etc. are complied and stored for monitoring and management activities. The results showed that the real-time image processing, histogram analysis, waste estimation and other bin information have been displayed in the GUI of the monitoring system. The real-time test and experimental results showed that the performance of the developed system was stable and satisfied the monitoring system with high practicability and validity. Copyright © 2011 Elsevier Ltd. All rights reserved.

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.

Observation model and parameter partials for the JPL geodetic (GPS) modeling software 'GPSOMC'

NASA Technical Reports Server (NTRS)

Sovers, O. J.

1990-01-01

The physical models employed in GPSOMC, the modeling module of the GIPSY software system developed at JPL for analysis of geodetic Global Positioning Satellite (GPS) measurements are described. Details of the various contributions to range and phase observables are given, as well as the partial derivatives of the observed quantities with respect to model parameters. A glossary of parameters is provided to enable persons doing data analysis to identify quantities with their counterparts in the computer programs. The present version is the second revision of the original document which it supersedes. The modeling is expanded to provide the option of using Cartesian station coordinates; parameters for the time rates of change of universal time and polar motion are also introduced.

An Alternative Wearable Tracking System Based on a Low-Power Wide-Area Network

PubMed Central

Fernández-Garcia, Raul; Gil, Ignacio

2017-01-01

This work presents an alternative wearable tracking system based on a low-power wide area network. A complete GPS receiver was integrated with a textile substrate, and the latitude and longitude coordinates were sent to the cloud by means of the SIM-less SIGFOX network. To send the coordinates over SIGFOX protocol, a specific codification algorithm was used and a customized UHF antenna on jeans fabric was designed, simulated and tested. Moreover, to guarantee the compliance to international regulations for human body exposure to electromagnetic radiation, the electromagnetic specific absorption rate of this antenna was analyzed. A specific remote server was developed to decode the latitude and longitude coordinates. Once the coordinates have been decoded, the remote server sends this information to the open source data viewer SENTILO to show the location of the sensor node in a map. The functionality of this system has been demonstrated experimentally. The results guarantee the utility and wearability of the proposed tracking system for the development of sensor nodes and point out that it can be a low cost alternative to other commercial products based on GSM networks. PMID:28335424

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.

GPS Water Vapor Tomography Based on Accurate Estimations of the GPS Tropospheric Parameters

NASA Astrophysics Data System (ADS)

Champollion, C.; Masson, F.; Bock, O.; Bouin, M.; Walpersdorf, A.; Doerflinger, E.; van Baelen, J.; Brenot, H.

2003-12-01

The Global Positioning System (GPS) is now a common technique for the retrieval of zenithal integrated water vapor (IWV). Further applications in meteorology need also slant integrated water vapor (SIWV) which allow to precisely define the high variability of tropospheric water vapor at different temporal and spatial scales. Only precise estimations of IWV and horizontal gradients allow the estimation of accurate SIWV. We present studies developed to improve the estimation of tropospheric water vapor from GPS data. Results are obtained from several field experiments (MAP, ESCOMPTE, OHM-CV, IHOP, .). First IWV are estimated using different GPS processing strategies and results are compared to radiosondes. The role of the reference frame and the a priori constraints on the coordinates of the fiducial and local stations is generally underestimated. It seems to be of first order in the estimation of the IWV. Second we validate the estimated horizontal gradients comparing zenith delay gradients and single site gradients. IWV, gradients and post-fit residuals are used to construct slant integrated water delays. Validation of the SIWV is under progress comparing GPS SIWV, Lidar measurements and high resolution meteorological models (Meso-NH). A careful analysis of the post-fit residuals is needed to separate tropospheric signal from multipaths. The slant tropospheric delays are used to study the 3D heterogeneity of the troposphere. We develop a tomographic software to model the three-dimensional distribution of the tropospheric water vapor from GPS data. The software is applied to the ESCOMPTE field experiment, a dense network of 17 dual frequency GPS receivers operated in southern France. Three inversions have been successfully compared to three successive radiosonde launches. Good resolution is obtained up to heights of 3000 m.

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.

Calibration of the TOPEX altimeter using a GPS buoy

NASA Technical Reports Server (NTRS)

Born, G. H.; Parke, Michael E.; Axelrad, P.; Gold, K. L.; Johnson, James; Key, K.; Kubitschek, Daniel G.; Christensen, Edward J.

1994-01-01

The use of a spar buoy equipped with a Global Positioning System (GPS) antenna to calibrate the height measurement of the TOPEX radar altimeter is described. In order to determine the height of the GPS antenna phase center above the ocean surface, the buoy was also equipped with instrumentation to measure the instantaneous location of the waterline, and tilt of the bouy from vertical. The experiment was conducted off the California coast near the Texaco offshore oil platform, Harvest, during cycle 34 of the TOPEX/POSEIDON observational period. GPS solutions were computed for the bouy position using two different software packages, K&RS and GIPSY-OASIS II. These solutions were combined with estimates of the waterline location on the bouy to yield the height of the ocean surface. The ocean surface height in an absolute coordinate system combined with knowledge of the spacecraft height from tracking data provides a computed altimeter range measurement. By comparing this computed value to the actual altimeter measurement, the altimeter bias can be calibrated. The altimeter height bias obtained with the buoy using K&RS was -14.6 +/- 4 cm, while with GIPSY-OASIS II it was -13.1 +/- 4 cm. These are 0.1 cm and 1.6 cm different from the -14.7 +/- 4 cm result obtained for this flight overflight with the tide gauge instruments located on Platform Harvest.

Saved by Iridium? An Alternative to GPS

DTIC Science & Technology

2012-05-17

know this. The enemy presents itself at any time, at any place, in many shapes and forms, often for no apparent reason. As Ecclesiastes 9:18 states...system. It also marked the first coordinated Tomahawk and manned-aircraft strike in history . Within the first few minutes of Operation Desert Storm...These physical architectures correspond to ground operations in scenarios ranging from complete air superiority to completely denied airspace.”86 A

Global Positioning Systems (GPS) Technology to Study Vector-Pathogen-Host Interactions

DTIC Science & Technology

2013-10-01

objective of this project is to examine the evolutionary consequences of introducing a tetravalent live- attenuated dengue virus vaccine into children...interdisciplinary team of university and military investigators have conducted coordinated studies to determine the effect vaccination with a candidate...tetravalent vaccine will have on genetic changes on wild-type dengue virus and how these changes will determine risk for severe dengue and serotype-specific

Bioluminescence Truth Data Measurement and Signature Detection

DTIC Science & Technology

2006-01-01

bioluminescence activity and related forcing factors. Kilroy sensors are shown attached to pilings with the senor system below water and the cell phone based...communications module attached to the top of the piling. A cell phone tower represents communication of data to shore. Also shown are distributed...installation are located based on GPS coordinates telemetered by the cell phone module. Icons point in direction of most recently measured flow and

Atmospheric pressure loading effects on Global Positioning System coordinate determinations

NASA Technical Reports Server (NTRS)

Vandam, Tonie M.; Blewitt, Geoffrey; Heflin, Michael B.

1994-01-01

Earth deformation signals caused by atmospheric pressure loading are detected in vertical position estimates at Global Positioning System (GPS) stations. Surface displacements due to changes in atmospheric pressure account for up to 24% of the total variance in the GPS height estimates. The detected loading signals are larger at higher latitudes where pressure variations are greatest; the largest effect is observed at Fairbanks, Alaska (latitude 65 deg), with a signal root mean square (RMS) of 5 mm. Out of 19 continuously operating GPS sites (with a mean of 281 daily solutions per site), 18 show a positive correlation between the GPS vertical estimates and the modeled loading displacements. Accounting for loading reduces the variance of the vertical station positions on 12 of the 19 sites investigated. Removing the modeled pressure loading from GPS determinations of baseline length for baselines longer than 6000 km reduces the variance on 73 of the 117 baselines investigated. The slight increase in variance for some of the sites and baselines is consistent with expected statistical fluctuations. The results from most stations are consistent with approximately 65% of the modeled pressure load being found in the GPS vertical position measurements. Removing an annual signal from both the measured heights and the modeled load time series leaves this value unchanged. The source of the remaining discrepancy between the modeled and observed loading signal may be the result of (1) anisotropic effects in the Earth's loading response, (2) errors in GPS estimates of tropospheric delay, (3) errors in the surface pressure data, or (4) annual signals in the time series of loading and station heights. In addition, we find that using site dependent coefficients, determined by fitting local pressure to the modeled radial displacements, reduces the variance of the measured station heights as well as or better than using the global convolution sum.

How and Why to Do VLBI on GPS

NASA Technical Reports Server (NTRS)

Dickey, J. M.

2010-01-01

In order to establish the position of the center of mass of the Earth in the International Celestial Reference Frame, observations of the Global Positioning Satellite (GPS) constellation using the IVS network are important. With a good frame-tie between the coordinates of the IVS telescopes and nearby GPS receivers, plus a common local oscillator reference signal, it should be possible to observe and record simultaneously signals from the astrometric calibration sources and the GPS satellites. The standard IVS solution would give the atmospheric delay and clock offsets to use in analysis of the GPS data. Correlation of the GPS signals would then give accurate orbital parameters of the satellites in the ICRF reference frame, i.e., relative to the positions of the astrometric sources. This is particularly needed to determine motion of the center of mass of the earth along the rotation axis.

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.

Joint Space Forces in Theater: Coordination is No Longer Sufficient

DTIC Science & Technology

2007-04-01

importantly, I am indebted to my wife, Caroline , and twin boys Joshua and Justin for their encouragement and constant reminders about what is truly...of GPS guided JDAMs fundamentally changed the American way of war. Lieutenant General Daniel Leaf , Air Component Coordination Element Commander

Accuracy of WAAS-Enabled GPS-RF Warning Signals When Crossing a Terrestrial Geofence

PubMed Central

Grayson, Lindsay M.; Keefe, Robert F.; Tinkham, Wade T.; Eitel, Jan U. H.; Saralecos, Jarred D.; Smith, Alistair M. S.; Zimbelman, Eloise G.

2016-01-01

Geofences are virtual boundaries based on geographic coordinates. When combined with global position system (GPS), or more generally global navigation satellite system (GNSS) transmitters, geofences provide a powerful tool for monitoring the location and movements of objects of interest through proximity alarms. However, the accuracy of geofence alarms in GNSS-radio frequency (GNSS-RF) transmitter receiver systems has not been tested. To achieve these goals, a cart with a GNSS-RF locator was run on a straight path in a balanced factorial experiment with three levels of cart speed, three angles of geofence intersection, three receiver distances from the track, and three replicates. Locator speed, receiver distance and geofence intersection angle all affected geofence alarm accuracy in an analysis of variance (p = 0.013, p = 2.58 × 10−8, and p = 0.0006, respectively), as did all treatment interactions (p < 0.0001). Slower locator speed, acute geofence intersection angle, and closest receiver distance were associated with reduced accuracy of geofence alerts. PMID:27322287

Accuracy of WAAS-Enabled GPS-RF Warning Signals When Crossing a Terrestrial Geofence.

PubMed

Grayson, Lindsay M; Keefe, Robert F; Tinkham, Wade T; Eitel, Jan U H; Saralecos, Jarred D; Smith, Alistair M S; Zimbelman, Eloise G

2016-06-18

Geofences are virtual boundaries based on geographic coordinates. When combined with global position system (GPS), or more generally global navigation satellite system (GNSS) transmitters, geofences provide a powerful tool for monitoring the location and movements of objects of interest through proximity alarms. However, the accuracy of geofence alarms in GNSS-radio frequency (GNSS-RF) transmitter receiver systems has not been tested. To achieve these goals, a cart with a GNSS-RF locator was run on a straight path in a balanced factorial experiment with three levels of cart speed, three angles of geofence intersection, three receiver distances from the track, and three replicates. Locator speed, receiver distance and geofence intersection angle all affected geofence alarm accuracy in an analysis of variance (p = 0.013, p = 2.58 × 10(-8), and p = 0.0006, respectively), as did all treatment interactions (p < 0.0001). Slower locator speed, acute geofence intersection angle, and closest receiver distance were associated with reduced accuracy of geofence alerts.

Seasonal Mass Changes and Crustal Vertical Deformations Constrained by GPS and GRACE in Northeastern Tibet

PubMed Central

Pan, Yuanjin; Shen, Wen-Bin; Hwang, Cheinway; Liao, Chaoming; Zhang, Tengxu; Zhang, Guoqing

2016-01-01

Surface vertical deformation includes the Earth’s elastic response to mass loading on or near the surface. Continuous Global Positioning System (CGPS) stations record such deformations to estimate seasonal and secular mass changes. We used 41 CGPS stations to construct a time series of coordinate changes, which are decomposed by empirical orthogonal functions (EOFs), in northeastern Tibet. The first common mode shows clear seasonal changes, indicating seasonal surface mass re-distribution around northeastern Tibet. The GPS-derived result is then assessed in terms of the mass changes observed in northeastern Tibet. The GPS-derived common mode vertical change and the stacked Gravity Recovery and Climate Experiment (GRACE) mass change are consistent, suggesting that the seasonal surface mass variation is caused by changes in the hydrological, atmospheric and non-tidal ocean loads. The annual peak-to-peak surface mass changes derived from GPS and GRACE results show seasonal oscillations in mass loads, and the corresponding amplitudes are between 3 and 35 mm/year. There is an apparent gradually increasing gravity between 0.1 and 0.9 μGal/year in northeast Tibet. Crustal vertical deformation is determined after eliminating the surface load effects from GRACE, without considering Glacial Isostatic Adjustment (GIA) contribution. It reveals crustal uplift around northeastern Tibet from the corrected GPS vertical velocity. The unusual uplift of the Longmen Shan fault indicates tectonically sophisticated processes in northeastern Tibet. PMID:27490550

Multi-GNSS phase delay estimation and PPP ambiguity resolution: GPS, BDS, GLONASS, Galileo

NASA Astrophysics Data System (ADS)

Li, Xingxing; Li, Xin; Yuan, Yongqiang; Zhang, Keke; Zhang, Xiaohong; Wickert, Jens

2017-10-01

This paper focuses on the precise point positioning (PPP) ambiguity resolution (AR) using the observations acquired from four systems: GPS, BDS, GLONASS, and Galileo (GCRE). A GCRE four-system uncalibrated phase delay (UPD) estimation model and multi-GNSS undifferenced PPP AR method were developed in order to utilize the observations from all systems. For UPD estimation, the GCRE-combined PPP solutions of the globally distributed MGEX and IGS stations are performed to obtain four-system float ambiguities and then UPDs of GCRE satellites can be precisely estimated from these ambiguities. The quality of UPD products in terms of temporal stability and residual distributions is investigated for GPS, BDS, GLONASS, and Galileo satellites, respectively. The BDS satellite-induced code biases were corrected for GEO, IGSO, and MEO satellites before the UPD estimation. The UPD results of global and regional networks were also evaluated for Galileo and BDS, respectively. As a result of the frequency-division multiple-access strategy of GLONASS, the UPD estimation was performed using a network of homogeneous receivers including three commonly used GNSS receivers (TRIMBLE NETR9, JAVAD TRE_G3TH DELTA, and LEICA). Data recorded from 140 MGEX and IGS stations for a 30-day period in January in 2017 were used to validate the proposed GCRE UPD estimation and multi-GNSS dual-frequency PPP AR. Our results show that GCRE four-system PPP AR enables the fastest time to first fix (TTFF) solutions and the highest accuracy for all three coordinate components compared to the single and dual system. An average TTFF of 9.21 min with 7{°} cutoff elevation angle can be achieved for GCRE PPP AR, which is much shorter than that of GPS (18.07 min), GR (12.10 min), GE (15.36 min) and GC (13.21 min). With observations length of 10 min, the positioning accuracy of the GCRE fixed solution is 1.84, 1.11, and 1.53 cm, while the GPS-only result is 2.25, 1.29, and 9.73 cm for the east, north, and vertical components, respectively. When the cutoff elevation angle is increased to 30{°} , the GPS-only PPP AR results are very unreliable, while 13.44 min of TTFF is still achievable for GCRE four-system solutions.

Multi-GNSS phase delay estimation and PPP ambiguity resolution: GPS, BDS, GLONASS, Galileo

NASA Astrophysics Data System (ADS)

Li, Xingxing; Li, Xin; Yuan, Yongqiang; Zhang, Keke; Zhang, Xiaohong; Wickert, Jens

2018-06-01

This paper focuses on the precise point positioning (PPP) ambiguity resolution (AR) using the observations acquired from four systems: GPS, BDS, GLONASS, and Galileo (GCRE). A GCRE four-system uncalibrated phase delay (UPD) estimation model and multi-GNSS undifferenced PPP AR method were developed in order to utilize the observations from all systems. For UPD estimation, the GCRE-combined PPP solutions of the globally distributed MGEX and IGS stations are performed to obtain four-system float ambiguities and then UPDs of GCRE satellites can be precisely estimated from these ambiguities. The quality of UPD products in terms of temporal stability and residual distributions is investigated for GPS, BDS, GLONASS, and Galileo satellites, respectively. The BDS satellite-induced code biases were corrected for GEO, IGSO, and MEO satellites before the UPD estimation. The UPD results of global and regional networks were also evaluated for Galileo and BDS, respectively. As a result of the frequency-division multiple-access strategy of GLONASS, the UPD estimation was performed using a network of homogeneous receivers including three commonly used GNSS receivers (TRIMBLE NETR9, JAVAD TRE_G3TH DELTA, and LEICA). Data recorded from 140 MGEX and IGS stations for a 30-day period in January in 2017 were used to validate the proposed GCRE UPD estimation and multi-GNSS dual-frequency PPP AR. Our results show that GCRE four-system PPP AR enables the fastest time to first fix (TTFF) solutions and the highest accuracy for all three coordinate components compared to the single and dual system. An average TTFF of 9.21 min with 7{°} cutoff elevation angle can be achieved for GCRE PPP AR, which is much shorter than that of GPS (18.07 min), GR (12.10 min), GE (15.36 min) and GC (13.21 min). With observations length of 10 min, the positioning accuracy of the GCRE fixed solution is 1.84, 1.11, and 1.53 cm, while the GPS-only result is 2.25, 1.29, and 9.73 cm for the east, north, and vertical components, respectively. When the cutoff elevation angle is increased to 30{°}, the GPS-only PPP AR results are very unreliable, while 13.44 min of TTFF is still achievable for GCRE four-system solutions.

Ppp Analisys with GPS and Glonass Integration in Periods Under Ionospheric Scintillation Effects

NASA Astrophysics Data System (ADS)

Marques, H. A. S.

2015-12-01

The GNSS is widely used nowadays either for geodetic positioning or scientific purposes. The GNSS currently includes GPS, GLONASS, Galileo among other emerging systems. The GPS and GLONASS are currently operational with a full satellite constellation. The GPS is still the most used nowadays and both GPS and GLONASS are under a modernization process. The geodetic positioning by using data from multi-constellation can provide better accuracy in positioning and also more reliability. The PPP is benefited once the satellite geometry is crucial in this method, mainly for kinematic scenarios. The satellite geometry can change suddenly for data collected in urban areas or in conditions of strong atmospheric effects such as Ionospheric Scintillation (IS) that causes weakening of signals with cycle slips and even loss of lock. The IS is caused by small irregularities in the ionosphere layer and is characterized by rapid change in amplitude and phase of the signal being stronger in equatorial and high latitudes regions. In this work the PPP is evaluated with GPS and GLONASS data collected by monitoring receivers from Brazilian CIGALA/CALIBRA network under IS conditions. The PPP processing was accomplished by using the GPSPPP software provided by Natural Resources Canadian (NRCAN). The IS effects were analyzed taking account the S4 and PHI60 indices. Considering periods with moderate IS effects, the use of only GPS data in the PPP presented several peaks in the coordinate time series due to cycle slips and loos of lock. In cycle slip conditions the ambiguity parameter are reinitialized by GPSPPP and considering loss of lock few satellites can be available in some epochs affecting the positioning geometry and consequently decreasing accuracy. In such situations, the PPP using GPS and GLONASS data presented improvements in positioning accuracy of the order to 70% in height component when compared with PPP using only GPS data. Analyses of GDOP and ambiguities parameters were also performed.

A signal strength priority based position estimation for mobile platforms

NASA Astrophysics Data System (ADS)

Kalgikar, Bhargav; Akopian, David; Chen, Philip

2010-01-01

Global Positioning System (GPS) products help to navigate while driving, hiking, boating, and flying. GPS uses a combination of orbiting satellites to determine position coordinates. This works great in most outdoor areas, but the satellite signals are not strong enough to penetrate inside most indoor environments. As a result, a new strain of indoor positioning technologies that make use of 802.11 wireless LANs (WLAN) is beginning to appear on the market. In WLAN positioning the system either monitors propagation delays between wireless access points and wireless device users to apply trilateration techniques or it maintains the database of location-specific signal fingerprints which is used to identify the most likely match of incoming signal data with those preliminary surveyed and saved in the database. In this paper we investigate the issue of deploying WLAN positioning software on mobile platforms with typically limited computational resources. We suggest a novel received signal strength rank order based location estimation system to reduce computational loads with a robust performance. The proposed system performance is compared to conventional approaches.

Sensors for isolation of anti-cancer compounds found within marine invertebrates

NASA Astrophysics Data System (ADS)

Wiegand, Gordon; LaRue, Amanda

2015-05-01

Highly evolved bacteria living within immobile marine animals are being targeted as a source of antitumor pharmaceuticals. This paper describes 2 electo-optical sensor systems developed for identifying species of tunicates and actinobacteria that live within them. Two stages of identification include 1) a benthic survey apparatus to locate species and 2) a laboratory housed cell analysis platform used to classify their bacterial micro-biome. Marine Optics Sampling- There are over 3000 species of Tunicates that thrive in diverse habitats. We use a system of cameras, GPS and the GPS/photo integration application on a PC laptop to compile a time / location stamp for each image taken during the dive survey. A shape-map of x/y coordinates of photos are stored for later identification and sampling. Flow Cytometers/cell sorters housed at The Medical University of South Carolina and The University of Maryland have been modified to produce low-noise, high signal wave forms used for bacteria analysis. We strive to describe salient contrasts between these two fundamentally different sensor systems. Accents are placed on analog transducers and initial step sensing systems and output.

Spatiotemporal Filtering Using Principal Component Analysis and Karhunen-Loeve Expansion Approaches for Regional GPS Network Analysis

NASA Technical Reports Server (NTRS)

Dong, D.; Fang, P.; Bock, F.; Webb, F.; Prawirondirdjo, L.; Kedar, S.; Jamason, P.

2006-01-01

Spatial filtering is an effective way to improve the precision of coordinate time series for regional GPS networks by reducing so-called common mode errors, thereby providing better resolution for detecting weak or transient deformation signals. The commonly used approach to regional filtering assumes that the common mode error is spatially uniform, which is a good approximation for networks of hundreds of kilometers extent, but breaks down as the spatial extent increases. A more rigorous approach should remove the assumption of spatially uniform distribution and let the data themselves reveal the spatial distribution of the common mode error. The principal component analysis (PCA) and the Karhunen-Loeve expansion (KLE) both decompose network time series into a set of temporally varying modes and their spatial responses. Therefore they provide a mathematical framework to perform spatiotemporal filtering.We apply the combination of PCA and KLE to daily station coordinate time series of the Southern California Integrated GPS Network (SCIGN) for the period 2000 to 2004. We demonstrate that spatially and temporally correlated common mode errors are the dominant error source in daily GPS solutions. The spatial characteristics of the common mode errors are close to uniform for all east, north, and vertical components, which implies a very long wavelength source for the common mode errors, compared to the spatial extent of the GPS network in southern California. Furthermore, the common mode errors exhibit temporally nonrandom patterns.

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 GPS Data Collected on the Greenland Ice Sheet

NASA Technical Reports Server (NTRS)

Larson, K.; Plumb, J.; Zwally, J.; Abdalati, W.; Koblinsky, Chester J. (Technical Monitor)

2001-01-01

For several years, GPS observations have been made year round at the Swiss Camp, Greenland. The GPS data are recorded for 12 hours every 10-15 days; data are stored in memory and downloaded during the annual field season. Traditional GPS analysis techniques, where the receiver is assumed not to move within a 24 hour period, is not appropriate at the Swiss Camp, where horizontal velocities are on the order of 30 cm/day. Comparison of analysis strategies for these GPS data indicate that a random walk parameterization, with a constraint of 1-2 x 10(exp -7) km/sqrt(sec) minimizes noise due to satellite outages without corrupting the estimated ice velocity. Low elevation angle observations should be included in the analysis in order to increase the number of satellites viewed at each data epoch. Carrier phase ambiguity resolution is important for improving the accuracy of receiver coordinates.

Measuring the Earth to within an inch using GPS satellites

NASA Astrophysics Data System (ADS)

Blewitt, Geoffrey

1992-01-01

A recently developed technique for “measuring the Earth” was demonstrated in 1991 using data from an experiment involving a world-wide network of receivers that track satellites of the Global Positioning System (GPS). Recent results indicate that distances between points separated by as much as 10,000 km on the surface of the Earth can be determined at the 2 cm level, and that the position of the pole of rotation at the Earth's surface can be estimated daily to better than 2 cm. Achieving this level of accuracy in a reliable, economical way is an important step towards building our understanding of the Earth as a rotating, deforming body.Funded by NASA's Solid Earth Science Program, the Jet Propulsion Laboratory coordinated participation of many international institutions in a 3-week experiment in January-February 1991 called GPS for International Earth Rotation Service (IERS) and Geodynamics '91 (GIG'91). Twenty-one receivers developed by J PL and scores of commercial receivers were simultaneously deployed. Several independent groups around the world analyzed the data and presented results at meetings in the summer and fall of 1991.

Global Plate Velocities from the Global Positioning System

NASA Technical Reports Server (NTRS)

Larson, Kristine M.; Freymueller, Jeffrey T.; Philipsen, Steven

1997-01-01

We have analyzed 204 days of Global Positioning System (GPS) data from the global GPS network spanning January 1991 through March 1996. On the basis of these GPS coordinate solutions, we have estimated velocities for 38 sites, mostly located on the interiors of the Africa, Antarctica, Australia, Eurasia, Nazca, North America, Pacific, and South America plates. The uncertainties of the horizontal velocity components range from 1.2 to 5.0 mm/yr. With the exception of sites on the Pacific and Nazca plates, the GPS velocities agree with absolute plate model predictions within 95% confidence. For most of the sites in North America, Antarctica, and Eurasia, the agreement is better than 2 mm/yr. We find no persuasive evidence for significant vertical motions (less than 3 standard deviations), except at four sites. Three of these four were sites constrained to geodetic reference frame velocities. The GPS velocities were then used to estimate angular velocities for eight tectonic plates. Absolute angular velocities derived from the GPS data agree with the no net rotation (NNR) NUVEL-1A model within 95% confidence except for the Pacific plate. Our pole of rotation for the Pacific plate lies 11.5 deg west of the NNR NUVEL-1A pole, with an angular speed 10% faster. Our relative angular velocities agree with NUVEL-1A except for some involving the Pacific plate. While our Pacific-North America angular velocity differs significantly from NUVEL-1A, our model and NUVEL-1A predict very small differences in relative motion along the Pacific-North America plate boundary itself. Our Pacific-Australia and Pacific- Eurasia angular velocities are significantly faster than NUVEL-1A, predicting more rapid convergence at these two plate boundaries. Along the East Pacific Pise, our Pacific-Nazca angular velocity agrees in both rate and azimuth with NUVFL-1A.

Variability in Hurricane Boundary Layer Characteristics Observed in a Long-Term Noaa Dropsonde Archive

DTIC Science & Technology

2014-06-01

storm-relative coordinate transformation; each green circle represents the Ziemba (2013) estimate of ix dropsonde position. A thick red vector...LIST OF TABLES Table 1. Specifications and estimated operational performance of the NCAR GPS dropsonde (from Ziemba 2013; after H99...BLANK 16 III. DATA AND METHODOLOGY A. THE NCAR GPS DROPSONDE Recent observational studies of tropical cyclones (e.g., Z11; Ziemba 2013) have

A Low Cost Automated Monitoring System for Landslides Using Dual Frequency GPS

NASA Astrophysics Data System (ADS)

Mills, H.; Edwards, S.

2006-12-01

Landslides are an existing and permanent threat to societies across the globe, generating financial and human losses whenever and wherever they occur. Drawing together the strands of science that provide increased understanding of landslide triggers through accurate modelling is therefore vital for the development of mitigation and management strategies. Together with climatic and geomorphological data a key input here is information on the precise location and timing of landslide events. However, the detailed monitoring of landslides and precursor movements is generally limited to episodic campaigns where limiting factors include equipment and mobilisation costs, time constraints and spatial resolution. This research has developed a geodetic tool of benefit to scientists involved in the development of closely coupled models that seek to explain trigger mechanisms such as rainfall duration and intensity and changes in groundwater pressure to actual real land movements. A fully automated low cost dual frequency GPS station for the continuous in-situ monitoring of landslide sites has been developed. System configuration combines a dual frequency GPS receiver, PC board with a GPRS modem and power supply to deliver 24hr/365day operation capability. Individual components have been chosen to provide the highest accuracies while minimising power consumption resulting in a system around half that of equivalent commercial systems. Measurement point-costs can be further reduced through the use of antenna switching and multi antenna arrays. Continuous data is delivered via mobile phone uplink and processed automatically using geodetic software. The developed system has been extensively tested on a purpose built platform capable of simulating ground movements. Co-mounted antennas have allowed direct comparisons with more expensive geodetic GPS receivers. The system is capable of delivering precise 3D coordinates with a 9 mm rms. The system can be up-scaled resulting in the increased spatial density of monitoring and yielding more detailed information on landslide movements for improved downstream modelling and monitoring.

Localization Based on Magnetic Markers for an All-Wheel Steering Vehicle

PubMed Central

Byun, Yeun Sub; Kim, Young Chol

2016-01-01

Real-time continuous localization is a key technology in the development of intelligent transportation systems. In these systems, it is very important to have accurate information about the position and heading angle of the vehicle at all times. The most widely implemented methods for positioning are the global positioning system (GPS), vision-based system, and magnetic marker system. Among these methods, the magnetic marker system is less vulnerable to indoor and outdoor environment conditions; moreover, it requires minimal maintenance expenses. In this paper, we present a position estimation scheme based on magnetic markers and odometry sensors for an all-wheel-steering vehicle. The heading angle of the vehicle is determined by using the position coordinates of the last two detected magnetic markers and odometer data. The instant position and heading angle of the vehicle are integrated with an extended Kalman filter to estimate the continuous position. GPS data with the real-time kinematics mode was obtained to evaluate the performance of the proposed position estimation system. The test results show that the performance of the proposed localization algorithm is accurate (mean error: 3 cm; max error: 9 cm) and reliable under unexpected missing markers or incorrect markers. PMID:27916827

Geomagnetic Storm Impact On GPS Code Positioning

NASA Astrophysics Data System (ADS)

Uray, Fırat; Varlık, Abdullah; Kalaycı, İbrahim; Öǧütcü, Sermet

2017-04-01

This paper deals with the geomagnetic storm impact on GPS code processing with using GIPSY/OASIS research software. 12 IGS stations in mid-latitude were chosen to conduct the experiment. These IGS stations were classified as non-cross correlation receiver reporting P1 and P2 (NONCC-P1P2), non-cross correlation receiver reporting C1 and P2 (NONCC-C1P2) and cross-correlation (CC-C1P2) receiver. In order to keep the code processing consistency between the classified receivers, only P2 code observations from the GPS satellites were processed. Four extreme geomagnetic storms October 2003, day of the year (DOY), 29, 30 Halloween Storm, November 2003, DOY 20, November 2004, DOY 08 and four geomagnetic quiet days in 2005 (DOY 92, 98, 99, 100) were chosen for this study. 24-hour rinex data of the IGS stations were processed epoch-by-epoch basis. In this way, receiver clock and Earth Centered Earth Fixed (ECEF) Cartesian Coordinates were solved for a per-epoch basis for each day. IGS combined broadcast ephemeris file (brdc) were used to partly compensate the ionospheric effect on the P2 code observations. There is no tropospheric model was used for the processing. Jet Propulsion Laboratory Application Technology Satellites (JPL ATS) computed coordinates of the stations were taken as true coordinates. The differences of the computed ECEF coordinates and assumed true coordinates were resolved to topocentric coordinates (north, east, up). Root mean square (RMS) errors for each component were calculated for each day. The results show that two-dimensional and vertical accuracy decreases significantly during the geomagnetic storm days comparing with the geomagnetic quiet days. It is observed that vertical accuracy is much more affected than the horizontal accuracy by geomagnetic storm. Up to 50 meters error in vertical component has been observed in geomagnetic storm day. It is also observed that performance of Klobuchar ionospheric correction parameters during geomagnetic storm days cannot guarantee the improving accuracy due to the ionospheric scintillation.

Develop Direct Geo-referencing System Based on Open Source Software and Hardware Platform

NASA Astrophysics Data System (ADS)

Liu, H. S.; Liao, H. M.

2015-08-01

Direct geo-referencing system uses the technology of remote sensing to quickly grasp images, GPS tracks, and camera position. These data allows the construction of large volumes of images with geographic coordinates. So that users can be measured directly on the images. In order to properly calculate positioning, all the sensor signals must be synchronized. Traditional aerial photography use Position and Orientation System (POS) to integrate image, coordinates and camera position. However, it is very expensive. And users could not use the result immediately because the position information does not embed into image. To considerations of economy and efficiency, this study aims to develop a direct geo-referencing system based on open source software and hardware platform. After using Arduino microcontroller board to integrate the signals, we then can calculate positioning with open source software OpenCV. In the end, we use open source panorama browser, panini, and integrate all these to open source GIS software, Quantum GIS. A wholesome collection of data - a data processing system could be constructed.

Temporal–Spatial Surface Seasonal Mass Changes and Vertical Crustal Deformation in South China Block from GPS and GRACE Measurements

PubMed Central

He, Meilin; Shen, Wenbin; Chen, Ruizhi; Ding, Hao; Guo, Guangyi

2017-01-01

The solid Earth deforms elastically in response to variations of surface atmosphere, hydrology, and ice/glacier mass loads. Continuous geodetic observations by Global Positioning System (CGPS) stations and Gravity Recovery and Climate Experiment (GRACE) record such deformations to estimate seasonal and secular mass changes. In this paper, we present the seasonal variation of the surface mass changes and the crustal vertical deformation in the South China Block (SCB) identified by GPS and GRACE observations with records spanning from 1999 to 2016. We used 33 CGPS stations to construct a time series of coordinate changes, which are decomposed by empirical orthogonal functions (EOFs) in SCB. The average weighted root-mean-square (WRMS) reduction is 38% when we subtract GRACE-modeled vertical displacements from GPS time series. The first common mode shows clear seasonal changes, indicating seasonal surface mass re-distribution in and around the South China Block. The correlation between GRACE and GPS time series is analyzed which provides a reference for further improvement of the seasonal variation of CGPS time series. The results of the GRACE observations inversion are the surface deformations caused by the surface mass change load at a rate of about −0.4 to −0.8 mm/year, which is used to improve the long-term trend of non-tectonic loads of the GPS vertical velocity field to further explain the crustal tectonic movement in the SCB and surroundings. PMID:29301236

A generic sun-tracking algorithm for on-axis solar collector in mobile platforms

NASA Astrophysics Data System (ADS)

Lai, An-Chow; Chong, Kok-Keong; Lim, Boon-Han; Ho, Ming-Cheng; Yap, See-Hao; Heng, Chun-Kit; Lee, Jer-Vui; King, Yeong-Jin

2015-04-01

This paper proposes a novel dynamic sun-tracking algorithm which allows accurate tracking of the sun for both non-concentrated and concentrated photovoltaic systems located on mobile platforms to maximize solar energy extraction. The proposed algorithm takes not only the date, time, and geographical information, but also the dynamic changes of coordinates of the mobile platforms into account to calculate the sun position angle relative to ideal azimuth-elevation axes in real time using general sun-tracking formulas derived by Chong and Wong. The algorithm acquires data from open-loop sensors, i.e. global position system (GPS) and digital compass, which are readily available in many off-the-shelf portable gadgets, such as smart phone, to instantly capture the dynamic changes of coordinates of mobile platforms. Our experiments found that a highly accurate GPS is not necessary as the coordinate changes of practical mobile platforms are not fast enough to produce significant differences in the calculation of the incident angle. On the contrary, it is critical to accurately identify the quadrant and angle where the mobile platforms are moving toward in real time, which can be resolved by using digital compass. In our implementation, a noise filtering mechanism is found necessary to remove unexpected spikes in the readings of the digital compass to ensure stability in motor actuations and effectiveness in continuous tracking. Filtering mechanisms being studied include simple moving average and linear regression; the results showed that a compound function of simple moving average and linear regression produces a better outcome. Meanwhile, we found that a sampling interval is useful to avoid excessive motor actuations and power consumption while not sacrificing the accuracy of sun-tracking.

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.

Ocean dynamics during the passage of Xynthia storm recorded by GPS

NASA Astrophysics Data System (ADS)

Nicolas, Joëlle; Ferenc, Marcell; Li, Zhao; van Dam, Tonie; Polidori, Laurent

2014-05-01

When computing the effect of atmospheric loading on geodetic coordinates, we must assign the response of the ocean to pressure loading. A pure inverted barometer and a solid Earth ocean response to pressure loading define the extremes of the response. At periods longer than a few days, the inverted barometer response is sufficient (Wunsch and Stammer, 1997). However, how does the ocean respond to fast moving storms? In this study we investigate the effect of a violent storm that progressed over Western Europe between the 27th of February and the 1st of March 2010 on sub-daily vertical GPS (Global Positioning System) position time series of the French GNSS permanent network (RGP). Xynthia was a huge low-pressure system (pressure drop of 40 mbar and a storm surge of 1.4 m (at La Rochelle tide gauge)) that crossed France from the southwest to the northeast over the course of about 20 hours. We study the different behaviour of the coastal and inland sites based on the comparison of the estimated 6-hourly stand-alone GPS position time series (GINS-PC software) with the local pressure and the predicted atmospheric pressure loading time series derived from the high resolution Modern-Era Retrospective Analysis for Research and Applications (NASA MERRA) and also the European Centre for Medium-Range Weather Forecasts (ECMWF) global dataset. We model the predicted displacements using the inverse barometer (IB) and the non-IB ocean response cases as endpoints. Predicted loading effects due to the atmospheric pressure and IB ocean reach up to 1.0, 1.3 and 13.7 mm for the east, north and up components, respectively. Then we attempt to use the GPS vertical surface displacements, the surface pressure, and tide gauge data (SONEL) to identify the true ocean dynamics on the continental shelf during the passage of this fast moving system. Keywords: GPS, GINS-PC, Xynthia, ocean dynamics, atmospheric pressure loading, deformation

Lane Level Localization; Using Images and HD Maps to Mitigate the Lateral Error

NASA Astrophysics Data System (ADS)

Hosseinyalamdary, S.; Peter, M.

2017-05-01

In urban canyon where the GNSS signals are blocked by buildings, the accuracy of measured position significantly deteriorates. GIS databases have been frequently utilized to improve the accuracy of measured position using map matching approaches. In map matching, the measured position is projected to the road links (centerlines) in this approach and the lateral error of measured position is reduced. By the advancement in data acquision approaches, high definition maps which contain extra information, such as road lanes are generated. These road lanes can be utilized to mitigate the positional error and improve the accuracy in position. In this paper, the image content of a camera mounted on the platform is utilized to detect the road boundaries in the image. We apply color masks to detect the road marks, apply the Hough transform to fit lines to the left and right road boundaries, find the corresponding road segment in GIS database, estimate the homography transformation between the global and image coordinates of the road boundaries, and estimate the camera pose with respect to the global coordinate system. The proposed approach is evaluated on a benchmark. The position is measured by a smartphone's GPS receiver, images are taken from smartphone's camera and the ground truth is provided by using Real-Time Kinematic (RTK) technique. Results show the proposed approach significantly improves the accuracy of measured GPS position. The error in measured GPS position with average and standard deviation of 11.323 and 11.418 meters is reduced to the error in estimated postion with average and standard deviation of 6.725 and 5.899 meters.

Ionospheric holes made by ballistic missiles from North Korea detected with a Japanese dense GPS array

NASA Astrophysics Data System (ADS)

Ozeki, Masaru; Heki, Kosuke

2010-09-01

A dense array of global positioning system (GPS) receivers is a useful tool to study ionospheric disturbances. Here we report observations by a Japanese GPS array of ionospheric holes, i.e., localized electron depletion. They were made by neutral molecules in exhaust plumes (e.g., water) of ballistic missiles from North Korea, Taepodong-1 and -2, launched on 31 August, 1998, and 5 April, 2009, respectively. Negative anomaly of electron density emerged ˜6 min after the launches in the middle of the Japan Sea, and extended eastward along the missile tracks. By comparing the numerical simulation of electron depletion and the observed change in ionospheric total electron content, we suggest that the exhaust plumes from the Taepodong-2 second stage effused up to ˜1.5 × 1026 water molecules per second. The ionospheric hole signature was used to constrain the Taepodong-2 trajectory together with other information, e.g., coordinates of the launch pad, time and coordinates of the first stage splashdown, and height and time of the second stage passage over Japan. The Taepodong-2 is considered to have reached the ionospheric F region in ˜6 min, flown above northeastern Japan ˜7 min after the launch, and crashed to the Pacific Ocean without attaining the first astronautical velocity. The ionospheric hole in the 1998 Taepodong-1 launch was much less in size, but it is difficult to compare directly the thrusts of the two missiles due to uncertainty of the Taepodong-1 trajectory.

Volcano monitoring using the Global Positioning System: Filtering strategies

USGS Publications Warehouse

Larson, K.M.; Cervelli, Peter; Lisowski, M.; Miklius, Asta; Segall, P.; Owen, S.

2001-01-01

Permanent Global Positioning System (GPS) networks are routinely used for producing improved orbits and monitoring secular tectonic deformation. For these applications, data are transferred to an analysis center each day and routinely processed in 24-hour segments. To use GPS for monitoring volcanic events, which may last only a few hours, real-time or near real-time data processing and subdaily position estimates are valuable. Strategies have been researched for obtaining station coordinates every 15 min using a Kalman filter; these strategies have been tested on data collected by a GPS network on Kilauea Volcano. Data from this network are tracked continuously, recorded every 30 s, and telemetered hourly to the Hawaiian Volcano Observatory. A white noise model is heavily impacted by data outages and poor satellite geometry, but a properly constrained random walk model fits the data well. Using a borehole tiltmeter at Kilauea's summit as ground-truth, solutions using different random walk constraints were compared. This study indicates that signals on the order of 5 mm/h are resolvable using a random walk standard deviation of 0.45 cm/???h. Values lower than this suppress small signals, and values greater than this have significantly higher noise at periods of 1-6 hours. Copyright 2001 by the American Geophysical Union.

Methods for sampling geographically mobile female traders in an East African market setting

PubMed Central

Achiro, Lillian; Kwena, Zachary A.; McFarland, Willi; Neilands, Torsten B.; Cohen, Craig R.; Bukusi, Elizabeth A.; Camlin, Carol S.

2018-01-01

Background The role of migration in the spread of HIV in sub-Saharan Africa is well-documented. Yet migration and HIV research have often focused on HIV risks to male migrants and their partners, or migrants overall, often failing to measure the risks to women via their direct involvement in migration. Inconsistent measures of mobility, gender biases in those measures, and limited data sources for sex-specific population-based estimates of mobility have contributed to a paucity of research on the HIV prevention and care needs of migrant and highly mobile women. This study addresses an urgent need for novel methods for developing probability-based, systematic samples of highly mobile women, focusing on a population of female traders operating out of one of the largest open air markets in East Africa. Our method involves three stages: 1.) identification and mapping of all market stall locations using Global Positioning System (GPS) coordinates; 2.) using female market vendor stall GPS coordinates to build the sampling frame using replicates; and 3.) using maps and GPS data for recruitment of study participants. Results The location of 6,390 vendor stalls were mapped using GPS. Of these, 4,064 stalls occupied by women (63.6%) were used to draw four replicates of 128 stalls each, and a fifth replicate of 15 pre-selected random alternates for a total of 527 stalls assigned to one of five replicates. Staff visited 323 stalls from the first three replicates and from these successfully recruited 306 female vendors into the study for a participation rate of 94.7%. Mobilization strategies and involving traders association representatives in participant recruitment were critical to the study’s success. Conclusion The study’s high participation rate suggests that this geospatial sampling method holds promise for development of probability-based samples in other settings that serve as transport hubs for highly mobile populations. PMID:29324780

Measurement and interpretation of crustal deformation rates associated with postglacial rebound

NASA Technical Reports Server (NTRS)

Davis, James L.

1994-01-01

Analysis of Global Positioning System (GPS) data from two sites separated by horizontal distance of only approximately 2.2 m yielded phase residuals exhibiting a systematic elevation angle dependence. One of the two GPS antennas was mounted on an approximately 1 m high concrete pillar, and the other was mounted on a standard wooden tripod. We performed elevation angle cutoff tests with these data, and established that the vertical coordinate of site position was sensitive to the minimum elevation angle (elevation cutoff) of the data analyzed. For example, the vertical coordinate of site position changed by 9.7 plus or minus 0.8 mm when the minimum elevation angle was increased from 10 to 25. We performed simulations based on a simple (ray tracing) multipath model with a single horizontal reflector, and demonstrated that the elevation angle cutoff test results and the pattern of the residual versus elevation angle could be qualitatively reproduced if the reflector were located 0.1-0.2 m beneath the antenna phase center. We therefore, hypothesized that the source of the elevation-angle-dependent error were multipath reflections and scattering and that the horizontal surface of the pillar, located a distance of approximately 0.2 m beneath the antenna phase center, was the primary reflector. We tested this hypothesis by placing microwave absorbing material between the antenna and the pillar in a number of configurations and analyzed the changes in apparent position of the antenna. The results indicate that (1) the horizontal surface of the pillar is indeed the main reflector, (2) both the concrete and the metal plate embedded in the pillar are significant reflectors, and (3) the reflection can be reduced to a great degree by the use of microwave absorbing materials. These results have significant implications for the accuracy of global GPS geodetic tracking networks which use pillar-antenna configuration identical or similar to the one used here (at the Westford WFRD GPS site).

KSC-98pc778

NASA Image and Video Library

1998-06-25

KENNEDY SPACE CENTER, FLA. -- A forest fire burning in Volusia County, Florida, is clearly visible from NASA's Huey UH-1 helicopter. The helicopter has been outfitted with a Forward Looking Infrared Radar (FLIR) and a portable global positioning satellite (GPS) system to support Florida's Division of Forestry as they fight the brush fires which have been plaguing the state as a result of extremely dry conditions and lightning storms. The FLIR includes a beach ball-sized infrared camera that is mounted on the helicopter's right siderail and a real-time television monitor and recorder installed inside. While the FLIR collects temperature data and images, the GPS system provides the exact coordinates of the fires being observed and transmits the data to the firefighters on the ground. The Kennedy Space Center (KSC) security team routinely uses the FLIR equipment prior to Shuttle launch and landing activities to ensure that the area surrounding the launch pad and runway are clear of unauthorized personnel. KSC's Base Operations Contractor, EG&G Florida, operates the NASA-owned helicopter

KSC-98pc774

NASA Image and Video Library

1998-06-25

KENNEDY SPACE CENTER, FLA. -- Sgt. Mark Hines, of Kennedy Space Center (KSC) Security, checks out equipment used to operate the Forward Looking Infrared Radar (FLIR) installed on NASA's Huey UH-1 helicopter. The helicopter has also been outfitted with a portable global positioning satellite (GPS) system to support Florida's Division of Forestry as they fight the brush fires which have been plaguing the state as a result of extremely dry conditions and lightning storms. The FLIR includes a beach ball-sized infrared camera that is mounted on the helicopter's right siderail and a real-time television monitor and recorder installed inside. While the FLIR collects temperature data and images, the GPS system provides the exact coordinates of the fires being observed and transmits the data to the firefighters on the ground. KSC's security team routinely uses the FLIR equipment prior to Shuttle launch and landing activities to ensure that the area surrounding the launch pad and runway are clear of unauthorized personnel. KSC's Base Operations Contractor, EG&G Florida, operates the NASA-owned helicopter

KSC-98pc775

NASA Image and Video Library

1998-06-25

KENNEDY SPACE CENTER, FLA. -- NASA's Huey UH-1 helicopter lands at the Shuttle Landing Facility to pick up Kennedy Space Center (KSC) Security personnel who operate the Forward Looking Infrared Radar (FLIR) installed on board. The helicopter has also been outfitted with a portable global positioning satellite (GPS) system to support Florida's Division of Forestry as they fight the brush fires which have been plaguing the state as a result of extremely dry conditions and lightning storms. The FLIR includes a beach ball-sized infrared camera that is mounted on the helicopter's right siderail and a real-time television monitor and recorder installed inside. While the FLIR collects temperature data and images, the GPS system provides the exact coordinates of the fires being observed and transmits the data to the firefighters on the ground. KSC's security team routinely uses the FLIR equipment prior to Shuttle launch and landing activities to ensure that the area surrounding the launch pad and runway are clear of unauthorized personnel. KSC's Base Operations Contractor, EG&G Florida, operates the NASA-owned helicopter

KSC-98pc776

NASA Image and Video Library

1998-06-25

KENNEDY SPACE CENTER, FLA. -- A beach ball-sized infrared camera, part of the Forward Looking Infrared Radar (FLIR), has been mounted on the right siderail of NASA's Huey UH-1 helicopter. The helicopter has also been outfitted with a portable global positioning satellite (GPS) system to support Florida's Division of Forestry as they fight the brush fires which have been plaguing the state as a result of extremely dry conditions and lightning storms. The FLIR also includes a real-time television monitor and recorder installed inside the helicopter. While the FLIR collects temperature data and images, the GPS system provides the exact coordinates of the fires being observed and transmits the data to the firefighters on the ground. The Kennedy Space Center (KSC) security team routinely uses the FLIR equipment prior to Shuttle launch and landing activities to ensure that the area surrounding the launch pad and runway are clear of unauthorized personnel. KSC's Base Operations Contractor, EG&G Florida, operates the NASA-owned helicopter

KSC-98pc777

NASA Image and Video Library

1998-06-25

KENNEDY SPACE CENTER, FLA. -- A beach ball-sized infrared camera, part of the Forward Looking Infrared Radar (FLIR), has been mounted on the right siderail of NASA's Huey UH-1 helicopter. A KSC pilot prepares to fly the helicopter, which has also been outfitted with a portable global positioning satellite (GPS) system, to support Florida's Division of Forestry as they fight the brush fires which have been plaguing the state as a result of extremely dry conditions and lightning storms. The FLIR also includes a real-time television monitor and recorder installed inside the helicopter. While the FLIR collects temperature data and images, the GPS system provides the exact coordinates of the fires being observed and transmits the data to the firefighters on the ground. The Kennedy Space Center (KSC) security team routinely uses the FLIR equipment prior to Shuttle launch and landing activities to ensure that the area surrounding the launch pad and runway are clear of unauthorized personnel. KSC's Base Operations Contractor, EG&G Florida, operates the NASA-owned helicopter

KSC-98pc779

NASA Image and Video Library

1998-06-25

KENNEDY SPACE CENTER, FLA. -- A beach ball-sized infrared camera, part of the Forward Looking Infrared Radar (FLIR), has been mounted on the right siderail of NASA's Huey UH-1 helicopter and is being used to search for fires in Volusia County, Florida. The helicopter has also been outfitted with a portable global positioning satellite (GPS) system to support Florida's Division of Forestry as they fight the brush fires which have been plaguing the state as a result of extremely dry conditions and lightning storms. The FLIR also includes a real-time television monitor and recorder installed inside the helicopter. While the FLIR collects temperature data and images, the GPS system provides the exact coordinates of the fires being observed and transmits the data to the firefighters on the ground. The Kennedy Space Center (KSC) security team routinely uses the FLIR equipment prior to Shuttle launch and landing activities to ensure that the area surrounding the launch pad and runway are clear of unauthorized personnel. KSC's Base Operations Contractor, EG&G Florida, operates the NASA-owned helicopter

Time Transfer Methodologies for International Atomic Time (TAI)

DTIC Science & Technology

2007-01-01

International Atomic Time (TAI) and Coordinated Universal Time (UTC) involve either GPS or Two Way Satellite Time and Frequency Transfer ( TWSTFT ). This paper...NRCan, provide real-time carrier-phase based time transfer as well [3,4] Beginning in 2000, time-transfer links using TWSTFT replaced some GPS...links as the primary operational link, and currently over half the clocks used for TAI-generation are linked to other sites via a direct TWSTFT link

Earth's Surface Displacements from the GPS Time Series

NASA Astrophysics Data System (ADS)

Haritonova, D.; Balodis, J.; Janpaule, I.; Morozova, K.

2015-11-01

The GPS observations of both Latvian permanent GNSS networks - EUPOS®-Riga and LatPos, have been collected for a period of 8 years - from 2007 to 2014. Local surface displacements have been derived from the obtained coordinate time series eliminating different impact sources. The Bernese software is used for data processing. The EUREF Permanent Network (EPN) stations in the surroundings of Latvia are selected as fiducial stations. The results have shown a positive tendency of vertical displacements in the western part of Latvia - station heights are increasing, and negative velocities are observed in the central and eastern parts. Station vertical velocities are ranging in diapason of 4 mm/year. In the case of horizontal displacements, site velocities are up to 1 mm/year and mostly oriented to the south. The comparison of the obtained results with data from the deformation model NKG_RF03vel has been made. Additionally, the purpose of this study is to analyse GPS time series obtained using two different data processing strategies: Precise Point Positioning (PPP) and estimation of station coordinates relatively to the positions of fiducial stations also known as Differential GNSS.

On the enhanced detectability of GPS anomalous behavior with relative entropy

NASA Astrophysics Data System (ADS)

Cho, Jeongho

2016-10-01

A standard receiver autonomous integrity monitoring (RAIM) technique for the global positioning system (GPS) has been dedicated to provide an integrity monitoring capability for safety-critical GPS applications, such as in civil aviation for the en-route (ER) through non-precision approach (NPA) or lateral navigation (LNAV). The performance of the existing RAIM method, however, may not meet more stringent aviation requirements for availability and integrity during the precision approach and landing phases of flight due to insufficient observables and/or untimely warning to the user beyond a specified time-to-alert in the event of a significant GPS failure. This has led to an enhanced RAIM architecture ensuring stricter integrity requirement by greatly decreasing the detection time when a satellite failure or a measurement error has occurred. We thus attempted to devise a user integrity monitor which is capable of identifying the GPS failure more rapidly than a standard RAIM scheme by incorporating the RAIM with the relative entropy, which is a likelihood ratio approach to assess the inconsistence between two data streams, quite different from a Euclidean distance. In addition, the delay-coordinate embedding technique needs to be considered and preprocessed to associate the discriminant measure obtained from the RAIM with the relative entropy in the new RAIM design. In simulation results, we demonstrate that the proposed user integrity monitor outperforms the standard RAIM with a higher level of detection rate of anomalies which could be hazardous to the users in the approach or landing phase and is a very promising alternative for the detection of deviations in GPS signal. The comparison also shows that it enables to catch even small anomalous gradients more rapidly than a typical user integrity monitor.

Geographical distribution of Musa gracilis Holttum in Peninsular Malaysia

NASA Astrophysics Data System (ADS)

Norfazlina, B.; Wickneswari, R.; Choong, C. Y.

2016-11-01

Musa gracilis (Musaceae) is placed under section Callimusa and was considered endemic to Peninsular Malaysia. The objective of this study was to evaluate the current occurrence of Musa gracilis in Peninsular Malaysia. The coordinates of each population was recorded using the Global Positioning System (GPS) and mapped to show the geographical distribution of Musa gracilis. This study revealed that Musa gracilis exhibits specific pattern of distribution, which exists only in a lowland areas on the eastern and southern part of Peninsular Malaysia.

Multi-GNSS Opportunities and Challenges

NASA Astrophysics Data System (ADS)

Al-Shaery, A.; Zhang, S.; Lim, S.; Rizos, C.

2012-04-01

The multi-GNSS era has began attracting more attention with the declaration of full operational capability of GLONASS , with a 24 satellites being set to 'healthy' on December 8th 2011 (IAC, 2011). This means that GPS is no longer the only GNSS that provides global positioning coverage. This status brings benefits for GNSS users in areas (e.g. 'urban canyon' environments or in deep open cut mines) where the number of visible satellites is limited because of shadowing effects. In such areas adding more functioning satellites, which is one of the aiding solutions, becomes easier, at no extra cost. The inclusion of GLONASS observations in positioning solutions will increase the available number of satellites and thus positioning accuracy may improve as a result of enhanced overall satellite geometry. Such an aiding solution is increasingly attractive due to the successful revitalisation of GLONASS. Another motivation is the availability of improved GLONASS orbits from the IGS and individual analysis centres of the IGS. The increasing availability of receivers with GPS/GLONASS tracking capability on the market is an additional motive. Consequently, most networks of continuously operating reference stations (CORS) are now equipped with receivers that can track both GPS and GLONASS satellite signals, and therefore network-based positioning with combined GPS and GLONASS observations is possible. However, adding GLONASS observations to GPS is not a straight forward process. This is attributable to a few system differences in reference frames for time and coordinates, and in signal structures. The first two differences are easy to deal with using well-defined conversion and transformation parameters (El-Mowafy, 2001). However, signal structure differences have some implications. The mathematical modelling of combined GPS/GLONASS observations is not performed as in the case of GPS-alone. Special care should be paid to such integration. Not only is the software part affected but also the hardware. Recent research has identified one of the challenges users may face if precise positioning is sought (Takac, 2009, Yamada et al., 2010, Wanninger, 2011). A user of heterogeneous receiver pairs will experience ambiguity fixing challenges due to inter-channel bias which cannot be cancelled by differencing GLONASS observations, pseudorange or carrier-phase. This paper outlines the opportunities and challenges of combining two currently fully operational GNSS systems (GPS and GLONASS) for precise positioning solutions. Discussion and analysis considering mathematical modelling challenges and users' selection of hardware constraints will be performed.

Global positioning system & Google Earth in the investigation of an outbreak of cholera in a village of Bengaluru Urban district, Karnataka.

PubMed

Masthi, N R Ramesh; Madhusudan, M; Puthussery, Yannick P

2015-11-01

The global positioning system (GPS) technology along with Google Earth is used to measure (spatial map) the accurate distribution of morbidity, mortality and planning of interventions in the community. We used this technology to find out its role in the investigation of a cholera outbreak, and also to identify the cause of the outbreak. This study was conducted in a village near Bengaluru, Karnataka in June 2013 during a cholera outbreak. House-to-house survey was done to identify acute watery diarrhoea cases. A hand held GPS receiver was used to record north and east coordinates of the households of cases and these values were subsequently plotted on Google Earth map. Water samples were collected from suspected sources for microbiological analysis. A total of 27 cases of acute watery diarrhoea were reported. Fifty per cent of cases were in the age group of 14-44 yr and one death was reported. GPS technology and Google Earth described the accurate location of household of cases and spot map generated showed clustering of cases around the suspected water sources. The attack rate was 6.92 per cent and case fatality rate was 3.7 per cent. Water samples collected from suspected sources showed the presence of Vibrio cholera O1 Ogawa. GPS technology and Google Earth were easy to use, helpful to accurately pinpoint the location of household of cases, construction of spot map and follow up of cases. Outbreak was found to be due to contamination of drinking water sources.

Celestial Navigation in the 21st Century

NASA Astrophysics Data System (ADS)

Kaplan, George H.

2014-05-01

Despite the ubiquity of GPS receivers in modern life for both timekeeping and geolocation, other forms of navigation remain important because of the weakness of the GPS signals (and those from similar sat-nav systems) and the ease with which they can be jammed. GPS jammers are available for sale on the Internet. The defense and civil aviation communities are particularly concerned about “GPS denial”, whether intentional or accidental, during critical operations.Automated star trackers for navigation have been available since the 1950s. Modern compact observing systems, operating in the far-red and near-IR bands, can detect useful numbers of stars even in the daytime at sea level. A capability to measure the directions of stars relative to some local set of coordinate axes is advantageous for many types of vehicles, whether on the ground, at sea, in the air, or in space, because it provides a direct connection to the inertial reference system represented by current star catalogs. Such a capability can yield precise absolute orientation information not available in any other way. Automated celestial observing systems can be effectively coupled to inertial navigation systems (INS), providing “truth” data for constraining the drift in the INS navigation solution, even if stellar observations are not continuously available due to weather. However, obtaining precise latitude and longitude from stellar observations alone, on a moving platform, remains a challenge, because it requires a determination of the direction to the center of the Earth, i.e., the gravity vertical. General relativity tells us that on-board (“lab”) measurements cannot separate the acceleration of gravity from the acceleration of the platform. Various schemes for overcoming this fundamental problem have been used in the past, at low accuracy, and better ones have been proposed for modern applications. This paper will review some recent developments in this rapidly advancing field.

The Gnomon Experiment

NASA Astrophysics Data System (ADS)

Krisciunas, Kevin

2007-12-01

A gnomon, or vertical pointed stick, can be used to determine the north-south direction at a site, as well as one's latitude. If one has accurate time and knows one's time zone, it is also possible to determine one's longitude. From observations on the first day of winter and the first day of summer one can determine the obliquity of the ecliptic. Since we can obtain accurate geographical coordinates from Google Earth or a GPS device, analysis of set of shadow length measurements can be used by students to learn about astronomical coordinate systems, time systems, systematic errors, and random errors. Systematic latitude errors of student datasets are typically 30 nautical miles (0.5 degree) or more, but with care one can achieve systematic and random errors less than 8 nautical miles. One of the advantages of this experiment is that it can be carried out during the day. Also, it is possible to determine if a student has made up his data.

Crustal Movements and Gravity Variations in the Southeastern Po Plain, Italy

NASA Astrophysics Data System (ADS)

Zerbini, S.; Bruni, S.; Errico, M.; Santi, E.; Wilmes, H.; Wziontek, H.

2014-12-01

At the Medicina observatory, in the southeastern Po Plain, in Italy, we have started a project of continuous GPS and gravity observations in mid 1996. The experiment, focused on a comparison between height and gravity variations, is still ongoing; these uninterrupted time series certainly constitute a most important data base to observe and estimate reliably long-period behaviors but also to derive deeper insights on the nature of the crustal deformation. Almost two decades of continuous GPS observations from two closely located receivers have shown that the coordinate time series are characterized by linear and non-linear variations as well as by sudden jumps. Both over long- and short-period time scales, the GPS height series show signals induced by different phenomena, for example, those related to mass transport in the Earth system. Seasonal effects are clearly recognizable and are mainly associated with the water table seasonal behavior. To understand and separate the contribution of different forcings is not an easy task; to this end, the information provided by the superconducting gravimeter observations and also by absolute gravity measurements offers a most important means to detect and understand mass contributions. In addition to GPS and gravity data, at Medicina, a number of environmental parameters time series are also regularly acquired, among them water table levels. We present the results of study investigating correlations between height, gravity and environmental parameters time series.

Combined GPS/GLONASS Precise Point Positioning with Fixed GPS Ambiguities

PubMed Central

Pan, Lin; Cai, Changsheng; Santerre, Rock; Zhu, Jianjun

2014-01-01

Precise point positioning (PPP) technology is mostly implemented with an ambiguity-float solution. Its performance may be further improved by performing ambiguity-fixed resolution. Currently, the PPP integer ambiguity resolutions (IARs) are mainly based on GPS-only measurements. The integration of GPS and GLONASS can speed up the convergence and increase the accuracy of float ambiguity estimates, which contributes to enhancing the success rate and reliability of fixing ambiguities. This paper presents an approach of combined GPS/GLONASS PPP with fixed GPS ambiguities (GGPPP-FGA) in which GPS ambiguities are fixed into integers, while all GLONASS ambiguities are kept as float values. An improved minimum constellation method (MCM) is proposed to enhance the efficiency of GPS ambiguity fixing. Datasets from 20 globally distributed stations on two consecutive days are employed to investigate the performance of the GGPPP-FGA, including the positioning accuracy, convergence time and the time to first fix (TTFF). All datasets are processed for a time span of three hours in three scenarios, i.e., the GPS ambiguity-float solution, the GPS ambiguity-fixed resolution and the GGPPP-FGA resolution. The results indicate that the performance of the GPS ambiguity-fixed resolutions is significantly better than that of the GPS ambiguity-float solutions. In addition, the GGPPP-FGA improves the positioning accuracy by 38%, 25% and 44% and reduces the convergence time by 36%, 36% and 29% in the east, north and up coordinate components over the GPS-only ambiguity-fixed resolutions, respectively. Moreover, the TTFF is reduced by 27% after adding GLONASS observations. Wilcoxon rank sum tests and chi-square two-sample tests are made to examine the significance of the improvement on the positioning accuracy, convergence time and TTFF. PMID:25237901

The benefits of co-location in primary care practices: the perspectives of general practitioners and patients in 34 countries.

PubMed

Bonciani, M; Schäfer, W; Barsanti, S; Heinemann, S; Groenewegen, P P

2018-02-21

There is no clear evidence as to whether the co-location of primary care professionals in the same facility positively influences their way of working and the quality of healthcare as perceived by patients. The aim of this study was to identify the relationships between general practitioner (GP) co-location with other GPs and/or other professionals and the GP outcomes and patients' experiences. We wanted to test whether GP co-location is related to a broader range of services provided, the use of clinical governance tools and inter-professional collaboration, and whether the patients of co-located GPs perceive a better quality of care in terms of accessibility, comprehensiveness and continuity of care with their GPs. The source of data was the QUALICOPC study (Quality and Costs of Primary Care in Europe), which involved surveys of GPs and their patients in 34 countries, mostly in Europe. In order to study the relationships between GP co-location and both GPs' outcomes and patients' experience, multilevel linear regression analysis was carried out. The GP questionnaire was filled in by 7183 GPs and the patient experience questionnaire by 61,931 patients. Being co-located with at least one other professional is the most common situation of the GPs involved in the study. Compared with single-handed GP practices, GP co-location are positively associated with the GP outcomes. Considering the patients' perspective, comprehensiveness of care has the strongest negative relationship of GP co-location of all the dimensions of patient experiences analysed. The paper highlights that GP mono- and multi-disciplinary co-location is related to positive outcomes at a GP level, such as a broader provision of technical procedures, increased collaboration among different providers and wider coordination with secondary care. However, GP co-location, particularly in a multidisciplinary setting, is related to less positive patient experiences, especially in countries with health systems characterised by a weak primary care structure.

Short-term variations of Icelandic ice cap mass inferred from cGPS coordinate time series

NASA Astrophysics Data System (ADS)

Compton, Kathleen; Bennett, Richard A.; Hreinsdóttir, Sigrún; van Dam, Tonie; Bordoni, Andrea; Barletta, Valentina; Spada, Giorgio

2017-06-01

As the global climate changes, understanding short-term variations in water storage is increasingly important. Continuously operating Global Positioning System (cGPS) stations in Iceland record annual periodic motion—the elastic response to winter accumulation and spring melt seasons—with peak-to-peak vertical amplitudes over 20 mm for those sites in the Central Highlands. Here for the first time for Iceland, we demonstrate the utility of these cGPS-measured displacements for estimating seasonal and shorter-term ice cap mass changes. We calculate unit responses to each of the five largest ice caps in central Iceland at each of the 62 cGPS locations using an elastic half-space model and estimate ice mass variations from the cGPS time series using a simple least squares inversion scheme. We utilize all three components of motion, taking advantage of the seasonal motion recorded in the horizontal. We remove secular velocities and accelerations and explore the impact that seasonal motions due to atmospheric, hydrologic, and nontidal ocean loading have on our inversion results. Our results match available summer and winter mass balance measurements well, and we reproduce the seasonal stake-based observations of loading and melting within the 1σ confidence bounds of the inversion. We identify nonperiodic ice mass changes associated with interannual variability in precipitation and other processes such as increased melting due to reduced ice surface albedo or decreased melting due to ice cap insulation in response to tephra deposition following volcanic eruptions, processes that are not resolved with once or twice-yearly stake measurements.

Evaluation of different approaches to modeling the second-order ionospheric delay on GPS measurements

NASA Astrophysics Data System (ADS)

Garcia-Fernandez, M.; Desai, S. D.; Butala, M. D.; Komjathy, A.

2013-12-01

This work evaluates various approaches to compute the second order ionospheric correction (SOIC) to Global Positioning System (GPS) measurements. When estimating the reference frame using GPS, applying this correction is known to primarily affect the realization of the origin of the Earth's reference frame along the spin axis (Z coordinate). Therefore, the Z translation relative to the International Terrestrial Reference Frame 2008 is used as the metric to evaluate various published approaches to determining the slant total electron content (TEC) for the SOIC: getting the slant TEC from GPS measurements, and using the vertical total electron content (TEC) given by a Global Ionospheric Model (GIM) to transform it to slant TEC via a mapping function. All of these approaches agree to 1 mm if the ionospheric shell height needed in GIM-based approaches is set to 600 km. The commonly used shell height of 450 km introduces an offset of 1 to 2 mm. When the SOIC is not applied, the Z axis translation can be reasonably modeled with a ratio of +0.23 mm/TEC units of the daily median GIM vertical TEC. Also, precise point positioning (PPP) solutions (positions and clocks) determined with and without SOIC differ by less than 1 mm only if they are based upon GPS orbit and clock solutions that have consistently applied or not applied the correction, respectively. Otherwise, deviations of few millimeters in the north component of the PPP solutions can arise due to inconsistencies with the satellite orbit and clock products, and those deviations exhibit a dependency on solar cycle conditions.

Assessments of higher-order ionospheric effects on GPS coordinate time series: A case study of CMONOC with longer time series

NASA Astrophysics Data System (ADS)

Jiang, Weiping; Deng, Liansheng; Zhou, Xiaohui; Ma, Yifang

2014-05-01

Higher-order ionospheric (HIO) corrections are proposed to become a standard part for precise GPS data analysis. For this study, we deeply investigate the impacts of the HIO corrections on the coordinate time series by implementing re-processing of the GPS data from Crustal Movement Observation Network of China (CMONOC). Nearly 13 year data are used in our three processing runs: (a) run NO, without HOI corrections, (b) run IG, both second- and third-order corrections are modeled using the International Geomagnetic Reference Field 11 (IGRF11) to model the magnetic field, (c) run ID, the same with IG but dipole magnetic model are applied. Both spectral analysis and noise analysis are adopted to investigate these effects. Results show that for CMONOC stations, HIO corrections are found to have brought an overall improvement. After the corrections are applied, the noise amplitudes decrease, with the white noise amplitudes showing a more remarkable variation. Low-latitude sites are more affected. For different coordinate components, the impacts vary. The results of an analysis of stacked periodograms show that there is a good match between the seasonal amplitudes and the HOI corrections, and the observed variations in the coordinate time series are related to HOI effects. HOI delays partially explain the seasonal amplitudes in the coordinate time series, especially for the U component. The annual amplitudes for all components are decreased for over one-half of the selected CMONOC sites. Additionally, the semi-annual amplitudes for the sites are much more strongly affected by the corrections. However, when diplole model is used, the results are not as optimistic as IGRF model. Analysis of dipole model indicate that HIO delay lead to the increase of noise amplitudes, and that HIO delays with dipole model can generate false periodic signals. When dipole model are used in modeling HIO terms, larger residual and noise are brought in rather than the effective improvements.

Comparison of Satellite Surveying to Traditional Surveying Methods for the Resources Industry

NASA Astrophysics Data System (ADS)

Osborne, B. P.; Osborne, V. J.; Kruger, M. L.

Modern ground-based survey methods involve detailed survey, which provides three-space co-ordinates for surveyed points, to a high level of accuracy. The instruments are operated by surveyors, who process the raw results to create survey location maps for the subject of the survey. Such surveys are conducted for a location or region and referenced to the earth global co- ordinate system with global positioning system (GPS) positioning. Due to this referencing the survey is only as accurate as the GPS reference system. Satellite survey remote sensing utilise satellite imagery which have been processed using commercial geographic information system software. Three-space co-ordinate maps are generated, with an accuracy determined by the datum position accuracy and optical resolution of the satellite platform.This paper presents a case study, which compares topographic surveying undertaken by traditional survey methods with satellite surveying, for the same location. The purpose of this study is to assess the viability of satellite remote sensing for surveying in the resources industry. The case study involves a topographic survey of a dune field for a prospective mining project area in Pakistan. This site has been surveyed using modern surveying techniques and the results are compared to a satellite survey performed on the same area.Analysis of the results from traditional survey and from the satellite survey involved a comparison of the derived spatial co- ordinates from each method. In addition, comparisons have been made of costs and turnaround time for both methods.The results of this application of remote sensing is of particular interest for survey in areas with remote and extreme environments, weather extremes, political unrest, poor travel links, which are commonly associated with mining projects. Such areas frequently suffer language barriers, poor onsite technical support and resources.

Study of Lever-Arm Effect Using Embedded Photogrammetry and On-Board GPS Receiver on Uav for Metrological Mapping Purpose and Proposal of a Free Ground Measurements Calibration Procedure

NASA Astrophysics Data System (ADS)

Daakir, M.; Pierrot-Deseilligny, M.; Bosser, P.; Pichard, F.; Thom, C.; Rabot, Y.

2016-03-01

Nowadays, Unmanned Aerial Vehicle (UAV) on-board photogrammetry knows a significant growth due to the democratization of using drones in the civilian sector. Also, due to changes in regulations laws governing the rules of inclusion of a UAV in the airspace which become suitable for the development of professional activities. Fields of application of photogrammetry are diverse, for instance: architecture, geology, archaeology, mapping, industrial metrology, etc. Our research concerns the latter area. Vinci-Construction- Terrassement is a private company specialized in public earthworks that uses UAVs for metrology applications. This article deals with maximum accuracy one can achieve with a coupled camera and GPS receiver system for direct-georeferencing of Digital Surface Models (DSMs) without relying on Ground Control Points (GCPs) measurements. This article focuses specially on the lever-arm calibration part. This proposed calibration method is based on two steps: a first step involves the proper calibration for each sensor, i.e. to determine the position of the optical center of the camera and the GPS antenna phase center in a local coordinate system relative to the sensor. A second step concerns a 3d modeling of the UAV with embedded sensors through a photogrammetric acquisition. Processing this acquisition allows to determine the value of the lever-arm offset without using GCPs.

Jason-2 systematic error analysis in the GPS derived orbits

NASA Astrophysics Data System (ADS)

Melachroinos, S.; Lemoine, F. G.; Zelensky, N. P.; Rowlands, D. D.; Luthcke, S. B.; Chinn, D. S.

2011-12-01

Several results related to global or regional sea level changes still too often rely on the assumption that orbit errors coming from station coordinates adoption can be neglected in the total error budget (Ceri et al. 2010). In particular Instantaneous crust-fixed coordinates are obtained by adding to the linear ITRF model the geophysical high-frequency variations. In principle, geocenter motion should also be included in this computation, in order to reference these coordinates to the center of mass of the whole Earth. This correction is currently not applied when computing GDR orbits. Cerri et al. (2010) performed an analysis of systematic errors common to all coordinates along the North/South direction, as this type of bias, also known as Z-shift, has a clear impact on MSL estimates due to the unequal distribution of continental surface in the northern and southern hemispheres. The goal of this paper is to specifically study the main source of errors which comes from the current imprecision in the Z-axis realization of the frame. We focus here on the time variability of this Z-shift, which we can decompose in a drift and a periodic component due to the presumably omitted geocenter motion. A series of Jason-2 GPS-only orbits have been computed at NASA GSFC, using both IGS05 and IGS08. These orbits have been shown to agree radially at less than 1 cm RMS vs our SLR/DORIS std0905 and std1007 reduced-dynamic orbits and in comparison with orbits produced by other analysis centers (Melachroinos et al. 2011). Our GPS-only JASON-2 orbit accuracy is assessed using a number of tests including analysis of independent SLR and altimeter crossover residuals, orbit overlap differences, and direct comparison to orbits generated at GSFC using SLR and DORIS tracking, and to orbits generated externally at other centers. Tests based on SLR-crossover residuals provide the best performance indicator for independent validation of the NASA/GSFC GPS-only reduced dynamic orbits. Reduced dynamic versus dynamic orbit differences are used to characterize the remaining force model error and TRF instability. At first, we quantify the effect of a North/South displacement of the tracking reference points for each of the three techniques. We then compare these results to the study of Morel and Willis (2005) and Ceri et al. (2010). We extend the analysis to the most recent Jason-2 cycles. We evaluate the GPS vs SLR & DORIS orbits produced using the GEODYN.

Interprofessional communication between oncologic specialists and general practitioners on end-of-life issues needs improvement.

PubMed

Oosterink, John J; Oosterveld-Vlug, Mariska G; Glaudemans, Jolien J; Pasman, H Roeline W; Willems, Dick L; Onwuteaka-Philipsen, Bregje D

2016-12-01

Timely end-of-life (EOL) discussions between patients and physicians are considered essential for high-quality EOL care, but research shows that these discussions frequently do not occur or occur late. In oncology, one barrier for timely EOL discussions is poor collaboration between oncologic specialists and GPs. To explore interprofessional communication and coordination between oncologic specialists and GPs on EOL discussions. We conducted in-depth interviews with 16 GPs and 14 oncologic specialists. Interviews were recorded, transcribed verbatim and analysed using qualitative content analysis. EOL discussions were primarily considered the role of the GP, but oncologists' perceptions of their own roles in discussing EOL issues varied. Interprofessional coordination on who discusses what and when was mostly absent. Interprofessional communication of EOL issues usually proceeded using the patient as intermediary. This functioned well but only if three essential conditions were met: the specialist being realistic to patients about limits of treatment, informing the GP adequately and the GP being proactive in initiating EOL issues in time. However, when these conditions were absent, timely EOL discussions did not seem to occur. EOL discussions are rarely a subject of direct interprofessional communication and mainly proceed through the patient as intermediary. For implementation of EOL discussions into regular care, earlier interprofessional communication and coordination is needed, particularly if barriers for such discussions occur. © The Author 2016. Published by Oxford University Press. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.

Airborne gravimetry, altimetry, and GPS navigation errors

NASA Technical Reports Server (NTRS)

Colombo, Oscar L.

1992-01-01

Proper interpretation of airborne gravimetry and altimetry requires good knowledge of aircraft trajectory. Recent advances in precise navigation with differential GPS have made it possible to measure gravity from the air with accuracies of a few milligals, and to obtain altimeter profiles of terrain or sea surface correct to one decimeter. These developments are opening otherwise inaccessible regions to detailed geophysical mapping. Navigation with GPS presents some problems that grow worse with increasing distance from a fixed receiver: the effect of errors in tropospheric refraction correction, GPS ephemerides, and the coordinates of the fixed receivers. Ionospheric refraction and orbit error complicate ambiguity resolution. Optimal navigation should treat all error sources as unknowns, together with the instantaneous vehicle position. To do so, fast and reliable numerical techniques are needed: efficient and stable Kalman filter-smoother algorithms, together with data compression and, sometimes, the use of simplified dynamics.

Inertial Pointing and Positioning System

NASA Technical Reports Server (NTRS)

Yee, Robert (Inventor); Robbins, Fred (Inventor)

1998-01-01

An inertial pointing and control system and method for pointing to a designated target with known coordinates from a platform to provide accurate position, steering, and command information. The system continuously receives GPS signals and corrects Inertial Navigation System (INS) dead reckoning or drift errors. An INS is mounted directly on a pointing instrument rather than in a remote location on the platform for-monitoring the terrestrial position and instrument attitude. and for pointing the instrument at designated celestial targets or ground based landmarks. As a result. the pointing instrument and die INS move independently in inertial space from the platform since the INS is decoupled from the platform. Another important characteristic of the present system is that selected INS measurements are combined with predefined coordinate transformation equations and control logic algorithms under computer control in order to generate inertial pointing commands to the pointing instrument. More specifically. the computer calculates the desired instrument angles (Phi, Theta. Psi). which are then compared to the Euler angles measured by the instrument- mounted INS. and forms the pointing command error angles as a result of the compared difference.

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.

Shuttle Global Positioning System (GPS) system design study

NASA Technical Reports Server (NTRS)

Nilsen, P. W.

1979-01-01

The various integration problems in the Shuttle GPS system were investigated. The analysis of the Shuttle GPS link was studied. A preamplifier was designed since the Shuttle GPS antennas must be located remotely from the receiver. Several GPS receiver architecture trade-offs were discussed. The Shuttle RF harmonics and intermode that fall within the GPS receiver bandwidth were analyzed. The GPS PN code acquisition was examined. Since the receiver clock strongly affects both GPS carrier and code acquisition performance, a clock model was developed.

A Newly Reanalyzed Dataset of GPS-determined Antarctic Vertical Rates

NASA Astrophysics Data System (ADS)

Thomas, I.; King, M.; Clarke, P. J.; Penna, N. T.; Lavallee, D. A.; Whitehouse, P.

2010-12-01

Accurate and precise measurements of vertical crustal motion offer useful constraints on glacial isostatic adjustment (GIA) models. Here we present a newly reprocessed data set of GPS-determined vertical rates for Antarctica. We give details of the global reanalysis of 15-years of GPS data, the overarching aim of which is to achieve homogeneous station coordinate time series, and hence surface velocities, for GPS receivers that are in regions of GIA interest in Antarctica. The means by which the reference frame is realized is crucial to obtaining accurate rates. Considerable effort has been spent on achieving a good global distribution of GPS stations, using data from IGS and other permanently recording stations, as well as a number of episodic campaigns in Antarctica. Additionally, we have focused on minimizing the inevitable imbalance in the number of sites in the northern and southern hemispheres. We align our daily non-fiducial solutions to ITRF2005, i.e. a CM frame. We present the results of investigations into the reference frame realization, and also consider a GPS-derived realization of the frame, and its effect on the vertical velocities. Vertical velocities are obtained for approximately 40 Antarctic locations. We compare our GPS derived Antarctic vertical rates with those predicted by the Ivins and James and ICE-5G models, after converting to a CE frame. We also compare to previously published GPS rates. Our GPS velocities are being used to help tune, and bound errors of, a new GIA model also presented in this session.

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.

KSC-98pc781

NASA Image and Video Library

1998-06-25

KENNEDY SPACE CENTER, FLA. -- A beach ball-sized infrared camera, part of the Forward Looking Infrared Radar (FLIR), has been mounted on the right siderail of NASA's Huey UH-1 helicopter and is being used to scan a large area of Volusia County, Florida, where a fire burns. The helicopter has also been outfitted with a portable global positioning satellite (GPS) system to support Florida's Division of Forestry as they fight the brush fires which have been plaguing the state as a result of extremely dry conditions and lightning storms. The FLIR also includes a real-time television monitor and recorder installed inside the helicopter. While the FLIR collects temperature data and images, the GPS system provides the exact coordinates of the fires being observed and transmits the data to the firefighters on the ground. The Kennedy Space Center (KSC) security team routinely uses the FLIR equipment prior to Shuttle launch and landing activities to ensure that the area surrounding the launch pad and runway are clear of unauthorized personnel. KSC's Base Operations Contractor, EG&G Florida, operates the NASA-owned helicopter

KSC-98pc780

NASA Image and Video Library

1998-06-25

KENNEDY SPACE CENTER, FLA. -- Sgt. Mark Hines, of Kennedy Space Center (KSC) Security, points out a view of a fire on the Forward Looking Infrared Radar (FLIR) video screen to Greg Dunn, of Florida's Division of Forestry, as KSC pilots fly NASA's Huey UH-1 helicopter over fires burning in Volusia County, Florida. The FLIR includes a beach-ball sized infrared camera that is mounted on the helicopter's right siderail and a real-time TV monitor and recorder installed inside. The helicopter has also been outfitted with a portable global positioning satellite (GPS) system to support the Division of Forestry as they fight the brush fires which have been plaguing the state as a result of extremely dry conditions and lightning storms. While the FLIR collects temperature data and images, the GPS system provides the exact coordinates of the fires being observed and transmits the data to the firefighters on the ground. KSC's security team routinely uses the FLIR equipment prior to Shuttle launch and landing activities to ensure that the area surrounding the launch pad and runway are clear of unauthorized personnel. KSC's Base Operations Contractor, EG&G Florida, operates the NASA-owned helicopter.

Improving multi-GNSS ultra-rapid orbit determination for real-time precise point positioning

NASA Astrophysics Data System (ADS)

Li, Xingxing; Chen, Xinghan; Ge, Maorong; Schuh, Harald

2018-03-01

Currently, with the rapid development of multi-constellation Global Navigation Satellite Systems (GNSS), the real-time positioning and navigation are undergoing dramatic changes with potential for a better performance. To provide more precise and reliable ultra-rapid orbits is critical for multi-GNSS real-time positioning, especially for the three merging constellations Beidou, Galileo and QZSS which are still under construction. In this contribution, we present a five-system precise orbit determination (POD) strategy to fully exploit the GPS + GLONASS + BDS + Galileo + QZSS observations from CDDIS + IGN + BKG archives for the realization of hourly five-constellation ultra-rapid orbit update. After adopting the optimized 2-day POD solution (updated every hour), the predicted orbit accuracy can be obviously improved for all the five satellite systems in comparison to the conventional 1-day POD solution (updated every 3 h). The orbit accuracy for the BDS IGSO satellites can be improved by about 80, 45 and 50% in the radial, cross and along directions, respectively, while the corresponding accuracy improvement for the BDS MEO satellites reaches about 50, 20 and 50% in the three directions, respectively. Furthermore, the multi-GNSS real-time precise point positioning (PPP) ambiguity resolution has been performed by using the improved precise satellite orbits. Numerous results indicate that combined GPS + BDS + GLONASS + Galileo (GCRE) kinematic PPP ambiguity resolution (AR) solutions can achieve the shortest time to first fix (TTFF) and highest positioning accuracy in all coordinate components. With the addition of the BDS, GLONASS and Galileo observations to the GPS-only processing, the GCRE PPP AR solution achieves the shortest average TTFF of 11 min with 7{°} cutoff elevation, while the TTFF of GPS-only, GR, GE and GC PPP AR solution is 28, 15, 20 and 17 min, respectively. As the cutoff elevation increases, the reliability and accuracy of GPS-only PPP AR solutions decrease dramatically, but there is no evident decrease for the accuracy of GCRE fixed solutions which can still achieve an accuracy of a few centimeters in the east and north components.

Implementation of a standard format for GPS common view data

NASA Technical Reports Server (NTRS)

Weiss, Marc A.; Thomas, Claudine

1995-01-01

A new format for standardizing common view time transfer data, recommended by the Consultative Committee for the Definition of the Second, is being implemented in receivers commonly used for contributing data for the generation of International Atomic Time. We discuss three aspects of this new format that potentially improve GPS common-view time transfer: (1) the standard specifies the method for treating short term data, (2) it presents data in consistent formats including needed terms not previously available, and (3) the standard includes a header of parameters important for the GPS common-view process. In coordination with the release of firmware conforming to this new format the Bureau International des Poids et Mesures will release future international track schedules consistent with the new standard.

Analysis of the GPS Observations of the Site Survey at Sheshan 25-m Radio Telescope in August 2008

NASA Technical Reports Server (NTRS)

Liu, L.; Cheng, Z. Y.; Li, J. L.

2010-01-01

The processing of the GPS observations of the site survey at Sheshan 25-m radio telescope in August 2008 is reported. Because each session in this survey is only about six hours, not allowing the subdaily high frequency variations in the station coordinates to be reasonably smoothed, and because there are serious cycle slips in the observations and a large volume of data would be rejected during the software automatic adjustment of slips, the ordinary solution settings of GAMIT needed to be adjusted by loosening the constraints in the a priori coordinates to 10 m, adopting the "quick" mode in the solution iteration, and combining Cview manual operation with GAMIT automatic fixing of cycle slips. The resulting coordinates of the local control polygon in ITRF2005 are then compared with conventional geodetic results. Due to large rotations and translations in the two sets of coordinates (geocentric versus quasi-topocentric), the seven transformation parameters cannot be solved for directly. With various trial solutions it is shown that with a partial pre-removal of the large parameters, high precision transformation parameters can be obtained with post-fit residuals at the millimeter level. This analysis is necessary to prepare the follow-on site and transformation survey of the VLBI and SLR telescopes at Sheshan

Enhacements to the TTS-502 time transfer system

NASA Astrophysics Data System (ADS)

Vandierendonck, A. J.; Hua, Q. D.

1985-04-01

Two years ago STI introduced an affordable, relatively compact time transfer system on the market -- the TTS-502, and described that system at the 1981 PTTI conference. Over the past few months, that system has been improved, and new features have been added. In addition, new options have been made available to further enhance the capabilities of the system. These enhancements include the addition of a positioning algorithm and new options providing a corrected 5 MHz output that is phase coherent with the 1 pps output, and providing an internal Rubidium Oscillator. The Positioning Algorithm was developed because not all time transfer users had the luxury of the Defense Mapping Agency's (DMA) services for determining their position in WGS-72 coordinates. The enhanced TTS-502 determines the GPS position anywhere in the world, independent of how many GPS satellites are concurrently visible. However, convergence time to a solution is inversely proportional to the number of satellites concurrently visible and the quality of frequency standard used in conjunction with the TTS-502. Real World solution results will be presented for a variety of cases and satellite scheduling scenarios. Typically, positioning accuracies were achieved better than 5 to 10 meters r.s.s. using the C/A code only at Sunnyvale, California.

Analysis of DGPS/INS and MLS/INS final approach navigation errors and control performance data

NASA Technical Reports Server (NTRS)

Hueschen, Richard M.; Spitzer, Cary R.

1992-01-01

Flight tests were conducted jointly by NASA Langley Research Center and Honeywell, Inc., on a B-737 research aircraft to record a data base for evaluating the performance of a differential DGPS/inertial navigation system (INS) which used GPS Course/Acquisition code receivers. Estimates from the DGPS/INS and a Microwave Landing System (MLS)/INS, and various aircraft parameter data were recorded in real time aboard the aircraft while flying along the final approach path to landing. This paper presents the mean and standard deviation of the DGPS/INS and MLS/INS navigation position errors computed relative to the laser tracker system and of the difference between the DGPS/INS and MLS/INS velocity estimates. RMS errors are presented for DGPS/INS and MLS/INS guidance errors (localizer and glideslope). The mean navigation position errors and standard deviation of the x position coordinate of the DGPS/INS and MLS/INS systems were found to be of similar magnitude while the standard deviation of the y and z position coordinate errors were significantly larger for DGPS/INS compared to MLS/INS.

Airborne multicamera system for geo-spatial applications

NASA Astrophysics Data System (ADS)

Bachnak, Rafic; Kulkarni, Rahul R.; Lyle, Stacey; Steidley, Carl W.

2003-08-01

Airborne remote sensing has many applications that include vegetation detection, oceanography, marine biology, geographical information systems, and environmental coastal science analysis. Remotely sensed images, for example, can be used to study the aftermath of episodic events such as the hurricanes and floods that occur year round in the coastal bend area of Corpus Christi. This paper describes an Airborne Multi-Spectral Imaging System that uses digital cameras to provide high resolution at very high rates. The software is based on Delphi 5.0 and IC Imaging Control's ActiveX controls. Both time and the GPS coordinates are recorded. Three successful test flights have been conducted so far. The paper present flight test results and discusses the issues being addressed to fully develop the system.

Evaluation of Mapping Methodologies at a Legacy Test Site

NASA Astrophysics Data System (ADS)

Sussman, A. J.; Schultz-Fellenz, E. S.; Roback, R. C.; Kelley, R. E.; Drellack, S.; Reed, D.; Miller, E.; Cooper, D. I.; Sandoval, M.; Wang, R.

2013-12-01

On June 12th, 1985, a nuclear test with an announced yield between 20-150kt was detonated in rhyolitic lava in a vertical emplacement borehole at a depth of 608m below the surface. This test did not collapse to the surface and form a crater, but rather resulted in a subsurface collapse with more subtle surface expressions of deformation, providing an opportunity to evaluate the site using a number of surface mapping methodologies. The site was investigated over a two-year time span by several mapping teams. In order to determine the most time efficient and accurate approach for mapping post-shot surface features at a legacy test site, a number of different techniques were employed. The site was initially divided into four quarters, with teams applying various methodologies, techniques, and instrumentations to each quarter. Early methods included transect lines and site gridding with a Brunton pocket transit, flagging tape, measuring tape, and stakes; surveying using a hand-held personal GPS to locate observed features with an accuracy of × 5-10m; and extensive photo-documentation. More recent methods have incorporated the use of near survey grade GPS devices to allow careful location and mapping of surface features. Initially, gridding was employed along with the high resolution GPS surveys, but this was found to be time consuming and of little observational value. Raw visual observation (VOB) data included GPS coordinates for artifacts or features of interest, field notes, and photographs. A categorization system was used to organize the myriad of items, in order to aid in database searches and for visual presentation of findings. The collected data set was imported into a geographic information system (GIS) as points, lines, or polygons and overlain onto a digital color orthophoto map of the test site. Once these data were mapped, spectral data were collected using a high resolution field spectrometer. In addition to geo-locating the field observations with 10cm resolution GPS, LiDAR and hyperspectral imagery were also acquired. The LiDAR and hyperspectral data are being processed and will be added to the existing geo-referenced database as separate information layers for remote sensing analysis of surface features associated with the legacy test. By consolidating the various components of a VOB data point (coordinates, photo and item description) into a standalone database, searching or querying for other components or collects such as subsurface geophysical and/or airborne imagery is made much easier. Work by Los Alamos National Laboratory was sponsored by the National Nuclear Security Administration Award No. DE-AC52-06NA25946/NST10-NCNS-PD00. Work by National Security Technologies, LLC, was performed under Contract No. DE AC52 06NA25946 with the U.S. Department of Energy.

The Effect of Improved Sub-Daily Earth Rotation Models on Global GPS Data Processing

NASA Astrophysics Data System (ADS)

Yoon, S.; Choi, K. K.

2017-12-01

Throughout the various International GNSS Service (IGS) products, strong periodic signals have been observed around the 14 day period. This signal is clearly visible in all IGS time-series such as those related to orbit ephemerides, Earth rotation parameters (ERP) and ground station coordinates. Recent studies show that errors in the sub-daily Earth rotation models are the main factors that induce such noise. Current IGS orbit processing standards adopted the IERS 2010 convention and its sub-daily Earth rotation model. Since the IERS convention had published, recent advances in the VLBI analysis have made contributions to update the sub-daily Earth rotation models. We have compared several proposed sub-daily Earth rotation models and show the effect of using those models on orbit ephemeris, Earth rotation parameters and ground station coordinates generated by the NGS global GPS data processing strategy.

The application of NAVSTAR Differential GPS to civil helicopter operations

NASA Technical Reports Server (NTRS)

Beser, J.; Parkinson, B. W.

1981-01-01

Principles concerning the operation of the NAVSTAR Global Positioning Systems (GPS) are discussed. Selective availability issues concerning NAVSTAR GPS and differential GPS concepts are analyzed. Civil support and market potential for differential GPS are outlined. It is concluded that differential GPS provides a variation on the baseline GPS system, and gives an assured, uninterrupted level of accuracy for the civilian community.

Geo-spatial reporting for monitoring of household immunization coverage through mobile phones: Findings from a feasibility study.

PubMed

Kazi, A M; Ali, M; K, Ayub; Kalimuddin, H; Zubair, K; Kazi, A N; A, Artani; Ali, S A

2017-11-01

The addition of Global Positioning System (GPS) to a mobile phone makes it a very powerful tool for surveillance and monitoring coverage of health programs. This technology enables transfer of data directly into computer applications and cross-references to Geographic Information Systems (GIS) maps, which enhances assessment of coverage and trends. Utilization of these systems in low and middle income countries is currently limited, particularly for immunization coverage assessments and polio vaccination campaigns. We piloted the use of this system and discussed its potential to improve the efficiency of field-based health providers and health managers for monitoring of the immunization program. Using "30×7" WHO sampling technique, a survey of children less than five years of age was conducted in random clusters of Karachi, Pakistan in three high risk towns where a polio case was detected in 2011. Center point of the cluster was calculated by the application on the mobile. Data and location coordinates were collected through a mobile phone. This data was linked with an automated mHealth based monitoring system for monitoring of Supplementary Immunization Activities (SIAs) in Karachi. After each SIA, a visual report was generated according to the coordinates collected from the survey. A total of 3535 participants consented to answer to a baseline survey. We found that the mobile phones incorporated with GIS maps can improve efficiency of health providers through real-time reporting and replacing paper based questionnaire for collection of data at household level. Visual maps generated from the data and geospatial analysis can also give a better assessment of the immunization coverage and polio vaccination campaigns. The study supports a model system in resource constrained settings that allows routine capture of individual level data through GPS enabled mobile phone providing actionable information and geospatial maps to local public health managers, policy makers and study staff monitoring immunization coverage. Copyright © 2017 Elsevier B.V. All rights reserved.

Immunization-based scores as independent prognostic predictors in soft tissue sarcoma patients

PubMed Central

Jiang, Shan-Shan; Jiang, Long; Weng, De-Sheng; Li, Yuan-fang; Pan, Qiu-Zhong; Zhao, Jing-Jing; Tang, Yan; Zhou, Zhi-Wei; Xia, Jian-Chuan

2017-01-01

Background: The purpose of this study was to examine and compare the prognostic value of different immunization-based scoring systems in patients with soft tissue sarcoma (STS). Methods: We conducted a retrospective study evaluating a cohort of 165 patients diagnosed with STS between July 2007 and July 2014. The relative Glasgow prognostic score (GPS) of these patients was calculated using 3 different systems: the traditional GPS system (tGPS), the modified GPS system 1 (m1GPS), and the modified GPS system 2 (m2GPS). Then, we evaluated the relationships between each GPS system and clinicopathological characteristics. The mean follow-up for survivors in the cohort was 73.7 months as of March 2015. Results: The most favorable overall survival (OS) rate was associated with the score 0 groups, and the poorest progression-free survival (PFS) rate was associated with the score 2 groups, regardless of which system was used to calculate the score. Specifically, the m1GPS provided the greatest accuracy in predicting OS and PFS. Moreover, the same effect was observed in a separate analysis restricted to patients with metastases. Remarkably, in patients with a score of 2 as measured by all 3 systems, local treatment resulted in a poorer prognosis compared to patients with a score of 2 who did not receive local treatment. Conclusion: The GPS is a valuable prognostic marker and has the capability to predict the appropriate treatment strategy for STS patients with metastases. The modified GPS systems demonstrated superior prognostic and predictive value compared with the traditional GPS system. PMID:28367240

Rip current monitoring using GPS buoy system

NASA Astrophysics Data System (ADS)

Song, DongSeob; Kim, InHo; Kang, DongSoo

2014-05-01

The occurrence of rip current in the Haeundae beach, which is one of the most famous beaches in South Korea, has been threatening beach-goers security in summer season annually. Many coastal scientists have been investigating rip currents by using field observations and measurements, laboratory measurements and wave tank experiments, and computer and numerical modeling. Rip current velocity is intermittent and may rapidly increase within minutes due to larger incoming wave groups or nearshore circulation instabilities. It is important to understand that changes in rip current velocity occur in response to changes in incoming wave height and period as well as changes in water level. GPS buoys have been used to acquire sea level change data, atmospheric parameters and other oceanic variables in sea for the purposes of vertical datum determination, tide correction, radar altimeter calibration, ocean environment and marine pollution monitoring. Therefore, we adopted GPS buoy system for an experiment which is to investigate rip current velocity; it is sporadic and may quickly upsurge within minutes due to larger arriving wave groups or nearshore flow uncertainties. In this study, for high accurate positioning of buy equipment, a Satellite Based Argumentation System DGPS data logger was deployed to investigate within floating object, and it can be acquired three-dimensional coordinate or geodetic position of buoy with continuous NMEA-0183 protocol during 24 hours. The wave height measured by in-situ hydrometer in a cross-shore array clearly increased before and after occurrence of rip current, and wave period also was lengthened around an event. These results show that wave height and period correlate reasonably well with long-shore current interaction in the Haeundae beach. Additionally, current meter data and GPS buoy data showed that rip current velocities, about 0.2 m/s, may become dangerously strong under specific conditions. Acknowledgement This research was supported by Basic Science Research Program through the National Research Foundation of Korea(NRF) funded by the Ministry of Education, Science and Technology(2010-0024670)

A regional programme to improve skin cancer management.

PubMed

McGeoch, Graham R; Sycamore, Mark J; Shand, Brett I; Simcock, Jeremy W

2015-12-01

In 2008, public specialist and general practice services in Canterbury were unable to manage demand for skin cancer treatment. Local clinicians decided the solution was to develop a see-and-treat skin excision clinic staffed by plastic surgeons and general practitioners (GPs), and the introduction of subsidised excisions in general practice. This paper describes the collaboration between clinicians, managers and funders and the results and quality management measures of these initiatives. There is an increasing incidence of skin cancer. GPs in Canterbury were unable to meet increasing demand for skin cancer treatment because some lacked confidence and competence in skin cancer management. There was no public funding for primary care management of skin cancer, driving patients to fully funded secondary care services. Secondary care services were at capacity, with no coordinated programme across primary and secondary care. The programme has resulted in a greater number of skin cancers being treated by the public health system, a reduction in waiting times for treatment, and fewer minor skin lesions being referred to secondary care. Quality measures have been achieved and are improving steadily. Development of the programme has improved working relationships between primary and secondary care clinicians. The strategy was to facilitate the working relationship between primary and secondary care and increase the capacity for skin lesion excisions in both sectors. Skin cancer management can be improved by a coordinated approach between primary and secondary care.

Contribution of TIGA reprocessing to the ITRF densification

NASA Astrophysics Data System (ADS)

Rudenko, S.; Dähnn, M.; Gendt, G.; Brandt, A.; Nischan, T.

2009-04-01

Analysis of tide gauge measurements with the purpose of sea level change investigations requires a well defined reference frame. Such reference frame can be realized through precise positions of GPS stations located at or near tide gauges (TIGA stations) and analyzed within the IGS GPS Tide Gauge Benchmark Monitoring Pilot Project (TIGA). To tie this reference frame to the International Terrestrial Reference Frame (ITRF), one should process simultaneously GPS data from TIGA and IGS stations included in the ITRF. A time series of GPS station positions has been recently derived by reprocessing GPS data from about 400 GPS stations globally distributed covering totally time span from 1998 till 2008 using EPOS-Potsdam software developed at GFZ and improved in the recent years. The analysis is based on the use of IERS Conventions 2003, ITRF2005 as a priori reference frame, FES2004 ocean tide loading model, absolute phase centre variations for GPS satellite transmit and ground receive antennae and other models. About 220 stations of the solution are IGS ones and about 180 are TIGA GPS stations that are not IGS ones. The solution includes weekly coordinates of GPS stations, daily values of the Earth rotation parameters and their rates, as well as satellite antenna offsets. On the other hand, our new solution can contribute to the ITRF densification by providing positions of about 200 stations being not present in ITRF2005. The solution can be also used for the integration of regional frames. The paper presents the results of the analysis and the comparison of our solution with ITRF2005 and the solutions of other TIGA and IGS Analysis Centres.

Automated Support for Rapid Coordination of Joint UUV Operation

DTIC Science & Technology

2015-03-01

automata , dead-reckoning, static plan, nmtime plan, rapid deployment, GPS 17. SECURITY CLASSIFICATION OF REPORT Unclassified 18. SECURITY...STATE MACHINES, MOORE AUTOMATA ..........................................9 A. MOORE AUTOMATA ...9 B. UUV PLANS AS MOORE AUTOMATA ...................................................11 C. SAMPLING RATE

Exploring the Scopes "Monkey" Trial in Dayton, Tennessee: A Guide to People & Places

ERIC Educational Resources Information Center

Cameron, Jacquelyn; Moore, Randy

2015-01-01

Many biology teachers visit Dayton, Tennessee, to experience "ground zero" of the evolution-creationism controversy. This article provides concise descriptions, addresses, and GPS coordinates for the trial-related sites in and around Dayton.

The Promise and Challenges of High Rate GNSS for Environmental Monitoring and Response

NASA Astrophysics Data System (ADS)

LaBrecque, John

2017-04-01

The decadal vision Global Geodetic Observing System recognizes the potential of high rate real time GNSS for environmental monitoring. The GGOS initiated a program to advance GNSS real time high rate measurements to augment seismic and other sensor systems for earthquake and tsunami early warning. High rate multi-GNSS networks can provide ionospheric tomography for the detection and tracking of land, ocean and atmospheric gravity waves that can provide coastal warning of tsunamis induced by earthquakes, volcanic eruptions, severe weather and other catastrophic events. NASA has collaborated on a microsatellite constellation of GPS receivers to measure ocean surface roughness to improve severe storm tracking and a equatorial system of GPS occultation receivers to measure ionospheric and atmospheric dynamics. Systems such as these will be significantly enhanced by the availability of a four fold increase in GNSS satellite systems with new and enhanced signal structures and by the densification of regional multi-GNSS networks. These new GNSS capabilities will rely upon improved and cost effective communications infrastructure for a network of coordinated real time analysis centers with input to national warning systems. Most important, the implementation of these new real time GNSS capabilities will rely upon the broad international support for the sharing of real time GNSS much as is done in weather and seismic observing systems and as supported by the Committee of Experts on UN Global Geodetic Information Management (UNGGIM).

U.S. Space Shuttle GPS navigation capability for all mission phases

NASA Technical Reports Server (NTRS)

Kachmar, Peter; Chu, William; Montez, Moises

1993-01-01

Incorporating a GPS capability on the Space Shuttle presented unique system integration design considerations and has led to an integration concept that has minimum impact on the existing Shuttle hardware and software systems. This paper presents the Space Shuttle GPS integrated design and the concepts used in implementing this GPS capability. The major focus of the paper is on the modifications that will be made to the navigation systems in the Space Shuttle General Purpose Computers (GPC) and on the Operational Requirements of the integrated GPS/GPC system. Shuttle navigation system architecture, functions and operations are discussed for the current system and with the GPS integrated navigation capability. The GPS system integration design presented in this paper has been formally submitted to the Shuttle Avionics Software Control Board for implementation in the on-board GPC software.

Present-Day Kinematics of the Central Mediterranean Plate Boundary Region from Large GPS Network Analysis Using the Ambizap Algorithm

NASA Astrophysics Data System (ADS)

D'Anastasio, E.; D'Agostino, N.; Avallone, A.; Blewitt, G.

2008-12-01

The large, recent increase of continuous GPS (CGPS) stations in the Central Mediterranean plate boundary zone offers the opportunity to study in detail the present-day kinematics of this actively deforming region. CGPS data from scientific and commercial networks in the Italian region is now available from more than 350 stations, including more than 130 from the RING network deployed by the Istituto Nazionale di Geofisica e Vulcanologia. The RING stations all have high quality GPS monuments and are co- located with broadband or very broadband seismometers and strong motion sensors. The analysis presented here also uses far-field data to provide reference frame control, bringing the total to over 580 CGPS stations. GPS ambiguity resolution of such a large amount of data presents a serious challenge in terms of processing time. Many scientific GPS data processing software packages address this problem by dividing the network into several clusters. In contrast, this analysis uses the new Ambizap GPS processing algorithm (Blewitt, 2008) to obtain unique, self-consistent daily ambiguity-fixed solutions for the entire network. Ambizap allows for a rapid and multiple reanalysis of large regional networks such the one presented in this work. Tests show that Ambizap reproduces solutions from time-prohibitive full-network ambiguity resolution to much less than 1 mm. Single station GPS data are first processed with the GIPSY-OASIS II software by the precise point positioning (PPP) strategy (Zumberge et al., 1997) using JPL products from ftp://sideshow.jpl.nasa.gov. Integer ambiguity resolution is then applied using Ambizap. The resulting daily solutions are aligned to the ITRF2005 reference frame. Then, using the CATS software (Williams, 2007), time series are cleaned to remove outliers and are analyzed for their noise properties, linear velocities, periodic signals and antenna jumps. Stable plate reference frames are realized by minimizing the horizontal velocities at more than 70 and 20 sites on the Eurasia and Nubia plates, respectively. The daily RMS scatter for the east coordinates (derived from PPP) in this frame is typically in the range 2-4 mm before applying Ambizap, and 1-2 mm after applying Ambizap. The solutions are then evaluated with regard to the numerous scientific motivations behind this project, ranging from the definition of strain distribution and microplate kinematics within the plate boundary, to the evaluation of tectonic strain accumulation on active faults. References: Blewitt, G. (2008), Fixed-point theorems of GPS carrier phase ambiguity resolution and their application to massive network processing: 'Ambizap', J. Geophys. Res., doi:10.1029/2008JB005736, in press. Williams, S.D.P. (2007), CATS: GPS coordinate time series analysis software, GPS solut., doi:10.1007/s10291-007-0086-4 Zumberge, J. F., M. B. Heflin, D. C. Jefferson, M. M. Watkins, and F. H. Webb (1997), Precise point positioning for the efficient and robust analysis of GPS data from large networks, J. Geophys. Res., 102, 5005-501

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.

77 FR 56254 - 89th Meeting: RTCA Special Committee 159, Global Positioning Systems (GPS)

Federal Register 2010, 2011, 2012, 2013, 2014

2012-09-12

... 159, Global Positioning Systems (GPS). SUMMARY: The FAA is issuing this notice to advise the public of the eighty-ninth meeting of the RTCA Special Committee 159, Global Positioning Systems (GPS). DATES... 159, Global Positioning Systems (GPS) AGENCY: Federal Aviation Administration (FAA), U.S. Department...

78 FR 13396 - 90th Meeting: RTCA Special Committee 159, Global Positioning Systems (GPS)

Federal Register 2010, 2011, 2012, 2013, 2014

2013-02-27

... 159, Global Positioning Systems (GPS) SUMMARY: The FAA is issuing this notice to advise the public of the eighty-ninth meeting of the RTCA Special Committee 159, Global Positioning Systems (GPS). DATES... 159, Global Positioning Systems (GPS) AGENCY: Federal Aviation Administration (FAA), U.S. Department...

76 FR 33022 - Eighty-Sixth Meeting: RTCA Special Committee 159: Global Positioning System (GPS)

Federal Register 2010, 2011, 2012, 2013, 2014

2011-06-07

... Committee 159: Global Positioning System (GPS) AGENCY: Federal Aviation Administration (FAA), DOT. ACTION: Notice of RTCA Special Committee 159 meeting: Global Positioning System (GPS). SUMMARY: The FAA is...), notice is hereby given for a Special Committee 159: Global Positioning System (GPS) meeting. The agenda...

GPS Time Series and Geodynamic Implications for the Hellenic Arc Area, Greece

NASA Astrophysics Data System (ADS)

Hollenstein, Ch.; Heller, O.; Geiger, A.; Kahle, H.-G.; Veis, G.

The quantification of crustal deformation and its temporal behavior is an important contribution to earthquake hazard assessment. With GPS measurements, especially from continuous operating stations, pre-, co-, post- and interseismic movements can be recorded and monitored. We present results of a continuous GPS network which has been operated in the Hellenic Arc area, Greece, since 1995. In order to obtain coordinate time series of high precision which are representative for crustal deformation, a main goal was to eliminate effects which are not of tectonic origin. By applying different steps of improvement, non-tectonic irregularities were reduced significantly, and the precision could be improved by an average of 40%. The improved time series are used to study the crustal movements in space and time. They serve as a base for the estimation of velocities and for the visualization of the movements in terms of trajectories. Special attention is given to large earthquakes (M>6), which occurred near GPS sites during the measuring time span.

Application of the Undifferenced GNSS Precise Positioning in Determining Coordinates in National Reference Frames

NASA Astrophysics Data System (ADS)

Krzan, Grzegorz; Stępniak, Katarzyna

2017-09-01

In high-accuracy positioning using GNSS, the most common solution is still relative positioning using double-difference observations of dual-frequency measurements. An increasingly popular alternative to relative positioning are undifferenced approaches, which are designed to make full use of modern satellite systems and signals. Positions referenced to global International Terrestrial Reference Frame (ITRF2008) obtained from Precise Point Positioning (PPP) or Undifferenced (UD) network solutions have to be transformed to national (regional) reference frame, which introduces additional bases related to the transformation process. In this paper, satellite observations from two test networks using different observation time series were processed. The first test concerns the positioning accuracy from processing one year of dual-frequency GPS observations from 14 EUREF Permanent Network (EPN) stations using NAPEOS 3.3.1 software. The results were transformed into a national reference frame (PL-ETRF2000) and compared to positions from an EPN cumulative solution, which was adopted as the true coordinates. Daily observations were processed using PPP and UD multi-station solutions to determine the final accuracy resulting from satellite positioning, the transformation to national coordinate systems and Eurasian intraplate plate velocities. The second numerical test involved similar processing strategies of post-processing carried out using different observation time series (30 min., 1 hour, 2 hours, daily) and different classes of GNSS receivers. The centimeter accuracy of results presented in the national coordinate system satisfies the requirements of many surveying and engineering applications.

Online Aerial Terrain Mapping for Ground Robot Navigation

PubMed Central

Peterson, John; Chaudhry, Haseeb; Abdelatty, Karim; Bird, John; Kochersberger, Kevin

2018-01-01

This work presents a collaborative unmanned aerial and ground vehicle system which utilizes the aerial vehicle’s overhead view to inform the ground vehicle’s path planning in real time. The aerial vehicle acquires imagery which is assembled into a orthomosaic and then classified. These terrain classes are used to estimate relative navigation costs for the ground vehicle so energy-efficient paths may be generated and then executed. The two vehicles are registered in a common coordinate frame using a real-time kinematic global positioning system (RTK GPS) and all image processing is performed onboard the unmanned aerial vehicle, which minimizes the data exchanged between the vehicles. This paper describes the architecture of the system and quantifies the registration errors between the vehicles. PMID:29461496

Online Aerial Terrain Mapping for Ground Robot Navigation.

PubMed

Peterson, John; Chaudhry, Haseeb; Abdelatty, Karim; Bird, John; Kochersberger, Kevin

2018-02-20

This work presents a collaborative unmanned aerial and ground vehicle system which utilizes the aerial vehicle's overhead view to inform the ground vehicle's path planning in real time. The aerial vehicle acquires imagery which is assembled into a orthomosaic and then classified. These terrain classes are used to estimate relative navigation costs for the ground vehicle so energy-efficient paths may be generated and then executed. The two vehicles are registered in a common coordinate frame using a real-time kinematic global positioning system (RTK GPS) and all image processing is performed onboard the unmanned aerial vehicle, which minimizes the data exchanged between the vehicles. This paper describes the architecture of the system and quantifies the registration errors between the vehicles.

76 FR 67019 - Eighty-Seventh: RTCA Special Committee 159: Global Positioning System (GPS)

Federal Register 2010, 2011, 2012, 2013, 2014

2011-10-28

... Committee 159: Global Positioning System (GPS) 87th meeting. DATES: The meeting will be held November 14-18... Committee 159, Global Positioning System (GPS). The agenda will include the following: November 14-17, 2011... Committee 159: Global Positioning System (GPS) AGENCY: Federal Aviation Administration (FAA), U.S...

GPS coordinate time series measurements in Ontario and Quebec, Canada

NASA Astrophysics Data System (ADS)

Samadi Alinia, Hadis; Tiampo, Kristy F.; James, Thomas S.

2017-06-01

New precise network solutions for continuous GPS (cGPS) stations distributed in eastern Ontario and western Québec provide constraints on the regional three-dimensional crustal velocity field. Five years of continuous observations at fourteen cGPS sites were analyzed using Bernese GPS processing software. Several different sub-networks were chosen from these stations, and the data were processed and compared to in order to select the optimal configuration to accurately estimate the vertical and horizontal station velocities and minimize the associated errors. The coordinate time series were then compared to the crustal motions from global solutions and the optimized solution is presented here. A noise analysis model with power-law and white noise, which best describes the noise characteristics of all three components, was employed for the GPS time series analysis. The linear trend, associated uncertainties, and the spectral index of the power-law noise were calculated using a maximum likelihood estimation approach. The residual horizontal velocities, after removal of rigid plate motion, have a magnitude consistent with expected glacial isostatic adjustment (GIA). The vertical velocities increase from subsidence of almost 1.9 mm/year south of the Great Lakes to uplift near Hudson Bay, where the highest rate is approximately 10.9 mm/year. The residual horizontal velocities range from approximately 0.5 mm/year, oriented south-southeastward, at the Great Lakes to nearly 1.5 mm/year directed toward the interior of Hudson Bay at stations adjacent to its shoreline. Here, the velocity uncertainties are estimated at less than 0.6 mm/year for the horizontal component and 1.1 mm/year for the vertical component. A comparison between the observed velocities and GIA model predictions, for a limited range of Earth models, shows a better fit to the observations for the Earth model with the smallest upper mantle viscosity and the largest lower mantle viscosity. However, the pattern of horizontal deformation is not well explained in the north, along Hudson Bay, suggesting that revisions to the ice thickness history are needed to improve the fit to observations.

Comparison of GPS TEC variations with Holt-Winter method and IRI-2012 over Langkawi, Malaysia

NASA Astrophysics Data System (ADS)

Elmunim, N. A.; Abdullah, M.; Hasbi, A. M.; Bahari, S. A.

2017-07-01

The Total Electron Content (TEC) is the ionospheric parameter that has the main effect on radio wave propagation. Therefore, it is crucial to evaluate the performance of the TEC models for the further improvement of the ionospheric modelling in equatorial regions. This work presents an analysis of the TEC, derived from the GPS Ionospheric Scintillation and TEC Monitor (GISTM) receiver at the Langkawi station, Malaysia, located at the geographic coordinates of 6.19°N, 99.51°E and the geomagnetic coordinates of 3.39°S, 172.42°E. The diurnal, monthly and seasonal variations in 2014 of the observed GPS-TEC were compared with the statistical Holt-Winter method and a recent version of the International Reference Ionosphere model (IRI-2012), using three different topside options of an electron density, which are the IRI-2001, IRI01-corr and NeQuick. The maximum peaks of the GPS-TEC were observed in the post-noon time and the minimum was observed during the early morning time. In addition, in monthly variations the Holt-Winter and the IRI-2012 topside options showed an underestimation that was in agreement with the GPS-TEC, except for the IRI-2001 model which showed an overestimation in June, July and August. Regarding the seasonal variation of the GPS-TEC, the lowest values were observed during summer and it reached its maximum value during the equinox season. The IRI-2001 showed the highest value of percentage deviation compared to the IRI01-corr, NeQuick and Holt-Winter method. Therefore, the accuracy of the models was found to be approximately 95% in the Holt-Winter method, 75% in the IRI01-corr, 73% in the NeQuick and 66% in the IRI-2001 model. Hence, it can be inferred that the Holt-Winter method showed a higher performance and better estimates of the TEC compared to the IRI01-corr and NeQuick, while the IRI-2001 showed a poor predictive performance in the equatorial region over Malaysia.

[Between individuality and "evidence-based medicine"--the role of the general practitioner within the scope of disease management programs].

PubMed

Szecsenyi, Joachim; Schneider, Antonius

2003-06-01

In Germany, the change from the "traditional", experience-based general practitioner (GP) to the evidence-based practising co-ordinator may be accelerated by the introduction of disease management programmes. Here, we will discuss some tools that can help to meet this challenge. Also, a set of requirements will be defined that the health care system will have to provide in support of GPs. Maintaining the relationship between doctor and patient and also allowing for individual care on the basis of evidence-based medicine will remain a challenge.

Addressing the problems associated with general practitioners' workload in nursing and residential homes: findings from a qualitative study.

PubMed Central

Jacobs, Sally

2003-01-01

BACKGROUND: Caring for older people in residential and nursing homes makes major demands on general practitioners (GPs). AIM: To investigate the perceptions and experiences of home managers and GPs of the provision of general medical services for older residents. DESIGN OF STUDY: In-depth qualitative study. SETTING: Forty-two nursing and residential homes in five locations in England, interviewing home managers and eight of their residents' GPs. METHOD: Semi-structured face-to-face and telephone interviews. RESULTS: Most homes endorse principles of continuity of care and patient choice. Although many homes therefore deal with a large number of GPs, with the inherent difficulties of coordinating care and duplication of GP effort, limitations in residents' choice of GP result in the majority of residents in many homes being registered with only one or two practices. Contracts between homes and GPs may provide opportunities for improving medical care but do not guarantee additional services and have implications for patient choice and residents' fees. Visits on request form the bulk of GPs' workload in homes but can be hard to obtain for residents and may not be appropriate. Regular weekly surgeries are preferred by many homes but may have additional workload implications for GPs. CONCLUSION: The assumption that patient choice and continuity in medical care are paramount for older people in nursing and residential homes is questioned. While recognition of the additional workload for GPs working in these settings is necessary, this should be accompanied by additional NHS remuneration. Further research is urgently required to identify which models of GP provision would most benefit both residents and GPs. PMID:12817356

Performance assessment of multi-GNSS real-time PPP over Iran

NASA Astrophysics Data System (ADS)

Abdi, Naser; Ardalan, Alireza A.; Karimi, Roohollah; Rezvani, Mohammad-Hadi

2017-06-01

With the advent of multi-GNSS constellations and thanks to providing the real-time precise products by IGS, multi-GNSS Real-Time PPP has been of special interest to the geodetic community. These products stream in the form of RTCM-SSR through NTRIP broadcaster. In this contribution, we aim at assessing the convergence time and positioning accuracy of Real-Time PPP over Iran by means of GPS, GPS + GLONASS, GPS + BeiDou, and GPS + GLONASS + BeiDou configurations. To this end, RINEX observations of six GNSS stations, within Iranian Permanent GNSS Network (IPGN), over consecutive sixteen days were processed via BKG NTRIP Client (BNC, v 2.12). In the processing steps, the IGS-MGEX broadcast ephemerides (BRDM, provided by TUM/DLR) and the pre-saved CLK93 broadcast corrections stream (provided by CNES) have been used as the satellites known information. The numerical results were compared against the station coordinates obtained from the double-difference solutions by Bernese GPS Software v 5.0. Accordingly, we have found that GPS + BeiDou combination can reduce the convergence time by 27%, 16% and 10% and improve the positioning accuracy by 22%, 18% and 2%, in the north, east and up components, respectively, as compared with the GPS PPP. Additionally, in comparison to the GPS + GLONASS results, GPS + GLONASS + BeiDou combination speeds up the convergence time by 9%, 8% and 9% and enhance the positioning accuracy by 8%, 5% and 6%, in the north, east and up components, respectively. Overall, thanks to the availability of the current BeiDou constellation observations, the considerable decrease in the convergence time on one hand, and the improvement in the positioning accuracy on the other, can verify the efficiency of utilizing multi-GNSS PPP for real-time applications over Iran.

77 FR 12106 - 88th Meeting: RTCA Special Committee 159, Global Positioning System (GPS)

Federal Register 2010, 2011, 2012, 2013, 2014

2012-02-28

... 159, Global Positioning System (GPS) AGENCY: Federal Aviation Administration (FAA), U.S. Department of Transportation (DOT). ACTION: Notice of RTCA Special Committee 159, Global Positioning System (GPS). SUMMARY: The..., Global Positioning System (GPS). DATES: The meeting will be held March 13-16, 2012, from 9 a.m.-4:30 p.m...

GPS-based system for satellite tracking and geodesy

NASA Technical Reports Server (NTRS)

Bertiger, Willy I.; Thornton, Catherine L.

1989-01-01

High-performance receivers and data processing systems developed for GPS are reviewed. The GPS Inferred Positioning System (GIPSY) and the Orbiter Analysis and Simulation Software (OASIS) are described. The OASIS software is used to assess GPS system performance using GIPSY for data processing. Consideration is given to parameter estimation for multiday arcs, orbit repeatability, orbit prediction, daily baseline repeatability, agreement with VLBI, and ambiguity resolution. Also, the dual-frequency Rogue receiver, which can track up to eight GPS satellites simultaneously, is discussed.

Pre-Flight Testing of Spaceborne GPS Receivers using a GPS Constellation Simulator

NASA Technical Reports Server (NTRS)

Kizhner, Semion; Davis, Edward; Alonso, R.

1999-01-01

The NASA Goddard Space Flight Center (GSFC) Global Positioning System (GPS) applications test facility has been established within the GSFC Guidance Navigation and Control Center. The GPS test facility is currently housing the Global Simulation Systems Inc. (GSSI) STR2760 GPS satellite 40-channel attitude simulator and a STR4760 12-channel navigation simulator. The facility also contains a few other resources such as an atomic time standard test bed, a rooftop antenna platform and a radome. It provides a new capability for high dynamics GPS simulations of space flight that is unique within the aerospace community. The GPS facility provides a critical element for the development and testing of GPS based technologies i.e. position, attitude and precise time determination used on-board a spacecraft, suborbital rocket balloon. The GPS simulation system is configured in a transportable rack and is available for GPS component development as well as for component, spacecraft subsystem and system level testing at spacecraft integration and tests sites. The GPS facility has been operational since early 1996 and has utilized by space flight projects carrying GPS experiments, such as the OrbView-2 and the Argentine SAC-A spacecrafts. The SAC-A pre-flight test data obtained by using the STR2760 simulator and the comparison with preliminary analysis of the GPS data from SAC-A telemetry are summarized. This paper describes pre-flight tests and simulations used to support a unique spaceborne GPS experiment. The GPS experiment mission objectives and the test program are described, as well as the GPS test facility configuration needed to verify experiment feasibility. Some operational and critical issues inherent in GPS receiver pre-flight tests and simulations using this GPS simulation, and test methodology are described. Simulation and flight data are presented. A complete program of pre-flight testing of spaceborne GPS receivers using a GPS constellation simulator is detailed.

Pre-Flight Testing of Spaceborne GPS Receivers Using a GPS Constellation Simulator

NASA Technical Reports Server (NTRS)

Kizhner, Semion; Davis, Edward; Alonso, Roberto

1999-01-01

The NASA Goddard Space Flight Center (GSFC) Global Positioning System (GPS) applications test facility has been established within the GSFC Guidance Navigation and Control Center. The GPS test facility is currently housing the Global Simulation Systems Inc. (GSSI) STR2760 GPS satellite 40-channel attitude simulator and a STR4760 12-channel navigation simulator. The facility also contains a few other resources such as an atomic time standard test bed, a rooftop antenna platform and a radome. It provides a new capability for high dynamics GPS simulations of space flight that is unique within the aerospace community. The GPS facility provides a critical element for the development and testing of GPS based technologies i.e. position, attitude and precise time determination used on-board a spacecraft, suborbital rocket or balloon. The GPS simulator system is configured in a transportable rack and is available for GPS component development as well as for component, spacecraft subsystem and system level testing at spacecraft integration and test sites. The GPS facility has been operational since early 1996 and has been utilized by space flight projects carrying GPS experiments, such as the OrbView-2 and the Argentine SAC-A spacecrafts. The SAC-A pre-flight test data obtained by using the STR2760 simulator and the comparison with preliminary analysis of the GPS data from SAC-A telemetry are summarized. This paper describes pre-flight tests and simulations used to support a unique spaceborne GPS experiment. The GPS experiment mission objectives and the test program are described, as well as the GPS test facility configuration needed to verify experiment feasibility. Some operational and critical issues inherent in GPS receiver pre-flight tests and simulations using this GPS simulator, and test methodology are described. Simulation and flight data are presented. A complete program of pre-flight testing of spaceborne GPS receivers using a GPS constellation simulator is detailed.

Attracting and retaining GPs: a stakeholder survey of priorities.

PubMed

Lorant, Vincent; Geerts, Charlotte; Duchesnes, Christiane; Goedhuys, Jo; Ryssaert, Lynn; Remmen, Roy; D'hoore, William

2011-07-01

Despite being a key player in the healthcare system, training and practising general practice has become less attractive in many countries and is in need of reform. To identify political priorities for improving GPs' attraction to the profession and their retention within it. Stakeholder face-to-face survey in Belgium, 2008. A total of 102 key stakeholders were recruited from policymakers, professional groups, academia, GP leaders, and the media. All interviewees were asked to score 23 policies on four criteria: effectiveness in attracting and retaining GPs, cost to society, acceptance by other health professionals, and accessibility of care. An overall performance score was computed (from -3 to +3) for each type of policy - training, financing, work-life balance, practice organisation, and governance - and for innovative versus conservative policies. Practice organisation policies and training policies received the highest scores (mean score ≥ 1.11). Financing policies, governance, and work-life balance policies scored poorly (mean score ≤ 0.65) because they had negative effects, particularly in relation to cost, acceptance, and accessibility of care. Stakeholders were keen on moving GPs towards team work, improving their role as care coordinator, and helping them to offload administrative tasks (score ≥ 1.4). They also favoured moves to increase the early and integrated exposure of all medical students to general practice. Overall, conservative policies were better scored than innovative ones (beta = -0.16, 95% confidence interval = -0.28 to -0.03). The reforming of general practice is made difficult by the small-step approach, as well as the importance of decision criteria related to cost, acceptance, and access.

Spaceborne GPS Current Status and Future Visions

NASA Technical Reports Server (NTRS)

Bauer, Frank H.; Hartman, Kate; Lightsey, E. Glenn

1998-01-01

The Global Positioning System (GPS), developed by the Department of Defense, is quickly revolutionizing the architecture of future spacecraft and spacecraft systems. Significant savings in spacecraft life cycle cost, in power, and in mass can be realized by exploiting Global Positioning System (GPS) technology in spaceborne vehicles. These savings are realized because GPS is a systems sensor-it combines the ability to sense space vehicle trajectory, attitude, time, and relative ranging between vehicles into one package. As a result, a reduced spacecraft sensor complement can be employed on spacecraft and significant reductions in space vehicle operations cost can be realized through enhanced on- board autonomy. This paper provides an overview of the current status of spaceborne GPS, a description of spaceborne GPS receivers available now and in the near future, a description of the 1997-1999 GPS flight experiments and the spaceborne GPS team's vision for the future.

Field tests of a handheld laser communications/position-finding binocular system

NASA Astrophysics Data System (ADS)

Chan, Victor J.; Rivers, Michael D.; Harris, Amy L.

1998-01-01

Lasers provide a means for transmitting larger quantities of data at higher rates than conventional radio frequency devices and can be utilized during radio silent operations on the battle field. A forward scout needs to be able to observe the positions of various targets and relay that information back to a tactical operations command center in a covert manner. The BiCom device built by Trex Communications provides laser ranging, azimuth and elevation angle to a target, GPS position information, data storage and transmit capability, and full duplex audio transmission capability, all in a 3 kg hand held package. The communication channel utilizes an eye safe lasercom transceiver for covert voice or data transfer at 100 kbps at distances of up to 5 km. The information gathered electronically by the unit is sufficient to calculate the actual GPS positions or military grid coordinates of the observed targets. Several dozen targets can be stored in memory for later transmission via lasercom. Field tests were conducted by US Army personnel to evaluate these units and compare the results with conventional means of target position determination and data transfer. A description of the system and results of these tests are presented.

Monitoring Sea Level by Tide Gauges and GPS at Barcelona and Estartit Harbours

NASA Astrophysics Data System (ADS)

Martinez Benjamin, J. J.; Gili, J.; Lopez, R.; Tapia, A.; Bosch, E.; Perez, B.; Pros, F.

2012-04-01

Sea level is an environmental variable which is widely recognised as being important in many scientific disciplines as a control parameter for coastal dynamical processes or climate processes in the coupled atmosphere-ocean systems, as well as engineering applications. A major source of sea-level data are the national networks of coastal tide gauges, in Spain belonging to different institutions as the Instituto Geográfico Nacional (IGN), Puertos del Estado (PE), Instituto Hidrográfico de la Marina (IHM), etc. The tide gauge of l'Estartit is a traditional floating gauge placed 21 years ago and has an accuracy of ± 2 mm. Since 1996, 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 2006, due to the work for the expansion of the harbour, the tide gauge had to be moved. Before the work started, appropiate GPS measurements were carried out in order to ensure the connection of the tide gauge data. During October 2006 and May 2008, the tide gauge was inactive and it has been moved on to a new location inside the harbour. In June 2008, new GPS and levelling measures have been done in order to tie the new location into SPGIC project and to co-locate old data respect the new one. Although l'Estartit does not have a GPS permanent station, it is possible to build a virtual one from the service "CATNET web" of the ICC. "CATNET web" is a data distribution system of a virtual GPS permanent station via web. From the coordinates where you want to place the virtual station, the time interval and the measurement rate, the system generates a RINEX file under the requested conditions. At Barcelona harbour there is one MIROS radar tide gauge belonging to Puertos del Estado (Spanish Harbours). It is placed at the dock 140 of the ENAGAS Building.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.This sensor also measures agitation and sends wave parameters each 20 min. A provisional tide gauge bench mark has been defined while the levelling has being done. There is a GPS station Leica Geosystems GRX1200 GG Pro and antenna 1202. Bathymetric campaigns inside the harbour have been made. The presentation is directed to the description of the actual situation of the geodetic infrastructure of Barcelona and l'Estartit sites for sea level determination and contribution to regional sea level rise.

Using Internet-Based Automated Software to Process GPS Data at Michigan Tech University

NASA Astrophysics Data System (ADS)

Crook, A.; Diehl, J. F.

2003-12-01

The Michigan Tech University GPS monument was made operational in October of 2002. The monument, which consists of a concrete pillar extending approximately 10 feet below the surface and protrudes 5 feet above ground, is located at the Houghton County Memorial Airport (47.171803° N, 88.498361° W). The primary purpose of the monument is to measure the velocity of the North American Plate at this location. A Trimble 4000ssi geodetic receiver with a Trimble Zephyr antenna is used to collect GPS data. The data are sent to a PC where they are processed using Auto-GIPSY, an internet-based GPS processing utility, which makes it possible to process GPS data, via email, without having knowledge of how the software works. Two Perl scripts were written to facilitate automation and to simplify processing of the GPS data even further. Twelve months of GPS data were processed, using Auto-GIPSY, which produced a velocity of -24 +/- 5 mm/yr and -4 +/- 6 mm/yr for the X and Y components respectively with an azimuth of 261° with respect to the ITRF2000. This calculated result compares well with the NNR-NUVEL1A velocity of -17 mm/yr and -1 mm/yr for the X and Y components respectively with an azimuth of 267° . The results from an alternative online processing service, the Scripps Coordinate Update Tool (SCOUT) that uses GAMIT, will also be presented as a comparative method.

Concept of AHRS Algorithm Designed for Platform Independent Imu Attitude Alignment

NASA Astrophysics Data System (ADS)

Tomaszewski, Dariusz; Rapiński, Jacek; Pelc-Mieczkowska, Renata

2017-12-01

Nowadays, along with the advancement of technology one can notice the rapid development of various types of navigation systems. So far the most popular satellite navigation, is now supported by positioning results calculated with use of other measurement system. The method and manner of integration will depend directly on the destination of system being developed. To increase the frequency of readings and improve the operation of outdoor navigation systems, one will support satellite navigation systems (GPS, GLONASS ect.) with inertial navigation. Such method of navigation consists of several steps. The first stage is the determination of initial orientation of inertial measurement unit, called INS alignment. During this process, on the basis of acceleration and the angular velocity readings, values of Euler angles (pitch, roll, yaw) are calculated allowing for unambiguous orientation of the sensor coordinate system relative to external coordinate system. The following study presents the concept of AHRS (Attitude and heading reference system) algorithm, allowing to define the Euler angles.The study were conducted with the use of readings from low-cost MEMS cell phone sensors. Subsequently the results of the study were analyzed to determine the accuracy of featured algorithm. On the basis of performed experiments the legitimacy of developed algorithm was stated.

The Performance Analysis of a Real-Time Integrated INS/GPS Vehicle Navigation System with Abnormal GPS Measurement Elimination

PubMed Central

Chiang, Kai-Wei; Duong, Thanh Trung; Liao, Jhen-Kai

2013-01-01

The integration of an Inertial Navigation System (INS) and the Global Positioning System (GPS) is common in mobile mapping and navigation applications to seamlessly determine the position, velocity, and orientation of the mobile platform. In most INS/GPS integrated architectures, the GPS is considered to be an accurate reference with which to correct for the systematic errors of the inertial sensors, which are composed of biases, scale factors and drift. However, the GPS receiver may produce abnormal pseudo-range errors mainly caused by ionospheric delay, tropospheric delay and the multipath effect. These errors degrade the overall position accuracy of an integrated system that uses conventional INS/GPS integration strategies such as loosely coupled (LC) and tightly coupled (TC) schemes. Conventional tightly coupled INS/GPS integration schemes apply the Klobuchar model and the Hopfield model to reduce pseudo-range delays caused by ionospheric delay and tropospheric delay, respectively, but do not address the multipath problem. However, the multipath effect (from reflected GPS signals) affects the position error far more significantly in a consumer-grade GPS receiver than in an expensive, geodetic-grade GPS receiver. To avoid this problem, a new integrated INS/GPS architecture is proposed. The proposed method is described and applied in a real-time integrated system with two integration strategies, namely, loosely coupled and tightly coupled schemes, respectively. To verify the effectiveness of the proposed method, field tests with various scenarios are conducted and the results are compared with a reliable reference system. PMID:23955434

Cancer surviving patients' rehabilitation – understanding failure through application of theoretical perspectives from Habermas

PubMed Central

Mikkelsen, Thorbjørn H; Soendergaard, Jens; Jensen, Anders B; Olesen, Frede

2008-01-01

This study aims to analyze whether the rehabilitation of cancer surviving patients (CSPs) can be better organized. The data for this paper consists of focus group interviews (FGIs) with CSPs, general practitioners (GPs) and hospital physicians. The analysis draws on the theoretical framework of Jürgen Habermas, utilizing his notions of 'the system and the life world' and 'communicative and strategic action'. In Habermas' terminology, the social security system and the healthcare system are subsystems that belong to what he calls the 'system', where actions are based on strategic actions activated by the means of media such as money and power which provide the basis for other actors' actions. The social life, on the other hand, in Habermas' terminology, belongs to what he calls the 'life world', where communicative action is based on consensual coordination among individuals. Our material suggests that, within the hospital world, the strategic actions related to diagnosis, treatment and cure in the biomedical discourse dominate. They function as inclusion/exclusion criteria for further treatment. However, the GPs appear to accept the CSPs' previous cancer diagnosis as a precondition sufficient for providing assistance. Although the GPs use the biomedical discourse and often give biomedical examples to exemplify rehabilitation needs, they find psychosocial aspects, so-called lifeworld aspects, to be an important component of their job when helping CSPs. In this way, they appear more open to communicative action in relation to the CSPs' lifeworld than do the hospital physicians. Our data also suggests that the CSPs' lifeworld can be partly colonized by the system during hospitalization, making it difficult for CSPs when they are discharged at the end of treatment. This situation seems to be crucial to our understanding of why CSPs often feel left in limbo after discharge. We conclude that the distinction between the system and the lifeworld and the implications of a possible colonization during hospitalization offers an important theoretical framework for determining and addressing different types of rehabilitation needs. PMID:18538001

GPS/REFSAT definition study report for low-cost terminals

NASA Technical Reports Server (NTRS)

1980-01-01

A relay transponder, located either on a satellite in geostationary orbit or on a local tower to relay acquisition-aiding data, ephemerides, etc, from a ground-based remote control station to a GPS civil user terminal located on a ship or land-transportation vehicle is described. Termed REFSAT (Reference Satellite), this concept reduces the circuit complexity and cost of user terminals. The various systems needed to implement the REFSAT concept for low-cost, GPS civil terminals are defined. The GPS/REFSAT system compatible with the NAVSTAR GPS system consists of a geostationary relay satellite, civil user terminals, and the central facility which performs operations common to all users for relay via the space segment. A GPS/REFSAT system utilizing a local tower for the relay transponder is described, results of a study of civil user requirements are presented, and specifications for the GPS/REFSAT system and its individual segments are included.

Measuring levee elevation heights in North Louisiana.

DOT National Transportation Integrated Search

2009-12-01

The primary goals of this research are to measure the elevation and centerline coordinates of the top of federal and local levees and to ensure that resulting GPS measurement data are within a precise interval of plus or minus 3/10ths of a foot verti...

PBO Southwest Region: Baja Earthquake Response and Network Operations

NASA Astrophysics Data System (ADS)

Walls, C. P.; Basset, A.; Mann, D.; Lawrence, S.; Jarvis, C.; Feaux, K.; Jackson, M. E.

2011-12-01

The SW region of the Plate Boundary Observatory consists of 455 continuously operating GPS stations located principally along the transform system of the San Andreas fault and Eastern California Shear Zone. In the past year network uptime exceeded an average of 97% with greater than 99% data acquisition. Communications range from CDMA modem (307), radio (92), Vsat (30), DSL/T1/other (25) to manual downloads (1). Sixty-three stations stream 1 Hz data over the VRS3Net typically with <0.5 second latency. Over 620 maintenance activities were performed during 316 onsite visits out of approximately 368 engineer field days. Within the past year there have been 7 incidences of minor (attempted theft) to moderate vandalism (solar panel stolen) with one total loss of receiver and communications gear. Security was enhanced at these sites through fencing and more secure station configurations. In the past 12 months, 4 new stations were installed to replace removed stations or to augment the network at strategic locations. Following the M7.2 El Mayor-Cucapah earthquake CGPS station P796, a deep-drilled braced monument, was constructed in San Luis, AZ along the border within 5 weeks of the event. In addition, UNAVCO participated in a successful University of Arizona-led RAPID proposal for the installation of six continuous GPS stations for post-seismic observations. Six stations are installed and telemetered through a UNAM relay at the Sierra San Pedro Martir. Four of these stations have Vaisala WXT520 meteorological sensors. An additional site in the Sierra Cucapah (PTAX) that was built by CICESE, an Associate UNAVCO Member institution in Mexico, and Caltech has been integrated into PBO dataflow. The stations will be maintained as part of the PBO network in coordination with CICESE. UNAVCO is working with NOAA to upgrade PBO stations with WXT520 meteorological sensors and communications systems capable of streaming real-time GPS and met data. The real-time GPS and meteorological sensor data streaming support watershed and flood analyses for regional early-warning systems related to NOAA's work with California Department of Water Resources. Currently 19 stations are online and streaming with 7 more in preparation. In 2008 PBO became the steward of 209 existing network stations of which 140 are in the SW region that included SCIGN, BARD, BARGEN stations. Due to the mix of incompatible equipment used between PBO and existing network stations a project was undertaken to standardize existing network GPS stations to PBO specifications by upgrading power systems and enclosures. To date 96 stations have been upgraded. UNAVCO is currently funded through a USGS ARRA grant to construct 8 new GPS stations in the San Francisco Bay Area capable of streaming high rate data. At present 6 stations are built with 2 permits outstanding.

Investigation some algorithms for solving problems of local geodynamics with using base GlonassGps stations. (Russian Title: Исследование некоторых алгоритмов решения задач локальной геодинамики с использованием базовых Глонасс/Gps станций)

NASA Astrophysics Data System (ADS)

Kuznetsova, E. V.; Bordovitsyna, T. V.; Chernitsov, A. M.

2011-07-01

In this paper mathematical modeling results of some algorithms for solving problems of local geodynamics by using base GLONASSGPS stations are presented. The statistical algorithm for trend discovering in coordinates of the point and ways of reduction of influencing random errors on results of coordinate determination with using third differences of measured distances are discussed.

Pilot implementation of a technologically advanced system for the optimization of pre-hospital, trauma patient care.

PubMed

Vagianos, Constantine E; Dimopoulou, Efi; Tsiftsis, Dimitrios; Spyropoulos, Charalambos; Spyrakopoulos, Panagiotis; Vagenas, Konstantinos

2010-07-01

Cooperation between medical informatics, wireless communication and pre-hospital emergency services is essential for the optimal pre-hospital patient treatment. The use of technological innovations improves medical care in the pre-hospital setting with regard to the organization of an integrated center, which coordinates all parties involved for the patient's best interest. A dispatch center was developed in the city of Patras, in southwestern Greece, equipped with a Geographic Information System (GIS), which immediately points out the location of emergency vehicles (EVs) on a digital map depicting the city plan. Additionally, three ambulances of the National Center of Immediate Aid (NCIA) were equipped with a decentralized traffic management system for the vehicle's traffic priority at signaled junctions. The system consisted of a cellular-based (GSM) telemedicine module, a Global Positioning System (GPS) and a web camera system in the vehicle cabin. The aforementioned system provided considerable assistance to the pre-hospital treatment first by selecting the ambulance closest to the accident's location and then by pinpointing the optimum route to the hospital, thus significantly reducing the overall transportation time. The project's objective to coordinate emergency hospital departments involved in the treatment of trauma patients with other emergency services by utilizing high technology was achieved within this interdisciplinary effort.

Line of sight pointing technology for laser communication system between aircrafts

NASA Astrophysics Data System (ADS)

Zhao, Xin; Liu, Yunqing; Song, Yansong

2017-12-01

In space optical communications, it is important to obtain the most efficient performance of line of sight (LOS) pointing system. The errors of position (latitude, longitude, and altitude), attitude angles (pitch, yaw, and roll), and installation angle among a different coordinates system are usually ineluctable when assembling and running an aircraft optical communication terminal. These errors would lead to pointing errors and make it difficult for the LOS system to point to its terminal to establish a communication link. The LOS pointing technology of an aircraft optical communication system has been researched using a transformation matrix between the coordinate systems of two aircraft terminals. A method of LOS calibration has been proposed to reduce the pointing error. In a flight test, a successful 144-km link was established between two aircrafts. The position and attitude angles of the aircraft have been obtained to calculate the pointing angle in azimuth and elevation provided by using a double-antenna GPS/INS system. The size of the field of uncertainty (FOU) and the pointing accuracy are analyzed based on error theory, and it has been also measured using an observation camera installed next to the optical LOS. Our results show that the FOU of aircraft optical communications is 10 mrad without a filter, which is the foundation to acquisition strategy and scanning time.

GPS Radio Occultation as Part of the Global Observing System for Atmosphere

NASA Technical Reports Server (NTRS)

Mannucci, Anthony J.; Ao, C. O.; Iijima, B. A.; Wilson, B. D.; Yunck, T. P.; Kursinski, E. R.

2008-01-01

Topics include: The Measurement (Physical retrievals based on time standards), GPS Retrieval Products, Retrievals and Radiances: CLARREO Mission, GPS RO and AIRS, GPS RO and Microwave, GPS RO and Radiosondes, GPS/GNSS Science, and Conclusions.

Smartphones Based Mobile Mapping Systems

NASA Astrophysics Data System (ADS)

Al-Hamad, A.; El-Sheimy, N.

2014-06-01

The past 20 years have witnessed an explosive growth in the demand for geo-spatial data. This demand has numerous sources and takes many forms; however, the net effect is an ever-increasing thirst for data that is more accurate, has higher density, is produced more rapidly, and is acquired less expensively. For mapping and Geographic Information Systems (GIS) projects, this has been achieved through the major development of Mobile Mapping Systems (MMS). MMS integrate various navigation and remote sensing technologies which allow mapping from moving platforms (e.g. cars, airplanes, boats, etc.) to obtain the 3D coordinates of the points of interest. Such systems obtain accuracies that are suitable for all but the most demanding mapping and engineering applications. However, this accuracy doesn't come cheaply. As a consequence of the platform and navigation and mapping technologies used, even an "inexpensive" system costs well over 200 000 USD. Today's mobile phones are getting ever more sophisticated. Phone makers are determined to reduce the gap between computers and mobile phones. Smartphones, in addition to becoming status symbols, are increasingly being equipped with extended Global Positioning System (GPS) capabilities, Micro Electro Mechanical System (MEMS) inertial sensors, extremely powerful computing power and very high resolution cameras. Using all of these components, smartphones have the potential to replace the traditional land MMS and portable GPS/GIS equipment. This paper introduces an innovative application of smartphones as a very low cost portable MMS for mapping and GIS applications.

Spaceborne GPS: Current Status and Future Visions

NASA Technical Reports Server (NTRS)

Bauer, Frank H.; Hartman, Kate; Lightsey, E. Glenn

1998-01-01

The Global Positioning System (GPS), developed by the Department of Defense is quickly revolutionizing the architecture of future spacecraft and spacecraft systems. Significant savings in spacecraft life cycle cost, in power, and in mass can be realized by exploiting GPS technology in spaceborne vehicles. These savings are realized because GPS is a systems sensor--it combines the ability to sense space vehicle trajectory, attitude, time, and relative ranging between vehicles into one package. As a result, a reduced spacecraft sensor complement can be employed and significant reductions in space vehicle operations cost can be realized through enhanced on-board autonomy. This paper provides an overview of the current status of spaceborne GPS, a description of spaceborne GPS receivers available now and in the near future, a description of the 1997-2000 GPS flight experiments, and the spaceborne GPS team's vision for the future.

USNO GPS program

NASA Technical Reports Server (NTRS)

Putkovich, K.

1981-01-01

Initial test results indicated that the Global Positioning System/Time Transfer Unit (GPS/TTU) performed well within the + or - 100 nanosecond range required by the original system specification. Subsequent testing involved the verification of GPS time at the master control site via portable clocks and the acquisition and tracking of as many passes of the space vehicles currently in operation as possible. A description and discussion of the testing, system modifications, test results obtained, and an evaluation of both GPS and the GPS/TTU are presented.

Competition policy for health care provision in the Netherlands.

PubMed

Schut, Frederik T; Varkevisser, Marco

2017-02-01

In the Netherlands in 2006 a major health care reform was introduced, aimed at reinforcing regulated competition in the health care sector. Health insurers were provided with strong incentives to compete and more room to negotiate and selectively contract with health care providers. Nevertheless, the bargaining position of health insurers vis-à-vis both GPs and hospitals is still relatively weak. GPs are very well organized in a powerful national interest association (LHV) and effectively exploit the long-standing trust relationship with their patients. They have been very successful in mobilizing public support against unfavorable contracting practices of health insurers and enforcement of the competition act. The rapid establishment of multidisciplinary care groups to coordinate care for patients with chronic diseases further strengthened their position. Due to ongoing horizontal consolidation, hospital markets in the Netherlands have become highly concentrated. Only recently the Dutch competition authority prohibited the first hospital merger. Despite the highly concentrated health insurance market, it is unclear whether insurers will have sufficient countervailing buyer power vis-à-vis GPs and hospitals to effectively fulfill their role as prudent buyer of care, as envisioned in the reform. To prevent further consolidation and anticompetitive coordination, strict enforcement of competition policy is crucially important for safeguarding the potential for effective insurer-provider negotiations about quality and price. Copyright © 2016 Elsevier Ireland Ltd. All rights reserved.

Spacecraft applications of advanced global positioning system technology

NASA Technical Reports Server (NTRS)

1988-01-01

This is the final report on the Texas Instruments Incorporated (TI) simulations study of Spacecraft Application of Advanced Global Positioning System (GPS) Technology. This work was conducted for the NASA Johnson Space Center (JSC) under contract NAS9-17781. GPS, in addition to its baselined capability as a highly accurate spacecraft navigation system, can provide traffic control, attitude control, structural control, and uniform time base. In Phase 1 of this program, another contractor investigated the potential of GPS in these four areas and compared GPS to other techniques. This contract was for the Phase 2 effort, to study the performance of GPS for these spacecraft applications through computer simulations. TI had previously developed simulation programs for GPS differential navigation and attitude measurement. These programs were adapted for these specific spacecraft applications. In addition, TI has extensive expertise in the design and production of advanced GPS receivers, including space-qualified GPS receivers. We have drawn on this background to augment the simulation results in the system level overview, which is Section 2 of this report.

Radiation-hardened fast acquisition/weak signal tracking system and method

NASA Technical Reports Server (NTRS)

Winternitz, Luke (Inventor); Boegner, Gregory J. (Inventor); Sirotzky, Steve (Inventor)

2009-01-01

A global positioning system (GPS) receiver and method of acquiring and tracking GPS signals comprises an antenna adapted to receive GPS signals; an analog radio frequency device operatively connected to the antenna and adapted to convert the GPS signals from an analog format to a digital format; a plurality of GPS signal tracking correlators operatively connected to the analog RF device; a GPS signal acquisition component operatively connected to the analog RF device and the plurality of GPS signal tracking correlators, wherein the GPS signal acquisition component is adapted to calculate a maximum vector on a databit correlation grid; and a microprocessor operatively connected to the plurality of GPS signal tracking correlators and the GPS signal acquisition component, wherein the microprocessor is adapted to compare the maximum vector with a predetermined correlation threshold to allow the GPS signal to be fully acquired and tracked.

Bioluminescence Truth Data Measurement and Signature Detection

DTIC Science & Technology

2007-09-30

cell phone based communications module attached to the top of the piling. A cell phone tower represents communication of data to shore. Also shown...representing each Kilroy installation are located based on GPS coordinates telemetered by the cell phone module. Icons point in direction of most recently

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.

Navstar Global Positioning System (GPS) clock program: Present and future

NASA Technical Reports Server (NTRS)

Tennant, D. M.

1981-01-01

Global Positioning System (GPS) program status are discussed and plans for ensuring the long term continuation of the program are presented. Performance of GPS clocks is presented in terms of on orbit data as portrayed by GPS master control station kalman filter processing. The GPS Clock reliability program is reviewed in depth and future plans fo the overall clock program are published.

Performance Analysis of BDS Medium-Long Baseline RTK Positioning Using an Empirical Troposphere Model.

PubMed

Shu, Bao; Liu, Hui; Xu, Longwei; Qian, Chuang; Gong, Xiaopeng; An, Xiangdong

2018-04-14

For GPS medium-long baseline real-time kinematic (RTK) positioning, the troposphere parameter is introduced along with coordinates, and the model is ill-conditioned due to its strong correlation with the height parameter. For BeiDou Navigation Satellite System (BDS), additional difficulties occur due to its special satellite constellation. In fact, relative zenith troposphere delay (RZTD) derived from high-precision empirical zenith troposphere models can be introduced. Thus, the model strength can be improved, which is also called the RZTD-constrained RTK model. In this contribution, we first analyze the factors affecting the precision of BDS medium-long baseline RTK; thereafter, 15 baselines ranging from 38 km to 167 km in different troposphere conditions are processed to assess the performance of RZTD-constrained RTK. Results show that the troposphere parameter is difficult to distinguish from the height component, even with long time filtering for BDS-only RTK. Due to the lack of variation in geometry for the BDS geostationary Earth orbit satellite, the long convergence time of ambiguity parameters may reduce the height precision of GPS/BDS-combined RTK in the initial period. When the RZTD-constrained model was used in BDS and GPS/BDS-combined situations compared with the traditional RTK, the standard deviation of the height component for the fixed solution was reduced by 52.4% and 34.0%, respectively.

Performance Analysis of BDS Medium-Long Baseline RTK Positioning Using an Empirical Troposphere Model

PubMed Central

Liu, Hui; Xu, Longwei; Qian, Chuang; Gong, Xiaopeng; An, Xiangdong

2018-01-01

For GPS medium-long baseline real-time kinematic (RTK) positioning, the troposphere parameter is introduced along with coordinates, and the model is ill-conditioned due to its strong correlation with the height parameter. For BeiDou Navigation Satellite System (BDS), additional difficulties occur due to its special satellite constellation. In fact, relative zenith troposphere delay (RZTD) derived from high-precision empirical zenith troposphere models can be introduced. Thus, the model strength can be improved, which is also called the RZTD-constrained RTK model. In this contribution, we first analyze the factors affecting the precision of BDS medium-long baseline RTK; thereafter, 15 baselines ranging from 38 km to 167 km in different troposphere conditions are processed to assess the performance of RZTD-constrained RTK. Results show that the troposphere parameter is difficult to distinguish from the height component, even with long time filtering for BDS-only RTK. Due to the lack of variation in geometry for the BDS geostationary Earth orbit satellite, the long convergence time of ambiguity parameters may reduce the height precision of GPS/BDS-combined RTK in the initial period. When the RZTD-constrained model was used in BDS and GPS/BDS-combined situations compared with the traditional RTK, the standard deviation of the height component for the fixed solution was reduced by 52.4% and 34.0%, respectively. PMID:29661999

Surveying Small Streams with COTS UAVs

NASA Astrophysics Data System (ADS)

McKean, J. A.; Wright, C. W.; Tonina, D.

2017-12-01

We tested the ability to make high resolution surveys of stream bathymetry and exposed banks using a commercial off-the-shelf unmanned quadcopter equipped with a 12 megapixel, gimbal stabilized, RGB camera, and L1-code-only GPS.Our study site is a canyon-wall confined gravel bed river with pool-riffle morphology. The survey reach was 15 m wide and on average 0.3 m deep with a maximum water depth during survey of approximately 1.2 m. Streambed material ranged between pea gravel to boulders. For accuracy comparison we field-surveyed the reach with an RTK GPS. The survey mapped large boulders and cobbles, stream banks and bed morphology, as well as the center of each of 9 black/white photo targets with a surface area of 22" x 16" that were placed around the perimeter of the reach. The water was clear, and the bottom substrate reflectivity was highly variable and rich in texture Nearly 1,000 photos were captured, many with sub-centimeter pixels. The photos were processed using Agisoft Photoscan and the resulting point cloud linked to the GPS coordinate system via the surveyed photo targets. The submerged portion of the data was separated from the sub-aerial data, corrected for refraction using external software and then rejoined to produce a seamless point cloud. Comparison between the merged results and ground-survey point shows good agreement with less than 10cm rmse.

Autonomous navigation system based on GPS and magnetometer data

NASA Technical Reports Server (NTRS)

Julie, Thienel K. (Inventor); Richard, Harman R. (Inventor); Bar-Itzhack, Itzhack Y. (Inventor)

2004-01-01

This invention is drawn to an autonomous navigation system using Global Positioning System (GPS) and magnetometers for low Earth orbit satellites. As a magnetometer is reliable and always provides information on spacecraft attitude, rate, and orbit, the magnetometer-GPS configuration solves GPS initialization problem, decreasing the convergence time for navigation estimate and improving the overall accuracy. Eventually the magnetometer-GPS configuration enables the system to avoid costly and inherently less reliable gyro for rate estimation. Being autonomous, this invention would provide for black-box spacecraft navigation, producing attitude, orbit, and rate estimates without any ground input with high accuracy and reliability.

Geostar - Navigation location system

NASA Astrophysics Data System (ADS)

Keyser, Donald A.

The author describes the Radiodetermination Satellite Service (RDSS). The initial phase of the RDSS provides for a unique service enabling central offices and headquarters to obtain position-location information and receive short digital messages from mobile user terminals throughout the contiguous United States, southern Canada, and northern Mexico. The system employs a spread-spectrum, CDMA modulation technique allowing multiple customers to use the system simultaneously, without preassigned coordination with fellow users. Position location is currently determined by employing an existing radio determination receiver, such as Loran-C, GPS, or Transit, in the mobile user terminal. In the early 1990s position location will be determined at a central earth station by time-differential ranging of the user terminals via two or more geostationary satellites. A brief overview of the RDSS system architecture is presented with emphasis on the user terminal and its diverse applications.

Application of DGPS for Collision Avoidance in Intelligent Transportation Systems In a Wireless Environment

DOT National Transportation Integrated Search

2001-02-19

The Global Positioning System (GPS) is a satellite based radio-navigation system. A relatively large number of vehicles are already equipped with GPS devices. This project evaluated the application of Global Positing System (GPS) technology in collis...

IVS Pilot Project - Tropospheric Parameters

NASA Astrophysics Data System (ADS)

Boehm, J.; Schuh, H.; Engelhardt, G.; MacMillan, D.; Lanotte, R.; Tomasi, P.; Vereshchagina, I.; Haas, R.; Negusini, M.; Gubanov, V.

2003-04-01

In April 2002 the IVS (International VLBI Service for Geodesy and Astrometry) set up the IVS Pilot Project - Tropospheric Parameters and the Institute of Geodesy and Geophysics (IGG), Vienna, was asked to coordinate the project. After a call for participation six IVS Analysis Centers have joined the project and submitted their estimates of tropospheric parameters (wet and total zenith delays, horizontal gradients) for all IVS-R1 and IVS-R4 sessions since January 1st, 2002, on a regular basis. Using a two-step procedure the individual submissions are combined to stable and robust tropospheric parameters with 1h resolution and high accuracy. The zenith delays derived by VLBI are also compared with those provided by IGS (International GPS Service). At collocated sites (VLBI and GPS antennas at the same station) rather constant biases are found between the GPS and VLBI derived zenith delays, although both techniques are subject to the same tropospheric delays. Possible reasons for these biases are discussed.

Seasonal and Surface Hydrologic Loading Signals at GPS Stations Processed by the GAGE Facility

NASA Astrophysics Data System (ADS)

Puskas, C. M.; Meertens, C. M.; Phillips, D.

2017-12-01

UNAVCO is now producing hydrologic displacement model time series at GPS station coordinates in the Geodesy Advancing Geosciences and EarthScope (GAGE) Facility, including the Plate Boundary Observatory (PBO). The surface loads are obtained from global and national land data assimilation systems (GLDAS and NLDAS, respectively) land surface models produced by the Goddard Earth Sciences Data and Information Services Center (GES DISC). The land surface models are available as monthly files of environmental parameters documenting water, pressure, temperature, and other measures mass/energy transfer on a grid at the Earth's surface. Grids are 1º for the global GLDAS models and 0.125º for the NLDAS models in the conterminous US. UNAVCO extracts the soil moisture, snowpack, and water stored in vegetation parameters and calculates displacements in an elastic half-space at selected points, i.e., GPS station locations. UNAVCO has recently upgraded its hydrologic data products from GLDAS version 1 to version 2 and added NLDAS-based models, and the new data products are now available from the UNAVCO ftp server (ftp://data-out.unavco.org/pub/products/hydro) and will soon be available through web services. The GLDAS v2 models supersede those based on v1, which will no longer be updated. UNAVCO updates its hydrologic products on a quarterly basis. Seasonal signals in the GAGE GPS position time series have amplitudes on the order of several millimeters, which vary across the PBO network depending on local climate and geology. The signals are thought to be a combination of elastic displacement from surface loading and poroelastic displacement from groundwater depletion and recharge. We present a description of the hydrologic displacement modeling and provide examples of loading and resulting displacement. The GLDAS and NLDAS models are compared with each other and with GPS position time series at selected stations in different geographic regions.

NASA's global differential GPS system and the TDRSS augmentation service for satellites

NASA Technical Reports Server (NTRS)

Bar-Sever, Yoaz; Young, Larry; Stocklin, Frank; Rush, John

2004-01-01

NASA is planning to launch a new service for Earth satellites providing them with precise GPS differential corrections and other ancillary information enabling decimeter level orbit determination accuracy, and nanosecond time-transfer accuracy, onboard, in real-time. The TDRSS Augmentation Service for Satellites (TASS) will broadcast its message on the S-band multiple access channel of NASA's Tracking and Data Relay Satellite System (TDRSS). The satellite's phase array antenna has been configured to provide a wide beam, extending coverage up to 1000 km altitude over the poles. Global coverage will be ensured with broadcast from three or more TDRSS satellites. The GPS differential corrections are provided by the NASA Global Differential GPS (GDGPS) System, developed and operated by NASA's Jet Propulsion Laboratory. The GDGPS System employs a global ground network of more than 70 GPS receivers to monitor the GPS constellation in real time. The system provides real-time estimates of the GPS satellite states, as well as many other real-time products such as differential corrections, global ionospheric maps, and integrity monitoring. The unique multiply redundant architecture of the GDGPS System ensures very high reliability, with 99.999% demonstrated since the inception of the system in Early 2000. The estimated real time GPS orbit and clock states provided by the GDGPS system are accurate to better than 20 cm 3D RMS, and have been demonstrated to support sub-decimeter real time positioning and orbit determination for a variety of terrestrial, airborne, and spaceborne applications. In addition to the GPS differential corrections, TASS will provide real-time Earth orientation and solar flux information that enable precise onboard knowledge of the Earth-fixed position of the spacecraft, and precise orbit prediction and planning capabilities. TASS will also provide 5 seconds alarms for GPS integrity failures based on the unique GPS integrity monitoring service of the GDGPS System.

EmerLoc: location-based services for emergency medical incidents.

PubMed

Maglogiannis, I; Hadjiefthymiades, S

2007-10-01

Recent developments in positioning systems and telecommunications have provided the technology needed for the development of location aware medical applications. We developed a system, named EmerLoc, which is based upon this technology and uses a set of sensors that are attached to the patient's body, a micro-computing unit which is responsible for processing the sensor readings and a central monitoring unit, which coordinates the data flow. To demonstrate that the proposed system is technically feasible and acceptable for the potential users. Transmission speed is assessed mostly by means of transmission of DICOM compliant images in various operational scenarios. The positioning functionality was established both outdoor using GPS and indoor using the UCLA Nibble system. User acceptability was assessed in a hospital setting by 15 physicians who filled in a questionnaire after having used the system in an experimental setting. Transmission speeds ranged from 88kB/s for a IEEE 802.11 infrastructure to 2.5kB/s for a GSM/GPRS scenario. Positioning accuracy based on GPS was 5-10m. The physicians rated the technical aspects on average above 3 on a 5-point scale. Only the data presentation was assessed to be not satisfactory (2.81 on a 5-point scale). The reported results prove the feasibility of the proposed architecture and its alignment with widely established practices and standards, while the reaction of potential users who evaluated the system is quite positive.

The Evolution of Global Positioning System (GPS) Technology.

ERIC Educational Resources Information Center

Kumar, Sameer; Moore, Kevin B.

2002-01-01

Describes technological advances in the Global Positioning System (GPS), which is also known as the NAVSTAR GPS satellite constellation program developed in 1937, and changes in the nature of our world by GPS in the areas of agriculture, health, military, transportation, environment, wildlife biology, surveying and mapping, space applications, and…

The Foundation GPS Water Vapor Inversion and its Application Research

NASA Astrophysics Data System (ADS)

Liu, R.; Lee, T.; Lv, H.; Fan, C.; Liu, Q.

2018-04-01

Using GPS technology to retrieve atmospheric water vapor is a new water vapor detection method, which can effectively compensate for the shortcomings of conventional water vapor detection methods, to provide high-precision, large-capacity, near real-time water vapor information. In-depth study of ground-based GPS detection of atmospheric water vapor technology aims to further improve the accuracy and practicability of GPS inversion of water vapor and to explore its ability to detect atmospheric water vapor information to better serve the meteorological services. In this paper, the influence of the setting parameters of initial station coordinates, satellite ephemeris and solution observation on the total delay accuracy of the tropospheric zenith is discussed based on the observed data. In this paper, the observations obtained from the observation network consisting of 8 IGS stations in China in June 2013 are used to inverse the water vapor data of the 8 stations. The data of Wuhan station is further selected and compared with the data of Nanhu Sounding Station in Wuhan The error between the two data was between -6mm-6mm, and the trend of the two was almost the same, the correlation reached 95.8 %. The experimental results also verify the reliability of ground-based GPS inversion of water vapor technology.

Reliable positioning in a sparse GPS network, eastern Ontario

NASA Astrophysics Data System (ADS)

Samadi Alinia, H.; Tiampo, K.; Atkinson, G. M.

2013-12-01

Canada hosts two regions that are prone to large earthquakes: western British Columbia, and the St. Lawrence River region in eastern Canada. Although eastern Ontario is not as seismically active as other areas of eastern Canada, such as the Charlevoix/Ottawa Valley seismic zone, it experiences ongoing moderate seismicity. In historic times, potentially damaging events have occurred in New York State (Attica, 1929, M=5.7; Plattsburg, 2002, M=5.0), north-central Ontario (Temiskaming, 1935, M=6.2; North Bay, 2000, M=5.0), eastern Ontario (Cornwall, 1944, M=5.8), Georgian Bay (2005, MN=4.3), and western Quebec (Val-Des-Bois,2010, M=5.0, MN=5.8). In eastern Canada, the analysis of detailed, high-precision measurements of surface deformation is a key component in our efforts to better characterize the associated seismic hazard. The data from precise, continuous GPS stations is necessary to adequately characterize surface velocities from which patterns and rates of stress accumulation on faults can be estimated (Mazzotti and Adams, 2005; Mazzotti et al., 2005). Monitoring of these displacements requires employing high accuracy GPS positioning techniques. Detailed strain measurements can determine whether the regional strain everywhere is commensurate with a large event occurring every few hundred years anywhere within this general area or whether large earthquakes are limited to specific areas (Adams and Halchuck, 2003; Mazzotti and Adams, 2005). In many parts of southeastern Ontario and western Québec, GPS stations are distributed quite sparsely, with spacings of approximately 100 km or more. The challenge is to provide accurate solutions for these sparse networks with an approach that is capable of achieving high-accuracy positioning. Here, various reduction techniques are applied to a sparse network installed with the Southern Ontario Seismic Network in eastern Ontario. Recent developments include the implementation of precise point positioning processing on acquired GPS raw data. These are based on precise GPS orbit and clock data products with centimeter accuracy computed beforehand. Here, the analysis of 1Hz GPS data is conducted in order to find the most reliable regional network from eight stations (STCO, TYNO, ACTO, INUQ, IVKQ, KLBO, MATQ and ALGO) that cover the study area in eastern Ontario. In this way, the estimated parameters are the total number of ambiguities and resolved ambiguities, posteriori rms of each baseline and the coordinates for each station and their differences with the known coordinates. The positioning accuracy, the corrections and the accuracy of interpolated corrections, and the initialization time required for precise positioning are presented for the various applications.

Golden Laboratories and Offices | NREL

Science.gov Websites

most research laboratories are located at our campus in Golden, Colorado, north of highway I-70 and Renewable Energy Laboratory 15013 Denver West Parkway Golden, CO 80401 303-275-3000 GPS Coordinates 39 your trip. Security Procedures Visitors must check in at the Site Entrance Building. Please see

Feasibility of Construction of the Continuously Operating Geodetic GPS Network of Sinaloa, Mexico

NASA Astrophysics Data System (ADS)

Vazquez, G. E.; Jacobo, C.

2011-12-01

This research is based on the study and analysis of feasibility for the construction of the geodetic network for GPS continuous operation for Sinaloa, hereafter called (RGOCSIN). A GPS network of continuous operation is defined as that materialized structure physically through permanent monuments where measurements to the systems of Global Positioning (GPS) is performed continuously throughout a region. The GPS measurements in this network are measurements of accuracy according to international standards to define its coordinates, thus constituting the basic structure of geodetic referencing for a country. In this context is that in the near future the RGOCSIN constitutes a system state only accurate and reliable georeferencing in real-time (continuous and permanent operation) and will be used for different purposes; i.e., in addition to being fundamental basis for any lifting topographic or geodetic survey, and other areas such as: (1) Different construction processes (control and monitoring of engineering works); (2) Studies of deformation of the Earth's crust (before and after a seismic event); (3) GPS meteorology (weather forecasting); (4) Demarcation projects (natural and political); (5) Establishment of bases to generate mapping (necessary for the economic and social development of the state); (6) Precision agriculture (optimization of economic resources to the various crops); (7) Geographic information systems (Organization and planning activities associated with the design and construction of public services); (8) Urban growth (possible settlements in the appropriate form and taking care of the environmental aspect), among others. However there are criteria and regulations according to the INEGI (Instituto Nacional de Estadística y Geografía, http://www.inegi.org.mx/) that must be met; even for this stage of feasibility of construction that sees this project as a first phase. The fundamental criterion to be taken into account according to INEGI is a geometric distribution appropriate to ensure the state coverage, so the radius of coverage is found in the 10 to 15 Km. station. Likewise INEGI recommends the implementation of GPS measurements a priori in the vertices where at the end of such measurements generate a report by station containing details of the conditions of visibility, the GPS equipment used, the methodology of measurement and field data processing mode and is intended to build the RGOCSIN. Based on the results of the final report for each one of the measures beforehand, it will be or not feasible to determine if it meets these specifications to be finally considered as part of the RGOCSIN. It should be noted that the selection of the potential places where is intended to carry out the study and analysis of feasibility for the construction of the RGOCSIN will be some of the weather stations of the Centro de Investigación en Alimentación y Desarrollo (CIAD) Culiacán (http://www.ciad.edu.mx/clima/pc.asp). These weather stations have some technical infrastructure which would be used in the future; In addition to providing meteorological information which will ensure success in the solution of scientific and technological problems in various sectors requiring our state.

GPS-based satellite tracking system for precise positioning

NASA Technical Reports Server (NTRS)

Yunck, T. P.; Melbourne, W. G.; Thornton, C. L.

1985-01-01

NASA is developing a Global Positioning System (GPS) based measurement system to provide precise determination of earth satellite orbits, geodetic baselines, ionospheric electron content, and clock offsets between worldwide tracking sites. The system will employ variations on the differential GPS observing technique and will use a network of nine fixed ground terminals. Satellite applications will require either a GPS flight receiver or an on-board GPS beacon. Operation of the system for all but satellite tracking will begin by 1988. The first major satellite application will be a demonstration of decimeter accuracy in determining the altitude of TOPEX in the early 1990's. By then the system is expected to yield long-baseline accuracies of a few centimeters and instantaneous time synchronization to 1 ns.

Attracting and retaining GPs: a stakeholder survey of priorities

PubMed Central

Lorant, Vincent; Geerts, Charlotte; Duchesnes, Christiane; Goedhuys, Jo; Ryssaert, Lynn; Remmen, Roy; D'hoore, William

2011-01-01

Background Despite being a key player in the healthcare system, training and practising general practice has become less attractive in many countries and is in need of reform. Aim To identify political priorities for improving GPs' attraction to the profession and their retention within it. Design and setting Stakeholder face-to-face survey in Belgium, 2008. Method A total of 102 key stakeholders were recruited from policymakers, professional groups, academia, GP leaders, and the media. All interviewees were asked to score 23 policies on four criteria: effectiveness in attracting and retaining GPs, cost to society, acceptance by other health professionals, and accessibility of care. An overall performance score was computed (from –3 to +3) for each type of policy — training, financing, work–life balance, practice organisation, and governance — and for innovative versus conservative policies. Results Practice organisation policies and training policies received the highest scores (mean score ≥1.11). Financing policies, governance, and work–life balance policies scored poorly (mean score ≤0.65) because they had negative effects, particularly in relation to cost, acceptance, and accessibility of care. Stakeholders were keen on moving GPs towards team work, improving their role as care coordinator, and helping them to offload administrative tasks (score ≥1.4). They also favoured moves to increase the early and integrated exposure of all medical students to general practice. Overall, conservative policies were better scored than innovative ones (beta = –0.16, 95% confidence interval = –0.28 to –0.03). Conclusion The reforming of general practice is made difficult by the small-step approach, as well as the importance of decision criteria related to cost, acceptance, and access. PMID:21722449

A new global grid model for the determination of atmospheric weighted mean temperature in GPS precipitable water vapor

NASA Astrophysics Data System (ADS)

Huang, Liangke; Jiang, Weiping; Liu, Lilong; Chen, Hua; Ye, Shirong

2018-05-01

In ground-based global positioning system (GPS) meteorology, atmospheric weighted mean temperature, T_m , plays a very important role in the progress of retrieving precipitable water vapor (PWV) from the zenith wet delay of the GPS. Generally, most of the existing T_m models only take either latitude or altitude into account in modeling. However, a great number of studies have shown that T_m is highly correlated with both latitude and altitude. In this study, a new global grid empirical T_m model, named as GGTm, was established by a sliding window algorithm using global gridded T_m data over an 8-year period from 2007 to 2014 provided by TU Vienna, where both latitude and altitude variations are considered in modeling. And the performance of GGTm was assessed by comparing with the Bevis formula and the GPT2w model, where the high-precision global gridded T_m data as provided by TU Vienna and the radiosonde data from 2015 are used as reference values. The results show the significant performance of the new GGTm model against other models when compared with gridded T_m data and radiosonde data, especially in the areas with great undulating terrain. Additionally, GGTm has the global mean RMS_{PWV} and RMS_{PWV} /PWV values of 0.26 mm and 1.28%, respectively. The GGTm model, fed only by the day of the year and the station coordinates, could provide a reliable and accurate T_m value, which shows the possible potential application in real-time GPS meteorology, especially for the application of low-latitude areas and western China.

A study of ionospheric grid modification technique for BDS/GPS receiver

NASA Astrophysics Data System (ADS)

Liu, Xuelin; Li, Meina; Zhang, Lei

2017-07-01

For the single-frequency GPS receiver, ionospheric delay is an important factor affecting the positioning performance. There are many kinds of ionospheric correction methods, common models are Bent model, IRI model, Klobuchar model, Ne Quick model and so on. The US Global Positioning System (GPS) uses the Klobuchar coefficients transmitted in the satellite signal to correct the ionospheric delay error for a single frequency GPS receiver, but this model can only reduce the ionospheric error of about 50% in the mid-latitudes. In the Beidou system, the accuracy of the correction delay is higher. Therefore, this paper proposes a method that using BD grid information to correct GPS ionospheric delay to improve the ionospheric delay for the BDS/GPS compatible positioning receiver. In this paper, the principle of ionospheric grid algorithm is introduced in detail, and the positioning accuracy of GPS system and BDS/GPS compatible positioning system is compared and analyzed by the real measured data. The results show that the method can effectively improve the positioning accuracy of the receiver in a more concise way.

Development of a GPS buoy system for monitoring tsunami, sea waves, ocean bottom crustal deformation and atmospheric water vapor

NASA Astrophysics Data System (ADS)

Kato, Teruyuki; Terada, Yukihiro; Nagai, Toshihiko; Koshimura, Shun'ichi

2010-05-01

We have developed a GPS buoy system for monitoring tsunami for over 12 years. The idea was that a buoy equipped with a GPS antenna and placed offshore may be an effective way of monitoring tsunami before its arrival to the coast and to give warning to the coastal residents. The key technology for the system is real-time kinematic (RTK) GPS technology. We have successfully developed the system; we have detected tsunamis of about 10cm in height for three large earthquakes, namely, the 23 June 2001 Peru earthquake (Mw8.4), the 26 September 2003 Tokachi earthquake (Mw8.3) and the 5 September 2004 earthquake (Mw7.4). The developed GPS buoy system is also capable of monitoring sea waves that are mainly caused by winds. Only the difference between tsunami and sea waves is their frequency range and can be segregated each other by a simple filtering technique. Given the success of GPS buoy experiments, the system has been adopted as a part of the Nationwide Ocean Wave information system for Port and HArborS (NOWPHAS) by the Ministry of Land, Infrastructure, Transport and Tourism of Japan. They have established more than eight GPS buoys along the Japanese coasts and the system has been operated by the Port and Airport Research Institute. As a future scope, we are now planning to implement some other additional facilities for the GPS buoy system. The first application is a so-called GPS/Acoustic system for monitoring ocean bottom crustal deformation. The system requires acoustic waves to detect ocean bottom reference position, which is the geometrical center of an array of transponders, by measuring distances between a position at the sea surface (vessel) and ocean bottom equipments to return the received sonic wave. The position of the vessel is measured using GPS. The system was first proposed by a research group at the Scripps Institution of Oceanography in early 1980's. The system was extensively developed by Japanese researchers and is now capable of detecting ocean bottom positions with a few centimeters in accuracy. The system is now operational for more than ten sites along the Japanese coasts. Currently, however, the measurements are not continuous but have been done once to several times a year using a boat. If a GPS and acoustic system is placed on a buoy, ocean bottom position could be monitored in near real-time and continuous manner. This will allow us to monitor more detailed and short term crustal deformations at the sea bottom. Another application plan is for an atmospheric research. Previous researchers have shown that GPS is capable of measuring atmospheric water vapor through estimating tropospheric zenith delay measurements of GPS at the sea surface. Information of water vapor content and its temporal variation over sea surface will much contribute to weather forecast on land which has mostly been conducted only by land observations. Considering that the atmospheric mass moves from west to east in general in and around Japanese islands, information of water vapor together with other atmospheric data from an array of GPS buoy placed in the west of Japanese Islands, will much improve weather forecast. We try to examine if this is also feasible. As a conclusion of a series of GPS buoy experiments, we could assert that GPS buoy system will be a powerful tool to monitor ocean surface and much contribute to provide safe and secure life of people.

Miniaturized GPS/MEMS IMU integrated board

NASA Technical Reports Server (NTRS)

Lin, Ching-Fang (Inventor)

2012-01-01

This invention documents the efforts on the research and development of a miniaturized GPS/MEMS IMU integrated navigation system. A miniaturized GPS/MEMS IMU integrated navigation system is presented; Laser Dynamic Range Imager (LDRI) based alignment algorithm for space applications is discussed. Two navigation cameras are also included to measure the range and range rate which can be integrated into the GPS/MEMS IMU system to enhance the navigation solution.

General Practitioners' Attitudes Toward a Web-Based Mental Health Service for Adolescents: Implications for Service Design and Delivery.

PubMed

Subotic-Kerry, Mirjana; King, Catherine; O'Moore, Kathleen; Achilles, Melinda; O'Dea, Bridianne

2018-03-23

Anxiety disorders and depression are prevalent among youth. General practitioners (GPs) are often the first point of professional contact for treating health problems in young people. A Web-based mental health service delivered in partnership with schools may facilitate increased access to psychological care among adolescents. However, for such a model to be implemented successfully, GPs' views need to be measured. This study aimed to examine the needs and attitudes of GPs toward a Web-based mental health service for adolescents, and to identify the factors that may affect the provision of this type of service and likelihood of integration. Findings will inform the content and overall service design. GPs were interviewed individually about the proposed Web-based service. Qualitative analysis of transcripts was performed using thematic coding. A short follow-up questionnaire was delivered to assess background characteristics, level of acceptability, and likelihood of integration of the Web-based mental health service. A total of 13 GPs participated in the interview and 11 completed a follow-up online questionnaire. Findings suggest strong support for the proposed Web-based mental health service. A wide range of factors were found to influence the likelihood of GPs integrating a Web-based service into their clinical practice. Coordinated collaboration with parents, students, school counselors, and other mental health care professionals were considered important by nearly all GPs. Confidence in Web-based care, noncompliance of adolescents and GPs, accessibility, privacy, and confidentiality were identified as potential barriers to adopting the proposed Web-based service. GPs were open to a proposed Web-based service for the monitoring and management of anxiety and depression in adolescents, provided that a collaborative approach to care is used, the feedback regarding the client is clear, and privacy and security provisions are assured. ©Mirjana Subotic-Kerry, Catherine King, Kathleen O'Moore, Melinda Achilles, Bridianne O'Dea. Originally published in JMIR Human Factors (http://humanfactors.jmir.org), 23.03.2018.

Implementing GPS into Pave-IR.

DOT National Transportation Integrated Search

2009-03-01

To further enhance the capabilities of the Pave-IR thermal segregation detection system developed at the Texas Transportation Institute, researchers incorporated global positioning system (GPS) data collection into the thermal profiles. This GPS capa...

Geocenter Motion Derived from GNSS and SLR Tracking Data of LEO

NASA Astrophysics Data System (ADS)

Li, Y. S.; Ning, F. S.; Tseng, K. H.; Tseng, T. P.; Wu, J. M.; Chen, K. L.

2017-12-01

Space geodesy techniques can provide the monitoring data of global variations with high precision and large coverage through the satellites. Geocenter motion (GM) describes the difference of CF (Center of Figure) respect to CM (Center of Mass of the Earth System) due to the re-distribution and deformation of the earth system. Because satellite tracking data between ground stations and satellites orbit around the CM, geocenter motion is related to the realization of the ITRF (International Terrestrial Reference Frame) origin. In this study, GPS (Global Positioning System) observation data of IGS (International GNSS Service) and SLR (Satellite Laser Ranging) tracking data are applied to estimate the coordinates of observing sites on Earth's surface. The GPS observing sites are distributed deliberately and globally by 15° ×15° grids. Meanwhile, two different global ocean tide models are applied here. The model used in ITRF comparison and combination is parameter transformation, which is a mathematical formula allowing to transform the different frames between ITRF and CM system. Following the parameter transformation, the results of geocenter motion can be determined. The FORMOSAT-7/COSMIC-2 (F7C2) mission is a constellation of LEO (Low-Earth-Orbit) satellites, which will be launched in 2018. Besides the observing system for Meteorology, Ionosphere, and Climate, the F7C2 will be equipped with LRR (Laser Ranging Retroreflector). This work is a pilot survey to study the application of LEO SLR data in Taiwan.

National aerospace meeting of the Institute of Navigation

NASA Astrophysics Data System (ADS)

Fell, Patrick

The program for this year's aerospace meeting of The Institute of Navigation addressed developments in the evolving Global Positioning System (GPS) of navigation satellites, inertial navigation systems, and other electronic navigation systems and their applications. Also included in the program were a limited number of papers addressing the geodetic use of the GPS system.The Global Positioning System is a constellation of 18 navigation satellites being developed by the Department of Defense to provide instantaneous worldwide navigation. The system will support a multitude of military applications. The first paper by Jacobson reviewed the engineering development of GPS navigation receivers stressing the use of common hardware and software modules. A later paper by Ould described the mechanization of a digital receiver for GPS applications designed for faster acquisition of the spread spectrum satellite transmissions than analog receivers. The paper by Brady discussed the worldwide coverage that is provided by the limited number of satellites that will constitute the GPS constellation through 1983. The capability provided by the satellites presently on orbit would support a variety of experiments at almost any location. Tables of multiple satellite availability are provided for numerous worldwide locations. For civil aviation applications, Vogel addressed the satellite geometry considerations for low cost GPS user equipment, Esposito described the Federal Aviation Administration acceptance tests of a GPS navigation receiver, and Hopkins discussed the design and capability of an integrated GPS strapdown attitude and heading reference system for avionics.

GENESIS: GPS Environmental and Earth Science Information System

NASA Technical Reports Server (NTRS)

Hajj, George

1999-01-01

This presentation reviews the GPS ENvironmental and Earth Science Information System (GENESIS). The objectives of GENESIS are outlined (1) Data Archiving, searching and distribution for science data products derived from Space borne TurboRogue Space Receivers for GPS science and other ground based GPS receivers, (2) Data browsing using integrated visualization tools, (3) Interactive web/java-based data search and retrieval, (4) Data subscription service, (5) Data migration from existing GPS archived data, (6) On-line help and documentation, and (7) participation in the WP-ESIP federation. The presentation reviews the products and services of Genesis, and the technology behind the system.

Test results of the STI GPS time transfer receiver

NASA Technical Reports Server (NTRS)

Hall, D. L.; Handlan, J.; Wheeler, P.

1983-01-01

Global time transfer, or synchronization, between a user clock and USNO UTC time can be performed using the Global Positioning System (GPS), and commercially available time transfer receivers. This paper presents the test results of time transfer using the GPS system and a Stanford Telecommunications, Inc. (STI) Time Transfer System (TTS) Model 502. Tests at the GPS Master Control Site (MCS) in Vandenburg, California and at the United States Naval Observatory (USNO) in Washington, D.C. are described. An overview of GPS, and the STI TTS 502 is presented. A discussion of the time transfer process and test concepts is included.

A low-cost GPS/INS integrated vehicle heading angle measurement system

NASA Astrophysics Data System (ADS)

Wu, Ye; Gao, Tongyue; Ding, Yi

2018-04-01

GPS can provide continuous heading information, but the accuracy is easily affected by the velocity and shelter from buildings or trees. For vehicle systems, we propose a low-cost heading angle update algorithm. Based on the GPS/INS integrated navigation kalman filter, we add the GPS heading angle to the measurement vector, and establish its error model. The experiment results show that this algorithm can effectively improve the accuracy of GPS heading angle.

Applications of Clocks to Space Navigation & "Planetary GPS"

NASA Technical Reports Server (NTRS)

Lichten, Stephen M.

2004-01-01

The ability to fly atomic clocks on GPS satellites has profoundly defined the capabilities and limitations of GPS in near-Earth applications. It is likely that future infrastructure for Lunar and Mars applications will be constrained by financial factors. The development of a low cost, small, high performance space clock -- or ultrahigh performance space clocks -- could revolutionize and drive the entire approach to GPS-like systems at the Moon (or Mars), and possibly even change the future of GPS at Earth. Many system trade studies are required. The performance of future GPS-like tracking systems at the Moon or Mars will depend critically on clock performance, availability of inertial sensors, and constellation coverage. Example: present-day GPS carry 10(exp -13) clocks and require several updates per day. With 10(exp -15) clocks, a constellation at Mars could operate autonomously with updates just once per month. Use of GPS tracking at the Moon should be evaluated in a technical study.

Modular Software for Spacecraft Navigation Using the Global Positioning System (GPS)

NASA Technical Reports Server (NTRS)

Truong, S. H.; Hartman, K. R.; Weidow, D. A.; Berry, D. L.; Oza, D. H.; Long, A. C.; Joyce, E.; Steger, W. L.

1996-01-01

The Goddard Space Flight Center Flight Dynamics and Mission Operations Divisions have jointly investigated the feasibility of engineering modular Global Positioning SYSTEM (GPS) navigation software to support both real time flight and ground postprocessing configurations. The goals of this effort are to define standard GPS data interfaces and to engineer standard, reusable navigation software components that can be used to build a broad range of GPS navigation support applications. The paper discusses the GPS modular software (GMOD) system and operations concepts, major requirements, candidate software architecture, feasibility assessment and recommended software interface standards. In additon, ongoing efforts to broaden the scope of the initial study and to develop modular software to support autonomous navigation using GPS are addressed,

77 FR 13350 - Certain Automotive GPS Navigation Systems, Components Thereof, and Products Containing Same...

Federal Register 2010, 2011, 2012, 2013, 2014

2012-03-06

... INTERNATIONAL TRADE COMMISSION [Investigation No. 337-TA-814] Certain Automotive GPS Navigation Systems, Components Thereof, and Products Containing Same; Determination Not To Review Initial... importation of certain automotive GPS navigation systems, components thereof, and products containing the same...

A low-cost and reliable technique to monitor the spread of an invasive seagrass in the Caribbean Sea

NASA Astrophysics Data System (ADS)

Jobsis, D.; Wyllie-Echeverria, S.

2016-02-01

In 2002 the seagrass Halophila stipulacea was observed in Grenada in the Eastern Caribbean Sea. Since then this invasive species has spread northward through the Lesser Antilles and Leeward Islands into the US Virgin Islands. There are native Halophila species as well as other seagrass species in Eastern Caribbean therefore it is essential to accurately identify H. stipulacea before an invasion event is reported. Moreover, because the consequences of H. stipulaceapresence and spread are not known in many locations, after accurate identification is made it is also important to map patch expansion as a first step in process studies designed to determine impact. We now report a low-cost (<$1000) and reliable technique to produce species specific, geo-referenced maps that can be used to track invasion spread. System components are: a GoPro video camera placed inside underwater housing, a weighted towfish and a GPS tracking device. The camera, set in the time-lapse mode, is fixed to the towfish; Afterward using a series of straight line transects, our array is towed at low speeds while synched to GPS. The accuracy of an underwater video system is based on knowing the accurate position of seagrass on the seafloor during filming (Norris et al. 1997). After sampling images and their associated GPS coordinates are imported to a spreadsheet and coded such that H. stipulaceais related to a known position on the bottom. With this system we produce accurate maps that specifically identify H. stipulacea patches, regardless of water depth, on the seafloor. During our poster presentation we will show a series of images from 2015 sampling and display mapping results. Since the 2002 sighting in Grenada, H. stipulaceae has spread northward to nineteen Eastern Caribbean Islands (Williette et al 2014). Our technique will allow those charged with protecting natural resources to track the spread of this invasion and potentially provide an early warning system for islands nations not yet invaded.

Evaluation of a Mobile Phone for Aircraft GPS Interference

NASA Technical Reports Server (NTRS)

Nguyen, Truong X.

2004-01-01

Measurements of spurious emissions from a mobile phone are conducted in a reverberation chamber for the Global Positioning System (GPS) radio frequency band. This phone model was previously determined to have caused interference to several aircraft GPS receivers. Interference path loss (IPL) factors are applied to the emission data, and the outcome compared against GPS receiver susceptibility. The resulting negative safety margins indicate there are risks to aircraft GPS systems. The maximum emission level from the phone is also shown to be comparable with some laptop computer's emissions, implying that laptop computers can provide similar risks to aircraft GPS receivers.

A review of GPS-based tracking techniques for TDRS orbit determination

NASA Technical Reports Server (NTRS)

Haines, B. J.; Lichten, S. M.; Malla, R. P.; Wu, S.-C.

1993-01-01

This article evaluates two fundamentally different approaches to the Tracking and Data Relay Satellite (TDRS) orbit determination utilizing Global Positioning System (GPS) technology and GPS-related techniques. In the first, a GPS flight receiver is deployed on the TDRS. The TDRS ephemerides are determined using direct ranging to the GPS spacecraft, and no ground network is required. In the second approach, the TDRS's broadcast a suitable beacon signal, permitting the simultaneous tracking of GPS and Tracking and Data Relay Satellite System satellites by ground receivers. Both strategies can be designed to meet future operational requirements for TDRS-II orbit determination.

Assessment of Photogrammetry Structure-from-Motion Compared to Terrestrial LiDAR Scanning for Generating Digital Elevation Models. Application to the Austre Lovéenbreen Polar Glacier Basin, Spitsbergen 79°N

NASA Astrophysics Data System (ADS)

Tolle, F.; Friedt, J. M.; Bernard, É.; Prokop, A.; Griselin, M.

2014-12-01

Digital Elevation Model (DEM) is a key tool for analyzing spatially dependent processes including snow accumulation on slopes or glacier mass balance. Acquiring DEM within short time intervals provides new opportunities to evaluate such phenomena at the daily to seasonal rates.DEMs are usually generated from satellite imagery, aerial photography, airborne and ground-based LiDAR, and GPS surveys. In addition to these classical methods, we consider another alternative for periodic DEM acquisition with lower logistics requirements: digital processing of ground based, oblique view digital photography. Such a dataset, acquired using commercial off the shelf cameras, provides the source for generating elevation models using Structure from Motion (SfM) algorithms. Sets of pictures of a same structure but taken from various points of view are acquired. Selected features are identified on the images and allow for the reconstruction of the three-dimensional (3D) point cloud after computing the camera positions and optical properties. This cloud point, generated in an arbitrary coordinate system, is converted to an absolute coordinate system either by adding constraints of Ground Control Points (GCP), or including the (GPS) position of the cameras in the processing chain. We selected the opensource digital signal processing library provided by the French Geographic Institute (IGN) called Micmac for its fine processing granularity and the ability to assess the quality of each processing step.Although operating in snow covered environments appears challenging due to the lack of relevant features, we observed that enough reference points could be identified for 3D reconstruction. Despite poor climatic environment of the Arctic region considered (Ny Alesund area, 79oN) is not a problem for SfM, the low lying spring sun and the cast shadows appear as a limitation because of the lack of color dynamics in the digital cameras we used. A detailed understanding of the processing steps is mandatory during the image acquisition phase: compliance with acquisition rules reducing digital processing errors helps minimizing the uncertainty on the point cloud absolute position in its coordinate system. 3D models from SfM are compared with terrestrial LiDAR acquisitions for resolution assesment.

Improving polio vaccination coverage in Nigeria through the use of geographic information system technology.

PubMed

Barau, Inuwa; Zubairu, Mahmud; Mwanza, Michael N; Seaman, Vincent Y

2014-11-01

Historically, microplanning for polio vaccination campaigns in Nigeria relied on inaccurate and incomplete hand-drawn maps, resulting in the exclusion of entire settlements and missed children. The goal of this work was to create accurate, coordinate-based maps for 8 polio-endemic states in northern Nigeria to improve microplanning and support tracking of vaccination teams, thereby enhancing coverage, supervision, and accountability. Settlement features were identified in the target states, using high-resolution satellite imagery. Field teams collected names and geocoordinates for each settlement feature, with the help of local guides. Global position system (GPS) tracking of vaccination teams was conducted in selected areas and daily feedback provided to supervisors. Geographic information system (GIS)-based maps were created for 2238 wards in the 8 target states. The resulting microplans included all settlements and more-efficient team assignments, owing to the improved spatial reference. GPS tracking was conducted in 111 high-risk local government areas, resulting in improved team performance and the identification of missed/poorly covered settlements. Accurate and complete maps are a necessary part of an effective polio microplan, and tracking vaccinators gives supervisors a tool to ensure that all settlements are visited. © The Author 2014. Published by Oxford University Press on behalf of the Infectious Diseases Society of America. All rights reserved. For Permissions, please e-mail: journals.permissions@oup.com.

Autonomous detection of indoor and outdoor signs

NASA Astrophysics Data System (ADS)

Holden, Steven; Snorrason, Magnus; Goodsell, Thomas; Stevens, Mark R.

2005-05-01

Most goal-oriented mobile robot tasks involve navigation to one or more known locations. This is generally done using GPS coordinates and landmarks outdoors, or wall-following and fiducial marks indoors. Such approaches ignore the rich source of navigation information that is already in place for human navigation in all man-made environments: signs. A mobile robot capable of detecting and reading arbitrary signs could be tasked using directions that are intuitive to hu-mans, and it could report its location relative to intuitive landmarks (a street corner, a person's office, etc.). Such ability would not require active marking of the environment and would be functional in the absence of GPS. In this paper we present an updated version of a system we call Sign Understanding in Support of Autonomous Navigation (SUSAN). This system relies on cues common to most signs, the presence of text, vivid color, and compact shape. By not relying on templates, SUSAN can detect a wide variety of signs: traffic signs, street signs, store-name signs, building directories, room signs, etc. In this paper we focus on the text detection capability. We present results summarizing probability of detection and false alarm rate across many scenes containing signs of very different designs and in a variety of lighting conditions.

GPS in ten years

DOT National Transportation Integrated Search

1997-09-16

What will GPS look like in ten years? This paper discusses improvements to the overall GPS system planned over the next ten years and examines their impact on system performance for several applications. The Presidential Decision Directive (PDD) rele...

76 FR 66750 - Certain Automotive GPS Navigation Systems, Components Thereof, and Products Containing Same...

Federal Register 2010, 2011, 2012, 2013, 2014

2011-10-27

... INTERNATIONAL TRADE COMMISSION [DN 2850] Certain Automotive GPS Navigation Systems, Components... given that the U.S. International Trade Commission has received a complaint entitled In Re Certain Automotive GPS Navigation Systems, Components Thereof, And Products Containing Same, DN 2850; the Commission...

A New Indoor Positioning System Architecture Using GPS Signals.

PubMed

Xu, Rui; Chen, Wu; Xu, Ying; Ji, Shengyue

2015-04-29

The pseudolite system is a good alternative for indoor positioning systems due to its large coverage area and accurate positioning solution. However, for common Global Positioning System (GPS) receivers, the pseudolite system requires some modifications of the user terminals. To solve the problem, this paper proposes a new pseudolite-based indoor positioning system architecture. The main idea is to receive real-world GPS signals, repeat each satellite signal and transmit those using indoor transmitting antennas. The transmitted GPS-like signal can be processed (signal acquisition and tracking, navigation data decoding) by the general receiver and thus no hardware-level modification on the receiver is required. In addition, all Tx can be synchronized with each other since one single clock is used in Rx/Tx. The proposed system is simulated using a software GPS receiver. The simulation results show the indoor positioning system is able to provide high accurate horizontal positioning in both static and dynamic situations.

General practitioners' attitudes toward reporting and learning from adverse events: results from a survey.

PubMed

Mikkelsen, Thorbjørn H; Sokolowski, Ineta; Olesen, Frede

2006-03-01

To investigate GPs' attitudes to and willingness to report and learn from adverse events and to study how a reporting system should function. Survey. General practice in Denmark. GPs' attitudes to exchange of experience with colleagues and others, and circumstances under which such exchange is accepted. A structured questionnaire sent to 1198 GPs of whom 61% responded. RESULTS. GPs had a positive attitude towards discussing adverse events in the clinic with colleagues and staff and in their continuing medical education groups. The GPs had a positive attitude to reporting adverse events to a database if the system granted legal and administrative immunity to reporters. The majority preferred a reporting system located at a research institute. GPs have a very positive attitude towards discussing and reporting adverse events. This project encourages further research and pilot projects testing concrete reporting systems.

Improvement of the Asia-Pacific TWSTFT network solutions by using DPN results.

PubMed

Lin, Huang-Tien; Huang, Yi-Jiun; Liao, Chia-Shu; Chu, Fang-Dar; Tseng, Wen-Hung

2012-03-01

Two major time and frequency transfer techniques, two-way satellite time and frequency transfer (TWSTFT) and global navigation satellite systems (GNSS: GPS, GALILEO, GLONASS, etc.), are used for the generation of Coordinated Universal Time (UTC)/International Atomic Time (TAI). These time and frequency transfer links comprise a worldwide network and the utilization of the highly redundant time and frequency data is an important topic. Two methods, either TW-only network (i.e., TWSTFT) or single-link combination of TW and Global Positioning System (GPS), have been developed for combining the redundant data from different techniques. In our previous study, we have proposed a feasible method, utilizing full time-transfer network data, to improve the results of TWSTFT network. The National Institute of Information and Communications Technology (NICT) has recently developed a software-based two-way time-transfer modem using a dual pseudo-random noise (DPN) signal. The first international DPN TWSTFT experiment, using these modems, was performed between NICT (Japan) and Telecommunication Laboratories (TL; Taiwan)and its ability to improve the time transfer precision was demonstrated. In comparison with the conventional NICT–TLTWSTFT link, the DPN time transfer results have higher precision and lower diurnal effects. The estimation also shows that DPN is comparable to GPS precise point positioning (PPP).Because the DPN results show better performance than the conventional TWSTFT results, we would adopt the DPN data for the NICT–TL link and solve the TW+DPN network solutions by using our proposed method. The concept of this application is similar to the so-called multi-technique-network time/frequency transfer. The encouraging results confirm that the TWSTFT network performance can benefit from DPN data by improving short-term stabilities and reducing diurnal effects.The results of TW+PPP network solutions are also illustrated.

76 FR 72442 - Certain Automotive GPS Navigation Systems, Components Thereof, and Products Containing Same...

Federal Register 2010, 2011, 2012, 2013, 2014

2011-11-23

... INTERNATIONAL TRADE COMMISSION [Inv. No. 337-TA-814] Certain Automotive GPS Navigation Systems... the sale within the United States after importation of certain automotive GPS navigation systems... further alleges that an industry in the United States exists as required by subsection (a)(2) of section...

76 FR 27744 - Eighty-Fifth Meeting: RTCA Special Committee 159: Global Positioning System (GPS)

Federal Register 2010, 2011, 2012, 2013, 2014

2011-05-12

... Committee 159: Global Positioning System (GPS) AGENCY: Federal Aviation Administration (FAA), DOT. ACTION: Notice of RTCA Special Committee 159 meeting: Global Positioning System (GPS). SUMMARY: The FAA is issuing this notice to advise the public of a meeting of RTCA Special Committee 159: Global Positioning...

75 FR 28318 - Eighty-Second Meeting: RTCA Special Committee 159: Global Positioning System (GPS)

Federal Register 2010, 2011, 2012, 2013, 2014

2010-05-20

... Committee 159: Global Positioning System (GPS) AGENCY: Federal Aviation Administration (FAA), DOT. ACTION: Notice of RTCA Special Committee 159 meeting: Global Positioning System (GPS). SUMMARY: The FAA is issuing this notice to advise the public of a meeting of RTCA Special Committee 159: Global Positioning...

75 FR 2581 - Eighty-First Meeting: RTCA Special Committee 159: Global Positioning System (GPS)

Federal Register 2010, 2011, 2012, 2013, 2014

2010-01-15

... Committee 159: Global Positioning System (GPS) AGENCY: Federal Aviation Administration (FAA), DOT. ACTION: Notice of RTCA Special Committee 159 meeting: Global Positioning System (GPS). SUMMARY: The FAA is issuing this notice to advise the public of a meeting of RTCA Special Committee 159: Global Positioning...

Fundamentals of satellite navigation

NASA Astrophysics Data System (ADS)

Stiller, A. H.

The basic operating principles and capabilities of conventional and satellite-based navigation systems for air, sea, and land vehicles are reviewed and illustrated with diagrams. Consideration is given to autonomous onboard systems; systems based on visible or radio beacons; the Transit, Cicada, Navstar-GPS, and Glonass satellite systems; the physical laws and parameters of satellite motion; the definition of time in satellite systems; and the content of the demodulated GPS data signal. The GPS and Glonass data format frames are presented graphically, and tables listing the GPS and Glonass satellites, their technical characteristics, and the (past or scheduled) launch dates are provided.

A Leo Satellite Navigation Algorithm Based on GPS and Magnetometer Data

NASA Technical Reports Server (NTRS)

Deutschmann, Julie; Harman, Rick; Bar-Itzhack, Itzhack

2001-01-01

The Global Positioning System (GPS) has become a standard method for low cost onboard satellite orbit determination. The use of a GPS receiver as an attitude and rate sensor has also been developed in the recent past. Additionally, focus has been given to attitude and orbit estimation using the magnetometer, a low cost, reliable sensor. Combining measurements from both GPS and a magnetometer can provide a robust navigation system that takes advantage of the estimation qualities of both measurements. Ultimately, a low cost, accurate navigation system can result, potentially eliminating the need for more costly sensors, including gyroscopes. This work presents the development of a technique to eliminate numerical differentiation of the GPS phase measurements and also compares the use of one versus two GPS satellites.

An update to the analysis of the Canadian Spatial Reference System

NASA Astrophysics Data System (ADS)

Ferland, R.; Piraszewski, M.; Craymer, M.

2015-12-01

The primary objective of the Canadian Spatial Reference System (CSRS) is to provide users access to a consistent geo-referencing infrastructure over the Canadian landmass. Global Navigation Satellite System (GNSS) positioning accuracy requirements ranges from meter level to mm level (e.g.: crustal deformation). The highest level of the Canadian infrastructure consist of a network of continually operating GPS and GNSS receivers, referred to as active control stations. The network includes all Canadian public active control stations, some bordering US CORS and Alaska stations, Greenland active control stations, as well as a selection of IGS reference frame stations. The Bernese analysis software is used for the daily processing and the combination into weekly solutions which form the basis for this analysis. IGS weekly final orbit, Earth Rotation parameters (ERP's) and coordinates products are used in the processing. For the more demanding users, the time dependant changes of station coordinates is often more important.All station coordinate estimates and related covariance information is used in this analysis. For each input solution, variance factor, translation, rotation and scale (and if needed their rates) or subsets of these are estimated. In the combination of these weekly solutions, station positions and velocities are estimated. Since the time series from the stations in these networks often experience changes in behavior, new (or reuse of) parameters are generally used in these situations. As is often the case with real data, unrealistic coordinates may occur. Automatic detection and removal of outliers is used in these cases. For the transformation, position and velocity parameters loose apriori estimates and uncertainties are provided. Alignment using the usual Helmert transformation to the latest IGb08 realization of ITRF is also performed during the adjustment.

Use and Protection of GPS Sidelobe Signals for Enhanced Navigation Performance in High Earth Orbit

NASA Technical Reports Server (NTRS)

Parker, Joel J. K.; Valdez, Jennifer E.; Bauer, Frank H.; Moreau, Michael C.

2016-01-01

The application of the Global Positioning System (GPS) for navigation of spacecraft in High and Geosynchronous Earth Orbit (HEO/GEO) has crossed a threshold and is now being employed in operational missions. Utilizing advanced GPS receivers optimized for these missions, space users have made extensive use of the sidelobe transmissions from the GPS satellites to realize navigation performance that far exceeds that predicted by pre-launch simulations. Unfortunately, the official specification for the GPS Space Service Volume (SSV), developed in 2006, assumes that only signals emanating from the main beam of the GPS transmit antenna are useful for navigation, which greatly under-estimates the number of signals available for navigation purposes. As a result, future high-altitude space users may be vulnerable to any GPS design changes that suppress the sidelobe transmissions, beginning with Block III space vehicles (SVs) 11-32. This paper presents proposed changes to the GPS system SSV requirements, as informed by data from recent experiments in the SSV and new mission applications that are enabled by GPS navigation in HEO/GEO regimes. The NASA/NOAA GOES-R series satellites are highlighted as an example of a mission that relies on this currently-unspecified GPS system performance to meet mission requirements.

75 FR 8928 - Announcement of IS-GPS-200, IS-GPS-705, IS-GPS-800 Interface Control Working Group (ICWG...

Federal Register 2010, 2011, 2012, 2013, 2014

2010-02-26

... DEPARTMENT OF DEFENSE Department of the Air Force Announcement of IS-GPS-200, IS-GPS-705, IS-GPS-800Interface Control Working Group (ICWG) Teleconference Meeting AGENCY: Department of the Air Force, DoD... Positioning Systems Wing will be hosting an Interface Control Working Group (ICWG) teleconference meeting for...

Space Shuttle Navigation in the GPS Era

NASA Technical Reports Server (NTRS)

Goodman, John L.

2001-01-01

The Space Shuttle navigation architecture was originally designed in the 1970s. A variety of on-board and ground based navigation sensors and computers are used during the ascent, orbit coast, rendezvous, (including proximity operations and docking) and entry flight phases. With the advent of GPS navigation and tightly coupled GPS/INS Units employing strapdown sensors, opportunities to improve and streamline the Shuttle navigation process are being pursued. These improvements can potentially result in increased safety, reliability, and cost savings in maintenance through the replacement of older technologies and elimination of ground support systems (such as Tactical Air Control and Navigation (TACAN), Microwave Landing System (MLS) and ground radar). Selection and missionization of "off the shelf" GPS and GPS/INS units pose a unique challenge since the units in question were not originally designed for the Space Shuttle application. Various options for integrating GPS and GPS/INS units with the existing orbiter avionics system were considered in light of budget constraints, software quality concerns, and schedule limitations. An overview of Shuttle navigation methodology from 1981 to the present is given, along with how GPS and GPS/INS technology will change, or not change, the way Space Shuttle navigation is performed in the 21 5 century.

The GPS Topex/Poseidon precise orbit determination experiment - Implications for design of GPS global networks

NASA Technical Reports Server (NTRS)

Lindqwister, Ulf J.; Lichten, Stephen M.; Davis, Edgar S.; Theiss, Harold L.

1993-01-01

Topex/Poseidon, a cooperative satellite mission between United States and France, aims to determine global ocean circulation patterns and to study their influence on world climate through precise measurements of sea surface height above the geoid with an on-board altimeter. To achieve the mission science aims, a goal of 13-cm orbit altitude accuracy was set. Topex/Poseidon includes a Global Positioning System (GPS) precise orbit determination (POD) system that has now demonstrated altitude accuracy better than 5 cm. The GPS POD system includes an on-board GPS receiver and a 6-station GPS global tracking network. This paper reviews early GPS results and discusses multi-mission capabilities available from a future enhanced global GPS network, which would provide ground-based geodetic and atmospheric calibrations needed for NASA deep space missions while also supplying tracking data for future low Earth orbiters. Benefits of the enhanced global GPS network include lower operations costs for deep space tracking and many scientific and societal benefits from the low Earth orbiter missions, including improved understanding of ocean circulation, ocean-weather interactions, the El Nino effect, the Earth thermal balance, and weather forecasting.

Characteristics of the BDS Carrier Phase Multipath and Its Mitigation Methods in Relative Positioning

PubMed Central

Dai, Wujiao; Shi, Qiang; Cai, Changsheng

2017-01-01

The carrier phase multipath effect is one of the most significant error sources in the precise positioning of BeiDou Navigation Satellite System (BDS). We analyzed the characteristics of BDS multipath, and found the multipath errors of geostationary earth orbit (GEO) satellite signals are systematic, whereas those of inclined geosynchronous orbit (IGSO) or medium earth orbit (MEO) satellites are both systematic and random. The modified multipath mitigation methods, including sidereal filtering algorithm and multipath hemispherical map (MHM) model, were used to improve BDS dynamic deformation monitoring. The results indicate that the sidereal filtering methods can reduce the root mean square (RMS) of positioning errors in the east, north and vertical coordinate directions by 15%, 37%, 25% and 18%, 51%, 27% in the coordinate and observation domains, respectively. By contrast, the MHM method can reduce the RMS by 22%, 52% and 27% on average. In addition, the BDS multipath errors in static baseline solutions are a few centimeters in multipath-rich environments, which is different from that of Global Positioning System (GPS) multipath. Therefore, we add a parameter representing the GEO multipath error in observation equation to the adjustment model to improve the precision of BDS static baseline solutions. And the results show that the modified model can achieve an average precision improvement of 82%, 54% and 68% in the east, north and up coordinate directions, respectively. PMID:28387744

Characteristics of the BDS Carrier Phase Multipath and Its Mitigation Methods in Relative Positioning.

PubMed

Dai, Wujiao; Shi, Qiang; Cai, Changsheng

2017-04-07

The carrier phase multipath effect is one of the most significant error sources in the precise positioning of BeiDou Navigation Satellite System (BDS). We analyzed the characteristics of BDS multipath, and found the multipath errors of geostationary earth orbit (GEO) satellite signals are systematic, whereas those of inclined geosynchronous orbit (IGSO) or medium earth orbit (MEO) satellites are both systematic and random. The modified multipath mitigation methods, including sidereal filtering algorithm and multipath hemispherical map (MHM) model, were used to improve BDS dynamic deformation monitoring. The results indicate that the sidereal filtering methods can reduce the root mean square (RMS) of positioning errors in the east, north and vertical coordinate directions by 15%, 37%, 25% and 18%, 51%, 27% in the coordinate and observation domains, respectively. By contrast, the MHM method can reduce the RMS by 22%, 52% and 27% on average. In addition, the BDS multipath errors in static baseline solutions are a few centimeters in multipath-rich environments, which is different from that of Global Positioning System (GPS) multipath. Therefore, we add a parameter representing the GEO multipath error in observation equation to the adjustment model to improve the precision of BDS static baseline solutions. And the results show that the modified model can achieve an average precision improvement of 82%, 54% and 68% in the east, north and up coordinate directions, respectively.

The Graphical Cadastre Problem in Turkey: The Case of Trabzon Province.

PubMed

Demir, Osman; Çoruhlu, Yakup Emre

2008-09-11

Cadastral projects in Turkey have been accelerated in recent years by the involvement of the private sector. These projects aim at completing the country's cadastre, along with producing bases in standards that could be a foundation for Land Registry and Cadastre Information System (LRCIS). It is possible to produce cadastral data with today's technological means. In this context, three dimensional cadastre data can be properly produced, especially in digital cadastre projects with the required point accuracy. Nevertheless this is not enough for LRCIS. The cadastre bases that have been produced so far by different methods with different scales and bases, with or without coordinates, should also be converted into digital form based on National Basic GPS Network of Turkey (NBGN) in required point-location accuracy. As the result of evaluation of graphical cadastre bases produced without coordinates, actual land measurements, and information obtained from sheets and field book data together, it was found out that there are significant base problems in the graphical maps. These bases, comprising 20% of Turkey's cadastre constitutes the most important bottleneck of completing the country's cadastre. In the scope of this paper, the possibilities of converting the field book measurement values of graphic cadastre bases into digital forms in national coordinate system by comparing them with actual land measurements are investigated, along with Turkey's Cadastre and its problems.

The Graphical Cadastre Problem in Turkey: The Case of Trabzon Province

PubMed Central

Demir, Osman; Çoruhlu, Yakup Emre

2008-01-01

Cadastral projects in Turkey have been accelerated in recent years by the involvement of the private sector. These projects aim at completing the country's cadastre, along with producing bases in standards that could be a foundation for Land Registry and Cadastre Information System (LRCIS). It is possible to produce cadastral data with today's technological means. In this context, three dimensional cadastre data can be properly produced, especially in digital cadastre projects with the required point accuracy. Nevertheless this is not enough for LRCIS. The cadastre bases that have been produced so far by different methods with different scales and bases, with or without coordinates, should also be converted into digital form based on National Basic GPS Network of Turkey (NBGN) in required point-location accuracy. As the result of evaluation of graphical cadastre bases produced without coordinates, actual land measurements, and information obtained from sheets and field book data together, it was found out that there are significant base problems in the graphical maps. These bases, comprising 20% of Turkey's cadastre constitutes the most important bottleneck of completing the country's cadastre. In the scope of this paper, the possibilities of converting the field book measurement values of graphic cadastre bases into digital forms in national coordinate system by comparing them with actual land measurements are investigated, along with Turkey's Cadastre and its problems. PMID:27873830

Global Positioning System: Observations on Quarterly Reports from the Air Force

DTIC Science & Technology

2016-10-17

Positioning System : Observations on Quarterly Reports from the Air Force The satellite-based Global Positioning System (GPS) provides positioning, navigation...infrastructure, and transportation safety. The Department of Defense (DOD)—specifically, the Air Force—develops and operates the GPS system , which...programs, including the most recent detailed assessment of the next generation operational control system (OCX) and development of military GPS

Secular changes in Earth's shape and surface mass loading derived from combinations of reprocessed global GPS networks

NASA Astrophysics Data System (ADS)

Booker, David; Clarke, Peter J.; Lavallée, David A.

2014-09-01

The changing distribution of surface mass (oceans, atmospheric pressure, continental water storage, groundwater, lakes, snow and ice) causes detectable changes in the shape of the solid Earth, on time scales ranging from hours to millennia. Transient changes in the Earth's shape can, regardless of cause, be readily separated from steady secular variation in surface mass loading, but other secular changes due to plate tectonics and glacial isostatic adjustment (GIA) cannot. We estimate secular station velocities from almost 11 years of high quality combined GPS position solutions (GPS weeks 1,000-1,570) submitted as part of the first international global navigation satellite system service reprocessing campaign. Individual station velocities are estimated as a linear fit, paying careful attention to outliers and offsets. We remove a suite of a priori GIA models, each with an associated set of plate tectonic Euler vectors estimated by us; the latter are shown to be insensitive to the a priori GIA model. From the coordinate time series residuals after removing the GIA models and corresponding plate tectonic velocities, we use mass-conserving continental basis functions to estimate surface mass loading including the secular term. The different GIA models lead to significant differences in the estimates of loading in selected regions. Although our loading estimates are broadly comparable with independent estimates from other satellite missions, their range highlights the need for better, more robust GIA models that incorporate 3D Earth structure and accurately represent 3D surface displacements.

SUPL support for mobile devices

NASA Astrophysics Data System (ADS)

Narisetty, Jayanthi; Soghoyan, Arpine; Sundaramurthy, Mohanapriya; Akopian, David

2012-02-01

Conventional Global Positioning System (GPS) receivers operate well in open-sky environments. But their performance degrades in urban canyons, indoors and underground due to multipath, foliage, dissipation, etc. To overcome such situations, several enhancements have been suggested such as Assisted GPS (A-GPS). Using this approach, orbital parameters including ephemeris and almanac along with reference time and coarse location information are provided to GPS receivers to assist in acquisition of weak signals. To test A-GPS enabled receivers high-end simulators are used, which are not affordable by many academic institutions. This paper presents an economical A-GPS supplement for inexpensive simulators which operates on application layer. Particularly proposed solution is integrated with National Instruments' (NI) GPS Simulation Toolkit and implemented using NI's Labview environment. This A-GPS support works for J2ME and Android platforms. The communication between the simulator and the receiver is in accordance with the Secure User Plane Location (SUPL) protocol encapsulated with Radio Resource Location Protocol (RRLP) applies to Global System for Mobile Communications (GSM) and Universal Mobile Telecommunications System (UMTS) cellular networks.

Kinematic-PPP using Single/Dual Frequency Observations from (GPS, GLONASS and GPS/GLONASS) Constellations for Hydrography

NASA Astrophysics Data System (ADS)

Farah, Ashraf

2018-03-01

Global Positioning System (GPS) technology is ideally suited for inshore and offshore positioning because of its high accuracy and the short observation time required for a position fix. Precise point positioning (PPP) is a technique used for position computation with a high accuracy using a single GNSS receiver. It relies on highly accurate satellite position and clock data that can be acquired from different sources such as the International GNSS Service (IGS). PPP precision varies based on positioning technique (static or kinematic), observations type (single or dual frequency) and the duration of observations among other factors. PPP offers comparable accuracy to differential GPS with safe in cost and time. For many years, PPP users depended on GPS (American system) which considered the solely reliable system. GLONASS's contribution in PPP techniques was limited due to fail in maintaining full constellation. Yet, GLONASS limited observations could be integrated into GPS-based PPP to improve availability and precision. As GLONASS reached its full constellation early 2013, there is a wide interest in PPP systems based on GLONASS only and independent of GPS. This paper investigates the performance of kinematic PPP solution for the hydrographic applications in the Nile river (Aswan, Egypt) based on GPS, GLONASS and GPS/GLONASS constellations. The study investigates also the effect of using two different observation types; single-frequency and dual frequency observations from the tested constellations.

Robust GPS autonomous signal quality monitoring

NASA Astrophysics Data System (ADS)

Ndili, Awele Nnaemeka

The Global Positioning System (GPS), introduced by the U.S. Department of Defense in 1973, provides unprecedented world-wide navigation capabilities through a constellation of 24 satellites in global orbit, each emitting a low-power radio-frequency signal for ranging. GPS receivers track these transmitted signals, computing position to within 30 meters from range measurements made to four satellites. GPS has a wide range of applications, including aircraft, marine and land vehicle navigation. Each application places demands on GPS for various levels of accuracy, integrity, system availability and continuity of service. Radio frequency interference (RFI), which results from natural sources such as TV/FM harmonics, radar or Mobile Satellite Systems (MSS), presents a challenge in the use of GPS, by posing a threat to the accuracy, integrity and availability of the GPS navigation solution. In order to use GPS for integrity-sensitive applications, it is therefore necessary to monitor the quality of the received signal, with the objective of promptly detecting the presence of RFI, and thus provide a timely warning of degradation of system accuracy. This presents a challenge, since the myriad kinds of RFI affect the GPS receiver in different ways. What is required then, is a robust method of detecting GPS accuracy degradation, which is effective regardless of the origin of the threat. This dissertation presents a new method of robust signal quality monitoring for GPS. Algorithms for receiver autonomous interference detection and integrity monitoring are demonstrated. Candidate test statistics are derived from fundamental receiver measurements of in-phase and quadrature correlation outputs, and the gain of the Active Gain Controller (AGC). Performance of selected test statistics are evaluated in the presence of RFI: broadband interference, pulsed and non-pulsed interference, coherent CW at different frequencies; and non-RFI: GPS signal fading due to physical blockage and multipath. Results are presented which verify the effectiveness of these proposed methods. The benefits of pseudolites in reducing service outages due to interference are demonstrated. Pseudolites also enhance the geometry of the GPS constellation, improving overall system accuracy. Designs for pseudolites signals, to reduce the near-far problem associated with pseudolite use, are also presented.

Global Positioning System (GPS) civil signal monitoring (CSM) trade study report

DOT National Transportation Integrated Search

2014-03-07

This GPS Civil Signal Monitoring (CSM) Trade Study has been performed at the direction of DOT/FAA Navigation Programs as the agency of reference for consolidating civil monitoring requirements on the Global Positioning System (GPS). The objective of ...

Exploration of GPS to enhance the safe transport of hazardous materials

DOT National Transportation Integrated Search

1997-12-01

The report (1) documents a set of requirements for the performance of location systems that utilize the Global Positioning System (GPS), (2) identifies potential uses of GPS in hazardous materials transport, (3) develops service descriptions for the ...

The Global Positioning System and Its Integration into College Geography Curricula.

ERIC Educational Resources Information Center

Wikle, Thomas A.; Lambert, Dean P.

1996-01-01

Introduces global positioning system (GPS) technology to nonspecialist geographers and recommends a framework for implementing GPS instructional modules in college geography courses. GPS was developed as a worldwide satellite-based system by the U.S. Department of Defense to simplify and improve military and civilian navigation and positioning.…

Innovative Navigation Systems to Support Digital Geophysical Mapping

DTIC Science & Technology

2004-02-01

9 Figure 8. Blackhawk/ Applanix GPS/INS System.................................................................10 Figure 9. Figure-Eight Traverse...Vulcan/LaserStation Line-of-sight laser Parsons Trimble INS/GPS DGPS and inertia guidance Blackhawk Applanix INS/GPS DGPS and inertia guidance...The Applanix Positioning and Orientation System for Land Survey (POS/LS) was used for the Phase I work. The system is similar to the Parsons

Assessing the role of GPs in Nordic health care systems.

PubMed

Quaye, Randolph K

2016-05-03

Purpose This paper examines the changing role of general practitioners (GPs) in Nordic countries of Sweden, Norway and Denmark. It aims to explore the "gate keeping" role of GPs in the face of current changes in the health care delivery systems in these countries. Design/methodology/approach Data were collected from existing literature, interviews with GPs, hospital specialists and representatives of Danish regions and Norwegian Medical Association. Findings The paper contends that in all these changes, the position of the GPs in the medical division of labor has been strengthened, and patients now have increased and broadened access to choice. Research limitations/implications Health care cost and high cancer mortality rates have forced Nordic countries of Sweden, Norway and Denmark to rethink their health care systems. Several attempts have been made to reduce health care cost through market reform and by strenghtening the position of GPs. The evidence suggests that in Norway and Denmark, right incentives are in place to achieve this goal. Sweden is not far behind. The paper has limitations of a small sample size and an exclusive focus on GPs. Practical implications Anecdotal evidence suggests that physicians are becoming extremely unhappy. Understanding the changing status of primary care physicians will yield valuable information for assessing the effectiveness of Nordic health care delivery systems. Social implications This study has wider implications of how GPs see their role as potential gatekeepers in the Nordic health care systems. The role of GPs is changing as a result of recent health care reforms. Originality/value This paper contends that in Norway and Denmark, right incentives are in place to strengthen the position of GPs.

Development of building security integration system using sensors, microcontroller and GPS (Global Positioning System) based android smartphone

NASA Astrophysics Data System (ADS)

Sihombing, P.; Siregar, Y. M.; Tarigan, J. T.; Jaya, I.; Turnip, A.

2018-03-01

Security system is one of the common problems to protect an environment such as personal house or a warehouse. There are numerous methods and technologies that can be used as part of a security system. In this paper, we present a security system that offers a better efficiency. The purpose of this study is to build a system that can monitor home security at any time in particular fire and theft. Through sensors, the system will be able to provide warning information of hazard conditions via LCD monitor, sound, and alarm. This information will be sent automatically to the home owner’s smartphone as well as to the corresponding to the security agency. Thus the prevention of theft and fire hazards can be immediately anticipated by the police and firefighters. The system will also notify the position of the coordinates of the location of the building (the house) by a link to the Google map in order to make it easier to get the location quickly.

The Performance Analysis of a 3d Map Embedded Ins/gps Fusion Algorithm for Seamless Vehicular Navigation in Elevated Highway Environments

NASA Astrophysics Data System (ADS)

Lee, Y. H.; Chiang, K. W.

2012-07-01

In this study, a 3D Map Matching (3D MM) algorithm is embedded to current INS/GPS fusion algorithm for enhancing the sustainability and accuracy of INS/GPS integration systems, especially the height component. In addition, this study propose an effective solutions to the limitation of current commercial vehicular navigation systems where they fail to distinguish whether the vehicle is moving on the elevated highway or the road under it because those systems don't have sufficient height resolution. To validate the performance of proposed 3D MM embedded INS/GPS integration algorithms, in the test area, two scenarios were considered, paths under the freeways and streets between tall buildings, where the GPS signal is obstacle or interfered easily. The test platform was mounted on the top of a land vehicle and also systems in the vehicle. The IMUs applied includes SPAN-LCI (0.1 deg/hr gyro bias) from NovAtel, which was used as the reference system, and two MEMS IMUs with different specifications for verifying the performance of proposed algorithm. The preliminary results indicate the proposed algorithms are able to improve the accuracy of positional components in GPS denied environments significantly with the use of INS/GPS integrated systems in SPP mode.

Mysterious Roving Rocks of Racetrack Playa

NASA Image and Video Library

2017-12-08

To investigate the rocks and trails, the interns collect many kinds of data, such as trail length, width, and depth; rock size; magnetic and radiation measurements; and GPS coordinates. The students also photograph the rocks, the trails and the cracks in the mud within and outside the trails. Photo credit: NASA/GSFC/Maggie McAdam To read a feature story on the Racetrack Playa go to: www.nasa.gov/topics/earth/features/roving-rocks.html NASA Goddard Space Flight Center is home to the nation's largest organization of combined scientists, engineers and technologists that build spacecraft, instruments and new technology to study the Earth, the sun, our solar system, and the universe. Follow us on Twitter Join us on Facebook

Application of neogeographic tools for geochemistry

NASA Astrophysics Data System (ADS)

Zhilin, Denis

2010-05-01

Neogeography is a usage of geographical tools for utilization by a non-expert group of users. It have been rapidly developing last ten years and is founded on (a) availability of Global Positioning System (GPS) receivers, that allows to obtain very precise geographical position (b) services, that allows linking geographical position with satellite images, GoogleEarth for example and (c) programs as GPS Track Maker or OziExplorer, that allows linking geographical coordinates with other raster images (for example, maps). However, the possibilities of neogeographic approach are much wider. It allows linking different parameters with geographical coordinates on the one hand and space image or map - on the other. If it is easy to measure a parameter, a great database could be collected for a very small time. The results can be presented in very different ways. One can plot a parameter versus the distance from a particular point (for example, a source of a substance), make two-dimension distribution of parameter of put the results onto a map or space image. In the case of chemical parameters it can help finding the source of pollution, trace the influence of pollution, reveal geochemical processes and patterns. The main advantage of neogeograpic approach is the employment of non-experts in collecting data. Now non-experts can easily measure electrical conductivity and pH of natural waters, concentration of different gases in the atmosphere, solar irradiation, radioactivity and so on. If the results are obtained (for example, by students of secondary schools) and shared, experts can proceed them and make significant conclusions. An interface of sharing the results (http://maps.sch192.ru/) was elaborated by V. Ilyin. Within the interface a user can load *.csv file with coordinates, type of parameter and the value of parameter in a particular point. The points are marked on the GoogleEarth map with the color corresponding the value of the parameter. The color scale can be edited manually. We would like to show some results of practical and scientific importance, obtained by non-experts. At 2006 our secondary school students investigated the distribution of snow salinity around Kosygina Street in Moscow. One can conclude that the distribution of salinity is reproducible and that the street influences the snow up to 150 meters. Another example obtained by our students is the distribution of electrical conductivity of swamp water showing extreme irregularity of this parameter within the small area (about 0.5x0.5 km) the electrical conductivity varied from 22 to 77 uS with no regularity. It points out the key role of local processes in swamp water chemistry. The third example (maps of electrical conductivity and pH of water on a large area) one can see at http://fenevo.narod.ru/maps/ec-maps.htm and http://fenevo.narod.ru/maps/ph-maps.htm. Basing on the map one can conclude mechanisms of formation of water mineralization in the area. Availability of GPS receivers and systems for easy measuring of chemical parameters can lead to neogeochemical revolution as GPS receivers have led to neogeographical. A great number of non-experts can share their geochemical results, forming huge amount of available geochemical data. It will help to falsify and visualize concepts of geochemistry and environmental chemistry and, maybe, develop new ones. Geophysical and biological data could be shared as well with the same advantages for corresponding sciences.

Implementation of a low-cost, commercial orbit determination system

NASA Technical Reports Server (NTRS)

Corrigan, Jim

1994-01-01

This paper describes the implementation and potential applications of a workstation-based orbit determination system developed by Storm Integration, Inc. called the Precision Orbit Determination System (PODS). PODS is offered as a layered product to the commercially-available Satellite Tool Kit (STK) produced by Analytical Graphics, Inc. PODS also incorporates the Workstation/Precision Orbit Determination (WS/POD) product offered by Van Martin System, Inc. The STK graphical user interface is used to access and invoke the PODS capabilities and to display the results. WS/POD is used to compute a best-fit solution to user-supplied tracking data. PODS provides the capability to simultaneously estimate the orbits of up to 99 satellites based on a wide variety of observation types including angles, range, range rate, and Global Positioning System (GPS) data. PODS can also estimate ground facility locations, Earth geopotential model coefficients, solar pressure and atmospheric drag parameters, and observation data biases. All determined data is automatically incorporated into the STK data base, which allows storage, manipulation and export of the data to other applications. PODS is offered in three levels: Standard, Basic GPS and Extended GPS. Standard allows processing of non-GPS observation types for any number of vehicles and facilities. Basic GPS adds processing of GPS pseudo-ranging data to the Standard capabilities. Extended GPS adds the ability to process GPS carrier phase data.

Towards GPS Surface Reflection Remote Sensing of Sea Ice Conditions

NASA Technical Reports Server (NTRS)

Komjathy, A.; Maslanik, J. A.; Zavorotny, V. U.; Axelrad, P.; Katzberg, S. J.

2000-01-01

This paper describes the research to extend the application of Global Positioning System (GPS) signal reflections, received by airborne instruments, to cryospheric remote sensing. The characteristics of the GPS signals and equipment afford the possibility of new measurements not possible with existing radar and passive microwave systems. In particular, the GPS receiving systems are small and light-weight, and as such are particularly well suited to be deployed on small aircraft or satellite platforms with minimal impact. Our preliminary models and experimental results indicate that reflected GPS signals have potential to provide information on the presence and condition of sea and fresh-water ice as well as the freeze/thaw state of frozen ground. In this paper we show results from aircraft experiments over the ice pack near Barrow, Alaska suggesting correlation between forward scattered GPS returns and RADARSAT backscattered signals.

Evaluating elk habitat interactions with GPS collars

Treesearch

Mark A. Rumble; Lakhdar Benkobi; Fredrick Lindzey; R. Scott Gamo

2001-01-01

Global positioning systems (GPS) are likely to revolutionize animal telemetry studies. GPS collars allow biologists to collect systematically scheduled data when VHF telemetry data is difficult or impossible to collect. Past studies have shown that the success of GPS telemetry is greater when animals are standing, or in open habitats. To make effective use of GPS...

Measuring precise sea level from a buoy using the Global Positioning System

NASA Technical Reports Server (NTRS)

Rocken, Christian; Kelecy, Thomas M.; Born, George H.; Young, Larry E.; Purcell, George H., Jr.; Wolf, Susan Kornreich

1990-01-01

The feasibility of using the Global Positioning System (GPS) for accurate sea surface positioning was examined. An experiment was conducted on the Scripps pier at La Jolla, California from December 13-15, 1989. A GPS-equipped buoy was deployed about 100 m off the pier. Two fixed reference GPS receivers, located on the pier and about 80 km away on Monument Peak, were used to estimate the relative position of the floater. Kinematic GPS processing software, developed at the National Geodetic Survey, and the Jet Propulsion Laboratory's GPS Infrared Processing System software were used to determine the floater position relative to land-fixing receivers. Calculations were made of sea level and ocean wave spectra from GPS measurements. It is found that the GPS sea level for the short 100 m baseline agrees with the PPT sea level at the 1 cm level and has an rms variation of 5 mm over a period of 4 hours.

Application of GPS attitude determination to gravity gradient stabilized spacecraft

NASA Technical Reports Server (NTRS)

Lightsey, E. G.; Cohen, Clark E.; Parkinson, Bradford W.

1993-01-01

Recent advances in the Global Positioning System (GPS) technology have initiated a new era in aerospace navigation and control. GPS receivers have become increasingly compact and affordable, and new developments have made attitude determination using subcentimeter positioning among two or more antennas feasible for real-time applications. GPS-based attitude control systems will become highly portable packages which provide time, navigation, and attitude information of sufficient accuracy for many aerospace needs. A typical spacecraft application of GPS attitude determination is a gravity gradient stabilized satellite in low Earth orbit that employs a GPS receiver and four body mounted patch antennas. The coupled, linearized equations of motion enable complete position and attitude information to be extracted from only two antennas. A discussion of the various error sources for spaceborne GPS attitude measurement systems is included. Attitude determination of better than 0.3 degrees is possible for 1 meter antenna separation. Suggestions are provided to improve the accuracy of the attitude solution.

General practitioners' perceptions of the barriers and solutions to good-quality palliative care in dementia.

PubMed

Carter, Gillian; van der Steen, Jenny T; Galway, Karen; Brazil, Kevin

2015-04-16

The general practitioner (GP) is in a pivotal position to initiate and adapt care for their patients living with dementia. This study aimed to elicit GPs' perceptions of the potential barriers and solutions to the provision of good-quality palliative care in dementia in their practices. A postal survey of GPs across Northern Ireland was conducted with open-ended items soliciting for barriers in their practices and possible solutions; 40.6% (138/340) were returned completed. Barriers to palliative care in dementia were perceived to be a dementia knowledge deficit for healthcare staff and the public, a resource shortfall within the GP practice and community, poor team coordination alongside inappropriate dementia care provision, and disagreements from and within families. These findings have significant implications for educators and clinicians as enhanced dementia education and training were highlighted as a strong agenda for GPs with the suggestions of dementia awareness programmes for the public. © The Author(s) 2015 Reprints and permissions: sagepub.co.uk/journalsPermissions.nav.

Using NASA`s Airborne Topographic Mapper IV to Quantify Geomorphic Change in Arid Southwestern Stream Systems

NASA Astrophysics Data System (ADS)

Finnegan, D. C.; Krabill, W.; Lichvar, R. W.; Ericsson, M. P.; Frederick, E.; Manizade, S.; Yungel, J.; Sonntag, J.; Swift, R.

2005-12-01

Understanding how arid stream systems respond to individual climatic events is often difficult given the dynamic and `flashy' nature of most watersheds and the unpredictable nature of individual storm events. Until recently conventional methods for quantifying change dictated the use of stream gauge measurements coupled with periodic cross-section measurements to quantify changes in large-scale channel geometry. Using this approach to quantify change across large areas often proves to be impractical and unattainable given the laborious nature of most surveying techniques including modern GPS systems. Alternately, airborne laser technologies such as NASA's Airborne Topographic Mapper (ATM) are capable of quantifying small-scale changes (~5-10cm) across large-scale terrain rapidly and accurately. The ATM was developed at the NASA-GSFC Wallops Flight Facility. Its current version, ATM-4, measures topography 5,000 times per second across a 45-degree swath below the aircraft by transmitting a 532nm (green) laser pulse and receiving the backscattered signal in a high-speed waveform digitizer. The laser range measurements are combined with aircraft location from GPS and attitude from an inertial navigation system (INS) to provide a precise XYZ coordinate for each (~1-meter diameter) laser footprint on the ground. Our work focuses on the use of airborne laser altimetry to quantify the nature of individual surfaces and the geomorphic change that occurs within small arid stream systems during significant storm events. In September of 2003 and 2005 acquisition surveys using NASA's ATM-IV were flown over Mission Creek, a small arid stream system in Southern California's Mojave Desert with a relatively long gauging history (>40yrs), allowing us to quantify the geomorphic change occurring within the channel as a result of the record storm events during the winter of 2004-2005. Preliminary results associated with our work are encouraging and lead us to believe that when compared to conventional GPS surveys that the accuracy of airborne data is well within the boundaries of data collection necessary for accurate scientific measurements.

FAA aircraft certification human factors and operations checklist for standalone GPS receivers (TSO C129 Class A)

DOT National Transportation Integrated Search

1995-04-01

This document is a checklist designed to assist Federal Aviation Administration(FAA) certification personnel and global : positioning system (GPS) receiver manufacturers in the evaluation of the pilot-system interface characteristlcs of GPS : recieve...

GPS for low-cost attitude determination. A review of concepts, in-flight experiences, and current developments

NASA Astrophysics Data System (ADS)

Chu, Q. P.; Van Woerkom, P. Th. L. M.

The Global Positioning System or GPS has been developed for the purpose of enabling accurate positioning and navigation anywhere on or near the surface of the Earth. In addition to the US system GPS-NAVSTAR, the Russian GLONASS system is also in place and operational. Other such systems are under study. The key measurement involved is the time of travel of signals from a particular GPS spacecraft to the navigating receiver. Navigation accuracies of the order of tenths of meters are achievable, and accuracies at the centimeter level can also be obtained with special enhancement techniques. In recent years spacecraft have already been exploring the use of GPS for in-orbit navigation. As the receiver is solid state, rugged, power-lean, and cheap, GPS for autonomous navigation will be an objective even for low-cost spacecraft of only modest sophistication. When the GPS receiver is equipped with multiple antennas with baselines even as low as about one meter, it can also give attitude information. In this case, the position of the spacecraft needs to be known with only very moderate accuracy. However, the phase differences between signals received by the different antennas now constitute the key measurements. In this case a centimeter level accuracy of range difference can be obtained. Receivers carrying out the processing of such measurements are already on the market, even in space-qualified versions. For spacecraft maneuvering at low rates, accuracies of the order of tenths of a degree are achievable. There are reasons for maintaining classical attitude sensor suites on a spacecraft even when a GPS receiver is added. In this case the classical sensors may be allowed to be of modest quality only, as subsequent fusion of their data with those from the GPS receiver may restore the accuracy of the final estimate again to an acceptable level. Hence, low-cost attitude sensors combined with a low-cost GPS receiver can still satisfy non-trivial attitude reconstitution accuracy requirements. As carrier phase difference measurements are ambiguous because of the unknown number of GPS signal cycles received, the estimated attitude is in principle ambiguous as well. Therefore, resolution of the GPS signal cycle ambiguity becomes a necessary task before determining the attitude for a stand-alone GPS attitude sensing system. This problem may be solved by introducing additional low-cost reference attitude sensors like three-axis magnetometers. This is also one of the advantages of integrated sensor systems. The paper is organized as follows. Global Positioning System and GPS observables are described in the first two sections. The main attitude determination concepts are presented in the next section. For small spacecraft, GPS integrated with other low-cost attitude sensors results in a data fusion concept, to be discussed next. The last section highlights experiences and on-going projects related to the spacecraft attitude determination using GPS.

Numerical Relations and Skill Level Constrain Co-Adaptive Behaviors of Agents in Sports Teams

PubMed Central

Silva, Pedro; Travassos, Bruno; Vilar, Luís; Aguiar, Paulo; Davids, Keith; Araújo, Duarte; Garganta, Júlio

2014-01-01

Similar to other complex systems in nature (e.g., a hunting pack, flocks of birds), sports teams have been modeled as social neurobiological systems in which interpersonal coordination tendencies of agents underpin team swarming behaviors. Swarming is seen as the result of agent co-adaptation to ecological constraints of performance environments by collectively perceiving specific possibilities for action (affordances for self and shared affordances). A major principle of invasion team sports assumed to promote effective performance is to outnumber the opposition (creation of numerical overloads) during different performance phases (attack and defense) in spatial regions adjacent to the ball. Such performance principles are assimilated by system agents through manipulation of numerical relations between teams during training in order to create artificially asymmetrical performance contexts to simulate overloaded and underloaded situations. Here we evaluated effects of different numerical relations differentiated by agent skill level, examining emergent inter-individual, intra- and inter-team coordination. Groups of association football players (national – NLP and regional-level – RLP) participated in small-sided and conditioned games in which numerical relations between system agents were manipulated (5v5, 5v4 and 5v3). Typical grouping tendencies in sports teams (major ranges, stretch indices, distances of team centers to goals and distances between the teams' opposing line-forces in specific team sectors) were recorded by plotting positional coordinates of individual agents through continuous GPS tracking. Results showed that creation of numerical asymmetries during training constrained agents' individual dominant regions, the underloaded teams' compactness and each team's relative position on-field, as well as distances between specific team sectors. We also observed how skill level impacted individual and team coordination tendencies. Data revealed emergence of co-adaptive behaviors between interacting neurobiological social system agents in the context of sport performance. Such observations have broader implications for training design involving manipulations of numerical relations between interacting members of social collectives. PMID:25191870

Numerical relations and skill level constrain co-adaptive behaviors of agents in sports teams.

PubMed

Silva, Pedro; Travassos, Bruno; Vilar, Luís; Aguiar, Paulo; Davids, Keith; Araújo, Duarte; Garganta, Júlio

2014-01-01

Similar to other complex systems in nature (e.g., a hunting pack, flocks of birds), sports teams have been modeled as social neurobiological systems in which interpersonal coordination tendencies of agents underpin team swarming behaviors. Swarming is seen as the result of agent co-adaptation to ecological constraints of performance environments by collectively perceiving specific possibilities for action (affordances for self and shared affordances). A major principle of invasion team sports assumed to promote effective performance is to outnumber the opposition (creation of numerical overloads) during different performance phases (attack and defense) in spatial regions adjacent to the ball. Such performance principles are assimilated by system agents through manipulation of numerical relations between teams during training in order to create artificially asymmetrical performance contexts to simulate overloaded and underloaded situations. Here we evaluated effects of different numerical relations differentiated by agent skill level, examining emergent inter-individual, intra- and inter-team coordination. Groups of association football players (national--NLP and regional-level--RLP) participated in small-sided and conditioned games in which numerical relations between system agents were manipulated (5v5, 5v4 and 5v3). Typical grouping tendencies in sports teams (major ranges, stretch indices, distances of team centers to goals and distances between the teams' opposing line-forces in specific team sectors) were recorded by plotting positional coordinates of individual agents through continuous GPS tracking. Results showed that creation of numerical asymmetries during training constrained agents' individual dominant regions, the underloaded teams' compactness and each team's relative position on-field, as well as distances between specific team sectors. We also observed how skill level impacted individual and team coordination tendencies. Data revealed emergence of co-adaptive behaviors between interacting neurobiological social system agents in the context of sport performance. Such observations have broader implications for training design involving manipulations of numerical relations between interacting members of social collectives.

Robust Real-Time Wide-Area Differential GPS Navigation

NASA Technical Reports Server (NTRS)

Yunck, Thomas P. (Inventor); Bertiger, William I. (Inventor); Lichten, Stephen M. (Inventor); Mannucci, Anthony J. (Inventor); Muellerschoen, Ronald J. (Inventor); Wu, Sien-Chong (Inventor)

1998-01-01

The present invention provides a method and a device for providing superior differential GPS positioning data. The system includes a group of GPS receiving ground stations covering a wide area of the Earth's surface. Unlike other differential GPS systems wherein the known position of each ground station is used to geometrically compute an ephemeris for each GPS satellite. the present system utilizes real-time computation of satellite orbits based on GPS data received from fixed ground stations through a Kalman-type filter/smoother whose output adjusts a real-time orbital model. ne orbital model produces and outputs orbital corrections allowing satellite ephemerides to be known with considerable greater accuracy than from die GPS system broadcasts. The modeled orbits are propagated ahead in time and differenced with actual pseudorange data to compute clock offsets at rapid intervals to compensate for SA clock dither. The orbital and dock calculations are based on dual frequency GPS data which allow computation of estimated signal delay at each ionospheric point. These delay data are used in real-time to construct and update an ionospheric shell map of total electron content which is output as part of the orbital correction data. thereby allowing single frequency users to estimate ionospheric delay with an accuracy approaching that of dual frequency users.

NASA Johnson Space Center: Mini AERCam Testing with GSS6560

NASA Technical Reports Server (NTRS)

Cryant, Scott P.

2004-01-01

This slide presentation reviews the testing of the Miniature Autonomous Extravehicular Robotic Camera (Mini AERCam) with the GPS/SBAS simulation system, GSS6560. There is a listing of several GPS based programs at NASA Johnson, including the testing of Shuttle testing of the GPS system. Including information about Space Integrated GPS/INS (SIGI) testing. There is also information about the standalone ISS SIGI test,and testing of the SIGI for the Crew Return Vehicle. The Mini AERCam is a small, free-flying camera for remote inspections of the ISS, it uses precise relative navigation with differential carrier phase GPS to provide situational awareness to operators. The closed loop orbital testing with and without the use of the GSS6550 system of the Mini AERCam system is reviewed.

Development of GPS survey data management protocols/policy.

DOT National Transportation Integrated Search

2010-08-01

This project developed a statewide policy and criteria for collecting, analyzing, and managing global position system (GPS) survey data. The research project determined the needs of the Department in adopting the GPS real time kinetic (GPS RTK) stake...

GPS=A Good Candidate for Data Assimilation?

NASA Technical Reports Server (NTRS)

Poli, P.; Joiner, J.; Kursinski, R.; Einaudi, Franco (Technical Monitor)

2000-01-01

The Global Positioning System (GPS) enables positioning anywhere about our planet. The microwave signals sent by the 24 transmitters are sensitive to the atmosphere. Using the radio occultation technique, it is possible to perform soundings, with a Low Earth Orbiter (700 km) GPS receiver. The insensitiveness to clouds and aerosols, the relatively high vertical resolution (1.5 km), the self-calibration and stability of the GPS make it a priori a potentially good observing system candidate for data assimilation. A low-computing cost simple method to retrieve both temperature and humidity will be presented. Comparisons with radiosonde show the capability of the GPS to resolve the tropopause. Options for using GPS for data assimilation and remaining issues will be discussed.

[Change in service provision and availability under the list patient system reform].

PubMed

Grytten, Jostein; Skau, Irene; Sørensen, Rune; Aasland, Olaf G

2004-02-05

In this article, we analyse the relationship between length of patient lists and general practitioners' (GPs') service provision in order to investigate whether the list patient system reform has led to reduced accessibility and/or supplier inducement. The data were collected from a comprehensive questionnaire survey among GPs in the list patient system in 2002 (2306 GPs) and from the National Insurance Administration in 2001 (1637 GPs). The relationship between length of patient lists and service provision was analysed using regression analysis. The relationship between length of patient lists and number of consultations per GP was almost proportional, as was the relationship between length of patient list and number of consultations initiated by GPs. GPs who wanted more patients on their list had fewer consultations than those who were satisfied with the length of their lists and they did not compensate by taking more laboratory tests per consultation. Analysis of the two independent sets of data gave almost identical results. Patients' access to their GPs is independent of the length of his or her patient list. Even GPs with long lists do not ration consultations. This probably reflects efficient organisation of the practice. Our results do not support the theory that GPs induce demand for their services; one explanation is that GPs with short lists have chosen to have precisely that and have no need to induce demand.

TOPEX/POSEIDON operational orbit determination results using global positioning satellites

NASA Technical Reports Server (NTRS)

Guinn, J.; Jee, J.; Wolff, P.; Lagattuta, F.; Drain, T.; Sierra, V.

1994-01-01

Results of operational orbit determination, performed as part of the TOPEX/POSEIDON (T/P) Global Positioning System (GPS) demonstration experiment, are presented in this article. Elements of this experiment include the GPS satellite constellation, the GPS demonstration receiver on board T/P, six ground GPS receivers, the GPS Data Handling Facility, and the GPS Data Processing Facility (GDPF). Carrier phase and P-code pseudorange measurements from up to 24 GPS satellites to the seven GPS receivers are processed simultaneously with the GDPF software MIRAGE to produce orbit solutions of T/P and the GPS satellites. Daily solutions yield subdecimeter radial accuracies compared to other GPS, LASER, and DORIS precision orbit solutions.

A simultaneously calibration approach for installation and attitude errors of an INS/GPS/LDS target tracker.

PubMed

Cheng, Jianhua; Chen, Daidai; Sun, Xiangyu; Wang, Tongda

2015-02-04

To obtain the absolute position of a target is one of the basic topics for non-cooperated target tracking problems. In this paper, we present a simultaneously calibration method for an Inertial navigation system (INS)/Global position system (GPS)/Laser distance scanner (LDS) integrated system based target positioning approach. The INS/GPS integrated system provides the attitude and position of observer, and LDS offers the distance between the observer and the target. The two most significant errors are taken into jointly consideration and analyzed: (1) the attitude measure error of INS/GPS; (2) the installation error between INS/GPS and LDS subsystems. Consequently, a INS/GPS/LDS based target positioning approach considering these two errors is proposed. In order to improve the performance of this approach, a novel calibration method is designed to simultaneously estimate and compensate these two main errors. Finally, simulations are conducted to access the performance of the proposed target positioning approach and the designed simultaneously calibration method.

Development of a High Precision Displacement Measurement System by Fusing a Low Cost RTK-GPS Sensor and a Force Feedback Accelerometer for Infrastructure Monitoring.

PubMed

Koo, Gunhee; Kim, Kiyoung; Chung, Jun Yeon; Choi, Jaemook; Kwon, Nam-Yeol; Kang, Doo-Young; Sohn, Hoon

2017-11-28

A displacement measurement system fusing a low cost real-time kinematic global positioning system (RTK-GPS) receiver and a force feedback accelerometer is proposed for infrastructure monitoring. The proposed system is composed of a sensor module, a base module and a computation module. The sensor module consists of a RTK-GPS rover and a force feedback accelerometer, and is installed on a target structure like conventional RTK-GPS sensors. The base module is placed on a rigid ground away from the target structure similar to conventional RTK-GPS bases, and transmits observation messages to the sensor module. Then, the initial acceleration, velocity and displacement responses measured by the sensor module are transmitted to the computation module located at a central monitoring facility. Finally, high precision and high sampling rate displacement, velocity, and acceleration are estimated by fusing the acceleration from the accelerometer, the velocity from the GPS rover, and the displacement from RTK-GPS. Note that the proposed displacement measurement system can measure 3-axis acceleration, velocity as well as displacement in real time. In terms of displacement, the proposed measurement system can estimate dynamic and pseudo-static displacement with a root-mean-square error of 2 mm and a sampling rate of up to 100 Hz. The performance of the proposed system is validated under sinusoidal, random and steady-state vibrations. Field tests were performed on the Yeongjong Grand Bridge and Yi Sun-sin Bridge in Korea, and the Xihoumen Bridge in China to compare the performance of the proposed system with a commercial RTK-GPS sensor and other data fusion techniques.

Comparative Study of the Volumetric Methods Calculation Using GNSS Measurements

NASA Astrophysics Data System (ADS)

Şmuleac, Adrian; Nemeş, Iacob; Alina Creţan, Ioana; Sorina Nemeş, Nicoleta; Şmuleac, Laura

2017-10-01

This paper aims to achieve volumetric calculations for different mineral aggregates using different methods of analysis and also comparison of results. To achieve these comparative studies and presentation were chosen two software licensed, namely TopoLT 11.2 and Surfer 13. TopoLT program is a program dedicated to the development of topographic and cadastral plans. 3D terrain model, level courves and calculation of cut and fill volumes, including georeferencing of images. The program Surfer 13 is produced by Golden Software, in 1983 and is active mainly used in various fields such as agriculture, construction, geophysical, geotechnical engineering, GIS, water resources and others. It is also able to achieve GRID terrain model, to achieve the density maps using the method of isolines, volumetric calculations, 3D maps. Also, it can read different file types, including SHP, DXF and XLSX. In these paper it is presented a comparison in terms of achieving volumetric calculations using TopoLT program by two methods: a method where we choose a 3D model both for surface as well as below the top surface and a 3D model in which we choose a 3D terrain model for the bottom surface and another 3D model for the top surface. The comparison of the two variants will be made with data obtained from the realization of volumetric calculations with the program Surfer 13 generating GRID terrain model. The topographical measurements were performed with equipment from Leica GPS 1200 Series. Measurements were made using Romanian position determination system - ROMPOS which ensures accurate positioning of reference and coordinates ETRS through the National Network of GNSS Permanent Stations. GPS data processing was performed with the program Leica Geo Combined Office. For the volumetric calculating the GPS used point are in 1970 stereographic projection system and for the altitude the reference is 1975 the Black Sea projection system.

A Comparison of Systemic Inflammation-Based Prognostic Scores in Patients on Regular Hemodialysis

PubMed Central

Kato, Akihiko; Tsuji, Takayuki; Sakao, Yukitoshi; Ohashi, Naro; Yasuda, Hideo; Fujimoto, Taiki; Takita, Takako; Furuhashi, Mitsuyoshi; Kumagai, Hiromichi

2013-01-01

Background/Aims Systemic inflammation-based prognostic scores have prognostic power in patients with cancer, independently of tumor stage and site. Although inflammatory status is associated with mortality in hemodialysis (HD) patients, it remains to be determined as to whether these composite scores are useful in predicting clinical outcomes. Methods We calculated the 6 prognostic scores [Glasgow prognostic score (GPS), modified GPS (mGPS), neutrophil-lymphocyte ratio (NLR), platelet lymphocyte ratio (PLR), prognostic index (PI) and prognostic nutritional index (PNI), which have been established as a useful scoring system in cancer patients. We enrolled 339 patients on regular HD (age: 64 ± 13 years; time on HD: 129 ± 114 months; males/females = 253/85) and followed them for 42 months. The area under the receiver-operating characteristics curve was used to determine which scoring system was more predictive of mortality. Results Elevated GPS, mGPS, NLR, PLR, PI and PNI were all associated with total mortality, independent of covariates. If GPS was raised, mGPS, NLR, PLR and PI were also predictive of all-cause mortality and/or hospitalization. GPS and PNI were associated with poor nutritional status. Using overall mortality as an endpoint, the area under the curve (AUC) was significant for a GPS of 0.701 (95% CI: 0.637-0.765; p < 0.01) and for a PNI of 0.616 (95% CI: 0.553-0.768; p = 0.01). However, AUC for hypoalbuminemia (<3.5 g/dl) was comparable to that of GPS (0.695, 95% CI: 0.632-0.759; p < 0.01). Conclusion GPS, based on serum albumin and highly sensitive C-reactive protein, has the most prognostic power for mortality prediction among the prognostic scores in HD patients. However, as the determination of serum albumin reflects mortality similarly to GPS, other composite combinations are needed to provide additional clinical utility beyond that of albumin alone in HD patients. PMID:24403910

Adaptive Resampling Particle Filters for GPS Carrier-Phase Navigation and Collision Avoidance System

NASA Astrophysics Data System (ADS)

Hwang, Soon Sik

This dissertation addresses three problems: 1) adaptive resampling technique (ART) for Particle Filters, 2) precise relative positioning using Global Positioning System (GPS) Carrier-Phase (CP) measurements applied to nonlinear integer resolution problem for GPS CP navigation using Particle Filters, and 3) collision detection system based on GPS CP broadcasts. First, Monte Carlo filters, called Particle Filters (PF), are widely used where the system is non-linear and non-Gaussian. In real-time applications, their estimation accuracies and efficiencies are significantly affected by the number of particles and the scheduling of relocating weights and samples, the so-called resampling step. In this dissertation, the appropriate number of particles is estimated adaptively such that the error of the sample mean and variance stay in bounds. These bounds are given by the confidence interval of a normal probability distribution for a multi-variate state. Two required number of samples maintaining the mean and variance error within the bounds are derived. The time of resampling is determined when the required sample number for the variance error crosses the required sample number for the mean error. Second, the PF using GPS CP measurements with adaptive resampling is applied to precise relative navigation between two GPS antennas. In order to make use of CP measurements for navigation, the unknown number of cycles between GPS antennas, the so called integer ambiguity, should be resolved. The PF is applied to this integer ambiguity resolution problem where the relative navigation states estimation involves nonlinear observations and nonlinear dynamics equation. Using the PF, the probability density function of the states is estimated by sampling from the position and velocity space and the integer ambiguities are resolved without using the usual hypothesis tests to search for the integer ambiguity. The ART manages the number of position samples and the frequency of the resampling step for real-time kinematics GPS navigation. The experimental results demonstrate the performance of the ART and the insensitivity of the proposed approach to GPS CP cycle-slips. Third, the GPS has great potential for the development of new collision avoidance systems and is being considered for the next generation Traffic alert and Collision Avoidance System (TCAS). The current TCAS equipment, is capable of broadcasting GPS code information to nearby airplanes, and also, the collision avoidance system using the navigation information based on GPS code has been studied by researchers. In this dissertation, the aircraft collision detection system using GPS CP information is addressed. The PF with position samples is employed for the CP based relative position estimation problem and the same algorithm can be used to determine the vehicle attitude if multiple GPS antennas are used. For a reliable and enhanced collision avoidance system, three dimensional trajectories are projected using the estimates of the relative position, velocity, and the attitude. It is shown that the performance of GPS CP based collision detecting algorithm meets the accuracy requirements for a precise approach of flight for auto landing with significantly less unnecessary collision false alarms and no miss alarms.

Comparison of Three Wind Measuring Systems for Flight Test

NASA Technical Reports Server (NTRS)

Teets, Edward H., Jr.; Harvey, Philip O.

2000-01-01

A preliminary field test of the accuracy of wind velocity measurements obtained using global positioning system-tracked rawinsonde balloons has been performed. Wind comparisons have been conducted using global positioning system (GPS) and radio automatic theodolite sounder (RATS) rawinsondes and a high-precision range instrumentation radar-tracked reflector. Wind velocity differences between the GPS rawinsondes and the radar were significantly less than between the RATS rawinsondes and the radar. These limited test results indicate a root-mean-square wind velocity difference from 4.98 kn (2.56 m/sec) for the radar and RATS to 1.09 kn (0.56 m/sec) for the radar and GPS. Differences are influenced by user reporting requirements, data processing techniques, and the inherent tracking accuracies of the system. This brief field test indicates that the GPS sounding system tracking data are more precise than the RATS system. When high-resolution wind data are needed, use of GPS rawinsonde systems can reduce the burden on range radar operations.

Anti-Jam GPS Antennas for Wearable Dismounted Soldier Navigation Systems

DTIC Science & Technology

2016-06-01

in this report are not to be construed as an official Department of the Army position unless so designated by other authorized documents. Citation...Approaches for the design and fabrication of a wearable anti-jam global positioning system (GPS) antenna are explored to support accurate and uninterrupted...including GPS antenna element and array designs , and algorithms for jammer mitigation, and the candidate technologies best fit for wearable anti-jam GPS

Localization system for use in GPS denied environments

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

Trueblood, J. J.

The military uses to autonomous platforms to complete missions to provide standoff for the warfighters. However autonomous platforms rely on GPS to provide their global position. In many missions spaces the autonomous platforms may encounter GPS denied environments which limits where the platform operates and requires the warfighters to takes its place. GPS denied environments can occur due to tall building, trees, canyon wall blocking the GPS satellite signals or a lack of coverage. An Inertial Navigation System (INS) uses sensors to detect the vehicle movement and direction its traveling to calculate the vehicle. One of biggest challenges with anmore » INS system is the accuracy and accumulation of errors over time of the sensors. If these challenges can be overcome the INS would provide accurate positioning information to the autonomous vehicle in GPS denied environments and allow them to provide the desired standoff for the warfighters.« less

High accurate time system of the Low Latitude Meridian Circle.

NASA Astrophysics Data System (ADS)

Yang, Jing; Wang, Feng; Li, Zhiming

In order to obtain the high accurate time signal for the Low Latitude Meridian Circle (LLMC), a new GPS accurate time system is developed which include GPS, 1 MC frequency source and self-made clock system. The second signal of GPS is synchronously used in the clock system and information can be collected by a computer automatically. The difficulty of the cancellation of the time keeper can be overcomed by using this system.

Sports teams as complex adaptive systems: manipulating player numbers shapes behaviours during football small-sided games.

PubMed

Silva, Pedro; Vilar, Luís; Davids, Keith; Araújo, Duarte; Garganta, Júlio

2016-01-01

Small-sided and conditioned games (SSCGs) in sport have been modelled as complex adaptive systems. Research has shown that the relative space per player (RSP) formulated in SSCGs can impact on emergent tactical behaviours. In this study we adopted a systems orientation to analyse how different RSP values, obtained through manipulations of player numbers, influenced four measures of interpersonal coordination observed during performance in SSCGs. For this purpose we calculated positional data (GPS 15 Hz) from ten U-15 football players performing in three SSCGs varying in player numbers (3v3, 4v4 and 5v5). Key measures of SSCG system behaviours included values of (1) players' dispersion, (2) teams' separateness, (3) coupling strength and time delays between participants' emerging movements, respectively. Results showed that values of participants' dispersion increased, but the teams' separateness remained identical across treatments. Coupling strength and time delay also showed consistent values across SSCGs. These results exemplified how complex adaptive systems, like football teams, can harness inherent degeneracy to maintain similar team spatial-temporal relations with opponents through changes in inter-individual coordination modes (i.e., players' dispersion). The results imply that different team behaviours might emerge at different ratios of field dimension/player numbers. Therefore, sport pedagogists should carefully evaluate the effects of changing RSP in SSCGs as a way of promoting increased or decreased pressure on players.

Global positioning system and associated technologies in animal behaviour and ecological research

PubMed Central

Tomkiewicz, Stanley M.; Fuller, Mark R.; Kie, John G.; Bates, Kirk K.

2010-01-01

Biologists can equip animals with global positioning system (GPS) technology to obtain accurate (less than or equal to 30 m) locations that can be combined with sensor data to study animal behaviour and ecology. We provide the background of GPS techniques that have been used to gather data for wildlife studies. We review how GPS has been integrated into functional systems with data storage, data transfer, power supplies, packaging and sensor technologies to collect temperature, activity, proximity and mortality data from terrestrial species and birds. GPS ‘rapid fixing’ technologies combined with sensors provide location, dive frequency and duration profiles, and underwater acoustic information for the study of marine species. We examine how these rapid fixing technologies may be applied to terrestrial and avian applications. We discuss positional data quality and the capability for high-frequency sampling associated with GPS locations. We present alternatives for storing and retrieving data by using dataloggers (biologging), radio-frequency download systems (e.g. very high frequency, spread spectrum), integration of GPS with other satellite systems (e.g. Argos, Globalstar) and potential new data recovery technologies (e.g. network nodes). GPS is one component among many rapidly evolving technologies. Therefore, we recommend that users and suppliers interact to ensure the availability of appropriate equipment to meet animal research objectives. PMID:20566494

Global positioning system and associated technologies in animal behaviour and ecological research

USGS Publications Warehouse

Tomkiewicz, Stanley M.; Fuller, Mark R.; Kie, John G.; Bates, Kirk K.

2010-01-01

Biologists can equip animals with global positioning system (GPS) technology to obtain accurate (less than or equal to 30 m) locations that can be combined with sensor data to study animal behaviour and ecology. We provide the background of GPS techniques that have been used to gather data for wildlife studies. We review how GPS has been integrated into functional systems with data storage, data transfer, power supplies, packaging and sensor technologies to collect temperature, activity, proximity and mortality data from terrestrial species and birds. GPS 'rapid fixing' technologies combined with sensors provide location, dive frequency and duration profiles, and underwater acoustic information for the study of marine species. We examine how these rapid fixing technologies may be applied to terrestrial and avian applications. We discuss positional data quality and the capability for high-frequency sampling associated with GPS locations. We present alternatives for storing and retrieving data by using dataloggers (biologging), radio-frequency download systems (e.g. very high frequency, spread spectrum), integration of GPS with other satellite systems (e.g. Argos, Globalstar) and potential new data recovery technologies (e.g. network nodes). GPS is one component among many rapidly evolving technologies. Therefore, we recommend that users and suppliers interact to ensure the availability of appropriate equipment to meet animal research objectives.

A Wireless Local Area Network Command and Control System for Explosive Ordnance Disposal Incident Response

DTIC Science & Technology

2001-09-01

43 4. GPS ......................................................................................................44 E. POWER SUPPLY HARDWARE...44 Figure 5.6 Earthmate GPS Receiver ........................................................................................45...and 5Watts at 25 Ft Effective Range Minimum range of wireless link is 5 miles. Positional awareness System requires GPS input to determine

Anomalous tidal loading signals in South-West England and Brittany

NASA Astrophysics Data System (ADS)

Keshin, M.; Penna, N. T.; Clarke, P. J.; Bos, M. S.; Baker, T. F.

2010-05-01

The tidal deformation of the Earth, including ocean tide loading (OTL), sheds light on the Earth's internal structure. Uncertainties in the knowledge of this deformation may be a source of both direct and propagated periodic errors in GPS geodesy. The increasing number of global GPS stations with long histories of observations, as well as recent developments in precise GPS geodesy such as the availability of reprocessed satellite orbits, enables further study of these geophysical and geodetic phenomena. There are more than 10 worldwide regions where OTL displacement amplitudes exceed 25mm. In our work we considered one such region covering South-West England and stretching southward along the coasts of France, Spain and Portugal. Estimates of three-dimensional harmonic site motion at each of the principal diurnal (K1, O1, P1, Q1) and semi-diurnal (K2, M2, N2, S2) frequencies were obtained for 40 European stations with at least 2 year observation span, using the GIPSY-OASIS II software package with reprocessed precise satellite orbits from JPL. All GPS data available from 2002.0 to 2010.0 were considered. 34 stations were situated close to the Atlantic coast; a further 6 inland stations at similar latitudes were processed as a check on solid Earth tide models. Inter-model OTL displacement differences are small, especially for the inland sites; the problematic Bristol Channel area of South-West England was excluded. We validated the quality of our GPS estimates by using and comparing three different analysis strategies: (1) Harmonic estimation of total tidal displacement in 24-hour Precise Point Positioning (PPP) batch solutions: harmonic displacements are estimated per coordinate component for each of the eight principal tidal constituents. OTL is not modelled a priori, and nodal corrections are applied in post-processing after combination of the daily results; (2) Harmonic estimation of residual tidal displacement in 24-hour PPP batch solutions: OTL is modelled a priori using the FES2004 model in the reference frame of the whole Earth system (CM); the residual harmonic displacements are estimated per component per principal tidal constituent. Minor tidal harmonics are removed a priori using the routine "hardisp" by D. Agnew. Because of this, post-processing nodal corrections are not applied; (3) Amplitude and phase from kinematic PPP processing: kinematic GPS processing with a priori OTL modelling using FES2004 and hardisp as in (2); amplitude spectra are later estimated from the entire coordinate time series using the Lomb-Scargle periodogram method. We typically obtain excellent (0.3-0.7mm except for the K1 and K2 constituents) phasor agreement between all three strategies, comparable to the inter-model agreement between computed OTL displacements and suggesting that the GPS analysis strategy robustly detects actual tidal displacements. For sites in inland Europe where computed OTL displacements are less than 10mm with inter-model differences of less than 0.2mm, residual harmonic amplitudes are also at the 0.3-0.7mm level, confirming that solid Earth tides are modelled to at least this accuracy. For GPS stations located in South-West England and Brittany, onshore of the continental shelf, anomalous residual tidal signals were detected of about 2-3mm magnitude for the vertical M2 OTL constituent (10% of the expected signal). In contrast, sites in the Iberian Peninsula, with similar expected OTL magnitudes, have residuals at the expected 0.3-0.7mm level. Sites near to the Bay of Biscay show transitional behaviour between these regimes. Therefore at these locations, the different modern ocean tide models that agree very well must all either be systematically in error, or the difference in behaviour may be caused by errors in the displacement Green's functions applicable to loads on the nearby continental shelf.

Global Positioning System Navigation Above 76,000 km for NASA's Magnetospheric Multiscale Mission

NASA Technical Reports Server (NTRS)

Winternitz, Luke B.; Bamford, William A.; Price, Samuel R.; Carpenter, J. Russell; Long, Anne C.; Farahmand, Mitra

2016-01-01

NASA's Magnetospheric Multiscale (MMS) mission, launched in March of 2015, consists of a controlled formation of four spin-stabilized spacecraft in similar highly elliptic orbits reaching apogee at radial distances of 12 and 25 Earth radii (RE) in the first and second phases of the mission. Navigation for MMS is achieved independently on-board each spacecraft by processing Global Positioning System (GPS) observables using NASA Goddard Space Flight Center (GSFC)'s Navigator GPS receiver and the Goddard Enhanced Onboard Navigation System (GEONS) extended Kalman filter software. To our knowledge, MMS constitutes, by far, the highest-altitude operational use of GPS to date and represents a high point of over a decade of high-altitude GPS navigation research and development at GSFC. In this paper we will briefly describe past and ongoing high-altitude GPS research efforts at NASA GSFC and elsewhere, provide details on the design of the MMS GPS navigation system, and present on-orbit performance data from the first phase. We extrapolate these results to predict performance in the second phase orbit, and conclude with a discussion of the implications of the MMS results for future high-altitude GPS navigation, which we believe to be broad and far-reaching.

Global Positioning System Navigation Above 76,000 km for NASA's Magnetospheric Multiscale Mission

NASA Technical Reports Server (NTRS)

Winternitz, Luke B.; Bamford, William A.; Price, Samuel R.; Carpenter, J. Russell; Long, Anne C.; Farahmand, Mitra

2016-01-01

NASA's Magnetospheric Multiscale (MMS) mission, launched in March of 2015, consists of a controlled formation of four spin-stabilized spacecraft in similar highly elliptic orbits reaching apogee at radial distances of 12 and 25 Earth radii (RE) in the first and second phases of the mission. Navigation for MMSis achieved independently on-board each spacecraft by processing Global Positioning System (GPS) observables using NASA Goddard Space Flight Center (GSFC)'s Navigator GPS receiver and the Goddard Enhanced Onboard Navigation System (GEONS) extended Kalman filter software. To our knowledge, MMS constitutes, by far, the highest-altitude operational use of GPS to date and represents a high point of over a decade of high-altitude GPS navigation research and development at GSFC. In this paper we will briefly describe past and ongoing high-altitude GPS research efforts at NASA GSFC and elsewhere, provide details on the design of the MMS GPS navigation system, and present on-orbit performance data from the first phase. We extrapolate these results to predict performance in the second phase orbit, and conclude with a discussion of the implications of the MMS results for future high-altitude GPS navigation, which we believe to be broad and far-reaching.

PiVoT GPS Receiver

NASA Technical Reports Server (NTRS)

Wennersten, Miriam; Banes, Vince; Boegner, Greg; Clagnett, Charles; Dougherty, Lamar; Edwards, Bernard; Roman, Joe; Bauer, Frank H. (Technical Monitor)

2001-01-01

NASA Goddard Space Flight Center has built an open architecture, 24 channel spaceflight Global Positioning System (GPS) receiver. The compact PCI PiVoT GPS receiver card is based on the Mitel/GEC Plessey Builder 2 board. PiVoT uses two Plessey 2021 correlators to allow tracking of up to 24 separate GPS SV's on unique channels. Its four front ends can support four independent antennas, making it a useful card for hosting GPS attitude determination algorithms. It has been built using space quality, radiation tolerant parts. The PiVoT card works at a lower signal to noise ratio than the original Builder 2 board. It also hosts an improved clock oscillator. The PiVoT software is based on the original Piessey Builder 2 software ported to the Linux operating system. The software is posix compliant and can be easily converted to other posix operating systems. The software is open source to anyone with a licensing agreement with Plessey. Additional tasks can be added to the software to support GPS science experiments or attitude determination algorithms. The next generation PiVoT receiver will be a single radiation hardened compact PCI card containing the microprocessor and the GPS receiver optimized for use above the GPS constellation.

GPS meteorology - Remote sensing of atmospheric water vapor using the Global Positioning System

NASA Technical Reports Server (NTRS)

Bevis, Michael; Businger, Steven; Herring, Thomas A.; Rocken, Christian; Anthes, Richard A.; Ware, Randolph H.

1992-01-01

We present a new approach to remote sensing of water vapor based on the Global Positioning System (GPS). Geodesists and geophysicists have devised methods for estimating the extent to which signals propagating from GPS satellites to ground-based GPS receivers are delayed by atmospheric water vapor. This delay is parameterized in terms of a time-varying zenith wet delay (ZWD) which is retrieved by stochastic filtering of the GPS data. Given surface temperature and pressure readings at the GPS receiver, the retrieved ZWD can be transformed with very little additional uncertainty into an estimate of the integrated water vapor (IWV) overlying that receiver. Networks of continuously operating GPS receivers are being constructed by geodesists, geophysicists, and government and military agencies, in order to implement a wide range of positioning capabilities. These emerging GPS networks offer the possibility of observing the horizontal distribution of IWV or, equivalently, precipitate water with unprecedented coverage and a temporal resolution of the order of 10 min. These measurements could be utilized in operational weather forecasting and in fundamental research into atmospheric storm systems, the hydrologic cycle, atmospheric chemistry, and global climate change.

Differential GPS/inertial navigation approach/landing flight test results

NASA Technical Reports Server (NTRS)

Snyder, Scott; Schipper, Brian; Vallot, Larry; Parker, Nigel; Spitzer, Cary

1992-01-01

In November of 1990 a joint Honeywell/NASA-Langley differential GPS/inertial flight test was conducted at Wallops Island, Virginia. The test objective was to acquire a system performance database and demonstrate automatic landing using an integrated differential GPS/INS (Global Positioning System/inertial navigation system) with barometric and radar altimeters. The flight test effort exceeded program objectives with over 120 landings, 36 of which were fully automatic differential GPS/inertial landings. Flight test results obtained from post-flight data analysis are discussed. These results include characteristics of differential GPS/inertial error, using the Wallops Island Laser Tracker as a reference. Data on the magnitude of the differential corrections and vertical channel performance with and without radar altimeter augmentation are provided.

The U.S. Federal Radionavigation Plan

NASA Astrophysics Data System (ADS)

Shirer, Heywood O.

The author presents an overview of the 1990 Federal Radionavigation Plan (FRP) policy and a discussion of the status of GPS (Global Positioning System), Loran-C, Omega, VOR/DME (VHF omnidirectional range/distance measuring equipment), VORTAC, TACAN, MLS (Microwave Landing System), ILS (instrument landing systems), Transit, and radiobeacons. The 1990 FRP contains significant changes regarding several of the radionavigation systems. It is concluded that it is difficult at best to ascertain the post-GPS final systems mix of federally provided radionavigation systems. The phase-out dates of other systems in favor of GPS still remain soft. Many uncertainties remain until the capabilities of GPS are verified for all classes of users. The federal radionavigation planning process accommodates such uncertainties, keeping pace with the constantly changing radionavigation user profile and rapid advancements in system technology.

The interchangeability of global positioning system and semiautomated video-based performance data during elite soccer match play.

PubMed

Harley, Jamie A; Lovell, Ric J; Barnes, Christopher A; Portas, Matthew D; Weston, Matthew

2011-08-01

In elite-level soccer, player motion characteristics are commonly generated from match play and training situations using semiautomated video analysis systems and global positioning system (GPS) technology, respectively. Before such data are used collectively to quantify global player load, it is necessary to understand both the level of agreement and direction of bias between the systems so that specific interventions can be made based on the reported results. The aim of this report was to compare data derived from both systems for physical match performances. Six elite-level soccer players were analyzed during a competitive match using semiautomated video analysis (ProZone® [PZ]) and GPS (MinimaxX) simultaneously. Total distances (TDs), high speed running (HSR), very high speed running (VHSR), sprinting distance (SPR), and high-intensity running distance (HIR; >4.0 m·s(-1)) were reported in 15-minute match periods. The GPS reported higher values than PZ did for TD (GPS: 1,755.4 ± 245.4 m; PZ: 1,631.3 ± 239.5 m; p < 0.05); PZ reported higher values for SPR and HIR than GPS did (SPR: PZ, 34.1 ± 24.0 m; GPS: 20.3 ± 15.8 m; HIR: PZ, 368.1 ± 129.8 m; GPS: 317.0 ± 92.5 m; p < 0.05). Caution should be exercised when using match-load (PZ) and training-load (GPS) data interchangeably.

Integration of the B-52G Offensive Avionics System (OAS) with the Global Positioning System (GPS)

NASA Astrophysics Data System (ADS)

Foote, A. L.; Pluntze, S. C.

Integration of the B-52G OAS with the GPS has been accomplished by modification of existing OAS software. GPS derived position and velocity data are used to enhance the quality of the OAS inertial and dead reckoning navigation systems. The engineering design and the software development process used to implement this design are presented.

GPS dependencies in the transportation sector : an inventory of Global Positioning System dependencies in the transportation sector, best practices for improved robustness of GPS devices, and potential alternative solutions for positioning, navigation and

DOT National Transportation Integrated Search

2016-08-01

The John A. Volpe National Transportation Systems Center (Volpe Center) was asked by the NOAA Office of Space Commercialization to analyze dependencies on Global Positioning System (GPS) positioning, navigation, and timing (PNT) services within the U...

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.

Innovation or Violation? Leveraging Mobile Technology to Conduct Socially Responsible Community Research.

PubMed

Roy, Amanda L

2017-12-01

Mobile technology is increasingly being used to measure individuals' moods, thoughts, and behaviors in real time. Current examples include the use of smartphones to collect ecological momentary assessments (EMAs; assessments delivered "in the moment"); wearable technology to passively collect objective measures of participants' movement, physical activity, sleep, and physiological response; and smartphones and wearable devices with global positioning system (GPS) capabilities to collect precise information about where participants spend their time. Although advances in mobile technology offer exciting opportunities for measuring and modeling individuals' experiences in their natural environments, they also introduce new ethical issues. Drawing on lessons learned while collecting GPS coordinates and EMAs measuring mood, companionship, and health-risk behavior with a sample of low-income, predominantly racial/ethnic minority youth living in Chicago, this manuscript discusses ethical challenges specific to the methodology (e.g., unanticipated access to personal information) and broader concerns related to data conceptualization and interpretation (e.g., the ethics of "monitoring" low-income youth of color). While encouraging researchers to embrace innovations offered by mobile technology, this discussion highlights some of the many ethical issues that also need to be considered. © Society for Community Research and Action 2017.

A Simple Method to Improve Autonomous GPS Positioning for Tractors

PubMed Central

Gomez-Gil, Jaime; Alonso-Garcia, Sergio; Gómez-Gil, Francisco Javier; Stombaugh, Tim

2011-01-01

Error is always present in the GPS guidance of a tractor along a desired trajectory. One way to reduce GPS guidance error is by improving the tractor positioning. The most commonly used ways to do this are either by employing more precise GPS receivers and differential corrections or by employing GPS together with some other local positioning systems such as electronic compasses or Inertial Navigation Systems (INS). However, both are complex and expensive solutions. In contrast, this article presents a simple and low cost method to improve tractor positioning when only a GPS receiver is used as the positioning sensor. The method is based on placing the GPS receiver ahead of the tractor, and on applying kinematic laws of tractor movement, or a geometric approximation, to obtain the midpoint position and orientation of the tractor rear axle more precisely. This precision improvement is produced by the fusion of the GPS data with tractor kinematic control laws. Our results reveal that the proposed method effectively reduces the guidance GPS error along a straight trajectory. PMID:22163917

Combining GPS, GIS, and accelerometry: methodological issues in the assessment of location and intensity of travel behaviors.

PubMed

Oliver, Melody; Badland, Hannah; Mavoa, Suzanne; Duncan, Mitch J; Duncan, Scott

2010-01-01

Global positioning systems (GPS), geographic information systems (GIS), and accelerometers are powerful tools to explain activity within a built environment, yet little integration of these tools has taken place. This study aimed to assess the feasibility of combining GPS, GIS, and accelerometry to understand transport-related physical activity (TPA) in adults. Forty adults wore an accelerometer and portable GPS unit over 7 consecutive days and completed a demographics questionnaire and 7-day travel log. Accelerometer and GPS data were extracted for commutes to/from workplace and integrated into a GIS database. GIS maps were generated to visually explore physical activity intensity, GPS speeds and routes traveled. GPS, accelerometer, and survey data were collected for 37 participants. Loss of GPS data was substantial due to a range of methodological issues, such as low battery life, signal drop out, and participant noncompliance. Nonetheless, greater travel distances and significantly higher speeds were observed for motorized trips when compared with TPA. Pragmatic issues of using GPS monitoring to understand TPA behaviors and methodological recommendations for future research were identified. Although methodologically challenging, the combination of GPS monitoring, accelerometry and GIS technologies holds promise for understanding TPA within the built environment.

Mapping where We Live and Play with GPS Technology

ERIC Educational Resources Information Center

Gentry, Deborah J.

2006-01-01

As a result of technological advances such as the Global Positioning System (GPS) and the Geographic Information System (GIS), mapping practices and applications have become far more sophisticated. This article suggests family and consumer sciences students and professionals consider using GPS technology to map their communities as a strategy to…

78 FR 67132 - GPS Satellite Simulator Control Working Group Meeting

Federal Register 2010, 2011, 2012, 2013, 2014

2013-11-08

... DEPARTMENT OF DEFENSE Department of the Air Force GPS Satellite Simulator Control Working Group Meeting AGENCY: Space and Missile Systems Center, Global Positioning Systems (GPS) Directorate, Air Force... Control Working Group (SSCWG) meeting on 6 December 2013 from 0900-1300 PST at Los Angeles Air Force Base...

77 FR 70421 - GPS Satellite Simulator Control Working Group Meeting

Federal Register 2010, 2011, 2012, 2013, 2014

2012-11-26

... DEPARTMENT OF DEFENSE Department of the Air Force GPS Satellite Simulator Control Working Group Meeting AGENCY: Space and Missile Systems Center, Global Positioning Systems (GPS) Directorate, Department... Control Working Group (SSCWG) meeting on 14 December 2012 from 0900-1600 PST at Los Angeles Air Force Base...

Advancing Technology: GPS and GIS Outreach Training for Agricultural Producers

ERIC Educational Resources Information Center

Flynn, Allison; Arnold, Shannon

2010-01-01

The use of the Global Positioning System (GPS) and Global Information Systems (GIS) has made significant impacts on agricultural production practices. However, constant changes in the technologies require continuing educational updates. The outreach program described here introduces the operation, use, and applications of GPS receivers and GIS…

Lessons Learned from Two Years of On-Orbit Global Positioning System Experience on International Space Station

NASA Technical Reports Server (NTRS)

Gomez, Susan F.; Lammers, Michael L.

2004-01-01

The Global Positioning System Subsystem (GPS) for International Space Station (ISS) was activated April 12,2002 following the installation of the SO truss segment that included the GPS antennas on Shuttle mission STS-110. The ISS GPS receiver became the primary source for position, velocity, and attitude information for ISS two days after activation. The GPS receiver also provides a time reference for manual control of ISS time, and will be used for automatic time updates after problems are resolved with the output from the receiver. After two years of on-orbit experience, the GPS continues to be used as the primary navigation source for ISS; however, enough problems have surfaced that the firmware in the GPS attitude code has had to be totally rewritten and new algorithms developed, the firmware that processed the time output from the GPS receiver had to be rewritten, while the GPS navigation code has had minor revisions. The factors contributing to the delivery of a GPS receiver for use on ISS that requires extensive operator intervention to function are discussed. Observations from two years worth of GPS solutions will also be discussed. The technical solutions to the anomalous GPS receiver behavior will be discussed.

Demonstration of precise estimation of polar motion parameters with the global positioning system: Initial results

NASA Technical Reports Server (NTRS)

Lichten, S. M.

1991-01-01

Data from the Global Positioning System (GPS) were used to determine precise polar motion estimates. Conservatively calculated formal errors of the GPS least squares solution are approx. 10 cm. The GPS estimates agree with independently determined polar motion values from very long baseline interferometry (VLBI) at the 5 cm level. The data were obtained from a partial constellation of GPS satellites and from a sparse worldwide distribution of ground stations. The accuracy of the GPS estimates should continue to improve as more satellites and ground receivers become operational, and eventually a near real time GPS capability should be available. Because the GPS data are obtained and processed independently from the large radio antennas at the Deep Space Network (DSN), GPS estimation could provide very precise measurements of Earth orientation for calibration of deep space tracking data and could significantly relieve the ever growing burden on the DSN radio telescopes to provide Earth platform calibrations.

2006 Precision Strike Technology Symposium

DTIC Science & Technology

2006-10-19

s Navy Unique Joint system 14 A/C Unique Components Framework JMPS Common Components Crypto Key GCCS-M Interface Carrier Intel Feed Carrier...210 GPS Prediction CUPC GPS Crypto Key TAMMAC SLAM-ER GPS Almanac ETIRMS PMA-281 NGMS PMA-209 Boeing PMA-201 Raytheon ESC (USAF) Hill AFB PMA-234 PMA...242 F/A-18 UPC GPS Prediction CUPC GPS Crypto Key TAMMAC SLAM-ER GPS Almanac HARM WASP Framework ARC-210 ETIRMS PMA-281 Integration/Test/ Support TLAM

Operation of a single-channel, sequential Navstar GPS receiver in a helicopter mission environment

NASA Technical Reports Server (NTRS)

Edwards, F. G.; Hamlin, J. R.

1984-01-01

It is pointed out that the future utilization of the Navstar Global Positioning System (GPS) by civil helicopters will provide an enhanced performance not obtainable with current navigations systems. GPS will supply properly equipped users with extremely accurate three-dimensional position and velocity information anywhere in the world. Preliminary studies have been conducted to investigate differential GPS concept mechanizations and cost, and to theoretically predict navigation performance and the impact of degradation of the GPS C/A code for national security considerations. The obtained results are encouraging, but certain improvements are needed. As a second step in the program, a single-channel sequential GPS navigator was installed and operated in the NASA SH-3G helicopter. A series of flight tests were conducted. It is found that performance of the Navstar GPS Z-set is quite acceptable to support area navigation and nonprecision approach operations.

Monitoring of GPS(Global Positioning System) System Performance

DOT National Transportation Integrated Search

1985-06-01

The Global Positioning System (GPS), a worldwide satellite-based navigation system developed by the Department of Defense, is scheduled to become operational in late 1988. The system has the potential to become the primary radionaviagation system for...

A LEO Satellite Navigation Algorithm Based on GPS and Magnetometer Data

NASA Technical Reports Server (NTRS)

Deutschmann, Julie; Bar-Itzhack, Itzhack; Harman, Rick; Bauer, Frank H. (Technical Monitor)

2000-01-01

The Global Positioning System (GPS) has become a standard method for low cost onboard satellite orbit determination. The use of a GPS receiver as an attitude and rate sensor has also been developed in the recent past. Additionally, focus has been given to attitude and orbit estimation using the magnetometer, a low cost, reliable sensor. Combining measurements from both GPS and a magnetometer can provide a robust navigation system that takes advantage of the estimation qualities of both measurements. Ultimately a low cost, accurate navigation system can result, potentially eliminating the need for more costly sensors, including gyroscopes.

FPGA-based real-time embedded system for RISS/GPS integrated navigation.

PubMed

Abdelfatah, Walid Farid; Georgy, Jacques; Iqbal, Umar; Noureldin, Aboelmagd

2012-01-01

Navigation algorithms integrating measurements from multi-sensor systems overcome the problems that arise from using GPS navigation systems in standalone mode. Algorithms which integrate the data from 2D low-cost reduced inertial sensor system (RISS), consisting of a gyroscope and an odometer or wheel encoders, along with a GPS receiver via a Kalman filter has proved to be worthy in providing a consistent and more reliable navigation solution compared to standalone GPS receivers. It has been also shown to be beneficial, especially in GPS-denied environments such as urban canyons and tunnels. The main objective of this paper is to narrow the idea-to-implementation gap that follows the algorithm development by realizing a low-cost real-time embedded navigation system capable of computing the data-fused positioning solution. The role of the developed system is to synchronize the measurements from the three sensors, relative to the pulse per second signal generated from the GPS, after which the navigation algorithm is applied to the synchronized measurements to compute the navigation solution in real-time. Employing a customizable soft-core processor on an FPGA in the kernel of the navigation system, provided the flexibility for communicating with the various sensors and the computation capability required by the Kalman filter integration algorithm.

FPGA-Based Real-Time Embedded System for RISS/GPS Integrated Navigation

PubMed Central

Abdelfatah, Walid Farid; Georgy, Jacques; Iqbal, Umar; Noureldin, Aboelmagd

2012-01-01

Navigation algorithms integrating measurements from multi-sensor systems overcome the problems that arise from using GPS navigation systems in standalone mode. Algorithms which integrate the data from 2D low-cost reduced inertial sensor system (RISS), consisting of a gyroscope and an odometer or wheel encoders, along with a GPS receiver via a Kalman filter has proved to be worthy in providing a consistent and more reliable navigation solution compared to standalone GPS receivers. It has been also shown to be beneficial, especially in GPS-denied environments such as urban canyons and tunnels. The main objective of this paper is to narrow the idea-to-implementation gap that follows the algorithm development by realizing a low-cost real-time embedded navigation system capable of computing the data-fused positioning solution. The role of the developed system is to synchronize the measurements from the three sensors, relative to the pulse per second signal generated from the GPS, after which the navigation algorithm is applied to the synchronized measurements to compute the navigation solution in real-time. Employing a customizable soft-core processor on an FPGA in the kernel of the navigation system, provided the flexibility for communicating with the various sensors and the computation capability required by the Kalman filter integration algorithm. PMID:22368460

Precise aircraft single-point positioning using GPS post-mission orbits and satellite clock corrections

NASA Astrophysics Data System (ADS)

Lachapelle, G.; Cannon, M. E.; Qiu, W.; Varner, C.

1996-09-01

Aircraft single point position accuracy is assessed through a comparison of the single point coordinates with corresponding DGPS-derived coordinates. The platform utilized for this evaluation is a Naval Air Warfare Center P-3 Orion aircraft. Data was collected over a period of about 40 hours, spread over six days, off Florida's East Coast in July 94, using DGPS reference stations in Jacksonville, FL, and Warminster, PA. The analysis of results shows that the consistency between aircraft single point and DGPS coordinates obtained in single point positioning mode and DGPS mode is about 1 m (rms) in latitude and longitude, and 2 m (rms) in height, with instantaneous errors of up to a few metres due to the effect of the ionosphere on the single point L1 solutions.

Evaluation of GPS Coverage for the X-33 Michael-6 Trajectory

NASA Technical Reports Server (NTRS)

Lundberg, John B.

1998-01-01

The onboard navigational system for the X-33 test flights will be based on the use of measurements collected from the Embedded Global Positioning System (GPS)/INS system. Some of the factors which will affect the quality of the GPS contribution to the navigational solution will be the number of pseudorange measurements collected at any instant in time, the distribution of the GPS satellites within the field of view, and the inherent noise level of the GPS receiver. The distribution of GPS satellites within the field of view of the receiver's antenna will depend on the receiver's position, the time of day, pointing direction of the antenna, and the effective cone angle of the antenna. The number of pseudorange measurements collected will depend upon these factors as well as the time required to lock onto a GPS satellite signal once the GPS satellite comes into the field of view of the antenna and the number of available receiver channels. The objective of this study is to evaluate the GPS coverage resulting from the proposed antenna pointing directions, the proposed antenna cone angles, and the effects due to the time of day for the X-33 Michael-6 trajectory from launch at Edwards AFB, California, to the start of the Terminal Area Energy Management (TAEM) phase on approach to Michael AAF, Utah.

The Importance of Semi-Major Axis Knowledge in the Determination of Near-Circular Orbits

NASA Technical Reports Server (NTRS)

Carpenter, J. Russell; Schiesser, Emil R.

1998-01-01

Modem orbit determination has mostly been accomplished using Cartesian coordinates. This usage has carried over in recent years to the use of GPS for satellite orbit determination. The unprecedented positioning accuracy of GPS has tended to focus attention more on the system's capability to locate the spacecraft's location at a particular epoch than on its accuracy in determination of the orbit, per se. As is well-known, the latter depends on a coordinated knowledge of position, velocity, and the correlation between their errors. Failure to determine a properly coordinated position/velocity state vector at a given epoch can lead to an epoch state that does not propagate well, and/or may not be usable for the execution of orbit adjustment maneuvers. For the quite common case of near-circular orbits, the degree to which position and velocity estimates are properly coordinated is largely captured by the error in semi-major axis (SMA) they jointly produce. Figure 1 depicts the relationships among radius error, speed error, and their correlation which exist for a typical low altitude Earth orbit. Two familiar consequences are the relationship Figure 1 shows are the following: (1) downrange position error grows at the per orbit rate of 3(pi) times the SMA error; (2) a velocity change imparted to the orbit will have an error of (pi) divided by the orbit period times the SMA error. A less familiar consequence occurs in the problem of initializing the covariance matrix for a sequential orbit determination filter. An initial covariance consistent with orbital dynamics should be used if the covariance is to propagate well. Properly accounting for the SMA error of the initial state in the construction of the initial covariance accomplishes half of this objective, by specifying the partition of the covariance corresponding to down-track position and radial velocity errors. The remainder of the in-plane covariance partition may be specified in terms of the flight path angle error of the initial state. Figure 2 illustrates the effect of properly and not properly initializing a covariance. This figure was produced by propagating the covariance shown on the plot, without process noise, in a circular low Earth orbit whose period is 5828.5 seconds. The upper subplot, in which the proper relationships among position, velocity, and their correlation has been used, shows overall error growth, in terms of the standard deviations of the inertial position coordinates, of about half of the lower subplot, whose initial covariance was based on other considerations.

On principles, methods and recent advances in studies towards a GPS-based control system for geodesy and geodynamics

NASA Technical Reports Server (NTRS)

Delikaraoglou, Demitris

1989-01-01

Although Very Long Baseline Interferometry (VLBI) and Satellite Laser Ranging (SLR) are becoming increasingly important tools for geodynamic studies, their future role may well be fulfilled by using alternative techniques such as those utilizing the signals from the Global Positioning System (GPS). GPS, without the full implementation of the system, already offers a favorable combination of cost and accuracy and has consistently demonstrated the capability to provide high precision densification control in the regional and local areas of the VLBI and SLR networks. This report reviews VLBI and SLR vis-a-vis GPS and outlines the capabilities and limitations of each technique and how their complementary application can be of benefit to geodetic and geodynamic operations. It demonstrates, albeit with a limited data set, that dual-frequency GPS observations and interferometric type analysis techniques make possible the modelling of the GPS orbits for several days with an accuracy of a few meters. The use of VLBI or SLR sites as fiducial stations together with refinements in the orbit determination procedures can greatly reduce the systematic errors in the GPS satellite orbits used to compute the positions of non-fiducial locations. In general, repeatability and comparison with VLBI of the GPS determined locations are of the order of between 2 parts in 10 to the 7th power and 5 parts in 10 to the 8th power for baseline lengths less than 2000 km. This report is mainly a synthesis of problems, assumptions, methods and recent advances in the studies towards the establishment of a GPS-based system for geodesy and geodynamics and is one phase in the continuing effort for the development of such a system. To some, including the author, it seems reasonable to expect within the next few years that more evidence will show GPS to be as a powerful and reliable a tool as mobile VLBI and SLR are today, but largely more economical.

78 FR 57672 - 91st Meeting: RTCA Special Committee 159, Global Positioning Systems (GPS)

Federal Register 2010, 2011, 2012, 2013, 2014

2013-09-19

... include the following: Working Group Sessions October 7 Working Group 2C, GPS/Inertial, ARINC & A4A Rooms October 8 Working Group 2, GPS/WAAS, McIntosh-NBAA Room and Colson Board Room October 9 Working Group 2, GPS/WAAS, ARINC & A4A Rooms, Afternoon, 1:00 p.m.-5:00 p.m., Working Group 4, GPS/Precision Landing...

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.

GPS/INS Sensor Fusion Using GPS Wind up Model

NASA Technical Reports Server (NTRS)

Williamson, Walton R. (Inventor)

2013-01-01

A method of stabilizing an inertial navigation system (INS), includes the steps of: receiving data from an inertial navigation system; and receiving a finite number of carrier phase observables using at least one GPS receiver from a plurality of GPS satellites; calculating a phase wind up correction; correcting at least one of the finite number of carrier phase observables using the phase wind up correction; and calculating a corrected IMU attitude or velocity or position using the corrected at least one of the finite number of carrier phase observables; and performing a step selected from the steps consisting of recording, reporting, or providing the corrected IMU attitude or velocity or position to another process that uses the corrected IMU attitude or velocity or position. A GPS stabilized inertial navigation system apparatus is also described.

A Low-Cost GPS GSM/GPRS Telemetry System: Performance in Stationary Field Tests and Preliminary Data on Wild Otters (Lutra lutra)

PubMed Central

Quaglietta, Lorenzo; Martins, Bruno Herlander; de Jongh, Addy; Mira, António; Boitani, Luigi

2012-01-01

Background Despite the increasing worldwide use of global positioning system (GPS) telemetry in wildlife research, it has never been tested on any freshwater diving animal or in the peculiar conditions of the riparian habitat, despite this latter being one of the most important habitat types for many animal taxa. Moreover, in most cases, the GPS devices used have been commercial and expensive, limiting their use in low-budget projects. Methodology/Principal Findings We have developed a low-cost, easily constructed GPS GSM/GPRS (Global System for Mobile Communications/General Packet Radio Service) and examined its performance in stationary tests, by assessing the influence of different habitat types, including the riparian, as well as water submersion and certain climatic and environmental variables on GPS fix-success rate and accuracy. We then tested the GPS on wild diving animals, applying it, for the first time, to an otter species (Lutra lutra). The rate of locations acquired during the stationary tests reached 63.2%, with an average location error of 8.94 m (SD = 8.55). GPS performance in riparian habitats was principally affected by water submersion and secondarily by GPS inclination and position within the riverbed. Temporal and spatial correlations of location estimates accounted for some variation in the data sets. GPS-tagged otters also provided accurate locations and an even higher GPS fix-success rate (68.2%). Conclusions/Significance Our results suggest that GPS telemetry is reliably applicable to riparian and even diving freshwater animals. They also highlight the need, in GPS wildlife studies, for performing site-specific pilot studies on GPS functioning as well as for taking into account eventual spatial and temporal correlation of location estimates. The limited price, small dimensions, and high performance of the device presented here make it a useful and cost-effective tool for studies on otters and other aquatic or terrestrial medium-to-large-sized animals. PMID:22242163

A low-cost GPS GSM/GPRS telemetry system: performance in stationary field tests and preliminary data on wild otters (Lutra lutra).

PubMed

Quaglietta, Lorenzo; Martins, Bruno Herlander; de Jongh, Addy; Mira, António; Boitani, Luigi

2012-01-01

Despite the increasing worldwide use of global positioning system (GPS) telemetry in wildlife research, it has never been tested on any freshwater diving animal or in the peculiar conditions of the riparian habitat, despite this latter being one of the most important habitat types for many animal taxa. Moreover, in most cases, the GPS devices used have been commercial and expensive, limiting their use in low-budget projects. We have developed a low-cost, easily constructed GPS GSM/GPRS (Global System for Mobile Communications/General Packet Radio Service) and examined its performance in stationary tests, by assessing the influence of different habitat types, including the riparian, as well as water submersion and certain climatic and environmental variables on GPS fix-success rate and accuracy. We then tested the GPS on wild diving animals, applying it, for the first time, to an otter species (Lutra lutra). The rate of locations acquired during the stationary tests reached 63.2%, with an average location error of 8.94 m (SD = 8.55). GPS performance in riparian habitats was principally affected by water submersion and secondarily by GPS inclination and position within the riverbed. Temporal and spatial correlations of location estimates accounted for some variation in the data sets. GPS-tagged otters also provided accurate locations and an even higher GPS fix-success rate (68.2%). Our results suggest that GPS telemetry is reliably applicable to riparian and even diving freshwater animals. They also highlight the need, in GPS wildlife studies, for performing site-specific pilot studies on GPS functioning as well as for taking into account eventual spatial and temporal correlation of location estimates. The limited price, small dimensions, and high performance of the device presented here make it a useful and cost-effective tool for studies on otters and other aquatic or terrestrial medium-to-large-sized animals.

Exploring the training and scope of practice of GPs in England, Germany and Spain.

PubMed

Glonti, Ketevan; Struckmann, Verena; Alconada, Alvaro; Pettigrew, Luisa M; Hernandez-Santiago, Virginia; Minue, Sergio; Risso-Gill, Isabelle; McKee, Martin; Legido-Quigley, Helena

2018-03-22

To explore general practitioner (GP) training, continuing professional development, scope of practice, ethical issues and challenges in the working environment in three European countries. Qualitative study of 35 GPs from England, Germany and Spain working in urban primary care practices. Participants were recruited using convenience and snowball sampling techniques. Semi-structured interviews were recorded, transcribed and analysed by four independent researchers adopting a thematic approach. Entrance to and length of GP training differ between the three countries, while continuing professional development is required in all three, although with different characteristics. Key variations in the scope of practice include whether there is a gatekeeping role, whether GPs work in multidisciplinary teams or singlehandedly, the existence of appraisal processes, and the balance between administrative and clinical tasks. However, similar challenges, including the need to adapt to an ageing population, end-of-life care, ethical dilemmas, the impact of austerity measures, limited time for patients and gaps in coordination between primary and secondary care are experienced by GPs in all three countries. Primary health care variations have strong historical roots, derived from the different national experiences and the range of clinical services delivered by GPs. There is a need for an accessible source of information for GPs themselves and those responsible for safety and quality standards of the healthcare workforce. This paper maps out the current situation before Brexit is being implemented in the UK which could see many of the current EU arrangements and legislation to assure professional mobility between the UK and the rest of Europe dismantled. Copyright © 2017. Publicado por Elsevier España, S.L.U.

[Comparison of Google and Yahoo applications for geocoding of postal addresses in epidemiological studies].

PubMed

Quesada, Jose Antonio; Nolasco, Andreu; Moncho, Joaquín

2013-01-01

Geocoding is the assignment of geographic coordinates to spatial points, which often are postal addresses. The error made in applying this process can introduce bias in estimates of spatiotemporal models in epidemiological studies. No studies have been found to measure the error made in applying this process in Spanish cities. The objective is to evaluate the errors in magnitude and direction from two free sources (Google and Yahoo) with regard to a GPS in two Spanish cities. 30 addresses were geocoded with those two sources and the GPS in Santa Pola (Alicante) and Alicante city. The distances were calculated in metres (median, CI95%) between the sources and the GPS, globally and according to the status reported by each source. The directionality of the error was evaluated by calculating the location quadrant and applying a Chi-Square test. The GPS error was evaluated by geocoding 11 addresses twice at 4 days interval. The overall median in Google-GPS was 23,2 metres (16,0-32,1) for Santa Pola, and 21,4 meters (14,9-31,1) for Alicante. The overall median in Yahoo was 136,0 meters (19,2-318,5) for Santa Pola, and 23,8 meters (13,6- 29,2) for Alicante. Between the 73% and 90% were geocoded by status as "exact or interpolated" (minor error), where Goggle and Yahoo had a median error between 19 and 23 metres in the two cities. The GPS had a median error of 13.8 meters (6,7-17,8). No error directionality was detected. Google error is acceptable and stable in the two cities, so that it is a reliable source for Para medir elgeocoding addresses in Spain in epidemiological studies.

Precise GPS orbits for geodesy

NASA Technical Reports Server (NTRS)

Colombo, Oscar L.

1994-01-01

The Global Positioning System (GPS) has become, in recent years, the main space-based system for surveying and navigation in many military, commercial, cadastral, mapping, and scientific applications. Better receivers, interferometric techniques (DGPS), and advances in post-processing methods have made possible to position fixed or moving receivers with sub-decimeter accuracies in a global reference frame. Improved methods for obtaining the orbits of the GPS satellites have played a major role in these achievements; this paper gives a personal view of the main developments in GPS orbit determination.

Human Factors and Operations Issues in GPS and WAAS Sensor Approvals A Review and Comparison of FAA and RTCA Documents

DOT National Transportation Integrated Search

1997-07-01

This report is the culmination of the first task in a project to evaluate human factors and operations issues associated : with the integration of Class C Global Positioning System (GPS) sensors and Class Beta GPS/Wide Area Augmentation System : (WAA...

Human factors and operations issues in GPS and WAAS sensor approvals : a review and comparison of FAA and RTCA documents

DOT National Transportation Integrated Search

1997-07-01

This report is the culmination of the first task in a project to evaluate human factors and operations issues associated with the integration of Class C Global Positioning System (GPS) sensors and Class Beta GPS/Wide Area Augmentation System (WAAS) s...

A web-based GPS system for displacement monitoring and failure mechanism analysis of reservoir landslide.

PubMed

Li, Yuanyao; Huang, Jinsong; Jiang, Shui-Hua; Huang, Faming; Chang, Zhilu

2017-12-07

It is important to monitor the displacement time series and to explore the failure mechanism of reservoir landslide for early warning. Traditionally, it is a challenge to monitor the landslide displacements real-timely and automatically. Globe Position System (GPS) is considered as the best real-time monitoring technology, however, the accuracies of the landslide displacements monitored by GPS are not assessed effectively. A web-based GPS system is developed to monitor the landslide displacements real-timely and automatically in this study. And the discrete wavelet transform (DWT) is proposed to assess the accuracy of the GPS monitoring displacements. Wangmiao landslide in Three Gorges Reservoir area in China is used as case study. The results show that the web-based GPS system has advantages of high precision, real-time, remote control and automation for landslide monitoring; the Root Mean Square Errors of the monitoring landslide displacements are less than 5 mm. Meanwhile, the results also show that a rapidly falling reservoir water level can trigger the reactivation of Wangmiao landslide. Heavy rainfall is also an important factor, but not a crucial component.

Results of an Internet-Based Dual-Frequency Global Differential GPS System

NASA Technical Reports Server (NTRS)

Muellerschoen, R.; Bertiger, W.; Lough, M.

2000-01-01

Observables from a global network of 18 GPS receivers are returned in real-time to JPL over the open Internet. 30 - 40 cm RSS global GPS orbits and precise dual-frequency GPS clocks are computed in real-time with JPL's Real Time Gipsy (RTG) software.

33 CFR 164.43 - Automatic Identification System Shipborne Equipment-Prince William Sound.

Code of Federal Regulations, 2011 CFR

2011-07-01

...GPS) receiver; (2) Marine band Non-Directional Beacon receiver capable of receiving dGPS error... frequency; and (4) Control unit. (b) An AISSE must have the following capabilities: (1) Use dGPS to sense... Recommended Standards for Differential NAVSTAR GPS Service in determining the required information; (3...

USGS earthquake hazards program (EHP) GPS use case : earthquake early warning (EEW) and shake alert

DOT National Transportation Integrated Search

2017-03-30

GPS Adjacent Band Workshop VI RTCA Inc., Washington D.C., 30 March 2017. USGS GPS receiver use case - Real-Time GPS for EEW -Continued: CRITICAL EFFECT - The GNSS component of the Shake Alert system augments the inertial sensors and is especial...

Real-time reconstruction of topside ionosphere scale height from coordinated GPS-TEC and ionosonde observations

NASA Astrophysics Data System (ADS)

Gulyaeva, Tamara; Poustovalova, Ljubov

The International Reference Ionosphere model extended to the plasmasphere, IRI-Plas, has been recently updated for assimilation of total electron content, TEC, derived from observations with Global Navigation Satellite System, GNSS. The ionosonde products of the F2 layer peak density (NmF2) and height (hmF2) ensure true electron density maximum at the F2 peak. The daily solar and magnetic indices used by IRI-Plas code are compiled in data files including the 3-hour ap and kp magnetic index from 1958 onward, 12-monthly smoothed sunspot number R12 and Global Electron Content GEC12, daily solar radio flux F10.7 and daily sunspot number Ri. The 3-h ap-index is available in Real Time, RT, mode from GFZ, Potsdam, Germany, daily update of F10.7 is provided by Space Weather Canada service, and daily estimated international sunspot number Ri is provided by Solar Influences Data Analysis Center, SIDC, Belgium. For IRI-Plas-RT operation in regime of the daily update and prediction of the F2 layer peak parameters, the proxy kp and ap forecast for 3 to 24 hours ahead based on data for preceding 12 hours is applied online at http://www.izmiran.ru/services/iweather/. The topside electron density profile of IRI-Plas code is expressed with complementary half-peak density anchor height above hmF2 which corresponds to transition O+/H+ height. The present investigation is focused on reconstruction of topside ionosphere scale height using vertical total electron content (TEC) data derived from the Global Positioning System GPS observations and the ionosonde derived F2 layer peak parameters from 25 observatories ingested into IRI-Plas model. GPS-TEC and ionosonde measurements at solar maximum (September, 2002, and October, 2003) for quiet, positively disturbed, and negatively disturbed days of the month are used to obtain the topside scale height, Htop, representing the range of altitudes from hmF2 to the height where NmF2 decay by e times occurs. Mapping of the F2 layer peak parameters and TEC allows interpolate these parameters at coordinated grid sites from independent GPS receivers and ionosondes data. Exponential scale height Htop exceeds scale height HT of the α-Chapman layer by 3 times - the latter refers to a narrow altitude range from hmF2 to the height of 1.2 times decay of NmF2. While typical quiet daytime value of the topside scale height is around 200 km, it can be enhanced by 2-3 times during the negative phase of the ionospheric storm as it is captured by IRI-Plas-RT model ingesting the F2 peak and TEC data. This study is supported by the joint grant of RFBR 13-02-91370-CT_a and TUBITAK 112E568.

International developments in revenues and incomes of general practitioners from 2000 to 2010

PubMed Central

2013-01-01

Background The remuneration system of General Practitioners (GPs) has changed in several countries in the past decade. The aim of our study was: to establish the effect of these changes on the revenues and income of GPs in the first decade of the 21st century. Methods Annual GP revenue and practice costs were collected from national institutes in the eight countries included in our study (Belgium, Denmark, Finland, France, Germany, The Netherlands, Sweden, The United Kingdom (UK)) from 2000–2010. The data were corrected for inflation and purchasing power. Data on the remuneration systems and changes herein were collected from the European Observatory Health Systems Reviews and country experts. Results Comprehensive changes in the remuneration system of GPs were associated with considerable changes in GP income. Incremental changes mainly coincided with a gradual increase in income after correction for inflation. Average GP income was higher in countries with a strong primary care structure. Conclusions The gap between the countries where GPs have a lower income (Belgium, Sweden, France and Finland) and the countries where GPs have a higher income (Netherlands, Germany and the UK) continues to exist over time and appeared to be related to dimensions of primary care, such as governance and access. New payment forms, such as integrated care payment systems, and new health care professionals that are working for GPs, increasingly blur the line between practice costs and income, making it more and more important to clearly define expenditures on GPs, to remain sight on the actual income of GPs. PMID:24152337

Determination of recent horizontal crustal movements and deformations of African and Eurasian plates in western Mediterranean region using geodetic-GPS computations extended to 2006 (from 1997) related to NAFREF and AFREF frames.

NASA Astrophysics Data System (ADS)

Azzouzi, R.

2009-04-01

Determination of recent horizontal crustal movements and deformations of African and Eurasian plates in western Mediterranean region using geodetic-GPS computations extended to 2006 (from 1997) related to NAFREF and AFREF frames. By: R. Azzouzi*, M. Ettarid*, El H. Semlali*, et A. Rimi+ * Filière de Formation en Topographie Institut Agronomique et Vétérinaire Hassan II B.P. 6202 Rabat-Instituts MAROC + Département de la Physique du Globe Université Mohammed V Rabat MAROC This study focus on the use of the geodetic spatial technique GPS for geodynamic purposes generally in the Western Mediterranean area and particularly in Morocco. It aims to exploit this technique first to determine the geodetic coordinates on some western Mediterranean sites. And also this technique is used to detect and to determine movements cross the boundary line between the two African and Eurasian crustal plates on some well chosen GPS-Geodynamics sites. It will allow us also to estimate crustal dynamic parameters of tension that results. These parameters are linked to deformations of terrestrial crust in the region. They are also associated with tectonic constraints of the study area. The usefulness of repeated measurements of these elements, the estimate of displacements and the determination of their temporal rates is indisputable. Indeed, sismo-tectonique studies allow a good knowledge of the of earthquake processes, their frequency their amplitude and even of their prediction in the world in general and in Moroccan area especially. They allow also contributing to guarantee more security for all most important management projects, as projects of building great works (dams, bridges, nuclear centrals). And also as preliminary study, for the most important joint-project between Europe and Africa through the Strait of Gibraltar. For our application, 23 GPS monitoring stations under the ITRF2000 reference frame are chosen in Eurasian and African plates. The sites are located around the Western Mediterranean and especially on Morocco. Exploiting parameters of positions and dispersions of these stations within the 1997-2003 period, the motion and the interaction types of interaction between African and Eurasian tectonic plates can be estimated. Similarly, the crustal dynamic parameters of tension of these sites will be computed. The time occupation on repeated observations sites is at least 72 hours. The measurements are continuous on permanent stations. The precise ephemerides are used in GPS computations. The post-treatments are done using commercial and scientific softwares. The coordinates obtained for two consecutive periods to and t within a period of 8 years will be used by programs established for this purpose to estimate crustal dynamic parameters of tension as well as to evaluate the appropriate movements. Even crustal dynamic parameters will be determined on each sites of the GPS-Geodynamics network, whose interest of seismic investigations is very important. This will allow best knowledge of substantial seismic activities of the surrounding zones. It can be deduced by measuring the motions and their parameter tensions using GPS. These estimations will contribute on the earthquake prediction by supervising the strain accumulation and its release in the active areas. For the geodetically aspect the GPS-Geodynamics sites computed in the ITRF frame can be used with other similar ounces' of Africa country and some well selected and convenient IGS, EUREF stations..to determine first the NAFREF and the AFRER frames.

sUAS Position Estimation and Fusion in GPS-Degraded and GPS-Denied Environments using an ADS-B Transponder and Local Area Multilateration

NASA Astrophysics Data System (ADS)

Larson, Robert Sherman

An Unmanned Aerial Vehicle (UAV) and a manned aircraft are tracked using ADS-B transponders and the Local Area Multilateration System (LAMS) in simulated GPS-degraded and GPS-denied environments. Several position estimation and fusion algorithms are developed for use with the Autonomous Flight Systems Laboratory (AFSL) TRansponder based Position Information System (TRAPIS) software. At the lowest level, these estimation and fusion algorithms use raw information from ADS-B and LAMS data streams to provide aircraft position estimates to the ground station user. At the highest level, aircraft position is estimated using a discrete time Kalman filter with real-time covariance updates and fusion involving weighted averaging of ADS-B and LAMS positions. Simulation and flight test results are provided, demonstrating the feasibility of incorporating an ADS-B transponder on a commercially-available UAS and maintaining situational awareness of aircraft positions in GPS-degraded and GPS-denied environments.

Quantifying multi-dimensional attributes of human activities at various geographic scales based on smartphone tracking.

PubMed

Zhou, Xiaolu; Li, Dongying

2018-05-09

Advancement in location-aware technologies, and information and communication technology in the past decades has furthered our knowledge of the interaction between human activities and the built environment. An increasing number of studies have collected data regarding individual activities to better understand how the environment shapes human behavior. Despite this growing interest, some challenges exist in collecting and processing individual's activity data, e.g., capturing people's precise environmental contexts and analyzing data at multiple spatial scales. In this study, we propose and implement an innovative system that integrates smartphone-based step tracking with an app and the sequential tile scan techniques to collect and process activity data. We apply the OpenStreetMap tile system to aggregate positioning points at various scales. We also propose duration, step and probability surfaces to quantify the multi-dimensional attributes of activities. Results show that, by running the app in the background, smartphones can measure multi-dimensional attributes of human activities, including space, duration, step, and location uncertainty at various spatial scales. By coordinating Global Positioning System (GPS) sensor with accelerometer sensor, this app can save battery which otherwise would be drained by GPS sensor quickly. Based on a test dataset, we were able to detect the recreational center and sports center as the space where the user was most active, among other places visited. The methods provide techniques to address key issues in analyzing human activity data. The system can support future studies on behavioral and health consequences related to individual's environmental exposure.

Applications of GPS technologies to field sports.

PubMed

Aughey, Robert J

2011-09-01

Global positioning system (GPS) technology was made possible after the invention of the atomic clock. The first suggestion that GPS could be used to assess the physical activity of humans followed some 40 y later. There was a rapid uptake of GPS technology, with the literature concentrating on validation studies and the measurement of steady-state movement. The first attempts were made to validate GPS for field sport applications in 2006. While GPS has been validated for applications for team sports, some doubts continue to exist on the appropriateness of GPS for measuring short high-velocity movements. Thus, GPS has been applied extensively in Australian football, cricket, hockey, rugby union and league, and soccer. There is extensive information on the activity profile of athletes from field sports in the literature stemming from GPS, and this includes total distance covered by players and distance in velocity bands. Global positioning systems have also been applied to detect fatigue in matches, identify periods of most intense play, different activity profiles by position, competition level, and sport. More recent research has integrated GPS data with the physical capacity or fitness test score of athletes, game-specific tasks, or tactical or strategic information. The future of GPS analysis will involve further miniaturization of devices, longer battery life, and integration of other inertial sensor data to more effectively quantify the effort of athletes.

Techniques for monitoring and controlling yaw attitude of a GPS satellite

NASA Technical Reports Server (NTRS)

Lichten, Stephen M. (Inventor); Bar-Sever, Yoaz (Inventor); Zumberge, James (Inventor); Bertiger, William I. (Inventor); Muellerschoen, Ronald J. (Inventor); Wu, Sien-Chong (Inventor); Hurst, Kenneth (Inventor); Blewitt, Geoff (Inventor); Yunck, Thomas (Inventor); Thornton, Catherine (Inventor)

2001-01-01

Techniques for monitoring and controlling yawing of a GPS satellite in an orbit that has an eclipsing portion out of the sunlight based on the orbital conditions of the GPS satellite. In one embodiment, a constant yaw bias is generated in the attitude control system of the GPS satellite to control the yawing of the GPS satellite when it is in the shadow of the earth.

Navigation: National Plans; NAVSTAR-GPS; Laser Gyros

DTIC Science & Technology

1982-08-31

REFERENC-~CP STER . TECHNICAL REPORT ! "NO. 12686,-’-. - NAVIGATION: NATIONAL PLANS ; NAVSTAR-GPS; LASER GYROS CONTRACT NO. DAAK30-80-C-0073 31 AUGUST...Technical ReportAW Ng. riiNational Plans ; Navstar-GPS; S... : NavstarGPS; a3 Sept 1980 - 31 Aug 1982 ....Lasr Gyros. 6. PERFORMING ORG. REPORT NUMBER PRA...identify by block number) Navigation Navigation Satellites Laser Gyros Position-Location . NAVSTAR-GPS Fiberoptic Gyros Planning Global Positioning System

Contribution of Multi-GNSS Constellation to SLR-Derived Terrestrial Reference Frame

NASA Astrophysics Data System (ADS)

Sośnica, K.; Bury, G.; Zajdel, R.

2018-03-01

All satellites of new Global Navigation Satellite Systems (GNSS) are equipped with laser retroreflectors dedicated to Satellite Laser Ranging (SLR). This paper demonstrates the contribution of SLR tracking of multi-GNSS constellations to the improved SLR-derived reference frame and scientific products. We show a solution strategy with estimating satellite orbits, SLR station coordinates, geocenter coordinates, and Earth rotation parameters using SLR observations to 2 Laser Geodynamics Satellites (LAGEOS) and 55 GNSS satellites: 1 GPS, 31 Globalnaya Navigatsionnaya Sputnikovaya Sistema, 18 Galileo, 3 BeiDou Inclined Geosynchronous Orbit, 1 BeiDou Medium Earth Orbit, and 1 Quasi-Zenith Satellite System satellite for the period 2014.0-2017.4. Due to a substantial number of GNSS observations, the number of weekly solutions for some SLR stations, for example, Arkhyz, Komsomolsk, Altay, and Brasilia, is larger up to 41% in the combined LAGEOS + GNSS solution when compared to the LAGEOS-only solution. The SLR observations to GNSS can transfer the orientation of the reference frame from GNSS to SLR solutions. As a result, the SLR-derived pole coordinates and length-of-day estimates become more consistent with GNSS microwave-based results. The root-mean-square errors of length-of-day are reduced from 122.5 μs/d to 43.0 μs/d, whereas mean offsets are reduced from -81.6 μs/d to 0.5 μs/d in LAGEOS only and in the combined LAGEOS + GNSS solutions, respectively.

Tightly coupled low cost 3D RISS/GPS integration using a mixture particle filter for vehicular navigation.

PubMed

Georgy, Jacques; Noureldin, Aboelmagd

2011-01-01

Satellite navigation systems such as the global positioning system (GPS) are currently the most common technique used for land vehicle positioning. However, in GPS-denied environments, there is an interruption in the positioning information. Low-cost micro-electro mechanical system (MEMS)-based inertial sensors can be integrated with GPS and enhance the performance in denied GPS environments. The traditional technique for this integration problem is Kalman filtering (KF). Due to the inherent errors of low-cost MEMS inertial sensors and their large stochastic drifts, KF, with its linearized models, has limited capabilities in providing accurate positioning. Particle filtering (PF) was recently suggested as a nonlinear filtering technique to accommodate for arbitrary inertial sensor characteristics, motion dynamics and noise distributions. An enhanced version of PF called the Mixture PF is utilized in this study to perform tightly coupled integration of a three dimensional (3D) reduced inertial sensors system (RISS) with GPS. In this work, the RISS consists of one single-axis gyroscope and a two-axis accelerometer used together with the vehicle's odometer to obtain 3D navigation states. These sensors are then integrated with GPS in a tightly coupled scheme. In loosely-coupled integration, at least four satellites are needed to provide acceptable GPS position and velocity updates for the integration filter. The advantage of the tightly-coupled integration is that it can provide GPS measurement update(s) even when the number of visible satellites is three or lower, thereby improving the operation of the navigation system in environments with partial blockages by providing continuous aiding to the inertial sensors even during limited GPS satellite availability. To effectively exploit the capabilities of PF, advanced modeling for the stochastic drift of the vertically aligned gyroscope is used. In order to benefit from measurement updates for such drift, which are loosely-coupled updates, a hybrid loosely/tightly coupled solution is proposed. This solution is suitable for downtown environments because of the long natural outages or degradation of GPS. The performance of the proposed 3D Navigation solution using Mixture PF for 3D RISS/GPS integration is examined by road test trajectories in a land vehicle and compared to the KF counterpart.

Tightly Coupled Low Cost 3D RISS/GPS Integration Using a Mixture Particle Filter for Vehicular Navigation

PubMed Central

Georgy, Jacques; Noureldin, Aboelmagd

2011-01-01

Satellite navigation systems such as the global positioning system (GPS) are currently the most common technique used for land vehicle positioning. However, in GPS-denied environments, there is an interruption in the positioning information. Low-cost micro-electro mechanical system (MEMS)-based inertial sensors can be integrated with GPS and enhance the performance in denied GPS environments. The traditional technique for this integration problem is Kalman filtering (KF). Due to the inherent errors of low-cost MEMS inertial sensors and their large stochastic drifts, KF, with its linearized models, has limited capabilities in providing accurate positioning. Particle filtering (PF) was recently suggested as a nonlinear filtering technique to accommodate for arbitrary inertial sensor characteristics, motion dynamics and noise distributions. An enhanced version of PF called the Mixture PF is utilized in this study to perform tightly coupled integration of a three dimensional (3D) reduced inertial sensors system (RISS) with GPS. In this work, the RISS consists of one single-axis gyroscope and a two-axis accelerometer used together with the vehicle’s odometer to obtain 3D navigation states. These sensors are then integrated with GPS in a tightly coupled scheme. In loosely-coupled integration, at least four satellites are needed to provide acceptable GPS position and velocity updates for the integration filter. The advantage of the tightly-coupled integration is that it can provide GPS measurement update(s) even when the number of visible satellites is three or lower, thereby improving the operation of the navigation system in environments with partial blockages by providing continuous aiding to the inertial sensors even during limited GPS satellite availability. To effectively exploit the capabilities of PF, advanced modeling for the stochastic drift of the vertically aligned gyroscope is used. In order to benefit from measurement updates for such drift, which are loosely-coupled updates, a hybrid loosely/tightly coupled solution is proposed. This solution is suitable for downtown environments because of the long natural outages or degradation of GPS. The performance of the proposed 3D Navigation solution using Mixture PF for 3D RISS/GPS integration is examined by road test trajectories in a land vehicle and compared to the KF counterpart. PMID:22163846

Inflammation-based prognostic score and number of lymph node metastases are independent prognostic factors in esophageal squamous cell carcinoma.

PubMed

Kobayashi, Takashi; Teruya, Masanori; Kishiki, Tomokazu; Kaneko, Susumu; Endo, Daisuke; Takenaka, Yoshiharu; Miki, Kenji; Kobayashi, Kaoru; Morita, Koji

2010-08-01

Few studies have investigated whether the Glasgow Prognostic Score (GPS), an inflammation-based prognostic score, is useful for postoperative prognosis of esophageal squamous cell carcinoma. GPS was calculated on the basis of admission data as follows: patients with elevated C-reactive protein level (>10 mg/l) and hypoalbuminemia (<35 g/l) were assigned to GPS2. Patients with one or no abnormal value were assigned to GPS1 or GPS0. A new scoring system was constructed using independent prognostic variables and was evaluated on whether it could be used to dictate the choice of clinical options. 65 patients with esophageal squamous cell carcinoma were enrolled. GPS and the number of lymph node metastases were found to be independent prognostic variables. The scoring system comprising GPS and the number of lymph node metastases was found to be effective in the prediction of a long-term outcome (p < 0.0001). Preoperative GPS may be useful for postoperative prognosis of patients with esophageal squamous cell carcinoma. GPS and the number of lymph node metastases could be used to identify a subgroup of patients with esophageal squamous cell carcinoma who are eligible for radical resection but show poor prognosis.

A comparison of mapped and measured total ionospheric electron content using global positioning system and beacon satellite observations

NASA Technical Reports Server (NTRS)

Lanyi, Gabor E.; Roth, Titus

1988-01-01

Total ionospheric electron contents (TEC) were measured by global positioning system (GPS) dual-frequency receivers developed by the Jet Propulsion Laboratory. The measurements included P-code (precise ranging code) and carrier phase data for six GPS satellites during multiple five-hour observing sessions. A set of these GPS TEC measurements were mapped from the GPS lines of sight to the line of sight of a Faraday beacon satellite by statistically fitting the TEC data to a simple model of the ionosphere. The mapped GPS TEC values were compared with the Faraday rotation measurements. Because GPS transmitter offsets are different for each satellite and because some GPS receiver offsets were uncalibrated, the sums of the satellite and receiver offsets were estimated simultaneously with the TEC in a least squares procedure. The accuracy of this estimation procedure is evaluated indicating that the error of the GPS-determined line of sight TEC can be at or below 1 x 10 to the 16th el/sq cm. Consequently, the current level of accuracy is comparable to the Faraday rotation technique; however, GPS provides superior sky coverage.

Performance Analysis on Carrier Phase-Based Tightly-Coupled GPS/BDS/INS Integration in GNSS Degraded and Denied Environments

PubMed Central

Han, Houzeng; Wang, Jian; Wang, Jinling; Tan, Xinglong

2015-01-01

The integration of Global Navigation Satellite Systems (GNSS) carrier phases with Inertial Navigation System (INS) measurements is essential to provide accurate and continuous position, velocity and attitude information, however it is necessary to fix ambiguities rapidly and reliably to obtain high accuracy navigation solutions. In this paper, we present the notion of combining the Global Positioning System (GPS), the BeiDou Navigation Satellite System (BDS) and low-cost micro-electro-mechanical sensors (MEMS) inertial systems for reliable navigation. An adaptive multipath factor-based tightly-coupled (TC) GPS/BDS/INS integration algorithm is presented and the overall performance of the integrated system is illustrated. A twenty seven states TC GPS/BDS/INS model is adopted with an extended Kalman filter (EKF), which is carried out by directly fusing ambiguity fixed double-difference (DD) carrier phase measurements with the INS predicted pseudoranges to estimate the error states. The INS-aided integer ambiguity resolution (AR) strategy is developed by using a dynamic model, a two-step estimation procedure is applied with adaptively estimated covariance matrix to further improve the AR performance. A field vehicular test was carried out to demonstrate the positioning performance of the combined system. The results show the TC GPS/BDS/INS system significantly improves the single-epoch AR reliability as compared to that of GPS/BDS-only or single satellite navigation system integrated strategy, especially for high cut-off elevations. The AR performance is also significantly improved for the combined system with adaptive covariance matrix in the presence of low elevation multipath related to the GNSS-only case. A total of fifteen simulated outage tests also show that the time to relock of the GPS/BDS signals is shortened, which improves the system availability. The results also indicate that TC integration system achieves a few centimeters accuracy in positioning based on the comparison analysis and covariance analysis, even in harsh environments (e.g., in urban canyons), thus we can see the advantage of positioning at high cut-off elevations that the combined GPS/BDS brings. PMID:25875191

Performance analysis on carrier phase-based tightly-coupled GPS/BDS/INS integration in GNSS degraded and denied environments.

PubMed

Han, Houzeng; Wang, Jian; Wang, Jinling; Tan, Xinglong

2015-04-14

The integration of Global Navigation Satellite Systems (GNSS) carrier phases with Inertial Navigation System (INS) measurements is essential to provide accurate and continuous position, velocity and attitude information, however it is necessary to fix ambiguities rapidly and reliably to obtain high accuracy navigation solutions. In this paper, we present the notion of combining the Global Positioning System (GPS), the BeiDou Navigation Satellite System (BDS) and low-cost micro-electro-mechanical sensors (MEMS) inertial systems for reliable navigation. An adaptive multipath factor-based tightly-coupled (TC) GPS/BDS/INS integration algorithm is presented and the overall performance of the integrated system is illustrated. A twenty seven states TC GPS/BDS/INS model is adopted with an extended Kalman filter (EKF), which is carried out by directly fusing ambiguity fixed double-difference (DD) carrier phase measurements with the INS predicted pseudoranges to estimate the error states. The INS-aided integer ambiguity resolution (AR) strategy is developed by using a dynamic model, a two-step estimation procedure is applied with adaptively estimated covariance matrix to further improve the AR performance. A field vehicular test was carried out to demonstrate the positioning performance of the combined system. The results show the TC GPS/BDS/INS system significantly improves the single-epoch AR reliability as compared to that of GPS/BDS-only or single satellite navigation system integrated strategy, especially for high cut-off elevations. The AR performance is also significantly improved for the combined system with adaptive covariance matrix in the presence of low elevation multipath related to the GNSS-only case. A total of fifteen simulated outage tests also show that the time to relock of the GPS/BDS signals is shortened, which improves the system availability. The results also indicate that TC integration system achieves a few centimeters accuracy in positioning based on the comparison analysis and covariance analysis, even in harsh environments (e.g., in urban canyons), thus we can see the advantage of positioning at high cut-off elevations that the combined GPS/BDS brings.

Accurate aircraft wind measurements using the global positioning system (GPS)

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

Dobosy, R.J.; Crawford, T.L., McMillen, R.T., Dumas, E.J.

1996-11-01

High accuracy measurements of the spatial distribution of wind speed are required in the study of turbulent exchange between the atmosphere and the earth. The use of a differential global positioning system (GPS) to determine the sensor velocity vector component of wind speed is discussed in this paper. The results of noise and rocking testing are summarized, and fluxes obtained from the GPS-based methods are compared to those measured from systems on towers and airplanes. The GPS-based methods provided usable measurements that compared well with tower and aircraft data at a significantly lower cost. 21 refs., 1 fig., 2 tabs.

Autonomous satellite navigation with the Global Positioning System

NASA Technical Reports Server (NTRS)

Fuchs, A. J.; Wooden, W. H., II; Long, A. C.

1977-01-01

This paper discusses the potential of using the Global Positioning System (GPS) to provide autonomous navigation capability to NASA satellites in the 1980 era. Some of the driving forces motivating autonomous navigation are presented. These include such factors as advances in attitude control systems, onboard science annotation, and onboard gridding of imaging data. Simulation results which demonstrate baseline orbit determination accuracies using GPS data on Seasat, Landsat-D, and the Solar Maximum Mission are presented. Emphasis is placed on identifying error sources such as GPS time, GPS ephemeris, user timing biases, and user orbit dynamics, and in a parametric sense on evaluating their contribution to the orbit determination accuracies.

Effect of forest canopy on GPS-based movement data

Treesearch

Nicholas J. DeCesare; John R. Squires; Jay A. Kolbe

2005-01-01

The advancing role of Global Positioning System (GPS) technology in ecology has made studies of animal movement possible for larger and more vagile species. A simple field test revealed that lengths of GPS-based movement data were strongly biased (P<0.001) by effects of forest canopy. Global Positioning System error added an average of 27.5% additional...

Is Pattern of Life Size-Invariant? Recovering the Underlying Intent of a Walker from Human Walking Trajectory Data

DTIC Science & Technology

2013-07-01

scripted walking actions were recorded using a Global Positioning System (GPS)-enabled BlackBerry (BB) smartphone. GPS data, consisting of latitude and...2014-1239; Cleared 26 March 2014   LIST OF ACRONYMS     AFRL Air Force Research Laboratory BB BlackBerry GPS Global Positioning System

Getting from Here to There and Knowing Where: Teaching Global Positioning Systems to Students with Visual Impairments

ERIC Educational Resources Information Center

Phillips, Craig L.

2011-01-01

Global Positioning Systems' (GPS) technology is available for individuals with visual impairments to use in wayfinding and address Lowenfeld's "three limitations of blindness." The considerations and methodologies for teaching GPS usage have developed over time as GPS information and devices have been integrated into orientation and mobility…

76 FR 8353 - Positioning Systems Directorate Will Be Hosting an Interface Control Working Group (ICWG) Meeting...

Federal Register 2010, 2011, 2012, 2013, 2014

2011-02-14

... an Interface Control Working Group (ICWG) Meeting for Document ICD-GPS-870 AGENCY: Interface Control Working Group (ICWG) meeting for document ICD-GPS-870. ACTION: Meeting Notice. SUMMARY: This notice... Working Group (ICWG) meeting for document ICD-GPS-870, Navstar Next Generation GPS Operational Control...

A demonstration of centimeter-level monitoring of polar motion with the Global Positioning System

NASA Technical Reports Server (NTRS)

Lindqwister, U. J.; Freedman, A. P.; Blewitt, G.

1992-01-01

Daily estimates of the Earth's pole position were obtained with the Global Positioning System (GPS) by using measurements obtained during the GPS IERS (International Earth Rotation Service) and Geodynamics (GIG'91) experiment from 22 Jan. to 13 Feb. 1991. Data from a globally distributed network consisting of 21 Rogue GPS receivers were chosen for the analysis. A comparison of the GPS polar motion series with nine 24-hour very long baseline interferometry (VLBI) estimates yielded agreement in the day-to-day pole position of about 1.5 cm for both X and Y polar motion. A similar comparison of GPS and satellite laser ranging (SLR) data showed agreement to about 1.0 cm. These preliminary results indicate that polar motion can be determined by GPS independent of, and at a level comparable to, that which is obtained from either VLBI or SLR. Furthermore, GPS can provide these data with a daily frequency that neither alternative technique can readily achieve. Thus, GPS promises to be a powerful tool for determining high-frequency platform parameter variation, essential for the ultraprecise spacecraft-tracking requirements of the coming years.

GPS Navigation Above 76,000 km for the MMS Mission

NASA Technical Reports Server (NTRS)

Winternitz, Luke; Bamford, Bill; Price, Samuel; Long, Anne; Farahmand, Mitra; Carpenter, Russell

2016-01-01

NASA's MMS mission, launched in March of 2015,consists of a controlled formation of four spin-stabilized spacecraft in similar highly elliptic orbits reaching apogee at radial distances of 12and 25 Earth radii in the first and second phases of the mission. Navigation for MMS is achieved independently onboard each spacecraft by processing GPS observables using NASA GSFC's Navigator GPS receiver and the Goddard Enhanced Onboard Navigation System (GEONS) extended Kalman filter software. To our knowledge, MMS constitutes, by far, the highest-altitude operational use of GPS to date and represents the culmination of over a decade of high-altitude GPS navigation research and development at NASA GSFC. In this paper we will briefly describe past and ongoing high-altitude GPS research efforts at NASA GSFC and elsewhere, provide details on the design of the MMS GPS navigation system, and present on-orbit performance data. We extrapolate these results to predict performance in the Phase 2b mission orbit, and conclude with a discussion of the implications of the MMS results for future high-altitude GPS navigation, which we believe to be broad and far-reaching.

BDS/GPS Dual Systems Positioning Based on the Modified SR-UKF Algorithm

PubMed Central

Kong, JaeHyok; Mao, Xuchu; Li, Shaoyuan

2016-01-01

The Global Navigation Satellite System can provide all-day three-dimensional position and speed information. Currently, only using the single navigation system cannot satisfy the requirements of the system’s reliability and integrity. In order to improve the reliability and stability of the satellite navigation system, the positioning method by BDS and GPS navigation system is presented, the measurement model and the state model are described. Furthermore, the modified square-root Unscented Kalman Filter (SR-UKF) algorithm is employed in BDS and GPS conditions, and analysis of single system/multi-system positioning has been carried out, respectively. The experimental results are compared with the traditional estimation results, which show that the proposed method can perform highly-precise positioning. Especially when the number of satellites is not adequate enough, the proposed method combine BDS and GPS systems to achieve a higher positioning precision. PMID:27153068

The limits of direct satellite tracking with the Global Positioning System (GPS)

NASA Technical Reports Server (NTRS)

Bertiger, W. I.; Yunck, T. P.

1988-01-01

Recent advances in high precision differential Global Positioning System-based satellite tracking can be applied to the more conventional direct tracking of low earth satellites. To properly evaluate the limiting accuracy of direct GPS-based tracking, it is necessary to account for the correlations between the a-priori errors in GPS states, Y-bias, and solar pressure parameters. These can be obtained by careful analysis of the GPS orbit determination process. The analysis indicates that sub-meter accuracy can be readily achieved for a user above 1000 km altitude, even when the user solution is obtained with data taken 12 hours after the data used in the GPS orbit solutions.

Performance Evaluation of Block Acquisition and Tracking Algorithms Using an Open Source GPS Receiver Platform

NASA Technical Reports Server (NTRS)

Ramachandran, Ganesh K.; Akopian, David; Heckler, Gregory W.; Winternitz, Luke B.

2011-01-01

Location technologies have many applications in wireless communications, military and space missions, etc. US Global Positioning System (GPS) and other existing and emerging Global Navigation Satellite Systems (GNSS) are expected to provide accurate location information to enable such applications. While GNSS systems perform very well in strong signal conditions, their operation in many urban, indoor, and space applications is not robust or even impossible due to weak signals and strong distortions. The search for less costly, faster and more sensitive receivers is still in progress. As the research community addresses more and more complicated phenomena there exists a demand on flexible multimode reference receivers, associated SDKs, and development platforms which may accelerate and facilitate the research. One of such concepts is the software GPS/GNSS receiver (GPS SDR) which permits a facilitated access to algorithmic libraries and a possibility to integrate more advanced algorithms without hardware and essential software updates. The GNU-SDR and GPS-SDR open source receiver platforms are such popular examples. This paper evaluates the performance of recently proposed block-corelator techniques for acquisition and tracking of GPS signals using open source GPS-SDR platform.

Leadership of healthcare commissioning networks in England: a mixed-methods study on clinical commissioning groups

PubMed Central

Zachariadis, Markos; Oborn, Eivor; Barrett, Michael; Zollinger-Read, Paul

2013-01-01

Objective To explore the relational challenges for general practitioner (GP) leaders setting up new network-centric commissioning organisations in the recent health policy reform in England, we use innovation network theory to identify key network leadership practices that facilitate healthcare innovation. Design Mixed-method, multisite and case study research. Setting Six clinical commissioning groups and local clusters in the East of England area, covering in total 208 GPs and 1 662 000 population. Methods Semistructured interviews with 56 lead GPs, practice managers and staff from the local health authorities (primary care trusts, PCT) as well as various healthcare professionals; 21 observations of clinical commissioning group (CCG) board and executive meetings; electronic survey of 58 CCG board members (these included GPs, practice managers, PCT employees, nurses and patient representatives) and subsequent social network analysis. Main outcome measures Collaborative relationships between CCG board members and stakeholders from their healthcare network; clarifying the role of GPs as network leaders; strengths and areas for development of CCGs. Results Drawing upon innovation network theory provides unique insights of the CCG leaders’ activities in establishing best practices and introducing new clinical pathways. In this context we identified three network leadership roles: managing knowledge flows, managing network coherence and managing network stability. Knowledge sharing and effective collaboration among GPs enable network stability and the alignment of CCG objectives with those of the wider health system (network coherence). Even though activities varied between commissioning groups, collaborative initiatives were common. However, there was significant variation among CCGs around the level of engagement with providers, patients and local authorities. Locality (sub) groups played an important role because they linked commissioning decisions with patient needs and brought the leaders closer to frontline stakeholders. Conclusions With the new commissioning arrangements, the leaders should seek to move away from dyadic and transactional relationships to a network structure, thereby emphasising on the emerging relational focus of their roles. Managing knowledge mobility, healthcare network coherence and network stability are the three clinical leadership processes that CCG leaders need to consider in coordinating their network and facilitating the development of good clinical commissioning decisions, best practices and innovative services. To successfully manage these processes, CCG leaders need to leverage the relational capabilities of their network as well as their clinical expertise to establish appropriate collaborations that may improve the healthcare services in England. Lack of local GP engagement adds uncertainty to the system and increases the risk of commissioning decisions being irrelevant and inefficient from patient and provider perspectives. PMID:23430596

Differential GPS for air transport: Status

NASA Technical Reports Server (NTRS)

Hueschen, Richard M.

1993-01-01

The presentation presents background on what the Global Navigation Satellite System (GNSS) is, desired target dates for initial GNSS capabilities for aircraft operations, and a description of differential GPS (Global Positioning System). The presentation also presents an overview of joint flight tests conducted by LaRC and Honeywell on an integrated differential GPS/inertial reference unit (IRU) navigation system. The overview describes the system tested and the results of the flight tests. The last item presented is an overview of a current grant with Ohio University from LaRC which has the goal of developing a precision DGPS navigation system based on interferometry techniques. The fundamentals of GPS interferometry are presented and its application to determine attitude and heading and precision positioning are shown. The presentation concludes with the current status of the grant.

Evaluation of Stiffness Changes in a High-Rise Building by Measurements of Lateral Displacements Using GPS Technology

PubMed Central

Choi, Se Woon; Kim, Ill Soo; Park, Jae Hwan; Kim, Yousok; Sohn, Hong Gyoo; Park, Hyo Seon

2013-01-01

The outrigger truss system is one of the most frequently used lateral load resisting structural systems. However, little research has been reported on the effect of installation of outrigger trusses on improvement of lateral stiffness of a high-rise building through full-scale measurements. In this paper, stiffness changes of a high-rise building due to installation of outrigger trusses have been evaluated by measuring lateral displacements using a global positioning system (GPS). To confirm the error range of the GPS measurement system used in the full-scale measurement tests, the GPS displacement monitoring system is investigated through a free vibration test of the experimental model. Then, for the evaluation of lateral stiffness of a high-rise building under construction, the GPS displacement monitoring system is applied to measurements of lateral displacements of a 66-story high-rise building before and after installation of outrigger truss. The stiffness improvement of the building before and after the installation is confirmed through the changes of the natural frequencies and the ratios of the base shear forces to the roof displacements. PMID:24233025

Precision Time Protocol-Based Trilateration for Planetary Navigation

NASA Technical Reports Server (NTRS)

Murdock, Ron

2015-01-01

Progeny Systems Corporation has developed a high-fidelity, field-scalable, non-Global Positioning System (GPS) navigation system that offers precision localization over communications channels. The system is bidirectional, providing position information to both base and mobile units. It is the first-ever wireless use of the Institute of Electrical and Electronics Engineers (IEEE) Precision Time Protocol (PTP) in a bidirectional trilateration navigation system. The innovation provides a precise and reliable navigation capability to support traverse-path planning systems and other mapping applications, and it establishes a core infrastructure for long-term lunar and planetary occupation. Mature technologies are integrated to provide navigation capability and to support data and voice communications on the same network. On Earth, the innovation is particularly well suited for use in unmanned aerial vehicles (UAVs), as it offers a non-GPS precision navigation and location service for use in GPS-denied environments. Its bidirectional capability provides real-time location data to the UAV operator and to the UAV. This approach optimizes assisted GPS techniques and can be used to determine the presence of GPS degradation, spoofing, or jamming.

Broadcasting GPS integrity information using Loran-C

NASA Astrophysics Data System (ADS)

Lo, Sherman Chih

The United States Federal Aviation Administration (FAA) will adopt the Global Positioning System (GPS) as its primary navigation systems for aviation as stated by the Federal Radionavigation Plans (FRP) of 1996 and 1999. The FRP also proposes the reduction or termination of some existing radionavigation system in favor of GPS and satellite navigation. It may be beneficial to retain some of these existing terrestrial navigation systems if they can provide increased safety and redundancy to the GPS based architecture. One manner in which this can be done is by using or creating a data link on these existing radionavigation systems. These systems thus can provide both navigation and an additional broadcast of GPS integrity information. This thesis examines the use of terrestrial data links to provide Wide Area Augmentation System (WAAS) based GPS integrity information for aviation. The thesis focuses on using Loran-C to broadcast WAAS data. Analysis and experimental results demonstrating the capabilities of these designs are also discussed. Using Loran for this purpose requires increasing its data capacity. Many Loran modulation schemes are developed and analyzed. The data rates developed significantly increased the Loran data capacity. However, retaining compatibility with Loran legacy users resulted in data rates below the WARS data rate of 250 bps. As a result, this thesis also examines means of reducing the data requirements for WAAS information. While higher data rates offer improved performance and compatibility with WAAS, this thesis demonstrates that higher rates incur greater interference. Therefore, this work develops and considers a 108 bps and 167 bps Loran GPS integrity channel (LOGIC) design. The performance of the two designs illustrates some of the advantages and disadvantages of using a higher data rate. Analysis demonstrated means of maintaining integrity with these low data rate systems and determined the theoretical capabilities of the systems. The system was tested empirically by developing software that generated the LOGIC message and applied these messages to a GPS user. The resulting 108 bps and 167 bps systems demonstrated capability to provide lateral navigation/vertical navigation (LNAV/VNAV) and approach with vertical guidance (APV) respectively.

78 FR 68861 - Certain Navigation Products, Including GPS Devices, Navigation and Display Systems, Radar Systems...

Federal Register 2010, 2011, 2012, 2013, 2014

2013-11-15

... Devices, Navigation and Display Systems, Radar Systems, Navigational Aids, Mapping Systems and Related... navigation products, including GPS devices, navigation and display systems, radar systems, navigational aids..., radar systems, navigational aids, mapping systems and related software by reason of infringement of one...

GPS-based tracking system for TOPEX orbit determination

NASA Technical Reports Server (NTRS)

Melbourne, W. G.

1984-01-01

A tracking system concept is discussed that is based on the utilization of the constellation of Navstar satellites in the Global Positioning System (GPS). The concept involves simultaneous and continuous metric tracking of the signals from all visible Navstar satellites by approximately six globally distributed ground terminals and by the TOPEX spacecraft at 1300-km altitude. Error studies indicate that this system could be capable of obtaining decimeter position accuracies and, most importantly, around 5 cm in the radial component which is key to exploiting the full accuracy potential of the altimetric measurements for ocean topography. Topics covered include: background of the GPS, the precision mode for utilization of the system, past JPL research for using the GPS in precision applications, the present tracking system concept for high accuracy satellite positioning, and results from a proof-of-concept demonstration.

Medical termination of pregnancy in general practice in Australia: a descriptive-interpretive qualitative study.

PubMed

Dawson, Angela J; Nicolls, Rachel; Bateson, Deborah; Doab, Anna; Estoesta, Jane; Brassil, Ann; Sullivan, Elizabeth A

2017-03-14

Australian Government approval in 2012 for the use of mifepristone and misoprostol for medical termination of pregnancy (MTOP) allows general practitioners (GPs) to provide early gestation abortion in primary care settings. However, uptake of the MTOP provision by GPs appears to be low and the reasons for this have been unclear. This study investigated the provision of and referral for MTOP by GPs. We undertook descriptive-interpretive qualitative research and selected participants for diversity using a matrix. Twenty-eight semi-structured interviews and one focus group (N = 4), were conducted with 32 GPs (8 MTOP providers, 24 non MTOP providers) in New South Wales, Australia. Interviews were recorded and transcribed verbatim. A framework to examine access to abortion services was used to develop the interview questions and emergent themes identified thematically. Three main themes emerged: scope of practice; MTOP demand, care and referral; and workforce needs. Many GPs saw abortion as beyond the scope of their practice (i.e. a service others provide in specialist private clinics). Some GPs had religious or moral objections; others regarded MTOP provision as complicated and difficult. While some GPs expressed interest in MTOP provision they were concerned about stigma and the impact it may have on perceptions of their practice and the views of colleagues. Despite a reported variance in demand most MTOP providers were busy but felt isolated. Difficulties in referral to a local public hospital in the case of complications or the provision of surgical abortion were noted. Exploring the factors which affect access to MTOP in general practice settings provides insights to assist the future planning and delivery of reproductive health services. This research identifies the need for support to increase the number of MTOP GP providers and for GPs who are currently providing MTOP. Alongside these actions provision in the public sector is required. In addition, formalised referral pathways to the public sector are required to ensure timely care in the case of complications or the provision of surgical options. Leadership and coordination across the health sector is needed to facilitate integrated abortion care particularly for rural and low income women.

Global Positioning Systems (GPS) Technology to Study Vector-Pathogen-Host Interactions

DTIC Science & Technology

2016-12-01

Award Number: W81XWH-11-2-0175 TITLE: Global Positioning Systems (GPS) Technology to Study Vector-Pathogen-Host Interactions PRINCIPAL...Positioning Systems (GPS) Technology to Study Vector-Pathogen-Host Interactions 5b. GRANT NUMBER W81XWH-11-2-0175 5c. PROGRAM ELEMENT NUMBER 6. AUTHOR(S...objective of this project is to examine the evolutionary consequences of introducing a tetravalent live- attenuated dengue virus vaccine into children in

Dynamic Positioning at Sea Using the Global Positioning System.

DTIC Science & Technology

1987-06-01

the Global Positioning System (GPS) acquired in Phase II of the Seafloor Benchmark Experiment on R/V Point Sur in August 1986. CPS position...data from the Global Positioning System (GPS) acquired in Phase 11 of the Seafloor Benchmark Experiment on R,:V Point Sur in August 1986. GPS position...The Seafloor Benchmark Experiment, a project of the Hydrographic Sciences Group of the Oceanography Department at the Naval Postgraduate School (NPS

SLR tracking of GPS-35

NASA Technical Reports Server (NTRS)

Pavlis, Erricos C.

1994-01-01

An experiment was designed to launch a corner cube retroreflector array on one of the Global Positioning Satellites (GPS). The launch on Aug. 31, 1993 ushered in the era of SLR tracking of GPS spacecraft. Once the space operations group finished the check-out procedures for the new satellite, the agreed upon SLR sites were allowed to track it. The first site to acquire GPS-35 was the Russian system at Maidanak and closely after the MLRS system at McDonald Observatory, Texas. The laser tracking network is currently tracking the GPS spacecraft known as GPS-35 or PRN 5 with great success. From the NASA side there are five stations that contribute data regularly and nearly as many from the international partners. Upcoming modifications to the ground receivers will allow for a further increase in the tracking capabilities of several additional sites and add some desperately needed southern hemisphere tracking. We are analyzing the data and are comparing SLR-derived orbits to those determined on the basis of GPS radiometric data.

Development of a Real-Time GPS/Seismic Displacement Meter: Applications to Civilian Infrastructure in Orange and Western Riverside Counties, California

NASA Technical Reports Server (NTRS)

Bock, Yehuda

2005-01-01

We propose a three-year applications project that will develop an Integrated Real-Time GPS/Seismic System and deploy it in Orange and Western Riverside Counties, spanning three major strike-slip faults in southern California (San Andreas, San Jacinto, and Elsinore) and significant populations and civilian infrastructure. The system relying on existing GPS and seismic networks will collect and analyze GPS and seismic data for the purpose of estimating and disseminating real-time positions and total ground displacements (dynamic, as well as static) during all phases of the seismic cycle, from fractions of seconds to years. Besides its intrinsic scientific use as a real-time displacement meter (transducer), the GPS/Seismic System will be a powerful tool for local and state decision makers for risk mitigation, disaster management, and structural monitoring (dams, bridges, and buildings). Furthermore, the GPS/Seismic System will become an integral part of California's spatial referencing and positioning infrastructure, which is complicated by tectonic motion, seismic displacements, and land subsidence. Finally, the GPS/Seismic system will also be applicable to navigation in any environment (land, sea, or air) by combining precise real-time instantaneous GPS positioning with inertial navigation systems. This development will take place under the umbrella of the California Spatial Reference Center, in partnership with local (Counties, Riverside County Flood and Water Conservation District, Metropolitan Water District), state (Caltrans), and Federal agencies (NGS, NASA, USGS), the geophysics community (SCIGN/SCEC2), and the private sector (RBF Consulting). The project will leverage considerable funding, resources, and R&D from SCIGN, CSRC and two NSF-funded IT projects at UCSD and SDSU: RoadNet (Real-Time Observatories, Applications and Data Management Network) and the High Performance Wireless Research and Education Network (HPWREN). These two projects are funded to develop both the wireless networks and the integrated, seamless, and transparent information management system that will deliver seismic, geodetic, oceanographic, hydrological, ecological, and physical data to a variety of end users in real-time in the San Diego region. CSRC is interested in providing users access to real-time, accurate GPS data for a wide variety of applications including RTK surveying/GIS and positioning of moving platforms such as aircraft and emergency vehicles. SCIGN is interested in upgrading sites to high-frequency real-time operations for rapid earthquake response and GPS seismology. The successful outcome of the project will allow the implementation of similar systems elsewhere, particularly in plate boundary zones with significant populations and civilian infrastructure. CSRC would like to deploy the GPS/Seismic System in other parts of California, in particular San Diego, Los Angeles County and the San Francisco Bay Area.

A shared electronic health record: lessons from the coalface.

PubMed

Silvester, Brett V; Carr, Simon J

2009-06-01

A shared electronic health record system has been successfully implemented in Australia by a Division of General Practice in northern Brisbane. The system grew out of coordinated care trials that showed the critical need to share summary patient information, particularly for patients with complex conditions who require the services of a wide range of multisector, multidisciplinary health care professionals. As at 30 April 2008, connected users of the system included 239 GPs from 66 general practices, two major public hospitals, three large private hospitals, 11 allied health and community-based provider organisations and 1108 registered patients. Access data showed a patient's shared record was accessed an average of 15 times over a 12-month period. The success of the Brisbane implementation relied on seven key factors: connectivity, interoperability, change management, clinical leadership, targeted patient involvement, information at the point of care, and governance. The Australian Commission on Safety and Quality in Health Care is currently evaluating the system for its potential to reduce errors relating to inadequate information transfer during clinical handover.

Autonomous GPS/INS navigation experiment for Space Transfer Vehicle

NASA Technical Reports Server (NTRS)

Upadhyay, Triveni N.; Cotterill, Stephen; Deaton, A. W.

1993-01-01

An experiment to validate the concept of developing an autonomous integrated spacecraft navigation system using on board Global Positioning System (GPS) and Inertial Navigation System (INS) measurements is described. The feasibility of integrating GPS measurements with INS measurements to provide a total improvement in spacecraft navigation performance, i.e. improvement in position, velocity and attitude information, was previously demonstrated. An important aspect of this research is the automatic real time reconfiguration capability of the system designed to respond to changes in a spacecraft mission under the control of an expert system.

Autonomous GPS/INS navigation experiment for Space Transfer Vehicle (STV)

NASA Technical Reports Server (NTRS)

Upadhyay, Triveni N.; Cotterill, Stephen; Deaton, A. Wayne

1991-01-01

An experiment to validate the concept of developing an autonomous integrated spacecraft navigation system using on board Global Positioning System (GPS) and Inertial Navigation System (INS) measurements is described. The feasibility of integrating GPS measurements with INS measurements to provide a total improvement in spacecraft navigation performance, i.e. improvement in position, velocity and attitude information, was previously demonstrated. An important aspect of this research is the automatic real time reconfiguration capability of the system designed to respond to changes in a spacecraft mission under the control of an expert system.

Autonomous GPS/INS navigation experiment for Space Transfer Vehicle

NASA Astrophysics Data System (ADS)

Upadhyay, Triveni N.; Cotterill, Stephen; Deaton, A. W.

1993-07-01

An experiment to validate the concept of developing an autonomous integrated spacecraft navigation system using on board Global Positioning System (GPS) and Inertial Navigation System (INS) measurements is described. The feasibility of integrating GPS measurements with INS measurements to provide a total improvement in spacecraft navigation performance, i.e. improvement in position, velocity and attitude information, was previously demonstrated. An important aspect of this research is the automatic real time reconfiguration capability of the system designed to respond to changes in a spacecraft mission under the control of an expert system.

Accuracy of GPS time transfer verified by closure around the world

NASA Technical Reports Server (NTRS)

Lewandowski, Wlodimierz W.; Petit, Gerard; Thomas, Claudine

1992-01-01

The precision of time transfer over intercontinental distances by the Global Positioning System common-view method, using measurements of ionospheric delays, precise ephemerides provided by the Defense Mapping Agency (DMA) and a consistent set of antenna coordinates, reaches 3 to 4 ns for a single 13-minute measurement, and decreases to 2 ns when averaging several measurements over the period of one day. It is thought that even this level of precision can be bettered by improving the ionospheric measurements, the ephemerides of satellites, and the antenna coordinates. In the same conditions, an estimation of the accuracy is attained by using three intercontinental links encircling the Earth to establish a closure condition; the three independent links should add to zero. We have computed such a closure condition over a period of 13 months using data recorded at the Paris Observatory, at the Communications Research Laboratory in Tokyo, and at the National Institute for Standards and Technology in Boulder, Colorado. The closure condition is verified to within a few nanoseconds, but a bias, varying with time, can be detected.

Supporting Australia's new veterans.

PubMed

Gill, Gerard F; Bain, Roderick; Seidl, Isaac

2016-03-01

The recent period of instability and conflict in parts of the world has exposed a new generation of Australian service members to conflict and its associated traumas. The aim of this article is to assist general practitioners (GPs) in engaging with younger veterans who have served in the Australian Defence Force (ADF) since 1990 and acquired health problems as a result of this service. It provides abbreviated advice on the resources available from the Department of Veterans' Affairs (DVA), particularly for mental health problems, and how to efficiently access DVA-funded services for newer veterans. Early detection of and attention to health problems (especially mental ill health) arising from military service, particularly from conflict or peacekeeping missions, has been found to improve veterans' health, their functioning and family happiness. GPs are ideally situated to arrange and coordinate this care.

Continuous GPS : pilot applications - Phase II

DOT National Transportation Integrated Search

2003-08-01

The primary objective of this research was to evaluate the feasibility of applying Global Positioning System (GPS) technology in the study of geotechnical phenomenon by developing, integrating, and test deploying a GPS-based instrumentation package u...

Vertical Guidance Performance Analysis of the L1–L5 Dual-Frequency GPS/WAAS User Avionics Sensor

PubMed Central

Jan, Shau-Shiun

2010-01-01

This paper investigates the potential vertical guidance performance of global positioning system (GPS)/wide area augmentation system (WAAS) user avionics sensor when the modernized GPS and Galileo are available. This paper will first investigate the airborne receiver code noise and multipath (CNMP) confidence (σair). The σair will be the dominant factor in the availability analysis of an L1–L5 dual-frequency GPS/WAAS user avionics sensor. This paper uses the MATLAB Algorithm Availability Simulation Tool (MAAST) to determine the required values for the σair, so that an L1–L5 dual-frequency GPS/WAAS user avionics sensor can meet the vertical guidance requirements of APproach with Vertical guidance (APV) II and CATegory (CAT) I over conterminous United States (CONUS). A modified MAAST that includes the Galileo satellite constellation is used to determine under what user configurations WAAS could be an APV II system or a CAT I system over CONUS. Furthermore, this paper examines the combinations of possible improvements in signal models and the addition of Galileo to determine if GPS/WAAS user avionics sensor could achieve 10 m Vertical Alert Limit (VAL) within the service volume. Finally, this paper presents the future vertical guidance performance of GPS user avionics sensor for the United States’ WAAS, Japanese MTSAT-based satellite augmentation system (MSAS) and European geostationary navigation overlay service (EGNOS). PMID:22319263

Cryospheric monitoring with new low power RTK dGPS systems

NASA Astrophysics Data System (ADS)

Martinez, K.; Hart, J. K.; Bragg, G. M.; Curry, J. S.

2017-12-01

Differential GPS is often used to measure the movement of glaciers. It requires data to be recorded at a fixed base station as well as the moving rover unit, followed by post-processing in order to compute the rover's positions. The typical dGPS units used consume considerable power and the recording times are often around one hour per reading. While this provides very precise (typically millimetre) precision it comes at a cost of power used and the data is rather large to send offsite regularly. Real-time kinematic modes of dGPS are typically used for rapid mapping and autonomous vehicles. New devices are lower cost and smaller size. They also provide a fix within a few minutes, which can be transmitted home. We describe the design, deployment and preliminary results of two tracking systems to monitor ice movement. The first used a normal GPS and Iridium satellite messaging to track the movement of a Greenland iceberg which calved from the Nattivit Apusiiat glacier (south west Greenland). This system followed the iceberg as it flowed 660 km south along the coast of Greenland. The second system was installed in Iceland to track the movement of glaciers using 2 different dGPS systems. A low power ARM Cortex M4-based controller ran Python code to schedule dGPS activity periodically and gather fixes. An Iridium short messaging unit (Rockblock) was used to transmit RTK location fixes. The aim was to experiment with the use of RTK dGPS as an alternative to recordings to measure how the glaciers responded to small scale changes in temperature and precipitation throughout the year.

National Coordination Office for Space-Based PNT

NASA Astrophysics Data System (ADS)

Shaw, M. E.

2008-12-01

In December 2004, President Bush issued the US Policy on space-based positioning, navigation, and timing (PNT), providing guidance on the management of the Global Positioning System (GPS) and other space- based PNT systems. The policy established the National Executive Committee (EXCOM) to advise and coordinate federal agencies on matters related to space-based PNT. Chaired jointly by the deputy secretaries of defense and transportation, the EXCOM includes equivalent level officials from the Departments of State, the Interior, Agriculture, Commerce, and Homeland Security, the Joint Chiefs of Staff, and the National Aeronautics and Space Administration (NASA). A National Coordination Office (NCO) supports the EXCOM through an interagency staff. Since establishing the EXCOM and NCO in 2005, the organizations have quickly grown in influence and effectiveness, leading or managing many interagency initiatives including the development of a Five-Year National Space-Based PNT Plan, the Space-Based PNT Interference Detection and Mitigation (IDM) Plan, and other strategic documents. The NCO has also facilitated interagency coordination on numerous policy issues and on external communications intended to spread a consistent, positive US message about space-based PNT. Role of the NCO - The purpose of the EXCOM is to provide top-level guidance to US agencies regarding space-based PNT infrastructure. The president established it at the deputy secretary level to ensure its strategic recommendations effect real change in agency budgets. Recognizing such high-level officials could only meet every few months, the president directed the EXCOM to establish an NCO to carry out its day-to-day business, including overseeing the implementation of EXCOM action items across the member agencies. These range from the resolution of funding issues to the assessment of strategic policy options. They also include the completion of specific tasks and documents requested by the EXCOM co-chairs. The NCO has established several processes for achieving interagency consensus on policy issues, including specialized staff-level working groups and an assistant secretary-level Executive Steering Group. The NCO also established a process for interagency coordination of US government communications related to space-based PNT, including speeches, presentations, and other externally released documents. The goal is to ensure government-wide consistency and accuracy in public and international statements made about space-based PNT. This is particularly important in addressing false or misleading information about GPS in the public arena. Conclusion - In less than three years, the NCO evolved from an idea into a highly active organization with substantial influence within the space-based PNT community. NCO efforts have helped build the EXCOM into an effective mechanism for raising issues to the attention of senior leadership and ensuring their guidance gets implemented. While it is still a work in progress, the NCO has many significant accomplishments. The organization will continue to mature as ongoing US government space-based PNT activities continue to bear fruit.

A statistical characterization of the Galileo-to-GPS inter-system bias

NASA Astrophysics Data System (ADS)

Gioia, Ciro; Borio, Daniele

2016-11-01

Global navigation satellite system operates using independent time scales and thus inter-system time offsets have to be determined to enable multi-constellation navigation solutions. GPS/Galileo inter-system bias and drift are evaluated here using different types of receivers: two mass market and two professional receivers. Moreover, three different approaches are considered for the inter-system bias determination: in the first one, the broadcast Galileo to GPS time offset is used to align GPS and Galileo time scales. In the second, the inter-system bias is included in the multi-constellation navigation solution and is estimated using the measurements available. Finally, an enhanced algorithm using constraints on the inter-system bias time evolution is proposed. The inter-system bias estimates obtained with the different approaches are analysed and their stability is experimentally evaluated using the Allan deviation. The impact of the inter-system bias on the position velocity time solution is also considered and the performance of the approaches analysed is evaluated in terms of standard deviation and mean errors for both horizontal and vertical components. From the experiments, it emerges that the inter-system bias is very stable and that the use of constraints, modelling the GPS/Galileo inter-system bias behaviour, significantly improves the performance of multi-constellation navigation.

An Artificial Neural Network Embedded Position and Orientation Determination Algorithm for Low Cost MEMS INS/GPS Integrated Sensors

PubMed Central

Chiang, Kai-Wei; Chang, Hsiu-Wen; Li, Chia-Yuan; Huang, Yun-Wen

2009-01-01

Digital mobile mapping, which integrates digital imaging with direct geo-referencing, has developed rapidly over the past fifteen years. Direct geo-referencing is the determination of the time-variable position and orientation parameters for a mobile digital imager. The most common technologies used for this purpose today are satellite positioning using Global Positioning System (GPS) and Inertial Navigation System (INS) using an Inertial Measurement Unit (IMU). They are usually integrated in such a way that the GPS receiver is the main position sensor, while the IMU is the main orientation sensor. The Kalman Filter (KF) is considered as the optimal estimation tool for real-time INS/GPS integrated kinematic position and orientation determination. An intelligent hybrid scheme consisting of an Artificial Neural Network (ANN) and KF has been proposed to overcome the limitations of KF and to improve the performance of the INS/GPS integrated system in previous studies. However, the accuracy requirements of general mobile mapping applications can’t be achieved easily, even by the use of the ANN-KF scheme. Therefore, this study proposes an intelligent position and orientation determination scheme that embeds ANN with conventional Rauch-Tung-Striebel (RTS) smoother to improve the overall accuracy of a MEMS INS/GPS integrated system in post-mission mode. By combining the Micro Electro Mechanical Systems (MEMS) INS/GPS integrated system and the intelligent ANN-RTS smoother scheme proposed in this study, a cheaper but still reasonably accurate position and orientation determination scheme can be anticipated. PMID:22574034

Performance Analysis of Web-Based Ppp Services with DİFFERENT Visibility Conditions

NASA Astrophysics Data System (ADS)

Albayrak, M.; Erkaya, H.; Ozludemir, M. T.; Ocalan, T.

2016-12-01

GNSS is being used effectively to precise position for many measuring and geodetic purposes at the present time. There is an increasing variety of these systems including the post-processing calculations in terms of number, quality and features and many different techniques are developed to determine position. Precise positioning intend to derive requires user experience and scientific or commercial software with costly license fees. However, in recent years important alternatives to this software that are user friendly and offer free web-based online precise point positioning service have become widely used in geodetic applications. The aim of this study is to test the performance of PPP techniques on ground control points with different visibility conditions. Within this framework, static observations were carried out for three hours a day repeatedly for six days, in YTU Davutpasa Campus on three different ground control points. The locations of these stations were selected by taking into account the impact of natural (trees, etc.) and artificial (buildings, etc.) obstacles. In order to compare the obtained GPS observations with PPP performances, first of all the accurate coordinates of the control points were computed with relative positioning technique in connection with the IGS stations using Bernese v5.0 software. Afterwards, three different web-based positioning services (CSRS-PPP, magicGNSS, GAPS) were used to analyze the GPS observations via PPP technique. To compare all of the obtained results, ITRF2008 datum measurement epoch coordinates were preferred by taking the service result criteria into consideration. In coordinate comparison, for the first station located nearby a building and possibly subjected to multipath effect horizontal discrepancies vary between 2-14.5 cm while vertical differences are between 3.5-16 cm. For the second point located partly in a forestry area, the discrepancies have been obtained as 1.5-8 cm and 2-10 cm for horizontal and vertical components, respectively. For the third point located in an area with no obstacles, 1.5-7 cm horizontal and 1-7 cm vertical differences have been obtained. The results show that the PPP technique could be used effectively in several positioning applications.

GPS radio collar 3D performance as influenced by forest structure and topography

Treesearch

R. Scott Gamo; Mark A. Rumble; Fred Lindzey; Matt Stefanich

2000-01-01

Global Positioning System (GPS) telemetry enables biologists to obtain accurate and systematic locations of animals. Vegetation can block signals from satellites to GPS radio collars. Therefore, a vegetation dependent bias to telemetry data may occur which if quantified, could be accounted for. We evaluated the performance of GPS collars in 6 structural stage...

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.

Detection of VHF lightning from GPS orbit

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

Suszcynsky, D. M.

2003-01-01

Satellite-based VHF' lightning detection is characterized at GPS orbit by using a VHF receiver system recently launched on the GPS SVN 54 satellite. Collected lightning triggers consist of Narrow Bipolar Events (80%) and strong negative return strokes (20%). The results are used to evaluate the performance of a future GPS-satellite-based VHF global lightning monitor.

Global positioning system for general aviation: Joint FAA-NASA Seminar. [conferences

NASA Technical Reports Server (NTRS)

1978-01-01

Programs to examine and develop means to utilize the global positioning system (GPS) for civil aviation functions are described. User requirements in this regard are discussed, the development of technologies in the areas of antennas, receivers, and signal processors for the GPS are examined, and modifications to the GPS to fit operational and design criteria are evaluated.

Processing Satellite Data for Slant Total Electron Content Measurements

NASA Technical Reports Server (NTRS)

Stephens, Philip John (Inventor); Komjathy, Attila (Inventor); Wilson, Brian D. (Inventor); Mannucci, Anthony J. (Inventor)

2016-01-01

A method, system, and apparatus provide the ability to estimate ionospheric observables using space-borne observations. Space-borne global positioning system (GPS) data of ionospheric delay are obtained from a satellite. The space-borne GPS data are combined with ground-based GPS observations. The combination is utilized in a model to estimate a global three-dimensional (3D) electron density field.

INS/GPS/LiDAR Integrated Navigation System for Urban and Indoor Environments Using Hybrid Scan Matching Algorithm

PubMed Central

Gao, Yanbin; Liu, Shifei; Atia, Mohamed M.; Noureldin, Aboelmagd

2015-01-01

This paper takes advantage of the complementary characteristics of Global Positioning System (GPS) and Light Detection and Ranging (LiDAR) to provide periodic corrections to Inertial Navigation System (INS) alternatively in different environmental conditions. In open sky, where GPS signals are available and LiDAR measurements are sparse, GPS is integrated with INS. Meanwhile, in confined outdoor environments and indoors, where GPS is unreliable or unavailable and LiDAR measurements are rich, LiDAR replaces GPS to integrate with INS. This paper also proposes an innovative hybrid scan matching algorithm that combines the feature-based scan matching method and Iterative Closest Point (ICP) based scan matching method. The algorithm can work and transit between two modes depending on the number of matched line features over two scans, thus achieving efficiency and robustness concurrently. Two integration schemes of INS and LiDAR with hybrid scan matching algorithm are implemented and compared. Real experiments are performed on an Unmanned Ground Vehicle (UGV) for both outdoor and indoor environments. Experimental results show that the multi-sensor integrated system can remain sub-meter navigation accuracy during the whole trajectory. PMID:26389906

INS/GPS/LiDAR Integrated Navigation System for Urban and Indoor Environments Using Hybrid Scan Matching Algorithm.

PubMed

Gao, Yanbin; Liu, Shifei; Atia, Mohamed M; Noureldin, Aboelmagd

2015-09-15

This paper takes advantage of the complementary characteristics of Global Positioning System (GPS) and Light Detection and Ranging (LiDAR) to provide periodic corrections to Inertial Navigation System (INS) alternatively in different environmental conditions. In open sky, where GPS signals are available and LiDAR measurements are sparse, GPS is integrated with INS. Meanwhile, in confined outdoor environments and indoors, where GPS is unreliable or unavailable and LiDAR measurements are rich, LiDAR replaces GPS to integrate with INS. This paper also proposes an innovative hybrid scan matching algorithm that combines the feature-based scan matching method and Iterative Closest Point (ICP) based scan matching method. The algorithm can work and transit between two modes depending on the number of matched line features over two scans, thus achieving efficiency and robustness concurrently. Two integration schemes of INS and LiDAR with hybrid scan matching algorithm are implemented and compared. Real experiments are performed on an Unmanned Ground Vehicle (UGV) for both outdoor and indoor environments. Experimental results show that the multi-sensor integrated system can remain sub-meter navigation accuracy during the whole trajectory.

GPS water level measurements for Indonesia's Tsunami Early Warning System

NASA Astrophysics Data System (ADS)

Schöne, T.; Pandoe, W.; Mudita, I.; Roemer, S.; Illigner, J.; Zech, C.; Galas, R.

2011-03-01

On Boxing Day 2004, a severe tsunami was generated by a strong earthquake in Northern Sumatra causing a large number of casualties. At this time, neither an offshore buoy network was in place to measure tsunami waves, nor a system to disseminate tsunami warnings to local governmental entities. Since then, buoys have been developed by Indonesia and Germany, complemented by NOAA's Deep-ocean Assessment and Reporting of Tsunamis (DART) buoys, and have been moored offshore Sumatra and Java. The suite of sensors for offshore tsunami detection in Indonesia has been advanced by adding GPS technology for water level measurements. The usage of GPS buoys in tsunami warning systems is a relatively new approach. The concept of the German Indonesian Tsunami Early Warning System (GITEWS) (Rudloff et al., 2009) combines GPS technology and ocean bottom pressure (OBP) measurements. Especially for near-field installations where the seismic noise may deteriorate the OBP data, GPS-derived sea level heights provide additional information. The GPS buoy technology is precise enough to detect medium to large tsunamis of amplitudes larger than 10 cm. The analysis presented here suggests that for about 68% of the time, tsunamis larger than 5 cm may be detectable.

[Statements of general practitioners on cooperation with specialists and a future health care system].

PubMed

Heintze, Christoph; Matysiak-Klose, Dorothea; Howorka, Antje; Kröhn, Thorsten; Braun, Vittoria

2004-08-15

Ideas of general practitioners (GPs) could be of value for the restructuring of the German ambulant health care system. The way managed care is seen by GPs is of particular interest. The aim of this study was to record opinions of GPs, working in Berlin, in regard to several aspects of their daily work. 14 female and 16 male GPs from Berlin participated in a qualitative survey. These 30 GPs were interviewed about their attitude toward cooperation with specialized colleagues and their opinions on a future medical care system. The interviews performed were summarized, structured and analyzed according to the qualitative content analysis by Mayring. From the GPs' point of view, ambulant cooperation is facilitated by knowing specialized colleagues, by staying in close contact to them via telephone and by being able to arrange short-term appointments with these specialists. A closer cooperation with specialists in a network as well as an advanced use of digital information systems for accessing patients' data were considered to be vital elements for a future health care system. An important reason for choosing the cooperation with specialists is to find quick comprehensive treatment strategies for patients. It may be concluded that ambulant managed care of patients could be optimized with the creation of medical networks.

Differential Solutions Using Long-Range Dual-Frequency GPS Correction Data

DTIC Science & Technology

2002-09-01

coordinates the network of CORS sites to provide range measurement data to users in the United States. The data is available, via the Internet , to...of 3-dimensional positioning activities throughout the United States (NGS, 2002). CORS data is posted daily on the Internet from which the user may...KING AZ Scottsdale COSA 1998/258 -------- 5 sec H CofS AZ Tolleson

Application of global positioning system methods for the study of obesity and hypertension risk among low-income housing residents in New York City: a spatial feasibility study

PubMed Central

Duncan, Dustin T.; Regan, Seann D.; Shelley, Donna; Day, Kristen; Ruff, Ryan R.; Al-Bayan, Maliyhah; Elbel, Brian

2016-01-01

The purpose of this study was to evaluate the feasibility of using global positioning system (GPS) methods to understand the spatial context of obesity and hypertension risk among a sample of low-income housing residents in New York City (n = 120). GPS feasibility among participants was measured with a pre- and post-survey as well as adherence to a protocol which included returning the GPS device as well as objective data analysed from the GPS devices. We also conducted qualitative interviews with 21 of the participants. Most of the sample was overweight (26.7%) or obese (40.0%). Almost one-third (30.8%) was pre-hypertensive and 39.2% was hypertensive. Participants reported high ratings of GPS acceptability, ease of use and low levels of wear-related concerns in addition to few concerns related to safety, loss or appearance, which were maintained after the baseline GPS feasibility data collection. Results show that GPS feasibility increased over time. The overall GPS return rate was 95.6%. Out of the total of 114 participants with GPS, 112 (98.2%) delivered at least one hour of GPS data for one day and 84 (73.7%) delivered at least one hour on 7 or more days. The qualitative interviews indicated that overall, participants enjoyed wearing the GPS devices, that they were easy to use and charge and that they generally forgot about the GPS device when wearing it daily. Findings demonstrate that GPS devices may be used in spatial epidemiology research in low-income and potentially other key vulnerable populations to understand geospatial determinants of obesity, hypertension and other diseases that these populations disproportionately experience. PMID:25545926

Accuracy assessment of high-rate GPS measurements for seismology

NASA Astrophysics Data System (ADS)

Elosegui, P.; Davis, J. L.; Ekström, G.

2007-12-01

Analysis of GPS measurements with a controlled laboratory system, built to simulate the ground motions caused by tectonic earthquakes and other transient geophysical signals such as glacial earthquakes, enables us to assess the technique of high-rate GPS. The root-mean-square (rms) position error of this system when undergoing realistic simulated seismic motions is 0.05~mm, with maximum position errors of 0.1~mm, thus providing "ground truth" GPS displacements. We have acquired an extensive set of high-rate GPS measurements while inducing seismic motions on a GPS antenna mounted on this system with a temporal spectrum similar to real seismic events. We found that, for a particular 15-min-long test event, the rms error of the 1-Hz GPS position estimates was 2.5~mm, with maximum position errors of 10~mm, and the error spectrum of the GPS estimates was approximately flicker noise. These results may however represent a best-case scenario since they were obtained over a short (~10~m) baseline, thereby greatly mitigating baseline-dependent errors, and when the number and distribution of satellites on the sky was good. For example, we have determined that the rms error can increase by a factor of 2--3 as the GPS constellation changes throughout the day, with an average value of 3.5~mm for eight identical, hourly-spaced, consecutive test events. The rms error also increases with increasing baseline, as one would expect, with an average rms error for a ~1400~km baseline of 9~mm. We will present an assessment of the accuracy of high-rate GPS based on these measurements, discuss the implications of this study for seismology, and describe new applications in glaciology.

Automatic dependent surveillance broadcast via GPS-Squitter: a major upgrade to the national airspace system

NASA Astrophysics Data System (ADS)

Jones, Ronnie D.; Knittel, George H.; Orlando, Vincent A.

1995-06-01

GPS-Squitter is a technology for surveillance of aircraft via broadcast of their GPS-determined positions to all listeners, using the Mode S data link. It can be used to provide traffic displays, on the ground for controllers and in the cockpit for pilots, and will enhance TCAS performance. It is compatible with the existing ground-based beacon interrogator radar system and is an evolutionary way to more from ground-based-radar surveillance to satellite-based surveillance. GPS-Squitter takes advantage of the substantial investment made by the U.S. in the powerful GPS position-determining system and has the potential to free the Federal Aviation Administration from having to continue maintaining a precise position-determining capability in ground-based radar. This would permit phasing out the ground-based secondary surveillance radar system over a period of 10 to 20 years and replacing it with much simpler ground stations, resulting in cost savings of hundreds of millions of dollars.

Real-time single-frequency GPS/MEMS-IMU attitude determination of lightweight UAVs.

PubMed

Eling, Christian; Klingbeil, Lasse; Kuhlmann, Heiner

2015-10-16

In this paper, a newly-developed direct georeferencing system for the guidance, navigation and control of lightweight unmanned aerial vehicles (UAVs), having a weight limit of 5 kg and a size limit of 1.5 m, and for UAV-based surveying and remote sensing applications is presented. The system is intended to provide highly accurate positions and attitudes (better than 5 cm and 0.5°) in real time, using lightweight components. The main focus of this paper is on the attitude determination with the system. This attitude determination is based on an onboard single-frequency GPS baseline, MEMS (micro-electro-mechanical systems) inertial sensor readings, magnetic field observations and a 3D position measurement. All of this information is integrated in a sixteen-state error space Kalman filter. Special attention in the algorithm development is paid to the carrier phase ambiguity resolution of the single-frequency GPS baseline observations. We aim at a reliable and instantaneous ambiguity resolution, since the system is used in urban areas, where frequent losses of the GPS signal lock occur and the GPS measurement conditions are challenging. Flight tests and a comparison to a navigation-grade inertial navigation system illustrate the performance of the developed system in dynamic situations. Evaluations show that the accuracies of the system are 0.05° for the roll and the pitch angle and 0.2° for the yaw angle. The ambiguities of the single-frequency GPS baseline can be resolved instantaneously in more than 90% of the cases.

Fine tuning GPS clock estimation in the MCS

NASA Technical Reports Server (NTRS)

Hutsell, Steven T.

1995-01-01

With the completion of a 24 operational satellite constellation, GPS is fast approaching the critical milestone, Full Operational Capability (FOC). Although GPS is well capable of providing the timing accuracy and stability figures required by system specifications, the GPS community will continue to strive for further improvements in performance. The GPS Master Control Station (MCS) recently demonstrated that timing improvements are always composite Clock, and hence, Kalman Filter state estimation, providing a small improvement to user accuracy.

The usefulness of GPS bicycle tracking data for evaluating the impact of infrastructure change on cycling behaviour.

PubMed

Heesch, Kristiann C; Langdon, Michael

2016-02-01

Issue addressed A key strategy to increase active travel is the construction of bicycle infrastructure. Tools to evaluate this strategy are limited. This study assessed the usefulness of a smartphone GPS tracking system for evaluating the impact of this strategy on cycling behaviour. Methods Cycling usage data were collected from Queenslanders who used a GPS tracking app on their smartphone from 2013-2014. 'Heat' and volume maps of the data were reviewed, and GPS bicycle counts were compared with surveillance data and bicycle counts from automatic traffic-monitoring devices. Results Heat maps broadly indicated that changes in cycling occurred near infrastructure improvements. Volume maps provided changes in counts of cyclists due to these improvements although errors were noted in geographic information system (GIS) geo-coding of some GPS data. Large variations were evident in the number of cyclists using the app in different locations. These variations limited the usefulness of GPS data for assessing differences in cycling across locations. Conclusion Smartphone GPS data are useful in evaluating the impact of improved bicycle infrastructure in one location. Using GPS data to evaluate differential changes in cycling across multiple locations is problematic when there is insufficient traffic-monitoring devices available to triangulate GPS data with bicycle traffic count data. So what? The use of smartphone GPS data with other data sources is recommended for assessing how infrastructure improvements influence cycling behaviour.

[Patient-centredness and Quality of Care in Germany in International Comparison - Results of a Telephone Survey of Patients in 11 Countries].

PubMed

Stock, S; Hertle, D; Veit, C

2015-10-01

The study was conducted to compare the results of the perceived quality of care in 11 industrialised countries from a patient perspective. This paper reports the German results and puts them in an international perspective. In a nationwide poll a random sample of high utilising patients was surveyed between March and June 2011. 59,984 random phone numbers were generated for this purpose. Topics were access and coordination of care, patient safety and patient-centredness. RESULTS were weighted according to age, sex, education, place of birth of parents, income and size of dwelling place and further sociodemographic variables. 1,200 patients of 2,048 contacted patients fulfilled the enrollment criteria. Approximately one third felt that overall the health-care system works well while 22% said that the system needs to be completely rebuild. Regarding access to care 22% reported financial barriers while 59% reported to be able to get an appointment the same or next day to see a doctor. With respect to patient safety patients reported increased numbers of nosocomial infections compared to 2005. Patient satisfaction with general practitioners (GPs) is exceptionally high in -Germany. Compared to 10 other industrialised nations the picture is heterogeneous. In some areas Germany ranks among the top (satisfaction with GPs) while approximately every fifth surveyed patient feels the system needs to be rebuilt completely. It remains a matter of debate whether this rating regarding the reform needs of the system applies to the financing and structures of the system or the quality of care. © Georg Thieme Verlag KG Stuttgart · New York.

Analysis the Source model of the 2009 Mw 7.6 Padang Earthquake in Sumatra Region using continuous GPS data

NASA Astrophysics Data System (ADS)

Amertha Sanjiwani, I. D. M.; En, C. K.; Anjasmara, I. M.

2017-12-01

A seismic gap on the interface along the Sunda subduction zone has been proposed among the 2000, 2004, 2005 and 2007 great earthquakes. This seismic gap therefore plays an important role in the earthquake risk on the Sunda trench. The Mw 7.6 Padang earthquake, an intraslab event, was occurred on September 30, 2009 located at ± 250 km east of the Sunda trench, close to the seismic gap on the interface. To understand the interaction between the seismic gap and the Padang earthquake, twelves continuous GPS data from SUGAR are adopted in this study to estimate the source model of this event. The daily GPS coordinates one month before and after the earthquake were calculated by the GAMIT software. The coseismic displacements were evaluated based on the analysis of coordinate time series in Padang region. This geodetic network provides a rather good spatial coverage for examining the seismic source along the Padang region in detail. The general pattern of coseismic horizontal displacements is moving toward epicenter and also the trench. The coseismic vertical displacement pattern is uplift. The highest coseismic displacement derived from the MSAI station are 35.0 mm for horizontal component toward S32.1°W and 21.7 mm for vertical component. The second largest one derived from the LNNG station are 26.6 mm for horizontal component toward N68.6°W and 3.4 mm for vertical component. Next, we will use uniform stress drop inversion to invert the coseismic displacement field for estimating the source model. Then the relationship between the seismic gap on the interface and the intraslab Padang earthquake will be discussed in the next step. Keyword: seismic gap, Padang earthquake, coseismic displacement.

Joint IRIS/PASSCAL UNAVCO Seismic and GPS Installations, Testing, and Development

NASA Astrophysics Data System (ADS)

Fowler, J.; Alvarez, M.; Beaudoin, B.; Jackson, M.; Feaux, K.; Ruud, O.; Andreatta, V.; Meertens, C.; Ingate, S.

2002-12-01

Future large-scale deformation initiatives such as EarthScope (http://www.earthscope.org/) will provide an opportunity for collocation and integration of GPS receivers and broadband and short period seismic instruments. Example integration targets include PBO backbone and cluster sites with USArray Transportable (Bigfoot) and Permanent Array. A GPS seismic integration and testing facility at the IRIS/PASSCAL Instrument Center in Socorro, NM is currently performing side-by-side testing of different seismometers, GPS receivers, communications hardware, power systems and data streaming software. One configuration tested uses an integrated VSAT data communications system and a broadband seismometer collocated with a geodetic quality GPS system. Data are routed through a VSAT hub and distributed to the UNAVCO Data Archive in Boulder and the IRIS Data Management Center in Seattle. Preliminary results indicate data availability approaching 100% with a maximum latency of 5 sec.

NAVSTAR GPS Simulation and Analysis Program (Interim Report)

DOT National Transportation Integrated Search

1983-10-01

This study assesses the capability of the planned NAVSTAR Global Positioning System (GPS) to meet civil navigation requirements. When it becomes operational in about 1983, NAVSTAR GPS will provide accurate two-dimensional and three-dimensional servic...

Autonomous Navigation Improvements for High-Earth Orbiters Using GPS

NASA Technical Reports Server (NTRS)

Long, Anne; Kelbel, David; Lee, Taesul; Garrison, James; Carpenter, J. Russell; Bauer, F. (Technical Monitor)

2000-01-01

The Goddard Space Flight Center is currently developing autonomous navigation systems for satellites in high-Earth orbits where acquisition of the GPS signals is severely limited This paper discusses autonomous navigation improvements for high-Earth orbiters and assesses projected navigation performance for these satellites using Global Positioning System (GPS) Standard Positioning Service (SPS) measurements. Navigation performance is evaluated as a function of signal acquisition threshold, measurement errors, and dynamic modeling errors using realistic GPS signal strength and user antenna models. These analyses indicate that an autonomous navigation position accuracy of better than 30 meters root-mean-square (RMS) can be achieved for high-Earth orbiting satellites using a GPS receiver with a very stable oscillator. This accuracy improves to better than 15 meters RMS if the GPS receiver's signal acquisition threshold can be reduced by 5 dB-Hertz to track weaker signals.

High accuracy autonomous navigation using the global positioning system (GPS)

NASA Technical Reports Server (NTRS)

Truong, Son H.; Hart, Roger C.; Shoan, Wendy C.; Wood, Terri; Long, Anne C.; Oza, Dipak H.; Lee, Taesul

1997-01-01

The application of global positioning system (GPS) technology to the improvement of the accuracy and economy of spacecraft navigation, is reported. High-accuracy autonomous navigation algorithms are currently being qualified in conjunction with the GPS attitude determination flyer (GADFLY) experiment for the small satellite technology initiative Lewis spacecraft. Preflight performance assessments indicated that these algorithms are able to provide a real time total position accuracy of better than 10 m and a velocity accuracy of better than 0.01 m/s, with selective availability at typical levels. It is expected that the position accuracy will be increased to 2 m if corrections are provided by the GPS wide area augmentation system.

Accuracy Analysis of Precise Point Positioning of Compass Navigation System Applied to Crustal Motion Monitoring

NASA Astrophysics Data System (ADS)

Wang, Yuebing

2017-04-01

Based on the observation data of Compass/GPSobserved at five stations, time span from July 1, 2014 to June 30, 2016. UsingPPP positioning model of the PANDA software developed by Wuhan University,Analyzedthe positioning accuracy of single system and Compass/GPS integrated resolving, and discussed the capability of Compass navigation system in crustal motion monitoring. The results showed that the positioning accuracy in the east-west directionof the Compass navigation system is lower than the north-south direction (the positioning accuracy de 3 times RMS), in general, the positioning accuracyin the horizontal direction is about 1 2cm and the vertical direction is about 5 6cm. The GPS positioning accuracy in the horizontal direction is better than 1cm and the vertical direction is about 1 2cm. The accuracy of Compass/GPS integrated resolving is quite to GPS. It is worth mentioning that although Compass navigation system precision point positioning accuracy is lower than GPS, two sets of velocity fields obtained by using the Nikolaidis (2002) model to analyze the Compass and GPS time series results respectively, the results showed that the maximum difference of the two sets of velocity field in horizontal directions is 1.8mm/a. The Compass navigation system can now be used to monitor the crustal movement of the large deformation area, based on the velocity field in horizontal direction.

Special not different: general practitioners' accounts of their care of dying people.

PubMed

Field, D

1998-05-01

In modern Britain the majority of terminal care occurs in people's own homes and many dying people and their carers would prefer the death itself to occur in the home. The quality of terminal care in the home and the possibility of a home death depend to a great extent upon the care provided by GPs and community nurses. This paper reports on GPs' experiences of caring for dying people and their attitudes towards such work. It is based on unstructured interviews with 25 GPs who graduated from the 1979 entry cohort to the University of Leicester medical school. The respondents were recruited via a questionnaire following up previous research with this cohort on 'fear of death'. Although self-selecting, interviewees were not significantly different from those who did not volunteer for interview in any of the statistical analyses of the questionnaire data. There were a number of similarities in their accounts of their care of dying people. Common themes were that the care of dying people was important, rewarding and satisfying; that the GPs saw themselves as part of a team of carers, frequently as team co-ordinators; good working relationships with district nurses but less satisfactory relationships with hospitals and social workers; that patient and family were both recipients of care; and honesty in communication with dying people, albeit tempered. Three issues of contemporary relevance were: tensions over the role of hospice and specialist terminal care services; care of people with chronic terminal illnesses other than cancer; and the role of GPs in the social construction of bereavement.

Navigation and Positioning System Using High Altitude Platforms Systems (HAPS)

NASA Astrophysics Data System (ADS)

Tsujii, Toshiaki; Harigae, Masatoshi; Harada, Masashi

Recently, some countries have begun conducting feasibility studies and R&D projects on High Altitude Platform Systems (HAPS). Japan has been investigating the use of an airship system that will function as a stratospheric platform for applications such as environmental monitoring, communications and broadcasting. If pseudolites were mounted on the airships, their GPS-like signals would be stable augmentations that would improve the accuracy, availability, and integrity of GPS-based positioning systems. Also, the sufficient number of HAPS can function as a positioning system independent of GPS. In this paper, a system design of the HAPS-based positioning system and its positioning error analyses are described.

Special Features in the Structure of Resonant Perturbations of Uncontrollable Objects of Glonass and GPS Navigating Systems. Influence on the Orbital Evolution

NASA Astrophysics Data System (ADS)

Tomilova, I. V.; Bordovitsyna, T. V.

2017-08-01

Results of investigation into the resonant structure of perturbations and long-term orbital evolution of space vehicles of GLONASS and GPS global navigating satellite systems (GNSS) under assumption that all of them have lost control on 08/01/2015 are presented. It is demonstrated that the majority of the examined objects are in the range of action of the secular resonances of various types. In addition, practically all satellites of the GPS system are within the scope of the 2:1 orbital resonance with rotation of the Earth. Results of the MEGNO analysis demonstrate that the motion of all objects of the GLONASS system during the 100-year period is regular, whereas the motion of the majority of objects of the GPS system is subject to chaotization.

A Tightly-Coupled GPS/INS/UWB Cooperative Positioning Sensors System Supported by V2I Communication

PubMed Central

Wang, Jian; Gao, Yang; Li, Zengke; Meng, Xiaolin; Hancock, Craig M.

2016-01-01

This paper investigates a tightly-coupled Global Position System (GPS)/Ultra-Wideband (UWB)/Inertial Navigation System (INS) cooperative positioning scheme using a Robust Kalman Filter (RKF) supported by V2I communication. The scheme proposes a method that uses range measurements of UWB units transmitted among the terminals as augmentation inputs of the observations. The UWB range inputs are used to reform the GPS observation equations that consist of pseudo-range and Doppler measurements and the updated observation equation is processed in a tightly-coupled GPS/UWB/INS integrated positioning equation using an adaptive Robust Kalman Filter. The result of the trial conducted on the roof of the Nottingham Geospatial Institute (NGI) at the University of Nottingham shows that the integrated solution provides better accuracy and improves the availability of the system in GPS denied environments. RKF can eliminate the effects of gross errors. Additionally, the internal and external reliabilities of the system are enhanced when the UWB observables received from the moving terminals are involved in the positioning algorithm. PMID:27355947

GPS net­work operations for the International GPS Geodynamics Service

USGS Publications Warehouse

Neilan, Ruth E.

1993-01-01

As GPS technology comes of age in the 1990’s, it is evident that an internationally sponsored GPS tracking system is called for to provide consistent, timely ground tracking data and data products to the geophysical community. The planning group for the International GPS Geodynamics Service (IGS), sponsored by the International Association of Geodesy (IAG), is addressing all elements of the end-to-end tracking system, ranging from data collection to data analysis and distribution of products (Mueller, 1992). Part of the planning process is to formulate how these various elements work together to create the common infrastructure needed to support a wide variety of GPS investigations. A key element for any permanent satellite tracking system is certainly the acquisition segment; the reliability and robustness of the ground network operations directly determine the fates and limitations of final products. The IGS planning group therefore included a committee tasked to develop and establish standards governing data acquisition and site-specific characteristics deemed necessary to ensure the collection of a high quality, continuous data set.

Measurement of shallow sea floor motion with GPS on a rigid buoy: system design and synthetic analysis

NASA Astrophysics Data System (ADS)

Dixon, T. H.; Xie, S.; Malservisi, R.; Lembke, C.; Iannaccone, G.; Law, J.; Rodgers, M.; Russell, R.; Voss, N. K.

2017-12-01

A GPS-buoy system has been built and is currently undergoing test to measure precise 3D sea floor motion in the shallow (less than 200 m) continental shelf environment. Offshore deformation is undersampled in most subduction zones. In Cascadia, the shallow shelf environment constitutes roughly 20%-25% of the offshore area between the coastline and the trench. In the system being tested, the GPS receiver at the top of the buoy is connected to the sea floor through a rigid structure supported by a float. A similar design has been used by INGV (Italy) to measure vertical deformation on the sea floor near the Campi Flegrei caldera. Synthetic analysis shows that by adding a 3-axis digital compass to measure heading and tilt, along with kinematic GPS measurements, position of the anchor can be recovered to an accuracy of several centimeters or better, depending on water depth and GPS baseline length. Synthetic resolution tests show that our ability to detect shallow slow slip events on subduction plate boundaries can be greatly improved by adding offshore GPS-buoy sites.

General practitioners' experiences with sickness certification: a comparison of survey data from Sweden and Norway

PubMed Central

2012-01-01

Background In most countries with sickness insurance systems, general practitioners (GPs) play a key role in the sickness-absence process. Previous studies have indicated that GPs experience several tasks and situations related to sickness certification consultations as problematic. The fact that the organization of primary health care and social insurance systems differ between countries may influence both GPs' experiences and certification. The aim of the present study was to gain more knowledge of GPs' experiences of sickness certification, by comparing data from Sweden and Norway, regarding frequencies and aspects of sickness certification found to be problematic. Methods Statistical analyses of cross-sectional survey data of sickness certification by GPs in Sweden and Norway. In Sweden, all GPs were included, with 3949 (60.6%) responding. In Norway, a representative sample of GPs was included, with 221 (66.5%) responding. Results Most GPs reported having consultations involving sickness certification at least once a week; 95% of the GPs in Sweden and 99% of the GPs in Norway. A majority found such tasks problematic; 60% of the GPs in Sweden and 53% in Norway. In a logistic regression, having a higher frequency of sickness certification consultations was associated with a higher risk of experiencing them as problematic, in both countries. A higher rate of GPs in Sweden than in Norway reported meeting patients wanting a sickness certification without a medical reason. GPs in Sweden found it more problematic to discuss the advantages and disadvantages of sick leave with patients and to issue a prolongation of a sick-leave period initiated by another physician. GPs in Norway more often worried that patients would go to another physician if they did not issue a certificate, and a higher proportion of Norwegian GPs found it problematic to handle situations where they and their patient disagreed on the need for sick leave. Conclusions The study confirms that many GPs experience sickness absence consultations as problematic. However, there were differences between the two countries in GPs' experiences, which may be linked to differences in social security regulations and the organization of GP services. Possible causes and consequences of national differences should be addressed in future studies. PMID:22375615

Feasibility and Acceptability of Global Positioning System (GPS) Methods to Study the Spatial Contexts of Substance Use and Sexual Risk Behaviors among Young Men Who Have Sex with Men in New York City: A P18 Cohort Sub-Study

PubMed Central

Duncan, Dustin T.; Kapadia, Farzana; Regan, Seann D.; Goedel, William C.; Levy, Michael D.; Barton, Staci C.; Friedman, Samuel R.; Halkitis, Perry N.

2016-01-01

Background No global positioning system (GPS) technology study has been conducted among a sample of young gay, bisexual, and other men who have sex with men (YMSM). As such, the purpose of this study was to evaluate the feasibility and acceptability of using GPS methods to understand the spatial context of substance use and sexual risk behaviors among a sample of YMSM in New York City, a high-risk population. Methods Data came from a subsample of the ongoing P18 Cohort Study (n = 75). GPS feasibility and acceptability among participants was measured with: 1) a pre- and post-survey and 2) adherence to the GPS protocol which included returning the GPS device, self-report of charging and carrying the GPS device as well as objective data analyzed from the GPS devices. Analyses of the feasibility surveys were treated as repeated measures as each participant had a pre- and post-feasibility survey. When comparing the similar GPS survey items asked at baseline and at follow-up, we present percentages and associated p-values based on chi-square statistics. Results Participants reported high ratings of pre-GPS acceptability, ease of use, and low levels of wear-related concerns in addition to few concerns related to safety, loss, or appearance, which were maintained after baseline GPS feasibility data collection. The GPS return rate was 100%. Most participants charged and carried the GPS device on most days. Of the total of 75 participants with GPS data, 75 (100%) have at least one hour of GPS data for one day and 63 (84%) had at least one hour on all 7 days. Conclusions Results from this pilot study demonstrate that utilizing GPS methods among YMSM is feasible and acceptable. GPS devices may be used in spatial epidemiology research in YMSM populations to understand place-based determinants of health such as substance use and sexual risk behaviors. PMID:26918766