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Sample records for positioning systems gps

  1. Shuttle Global Positioning System (GPS) design study

    NASA Technical Reports Server (NTRS)

    Nilsen, P. W.

    1979-01-01

    The effects of oscillator noise on Shuttle Global Positioning System (GPS) receiver performance, GPS navigation system self-test, GPS ground transmitter design to augment shuttle navigation, the effect of ionospheric delay modelling on GPS receiver design, and GPS receiver tracking of Shuttle transient maneuvers were investigated.

  2. Shuttle Global Positioning (GPS) System design study

    NASA Technical Reports Server (NTRS)

    Nilsen, P.; Huth, G. K.

    1980-01-01

    Investigations of certain aspects and problems of the shuttle global positioning system GPS, are presented. Included are: test philosophy and test outline; development of a phase slope specification for the shuttle GPS antenna; an investigation of the shuttle jamming vulnerability; and an expression for the GPS signal to noise density ratio for the thermal protection system.

  3. 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.

  4. 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…

  5. A New Indoor Positioning System Architecture Using GPS Signals

    PubMed Central

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

    2015-01-01

    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. PMID:25938199

  6. A New Indoor Positioning System Architecture Using GPS Signals.

    PubMed

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

    2015-01-01

    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. PMID:25938199

  7. Integrated Global Positioning Systems (GPS) Laboratory

    NASA Technical Reports Server (NTRS)

    Brown, Dewayne Randolph

    2002-01-01

    The purpose of this research is to develop a user-friendly Integrated GPS lab manual. This manual will help range engineers at NASA to integrate the use of GPS Simulators, GPS receivers, computers, MATLAB software, FUGAWI software and SATELLITE TOOL KIT software. The lab manual will be used in an effort to help NASA engineers predict GPS Coverage of planned operations and analyze GPS coverage of operation post mission. The Integrated GPS Laboratory was used to do GPS Coverage for two extensive case studies. The first scenario was an airplane trajectory in which an aircraft flew from Cape Canaveral to Los Angeles, California. In the second scenario, a rocket trajectory was done whereas a rocket was launched from Cape Canaveral to one thousand kilometers due east in the Atlantic Ocean.

  8. Evaluating the Effect of Global Positioning System (GPS) Satellite Clock Error via GPS Simulation

    NASA Astrophysics Data System (ADS)

    Sathyamoorthy, Dinesh; Shafii, Shalini; Amin, Zainal Fitry M.; Jusoh, Asmariah; Zainun Ali, Siti

    2016-06-01

    This study is aimed at evaluating the effect of Global Positioning System (GPS) satellite clock error using GPS simulation. Two conditions of tests are used; Case 1: All the GPS satellites have clock errors within the normal range of 0 to 7 ns, corresponding to pseudorange error range of 0 to 2.1 m; Case 2: One GPS satellite suffers from critical failure, resulting in clock error in the pseudorange of up to 1 km. It is found that increase of GPS satellite clock error causes increase of average positional error due to increase of pseudorange error in the GPS satellite signals, which results in increasing error in the coordinates computed by the GPS receiver. Varying average positional error patterns are observed for the each of the readings. This is due to the GPS satellite constellation being dynamic, causing varying GPS satellite geometry over location and time, resulting in GPS accuracy being location / time dependent. For Case 1, in general, the highest average positional error values are observed for readings with the highest PDOP values, while the lowest average positional error values are observed for readings with the lowest PDOP values. For Case 2, no correlation is observed between the average positional error values and PDOP, indicating that the error generated is random.

  9. 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.

  10. Accurate aircraft wind measurements using the global positioning system (GPS)

    SciTech Connect

    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.

  11. 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.

  12. Investigation of GPS/IMU Positioning System for Mining Equipment

    SciTech Connect

    Ken L. Stratton

    2006-09-13

    The objective of this project is to investigate the applicability of a combined Global Positioning System and Inertial Measurement Unit (GPS/IMU) for information based displays on earthmoving machines and for automated earthmoving machines in the future. This technology has the potential of allowing an information-based product like Caterpillar's Computer Aided Earthmoving System (CAES) to operate in areas with satellite shading. Satellite shading is an issue in open pit mining because machines are routinely required to operate close to high walls, which reduces significantly the amount of the visible sky to the GPS antenna mounted on the machine. An inertial measurement unit is a product, which provides data for the calculation of position based on sensing accelerations and rotation rates of the machine's rigid body. When this information is coupled with GPS it results in a positioning system that can maintain positioning capability during time periods of shading.

  13. 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.

  14. IMU/GPS System Provides Position and Attitude Data

    NASA Technical Reports Server (NTRS)

    Lin, Ching Fang

    2006-01-01

    A special navigation system is being developed to provide high-quality information on the position and attitude of a moving platform (an aircraft or spacecraft), for use in pointing and stabilization of a hyperspectral remote-sensing system carried aboard the platform. The system also serves to enable synchronization and interpretation of readouts of all onboard sensors. The heart of the system is a commercially available unit, small enough to be held in one hand, that contains an integral combination of an inertial measurement unit (IMU) of the microelectromechanical systems (MEMS) type, Global Positioning System (GPS) receivers, a differential GPS subsystem, and ancillary data-processing subsystems. The system utilizes GPS carrier-phase measurements to generate time data plus highly accurate and continuous data on the position, attitude, rotation, and acceleration of the platform. Relative to prior navigation systems based on IMU and GPS subsystems, this system is smaller, is less expensive, and performs better. Optionally, the system can easily be connected to a laptop computer for demonstration and evaluation. In addition to airborne and spaceborne remote-sensing applications, there are numerous potential terrestrial sensing, measurement, and navigation applications in diverse endeavors that include forestry, environmental monitoring, agriculture, mining, and robotics.

  15. International GPS (Global Positioning System) Service for Geodynamics

    NASA Technical Reports Server (NTRS)

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

    1995-01-01

    The International GPS (Global Positioning System) Service for Geodynamics (IGS) began formal operation on January 1, 1994. This first annual report is divided into sections, which mirror different aspects of the service. Section (1) contains general information, including the history of the IGS, its organization, and the global network of GPS tracking sites; (2) contains information on the Central Bureau Information System; (3) describes the International Earth Rotation Service (IERS); (4) details collecting and distributing IGS data in Data Center reports; (6) describes how the IGS Analysis Centers generate their products; (7) contains miscellaneous contributions from other organizations that share common interests with the IGS.

  16. 76 FR 33022 - Eighty-Sixth Meeting: RTCA Special Committee 159: Global Positioning System (GPS)

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-06-07

    ... 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 System (GPS). DATES: The meeting... for a Special Committee 159: Global Positioning System (GPS) meeting. The agenda will...

  17. 75 FR 2581 - Eighty-First Meeting: RTCA Special Committee 159: Global Positioning System (GPS)

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-01-15

    ... 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 System (GPS). DATES: The meeting... hereby given for a Special Committee 159: Global Positioning System (GPS) meeting. The agenda...

  18. 78 FR 13396 - 90th Meeting: RTCA Special Committee 159, Global Positioning Systems (GPS)

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-02-27

    ... Federal Aviation Administration 90th Meeting: RTCA Special Committee 159, Global Positioning Systems (GPS... Notice of RTCA Special Committee 159, RTCA Special Committee 159, Global Positioning Systems (GPS... Special Committee 159, Global Positioning Systems (GPS). DATES: The meeting will be held March 12-15,...

  19. 78 FR 57672 - 91st Meeting: RTCA Special Committee 159, Global Positioning Systems (GPS)

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-09-19

    ... Federal Aviation Administration 91st Meeting: RTCA Special Committee 159, Global Positioning Systems (GPS... Notice of RTCA Special Committee 159, RTCA Special Committee 159, Global Positioning Systems (GPS... Special Committee 159, Global Positioning Systems (GPS) DATES: The meeting will be held October 7-11,...

  20. 76 FR 27744 - Eighty-Fifth Meeting: RTCA Special Committee 159: Global Positioning System (GPS)

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-05-12

    ... 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 System (GPS). DATES: The meeting...), notice is hereby given for a Special Committee 159: Global Positioning System (GPS) meeting. The...

  1. 77 FR 56254 - 89th Meeting: RTCA Special Committee 159, Global Positioning Systems (GPS)

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-09-12

    ... Federal Aviation Administration 89th Meeting: RTCA Special Committee 159, Global Positioning Systems (GPS... Notice of RTCA Special Committee 159, RTCA Special Committee 159, Global Positioning Systems (GPS... Special Committee 159, Global Positioning Systems (GPS). DATES: The meeting will be held October 5,...

  2. Multi buoy system observation for GPS/A seafloor positioning

    NASA Astrophysics Data System (ADS)

    Mukaiyama, H.; Ikuta, R.; Tadokoro, K.; Yasuda, K.; Watanabe, T.; Chiba, H.; Sayanagi, K.

    2014-12-01

    We are developing a method for observation of seafloor crustal deformation using kinematic GPS and acoustic ranging system. The system measures seafloor crustal deformation by determining position of benchmarks on the seafloor using a vessel which link-up GPS and acoustic signals. Acoustic ranging is used to measure distance between the vessel and the seafloor benchmarks. And kinematic GPS is used to locate the moving vessel every 0.2 seconds. Now we have deployed 4 seafloor benchmark units at Suruga Bay and 4 units at Kumano Basin both off-pacific coast Japan. At each survey site, three seafloor transponders are settled to define a benchmark unit. In this system, each measurement takes about ten hours and both sound speed structure and the benchmark unit positions were determined simultaneously for the each measurement using a tomographic technique. This tomographic technique was adopted based on assumption that the sound speed structure is horizontally layered and changes only in time, not in space. However, when sound speed structure has a heterogeneity, the assumption of a horizontal layering causes systematic error in the determination of seafloor benchmarks(Ikuta et al 2009AGU). So we are developing a new system using multi-buoy. Multi-buoy plays the role of vessel. Conducting observation using the buoys, we can estimate spatial variation of sound speed structures as a sloped structure every moment. With the single vessel system, we solve a kind of average sound speed over the different paths to the three seafloor transponders. Using the multi-buoy system, they can detect the lateral variation as difference of the average sound speeds obtained by different buoys, which improve the accuracy of the benchmark locations. In November 2013, Observation of seafloor crustal deformation using the buoys was held in Suruga Bay. In this study, we report the result of estimations of heterogeneous sound speed structures.

  3. 75 FR 28318 - Eighty-Second Meeting: RTCA Special Committee 159: Global Positioning System (GPS)

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-05-20

    ... 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 System (GPS). DATES: The...

  4. GPS aiding of ocean current determination. [Global Positioning System

    NASA Technical Reports Server (NTRS)

    Mohan, S. N.

    1981-01-01

    The navigational accuracy of an oceangoing vessel using conventional GPS p-code data is examined. The GPS signal is transmitted over two carrier frequencies in the L-band at 1575.42 and 1227.6 MHz. Achievable navigational uncertainties of differenced positional estimates are presented as a function of the parameters of the problem, with particular attention given to the effect of sea-state, user equivalent range error, uncompensated antenna motion, varying delay intervals, and reduced data rate examined in the unaided mode. The unmodeled errors resulting from satellite ephemeris uncertainties are shown to be negligible for the GPS-NDS (Navigation Development) satellites. Requirements are met in relatively calm seas, but accuracy degradation by a factor of at least 2 must be anticipated in heavier sea states. The aided mode of operation is examined, and it is shown that requirements can be met by using an inertial measurement unit (IMU) to aid the GPS receiver operation. Since the use of an IMU would mean higher costs, direct Doppler from the GPS satellites is presented as a viable alternative.

  5. 76 FR 67019 - Eighty-Seventh: RTCA Special Committee 159: Global Positioning System (GPS)

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-10-28

    ... Federal Aviation Administration Eighty-Seventh: RTCA Special Committee 159: Global Positioning System (GPS... 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 System...

  6. 77 FR 12106 - 88th Meeting: RTCA Special Committee 159, Global Positioning System (GPS)

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-02-28

    ... Federal Aviation Administration 88th Meeting: RTCA Special Committee 159, Global Positioning System (GPS... RTCA Special Committee 159, Global Positioning System (GPS). SUMMARY: The FAA is issuing this notice to advise the public of the 88th meeting of RTCA Special Committee 159, Global Positioning System...

  7. Position, Navigation, and Timing: GPS Scientific Applications

    NASA Technical Reports Server (NTRS)

    Neilan, Ruth E.

    2008-01-01

    This slide presentation reviews the development and deployment of the Global Positioning System (GPS). This presentation also includes measuring space and time, GPS as a tool for science, development of high precision JPL GPS receivers, and technology and applications developments.

  8. Space Shuttle Global Positioning System (GPS) testing at NASA Johnson Space Center

    NASA Technical Reports Server (NTRS)

    Pawlowski, J. F.; Quinn, M.

    1982-01-01

    The present investigation is concerned with the significance of the use of the Global Positioning System (GPS) for the Space Shuttle. On the basis of a study regarding the use of the GPS on the Space Shuttle, it was decided that such a system would greatly benefit Space Shuttle navigation. Studies with GPS user equipment were, therefore, conducted to obtain data and information which would provide a base for the formulation and the further refinement of NASA requirements with respect to the type of set the Shuttle would need. Attention is given to orbit determination, satellite numbers, background information concerning the GPS, the currently available GPS sets, the conducted studies, Shuttle sonic boom recording sites, tests performed with the aid of the Kuiper airborne observatory, and questions regarding the test applicability to Shuttle GPS.

  9. 76 FR 50808 - Airborne Supplemental Navigation Equipment Using the Global Positioning System (GPS)

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-08-16

    ... cancel TSO-C129a, Airborne Supplemental Navigation Equipment Using the Global Positioning System (GPS... Global Positioning System Equipment Using Aircraft-Based Augmentation; an updated minimum performance... system (TSO-C145c, Airborne Navigation Sensors Using the Global Positioning System Augmented by...

  10. BDS/GPS Dual Systems Positioning Based on the Modified SR-UKF Algorithm.

    PubMed

    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

  11. 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

  12. GPS Position Time Series @ JPL

    NASA Technical Reports Server (NTRS)

    Owen, Susan; Moore, Angelyn; Kedar, Sharon; Liu, Zhen; Webb, Frank; Heflin, Mike; Desai, Shailen

    2013-01-01

    Different flavors of GPS time series analysis at JPL - Use same GPS Precise Point Positioning Analysis raw time series - Variations in time series analysis/post-processing driven by different users. center dot JPL Global Time Series/Velocities - researchers studying reference frame, combining with VLBI/SLR/DORIS center dot JPL/SOPAC Combined Time Series/Velocities - crustal deformation for tectonic, volcanic, ground water studies center dot ARIA Time Series/Coseismic Data Products - Hazard monitoring and response focused center dot ARIA data system designed to integrate GPS and InSAR - GPS tropospheric delay used for correcting InSAR - Caltech's GIANT time series analysis uses GPS to correct orbital errors in InSAR - Zhen Liu's talking tomorrow on InSAR Time Series analysis

  13. Office of Spaceflight Standard Spaceborne Global Positioning System (GPS) user equipment project

    NASA Technical Reports Server (NTRS)

    Saunders, Penny E.

    1991-01-01

    The Global Positioning System (GPS) provides the following: (1) position and velocity determination to support vehicle GN&C, precise orbit determination, and payload pointing; (2) time reference to support onboard timing systems and data time tagging; (3) relative position and velocity determination to support cooperative vehicle tracking; and (4) attitude determination to support vehicle attitude control and payload pointing.

  14. 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,

  15. Positional accuracy of the Wide Area Augmentation System in consumer-grade GPS units

    NASA Astrophysics Data System (ADS)

    Arnold, Lisa L.; Zandbergen, Paul A.

    2011-07-01

    Global Positioning System devices are increasingly being used for data collection in many fields. Consumer-grade GPS units without differential correction have a published horizontal positional accuracy of approximately 10-15 m (average positional accuracy). An attractive option for differential correction for these GPS units is the Wide Area Augmentation System (WAAS). Most consumer-grade GPS units on the market are WAAS capable. According to the Federal Aviation Authority (FAA), the WAAS broadcast message provides integrity information about the GPS signal as well as accuracy improvements, which are reported to improve accuracy to 3-5 m. Limited empirical evidence has been published on the accuracy of WAAS-enabled GPS compared to autonomous GPS. An empirical study was conducted comparing the horizontal and vertical accuracy of WAAS-corrected GPS and autonomous GPS under ideal conditions using consumer-grade receivers. Data were collected for 30-min time spans over accurately surveyed control points. Metrics of median, 68th and 95th percentile, Root Mean Squared Error (RMSE), and average positional accuracy in the horizontal and vertical dimensions were computed and statistically compared. No statistically significant difference was found between WAAS and autonomous position fixes when using two different consumer-grade units. When using WAAS, a third unit type exhibited a statistically significant improvement in positional accuracy. Analysis of data collected for a 27-h time span indicates that while WAAS is altering the estimated position of a point compared to an autonomous position estimate, WAAS augmentation actually appears to decrease the positional accuracy.

  16. 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.

  17. Monitoring mobility in older adults using global positioning system (GPS) watches and accelerometers: a feasibility study.

    PubMed

    Webber, Sandra C; Porter, Michelle M

    2009-10-01

    This exploratory study examined the feasibility of using Garmin global positioning system (GPS) watches and ActiGraph accelerometers to monitor walking and other aspects of community mobility in older adults. After accuracy at slow walking speeds was initially determined, 20 older adults (74.4 +/- 4.2 yr) wore the devices for 1 day. Steps, distances, and speeds (on foot and in vehicle) were determined. GPS data acquisition varied from 43 min to over 12 hr, with 55% of participants having more than 8 hr between initial and final data-collection points. When GPS data were acquired without interruptions, detailed mobility information was obtained regarding the timing, distances covered, and speeds reached during trips away from home. Although GPS and accelerometry technology offer promise for monitoring community mobility patterns, new GPS solutions are required that allow for data collection over an extended period of time between indoor and outdoor environments. PMID:19940324

  18. 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.

  19. 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.

  20. Error Analysis System for Spacecraft Navigation Using the Global Positioning System (GPS)

    NASA Technical Reports Server (NTRS)

    Truong, S. H.; Hart, R. C.; Hartman, K. R.; Tomcsik, T. L.; Searl, J. E.; Bernstein, A.

    1997-01-01

    The Flight Dynamics Division (FDD) at the National Aeronautics and Space Administration (NASA) Goddard Space Flight Center (GSFC) is currently developing improved space-navigation filtering algorithms to use the Global Positioning System (GPS) for autonomous real-time onboard orbit determination. In connection with a GPS technology demonstration on the Small Satellite Technology Initiative (SSTI)/Lewis spacecraft, FDD analysts and programmers have teamed with the GSFC Guidance, Navigation, and Control Branch to develop the GPS Enhanced Orbit Determination Experiment (GEODE) system. The GEODE system consists of a Kalman filter operating as a navigation tool for estimating the position, velocity, and additional states required to accurately navigate the orbiting Lewis spacecraft by using astrodynamic modeling and GPS measurements from the receiver. A parallel effort at the FDD is the development of a GPS Error Analysis System (GEAS) that will be used to analyze and improve navigation filtering algorithms during development phases and during in-flight calibration. For GEAS, the Kalman filter theory is extended to estimate the errors in position, velocity, and other error states of interest. The estimation of errors in physical variables at regular intervals will allow the time, cause, and effect of navigation system weaknesses to be identified. In addition, by modeling a sufficient set of navigation system errors, a system failure that causes an observed error anomaly can be traced and accounted for. The GEAS software is formulated using Object Oriented Design (OOD) techniques implemented in the C++ programming language on a Sun SPARC workstation. The Phase 1 of this effort is the development of a basic system to be used to evaluate navigation algorithms implemented in the GEODE system. This paper presents the GEAS mathematical methodology, systems and operations concepts, and software design and implementation. Results from the use of the basic system to evaluate

  1. Evaluating the velocity accuracy of an integrated GPS/INS system: Flight test results. [Global positioning system/inertial navigation systems (GPS/INS)

    SciTech Connect

    Owen, T.E.; Wardlaw, R.

    1991-01-01

    Verifying the velocity accuracy of a GPS receiver or an integrated GPS/INS system in a dynamic environment is a difficult proposition when many of the commonly used reference systems have velocity uncertainities of the same order of magnitude or greater than the GPS system. The results of flight tests aboard an aircraft in which multiple reference systems simultaneously collected data to evaluate the accuracy of an integrated GPS/INS system are reported. Emphasis is placed on obtaining high accuracy estimates of the velocity error of the integrated system in order to verify that velocity accuracy is maintained during both linear and circular trajectories. Three different reference systems operating in parallel during flight tests are used to independently determine the position and velocity of an aircraft in flight. They are a transponder/interrogator ranging system, a laser tracker, and GPS carrier phase processing. Results obtained from these reference systems are compared against each other and against an integrated real time differential based GPS/INS system to arrive at a set of conclusions about the accuracy of the integrated system.

  2. Portable device to assess dynamic accuracy of global positioning systems (GPS) receivers used in agricultural aircraft

    Technology Transfer Automated Retrieval System (TEKTRAN)

    A device was designed to test the dynamic accuracy of Global Positioning System (GPS) receivers used in aerial vehicles. The system works by directing a sun-reflected light beam from the ground to the aircraft using mirrors. A photodetector is placed pointing downward from the aircraft and circuitry...

  3. The Utility and Validity of Kinematic GPS Positioning for the Geosar Airborne Terrain Mapping Radar System

    NASA Technical Reports Server (NTRS)

    Freedman, Adam; Hensley, Scott; Chapin, Elaine; Kroger, Peter; Hussain, Mushtaq; Allred, Bruce

    1999-01-01

    GeoSAR is an airborne, interferometric Synthetic Aperture Radar (IFSAR) system for terrain mapping, currently under development by a consortium including NASA's Jet Propulsion Laboratory (JPL), Calgis, Inc., a California mapping sciences company, and the California Department of Conservation (CaIDOC), with funding provided by the U.S. Army Corps of Engineers Topographic Engineering Center (TEC) and the U.S. Defense Advanced Research Projects Agency (DARPA). IFSAR data processing requires high-accuracy platform position and attitude knowledge. On 9 GeoSAR, these are provided by one or two Honeywell Embedded GPS Inertial Navigation Units (EGI) and an Ashtech Z12 GPS receiver. The EGIs provide real-time high-accuracy attitude and moderate-accuracy position data, while the Ashtech data, post-processed differentially with data from a nearby ground station using Ashtech PNAV software, provide high-accuracy differential GPS positions. These data are optimally combined using a Kalman filter within the GeoSAR motion measurement software, and the resultant position and orientation information are used to process the dual frequency (X-band and P-band) radar data to generate high-accuracy, high -resolution terrain imagery and digital elevation models (DEMs). GeoSAR requirements specify sub-meter level planimetric and vertical accuracies for the resultant DEMS. To achieve this, platform positioning errors well below one meter are needed. The goal of GeoSAR is to obtain 25 cm or better 3-D positions from the GPS systems on board the aircraft. By imaging a set of known point target corner-cube reflectors, the GeoSAR system can be calibrated. This calibration process yields the true position of the aircraft with an uncertainty of 20- 50 cm. This process thus allows an independent assessment of the accuracy of our GPS-based positioning systems. We will present an overview of the GeoSAR motion measurement system, focusing on the use of GPS and the blending of position data from the

  4. Autonomous Navigation of the SSTI/Lewis Spacecraft Using the Global Positioning System (GPS)

    NASA Technical Reports Server (NTRS)

    Hart, R. C.; Long, A. C.; Lee, T.

    1997-01-01

    The National Aeronautics and Space Administration (NASA) Goddard Space Flight Center (GSFC) Flight Dynamics Division (FDD) is pursuing the application of Global Positioning System (GPS) technology to improve the accuracy and economy of spacecraft navigation. High-accuracy autonomous navigation algorithms are being flight qualified in conjunction with GSFC's GPS Attitude Determination Flyer (GADFLY) experiment on the Small Satellite Technology Initiative (SSTI) Lewis spacecraft, which is scheduled for launch in 1997. Preflight performance assessments indicate that these algorithms can provide a real-time total position accuracy of better than 10 meters (1 sigma) and velocity accuracy of better than 0.01 meter per second (1 sigma), with selective availability at typical levels. This accuracy is projected to improve to the 2-meter level if corrections to be provided by the GPS Wide Area Augmentation System (WAAS) are included.

  5. Global Positioning System (GPS) Precipitable Water in Forecasting Lightning at Spaceport Canaveral

    NASA Technical Reports Server (NTRS)

    Kehrer, Kristen C.; Graf, Brian; Roeder, William

    2006-01-01

    This paper evaluates the use of precipitable water (PW) from Global Positioning System (GPS) in lightning prediction. Additional independent verification of an earlier model is performed. This earlier model used binary logistic regression with the following four predictor variables optimally selected from a candidate list of 23 candidate predictors: the current precipitable water value for a given time of the day, the change in GPS-PW over the past 9 hours, the KIndex, and the electric field mill value. This earlier model was not optimized for any specific forecast interval, but showed promise for 6 hour and 1.5 hour forecasts. Two new models were developed and verified. These new models were optimized for two operationally significant forecast intervals. The first model was optimized for the 0.5 hour lightning advisories issued by the 45th Weather Squadron. An additional 1.5 hours was allowed for sensor dwell, communication, calculation, analysis, and advisory decision by the forecaster. Therefore the 0.5 hour advisory model became a 2 hour forecast model for lightning within the 45th Weather Squadron advisory areas. The second model was optimized for major ground processing operations supported by the 45th Weather Squadron, which can require lightning forecasts with a lead-time of up to 7.5 hours. Using the same 1.5 lag as in the other new model, this became a 9 hour forecast model for lightning within 37 km (20 NM)) of the 45th Weather Squadron advisory areas. The two new models were built using binary logistic regression from a list of 26 candidate predictor variables: the current GPS-PW value, the change of GPS-PW over 0.5 hour increments from 0.5 to 12 hours, and the K-index. The new 2 hour model found the following for predictors to be statistically significant, listed in decreasing order of contribution to the forecast: the 0.5 hour change in GPS-PW, the 7.5 hour change in GPS-PW, the current GPS-PW value, and the KIndex. The new 9 hour forecast model found

  6. Inter-system biases estimation in multi-GNSS relative positioning with GPS and Galileo

    NASA Astrophysics Data System (ADS)

    Deprez, Cecile; Warnant, Rene

    2016-04-01

    The recent increase in the number of Global Navigation Satellite Systems (GNSS) opens new perspectives in the field of high precision positioning. Particularly, the European Galileo program has experienced major progress in 2015 with the launch of 6 satellites belonging to the new Full Operational Capability (FOC) generation. Associated with the ongoing GPS modernization, many more frequencies and satellites are now available. Therefore, multi-GNSS relative positioning based on GPS and Galileo overlapping frequencies should entail better accuracy and reliability in position estimations. However, the differences between satellite systems induce inter-system biases (ISBs) inside the multi-GNSS equations of observation. Once these biases estimated and removed from the model, a solution involving a unique pivot satellite for the two considered constellations can be obtained. Such an approach implies that the addition of even one single Galileo satellite to the GPS-only model will strengthen it. The combined use of L1 and L5 from GPS with E1 and E5a from Galileo in zero baseline double differences (ZB DD) based on a unique pivot satellite is employed to resolve ISBs. This model removes all the satellite- and receiver-dependant error sources by differentiating and the zero baseline configuration allows atmospheric and multipath effects elimination. An analysis of the long-term stability of ISBs is conducted on various pairs of receivers over large time spans. The possible influence of temperature variations inside the receivers over ISB values is also investigated. Our study is based on the 5 multi-GNSS receivers (2 Septentrio PolaRx4, 1 Septentrio PolaRxS and 2 Trimble NetR9) installed on the roof of our building in Liege. The estimated ISBs are then used as corrections in the multi-GNSS observation model and the resulting accuracy of multi-GNSS positioning is compared to GPS and Galileo standalone solutions.

  7. Codeless GPS systems for positioning of offshore platforms and 3D seismic surveys

    NASA Astrophysics Data System (ADS)

    MacDoran, P. F.; Miller, R. B.; Buennagel, L. A.; Fliegel, H. F.; Tanida, L.

    The Satellite Emission Range Inferred Earth Surveying (SERIES) method was originally intended for subdecimeter accuracy measurements of the crust of the earth in search of tell-tale patterns which could be exploited for research into earthquake prediction. The present paper is concerned with a specific application of the SERIES technology, taking into account high accuracy positioning related to exploration for oil and gas reserves in the offshore environment. One of the most advanced methods of exploration for hydrocarbon resources is known as 3D seismic surveying. Morgan (1983) has discussed this method, giving attention to the possible benefits of using the Global Positioning System (GPS). The present paper presents the SERIES-GPS method. It is shown that wide civil use of the Navstar is possible to levels of accuracy well beyond the Precise Positioning Service (PPS). Such a use is feasible without the DOD for Navstar codes and orbits.

  8. A Self-Tuning Kalman Filter for Autonomous Navigation Using the Global Positioning System (GPS)

    NASA Technical Reports Server (NTRS)

    Truong, Son H.

    1999-01-01

    Most navigation systems currently operated by NASA are ground-based, and require extensive support to produce accurate results. Recently developed systems that use Kalman filter and GPS (Global Positioning Systems) data for orbit determination greatly reduce dependency on ground support, and have potential to provide significant economies for NASA spacecraft navigation. These systems, however, still rely on manual tuning from analysts. A sophisticated neuro-fuzzy component fully integrated with the flight navigation system can perform the self-tuning capability for the Kalman filter and help the navigation system recover from estimation errors in real time.

  9. ProSEDS Telemetry System Utilization of GPS Position Data for Transmitter Cycling

    NASA Technical Reports Server (NTRS)

    Kennedy, Paul; Sims, Herb

    2000-01-01

    NASA Marshall Space Flight Center will launch the Propulsive Small Expendable Deployer System (ProSEDS) space experiment in late 2000. ProSEDS will demonstrate the use of an electrodynamic tether propulsion system and will utilize a conducting wire tether to generate limited spacecraft power. This paper will provide an overview of the ProSEDS mission and will discuss the design, development and test of the spacecraft telemetry system which utilizes a custom designed GPS subsystem to determine spacecraft position relative to ground station location and to control transmitter on/off cycling based on spacecraft state vector and ground station visibility.

  10. Development of a GPS-aided motion measurement, pointing, and stabilization system for a Synthetic Aperture Radar. [Global Positioning System (GPS)

    SciTech Connect

    Fellerhoff, J.R.; Kohler, S.M.

    1991-01-01

    An advanced Synthetic Aperture Radar Motion Compensation System has been developed by Sandia National Laboratories (SNL). The system includes a miniaturized high accuracy ring laser gyro inertial measurement unit, a three axis gimbal pointing and stabilization assembly, a differential Global Positioning System (GPS) navigation aiding system, and a pilot guidance system. The system provides several improvements over previous SNL motion compensation systems and is capable of antenna stabilization to less than 0.01 degrees RMS and absolute position measurement to less than 5.0 meters RMS. These accuracies have been demonstrated in recent flight testing aboard a DHC-6-300 Twin Otter'' aircraft.

  11. Precise Real-Time Low-Earth-Orbiter Navigation With the Global Positioning System (GPS)

    NASA Astrophysics Data System (ADS)

    Bertiger, W.; Haines, B.; Kuang, D.; Lough, M.; Lichten, S.; Muellerschoen, R. J.; Vigue-Rodi, Y.; Wu, S.

    1999-01-01

    Technology currently is available to support real-time onboard knowledge of the position of a low Earth orbiter at the 5- to 15-m level using the civilian broadcast Global Positioning System (GPS) signal with sophisticated models and filtering techniques onboard the spacecraft. Without these techniques, the standard positioning service yields 50 to 100 m with the current level of selective availability (SA). Proposed augmentations and/or enhancements to the GPS system will make rms accuracies of from 10 centimeters to a few decimeters available to the real-time onboard user. Presently, near-real-time processing of GPS tracking data can routinely provide low-Earth-orbit determination accuracy at the level of 5 cm. Such processing systems can, in fact, be fully automated; recent results from the Jet Propulsion Laboratory (JPL), where ongoing daily processing of low Earth GPS tracking data has been undertaken for several years, are presented in this article, showing orbit determination accuracies at the sub-10-cm level. At the present time, such solutions can be produced with about a 10-h delay after real time, but recent improvements in JPL's processing system soon will enable turnaround at the 1-h level or better for such precise orbit determination. We anticipate that orbit determination at the 1-cm-accuracy level will be demonstrated, with some refinements to the current system, in the not too distant future. Continuing enhancements in the automation of data retrieval and precise orbit processing will result in continuing decreases in latency for ground-based generation of precise orbit products for Earth orbiters. Such ephemerides can be propagated slightly ahead to provide real-time knowledge. However, there are advantages to an onboard, real-time orbit-determination capability. These include unique mission requirements (military, strategic, and scientific), as well as the potential to dramatically lower navigation operations costs through the enabling of a

  12. A worldwide unification of GPS (Global Positioning System) antenna coordinates for high accuracy time transfer.

    NASA Astrophysics Data System (ADS)

    Lewandowski, W.

    In the present state of the art of atomic clocks it is desirable that comparisons of these clocks, located in the time metrology laboratories spread around the world, be at the level of a few nanoseconds of accuracy. At present the sole operational way to provide such performance is through the system of GPS satellites. As GPS is a one-way system this implies that special attention must be given to geometrical errors. In order to achieve nanosecond accuracy, the error due to the ground-antenna coordinates should not exceed 1 ns in the global budget of errors of GPS time transfer. To attain this goal the ground-antenna coordinates must be accurately determined in a common worldwide homogeneous geodetic reference frame with uncertainties of order 30 cm. This paper considers the choice of a global reference frame for accurate GPS time transfer and then reports on a worldwide homogenization of GPS antenna coordinates in the principal timing centres.

  13. 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.

  14. How useful is satellite positioning system (GPS) to track gait parameters? A review

    PubMed Central

    Terrier, Philippe; Schutz, Yves

    2005-01-01

    Over the last century, numerous techniques have been developed to analyze the movement of humans while walking and running. The combined use of kinematics and kinetics methods, mainly based on high speed video analysis and forceplate, have permitted a comprehensive description of locomotion process in terms of energetics and biomechanics. While the different phases of a single gait cycle are well understood, there is an increasing interest to know how the neuro-motor system controls gait form stride to stride. Indeed, it was observed that neurodegenerative diseases and aging could impact gait stability and gait parameters steadiness. From both clinical and fundamental research perspectives, there is therefore a need to develop techniques to accurately track gait parameters stride-by-stride over a long period with minimal constraints to patients. In this context, high accuracy satellite positioning can provide an alternative tool to monitor outdoor walking. Indeed, the high-end GPS receivers provide centimeter accuracy positioning with 5–20 Hz sampling rate: this allows the stride-by-stride assessment of a number of basic gait parameters – such as walking speed, step length and step frequency – that can be tracked over several thousand consecutive strides in free-living conditions. Furthermore, long-range correlations and fractal-like pattern was observed in those time series. As compared to other classical methods, GPS seems a promising technology in the field of gait variability analysis. However, relative high complexity and expensiveness – combined with a usability which requires further improvement – remain obstacles to the full development of the GPS technology in human applications. PMID:16138922

  15. Using Evolutionary Computation on GPS Position Correction

    PubMed Central

    2014-01-01

    More and more devices are equipped with global positioning system (GPS). However, those handheld devices with consumer-grade GPS receivers usually have low accuracy in positioning. A position correction algorithm is therefore useful in this case. In this paper, we proposed an evolutionary computation based technique to generate a correction function by two GPS receivers and a known reference location. Locating one GPS receiver on the known location and combining its longitude and latitude information and exact poisoning information, the proposed technique is capable of evolving a correction function by such. The proposed technique can be implemented and executed on handheld devices without hardware reconfiguration. Experiments are conducted to demonstrate performance of the proposed technique. Positioning error could be significantly reduced from the order of 10 m to the order of 1 m. PMID:24578657

  16. Uav Onboard GPS in Positioning Determination

    NASA Astrophysics Data System (ADS)

    Tahar, K. N.; Kamarudin, S. S.

    2016-06-01

    The establishment of ground control points is a critical issue in mapping field, especially for large scale mapping. The fast and rapid technique for ground control point's establishment is very important for small budget projects. UAV onboard GPS has the ability to determine the point positioning. The objective of this research is to assess the accuracy of unmanned aerial vehicle onboard global positioning system in positioning determination. Therefore, this research used UAV onboard GPS as an alternative to determine the point positioning at the selected area. UAV is one of the powerful tools for data acquisition and it is used in many applications all over the world. This research concentrates on the error contributed from the UAV onboard GPS during observation. There are several points that have been used to study the pattern of positioning error. All errors were analyzed in world geodetic system 84- coordinate system, which is the basic coordinate system used by the global positioning system. Based on this research, the result of UAV onboard GPS positioning could be used in ground control point establishment with the specific error. In conclusion, accurate GCP establishment could be achieved using UAV onboard GPS by applying a specific correction based on this research.

  17. Tracking the movement of Hawaiian volcanoes; Global Positioning System (GPS) measurement

    USGS Publications Warehouse

    Dvorak, J.J.

    1992-01-01

    At some well-studied volcanoes, surface movements of at least several centimeters take place out to distances of about 10 km from the summit of the volcano. Widespread deformation of this type is relatively easy to monitor, because the necessary survey stations can be placed at favorable sites some distance from the summit of the volcano. Examples of deformation of this type include Kilauea and Mauna Loa in Hawaii, Krafla in Iceland, Long Valley in California, Camp Flegrei in Italy, and Sakurajima in Japan. In contrast, surface movement at some other volcanoes, usually volcanoes with steep slopes, is restricted to places within about 1 km of their summits. Examples of this class of volcanoes include Mount St. Helens in Washington, Etna in Italy, and Tangkuban Parahu in Indonesia. Local movement on remote, rugged volcanoes of this type is difficult to observe using conventional methods of measuring ground movement, which generally require a clear line-of-sight between points of interest. However, a revolutionary new technique, called the Global Positional System (GPS), provides a very efficient, alternative method of making such measurements. GPS, which uses satellites and ground-based receivers to accurately record slight crustal movements, is rapidly becoming the method of choice to measure deformation at volcanoes. 

  18. GPS Position and Heading Circuitry for Ships

    NASA Technical Reports Server (NTRS)

    Cooke, Michael P.; Yim, Hester J.; Gomez, Susan F.

    2003-01-01

    Circuit boards that contain radio-frequency (RF) and digital circuitry have been developed by NASA to satisfy a requirement of the Port of Houston Authority for relatively inexpensive Global Positioning System (GPS) receivers that indicate the azimuthal headings as well as the positions of ships. The receiver design utilizes the unique architecture of the Mitel commercial chip-set, which provides for an accurate GPS-based heading-determination device. The major components include two RF front ends (each connected to a separate antenna), a surface-acoustic-wave intermediate-frequency filter between second- and third-stage mixers, a correlator, and a reduced-instruction- set computer. One of the RF front ends operates as a master, the other as a slave. Both RF front ends share a 10-MHz sinusoidal clock oscillator, which provides for more accurate carrier phase measurements between the two antennas. The outputs of the RF front ends are subjected to conventional GPS processing. The commercial-based chip-set design approach provides an inexpensive open architecture GPS platform, which can be used in developing and implementing unique GPS-heading and attitude-determination algorithms for specific applications. The heading is estimated from the GPS position solutions of the two antennas by an algorithm developed specifically for this application. If a third (and preferably a fourth) antenna were added, it would be possible to estimate the attitude of the GPS receiver in three dimensions instead of only its heading in a horizontal plane.

  19. Global Positioning System (GPS) advances in autonomous user system (Norway demonstration)

    NASA Astrophysics Data System (ADS)

    Ananda, Mohan P.; Bernstein, Harold; Feess, William A.; Kells, Ronald C.; Wortham, J. H.

    Using a new autonomous user (AU) system algorithm extends the AU system concept by permitting the use of a crystal frequency reference instead of an atomic reference. Results obtained using both crystal and atomic frequency references are presented. To supply interim full-system accuracy in the event of loss of the operational control segment (OCS) of GPS, an AU system needing only user segment modification has been implemented. During the summer of 1988 a demonstration of the system was conducted in Tromso, Norway. It is indicated, that in this 180-day test period, the autonomous user with a crystal reference could achieve a navigation accuracy of the same order of magnitude as when the OCS was operating. Furthermore, other navigation systems may utilize the concepts of this autonomous user system.

  20. A pilot study using global positioning systems (GPS) devices and surveys to ascertain older adults' travel patterns.

    PubMed

    Yen, Irene H; Leung, Cindy W; Lan, Mars; Sarrafzadeh, Majid; Kayekjian, Karen C; Duru, O Kenrik

    2015-04-01

    Some studies indicate that older adults lead active lives and travel to many destinations including those not in their immediate residential neighborhoods. We used global positioning system (GPS) devices to track the travel patterns of 40 older adults (mean age: 69) in San Francisco and Los Angeles. Study participants wore the GPS devices for 7 days in fall 2010 and winter 2011. We collected survey responses concurrently about travel patterns. GPS data showed a mean of four trips/day, and a mean trip distance of 7.6 km. Survey data indicated that older adults commonly made trips for four activities (e.g., volunteering, work, visiting friends) at least once each week. Older adults regularly travel outside their residential neighborhoods. GPS can document the mode of travel, the path of travel, and the destinations. Surveys can document the purpose of the travel and the impressions or experiences in the specific locations. PMID:24652872

  1. 75 FR 61818 - Eighty-Third Meeting: RTCA Special Committee 159: Global Positioning System (GPS).

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-10-06

    ... 7, GPS/Antennas, ARINC Room. Friday, October 29 Plenary Session--See Agenda Below Agenda--Plenary...-4) GPS/Airport Surface Surveillance (WG-5) GPS/Interference (WG-6) GPS/Antennas (WG-7) Review...

  2. Evaluating home range techniques: use of Global Positioning System (GPS) collar data from chacma baboons.

    PubMed

    Pebsworth, Paula A; Morgan, Hanna R; Huffman, Michael A

    2012-10-01

    Global Positioning System (GPS) collars have revolutionized the field of spatial ecology, but to date, few primate studies have used them. We fitted a free-ranging, semi-habituated, juvenile male chacma baboon (Papio hamadryas ursinus) with an automatic self-releasing GPS collar and tracked his movements for 359 days. The collar captured 4254 fixes out of 5719 programmed opportunities, a 74.4 % acquisition rate, suggesting that the collar effectively tracked this baboon in a variety of habitat types. Of the data points captured, 73.7 % were three-dimensional fixes, and of these fixes, 66.9 % were highly accurate, having a dilution of precision of less than four. We calculated home range using three protocols with three estimation methods: minimum convex polygon, fixed kernel-density estimation (KDE), and fixed r local convex hull. Using all data points and the 95 % contour, these methods created home range estimations ranging from 10.8 to 23.1 km(2) for this baboon troop. Our results indicate that the KDE output using all data locations most accurately represented our data set, as it created a continuous home range boundary that excluded unused areas and outlying, potentially exploratory data points while including all seven sleeping sites and a movement corridor. However, home range estimations generated from KDE varied from 15.4 to 18.8 km(2) depending on the smoothing parameter used. Our results demonstrated that the ad hoc smoothing parameter selection technique was a better method for our data set than either the least squares cross-validation or biased cross-validation techniques. Our results demonstrate the need for primatologists to develop a standardized reporting method which documents the tool, screening protocol, and smoothing parameter used in the creation of home range estimations in order to make comparisons that are meaningful. PMID:22476515

  3. GPS-based positioning for autonomous underwater vehicle

    NASA Astrophysics Data System (ADS)

    Huang, Wenling; Fang, Huajing; Chen, Yingchun; Yuan, Bingcheng; Zhou, Xuchang

    2005-11-01

    GPS-based positioning for AUV is a field of active researches, which integrates DGPS, radio sonobuoy, DSP, high speed data transmission technology with underwater telecommunication technogy. Many problems remain to be solved for GPS application to AUV because of the peculiarity of underwater environment. Some subjects in a GPS-based positioning system for AUV are reviewed in the paper. The development of underwater positioning and underwater GPS technology is introduced first. Secondly, the methods of underwater positioning are analyzed, followed with GPS-based AUV positioning algorithms. Thirdly, the origin of GPS error and its countermeasures are tudied. Finally, a conclusion is drawn that the GPS-based positioning system can provide high precesion positioning for 3D AUV in real time. It is promising in underwater applications. Some key technologies in underwater positioning are presented for future work.

  4. Integrated inertial navigation system/Global Positioning System (INS/GPS) for manned return vehicle autoland application

    NASA Astrophysics Data System (ADS)

    Braden, Kevin; Browning, Clint; Gelderloos, Hendrik; Smith, Fred; Marttila, Chuck

    It is noted that with the development of the International Space Station Freedom, people will permanently live in space and require routine access and an assured crew return capability in case of emergencies in space. The extended duration in space requires a manned return vehicle that is less demanding on the crew and provides an autonomous deorbit, entry, and autoland capability. The authors discuss an autoland capability with an integrated differential GPS/INS that provides the required position and velocity accuracies without the need for tactical aircraft navigation (TACAN) and Microwave Landing System (MLS) navigation aides. Simulation results are used to demonstrate the feasibility of autoland using differential GPS aided with a high-precision altimeter. This concept applies to several manned space applications, such as Assured Crew Return Vehicle (ACRV), Assured Shuttle Availability (ASA), Advanced Manned Launch System (AMLS), and National Aerospace Plane (NASP), and to unmanned return vehicles such as the Propulsion Avionics Module (P/AM).

  5. A Tightly-Coupled GPS/INS/UWB Cooperative Positioning Sensors System Supported by V2I Communication.

    PubMed

    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

  6. 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

  7. 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.

  8. Geodetic point positioning with GPS (Global Positioning System) carrier beat phase data from the CASA (Central and South America) Uno experiment

    SciTech Connect

    Malys, S.; Jensen, P.A. )

    1990-04-01

    The Global Positioning System (GPS) carrier beat phase data collected by the TI4100 GPS receiver has been successfully utilized by the US Defense Mapping Agency in an algorithm which is designed to estimate individual absolute geodetic point positions from data collected over a few hours. The algorithm uses differenced data from one station and two to four GPS satellites at a series of epochs separated by 30 second intervals. The precise GPS ephemerides and satellite clock states, held fixed in the estimation process, are those estimated by the Naval Surface Warfare Center (NSWC). Broadcast ephemerides and clock states are also utilized for comparative purposes. An outline of the data corrections applied, the mathematical model and the estimation algorithm are presented. Point positioning results and statistics are presented for a globally-distributed set of stations which contributed to the CASA Uno experiment. Statistical assessment of 114 GPS point positions at 11 CASA Uno stations indicates that the overall standard deviation of a point position component, estimated from a few hours of data, is 73 centimeters. Solution of the long line geodetic inverse problem using repeated point positions such as these can potentially offer a new tool for those studying geodynamics on a global scale.

  9. A Self-Tuning Kalman Filter for Autonomous Navigation using the Global Positioning System (GPS)

    NASA Technical Reports Server (NTRS)

    Truong, S. H.

    1999-01-01

    Most navigation systems currently operated by NASA are ground-based, and require extensive support to produce accurate results. Recently developed systems that use Kalman filter and GPS data for orbit determination greatly reduce dependency on ground support, and have potential to provide significant economies for NASA spacecraft navigation. These systems, however, still rely on manual tuning from analysts. A sophisticated neuro-fuzzy component fully integrated with the flight navigation system can perform the self-tuning capability for the Kalman filter and help the navigation system recover from estimation errors in real time.

  10. Centimeter-level relative positioning with GPS

    NASA Technical Reports Server (NTRS)

    Counselman, C. C., III; Abbot, R. I.; Gourevitch, S. A.; King, R. W.; Paradis, A. R.

    1983-01-01

    Although the Global Positioning System (GPS) was designed primarily for real-time navigation and positioning applications at the decameter level of accuracy, the GPS has been used to determine all three relative position coordinates of fixed points with centimeter-level accuracy, when the distance between the points has been of the order of 10 km. For intersite distances less than 1 km the uncertainty is about 3 mm, and for distances greater than 10 km the uncertainty in each coordinate is about 1-2 ppm of the distance. These results have been obtained with commercially available production equipment (Macrometer model V-1000 interferometric surveyors) operated by regular surveying personnel under real field conditions, not just by university scientists under ideal laboratory conditions. Techniques that promise to reduce the uncertainty to 0.1 ppm for distances greater than 10 km are being developed.

  11. Global positioning system (GPS) supported block adjustment with self-calibration parameters

    NASA Astrophysics Data System (ADS)

    Blankenberg, Leif E.

    1994-08-01

    Systematic errors in the image coordinates is often a problem when working with high accuracy bundle block adjustment. These errors can be modeled by introducing self calibration parameters in the adjustment. In a traditional block adjustment, a dense network of ground control points are required to ensure a reliable estimate of these parameters. In the case of GPS-supported block adjustment, there is usually very little ground control available, but as shown in this paper, it is still possible to estimate the self calibration parameters. This is because of the stabilizing effect the GPS-determined perspective center coordinates have on the block. In this paper, both simulated data and real block data are used to evaluate the accuracy properties of GPS-supported blocks with additional self calibration parameters. Two different sets of additional parameters are evaluated. In the GPS-supported test blocks, the introduction of self calibration parameters improves the empirical tie point accuracy by 30 - 40%.

  12. The Global Positioning System--Direction for the Future [and] GPS Technology and Agriculture.

    ERIC Educational Resources Information Center

    Edmondson, Paul R.; Ginsburg, Alan

    1996-01-01

    Edmondson introduces a satellite-based radio navigation, positioning, and timing system that can be integrated into a variety of curriculum areas. Ginsburg describes how the global positioning system brings far-reaching benefits for crop growers and the environment. (Author)

  13. A new tool to monitor training and performance of sport horses using global positioning system (GPS) with integrated GSM capabilities.

    PubMed

    Hebenbrock, M; Düe, M; Holzhausen, H; Sass, A; Stadler, P; Ellendorff, F

    2005-07-01

    Global Positioning Systems (GPS) are considered suitable to monitor the position and velocity of horses during cross-country competition or in training. Furthermore, simultaneous recording of life data such as heart rate could be useful to assess the horse's condition during exercise. To test the suitability and reliability of a commercially available GPS system with integrated heart rate recording system and with built in GSM for data transmission, the Fidelak Equipilot Type EP-2003-15/G-2.11 (EP-15/G) was evaluated first for reliability of pulse recording from a pulse generator within the physiological range of horses; furthermore distance, velocity and heart rate recordings were carried out on a standard 1000 m field track with five repetitions. Agreement (% deviation from actually measured distance and from stopwatch-distance based velocity calculations) and variability (Coefficient of Variation for distance, velocity, heart rate) were calculated. From the results it was safe to assume that the heart rate sensor recorded horse heart rates at a high degree of accuracy. Overall distances and velocities are in high agreement with actually measured values. However, overall variability expressed in terms of relative variability (C.V.) is smaller for distance recording (C.V. 0.68%) when compared to velocity (C.V. 1.01%). The system tested is suitable and reliable for simultaneously recording of distance, velocity and heart rates for horses during cross country exercise. GPS-based monitoring of movement along with simultaneous recording of physiological data and the possibility to call upon data will not only be of benefit for training horses or for surveillance during competition, it may also be suitable for distant patient monitoring and in behavioural studies as well as in veterinary medicine in general. PMID:16124700

  14. Time and position accuracy using codeless GPS

    NASA Technical Reports Server (NTRS)

    Dunn, C. E.; Jefferson, D. C.; Lichten, S. M.; Thomas, J. B.; Vigue, Y.; Young, L. E.

    1994-01-01

    The Global Positioning System has allowed scientists and engineers to make measurements having accuracy far beyond the original 15 meter goal of the system. Using global networks of P-Code capable receivers and extensive post-processing, geodesists have achieved baseline precision of a few parts per billion, and clock offsets have been measured at the nanosecond level over intercontinental distances. A cloud hangs over this picture, however. The Department of Defense plans to encrypt the P-Code (called Anti-Spoofing, or AS) in the fall of 1993. After this event, geodetic and time measurements will have to be made using codeless GPS receivers. However, there appears to be a silver lining to the cloud. In response to the anticipated encryption of the P-Code, the geodetic and GPS receiver community has developed some remarkably effective means of coping with AS without classified information. We will discuss various codeless techniques currently available and the data noise resulting from each. We will review some geodetic results obtained using only codeless data, and discuss the implications for time measurements. Finally, we will present the status of GPS research at JPL in relation to codeless clock measurements.

  15. Precise positioning with current multi-constellation Global Navigation Satellite Systems: GPS, GLONASS, Galileo and BeiDou.

    PubMed

    Li, Xingxing; Zhang, Xiaohong; Ren, Xiaodong; Fritsche, Mathias; Wickert, Jens; Schuh, Harald

    2015-01-01

    The world of satellite navigation is undergoing dramatic changes with the rapid development of multi-constellation Global Navigation Satellite Systems (GNSSs). At the moment more than 70 satellites are already in view, and about 120 satellites will be available once all four systems (BeiDou + Galileo + GLONASS + GPS) are fully deployed in the next few years. This will bring great opportunities and challenges for both scientific and engineering applications. In this paper we develop a four-system positioning model to make full use of all available observations from different GNSSs. The significant improvement of satellite visibility, spatial geometry, dilution of precision, convergence, accuracy, continuity and reliability that a combining utilization of multi-GNSS brings to precise positioning are carefully analyzed and evaluated, especially in constrained environments. PMID:25659949

  16. Precise positioning with current multi-constellation Global Navigation Satellite Systems: GPS, GLONASS, Galileo and BeiDou

    PubMed Central

    Li, Xingxing; Zhang, Xiaohong; Ren, Xiaodong; Fritsche, Mathias; Wickert, Jens; Schuh, Harald

    2015-01-01

    The world of satellite navigation is undergoing dramatic changes with the rapid development of multi-constellation Global Navigation Satellite Systems (GNSSs). At the moment more than 70 satellites are already in view, and about 120 satellites will be available once all four systems (BeiDou + Galileo + GLONASS + GPS) are fully deployed in the next few years. This will bring great opportunities and challenges for both scientific and engineering applications. In this paper we develop a four-system positioning model to make full use of all available observations from different GNSSs. The significant improvement of satellite visibility, spatial geometry, dilution of precision, convergence, accuracy, continuity and reliability that a combining utilization of multi-GNSS brings to precise positioning are carefully analyzed and evaluated, especially in constrained environments. PMID:25659949

  17. The Global Positioning System (GPS) and attitude determination: Applications and activities in the Flight Dynamics Division

    NASA Technical Reports Server (NTRS)

    Ketchum, Eleanor; Garrick, Joe

    1995-01-01

    The application of GPS to spacecraft attitude determination is a new and growing field. Although the theoretical literature is extensive, space flight testing is currently sparse and inadequate. As an operations organization, the Flight Dynamics Division (FDD) has the responsibility to investigate this new technology, and determine how best to implement the innovation to provide adequate support for future missions. This paper presents some of the current efforts within FDD with regard to GPS attitude determination. This effort specifically addresses institutional capabilities to accommodate a new type of sensor, critically evaluating the literature for recent advancements, and in examining some available -albeit crude- flight data.

  18. 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

  19. A simple method to improve autonomous GPS positioning for tractors.

    PubMed

    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

  20. 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."

  1. Combined GPS and GALILEO instantaneous precise positioning

    NASA Astrophysics Data System (ADS)

    Wielgosz, P.; Paziewski, J.; Stepniak, K.

    2011-12-01

    This presentation provides results of the research aimed at precise positioning using single-epoch GPS and Galileo observations. The main goal was to develop algorithms that allow obtaining reliable centimeter-level position when using just a single epoch of pseudorange and carrier phase GPS and Galileo data in a single functional model. The presented algorithms are based on relative precise positioning using double-differenced observations in both single baseline and network mode. Fast and reliable ambiguity resolution is the key for rapid and single-epoch precise positioning. In order to support ambiguity resolution using small amount of data, special emphasis was put on mitigation of ionospheric and tropospheric delays. The functional model was based on constrained least squares estimation. The LAMBDA method was applied for ambiguity resolution and a multi-criteria statistical tests are used for ambiguity validation. These algorithms were implemented in GINPOS software developed at the University of Warmia and Mazury in Olsztyn. The results of combined GPS+Galileo processing were compared to the solutions obtained using GPS-only and Galileo-only data. Since there are just two test Galileo satellites on orbit, Spirent multi-GNSS simulator was used to obtain Galileo and GPS signals. The processed baselines reached up to 35-70 km. The results based on the simulated data show that even though single-epoch precise positioning is possible with GPS only, adding Galileo data increases availability and reliability of the user position.

  2. Real-Time Point Positioning Performance Evaluation of Single-Frequency Receivers Using NASA's Global Differential GPS System

    NASA Technical Reports Server (NTRS)

    Muellerschoen, Ronald J.; Iijima, Byron; Meyer, Robert; Bar-Sever, Yoaz; Accad, Elie

    2004-01-01

    This paper evaluates the performance of a single-frequency receiver using the 1-Hz differential corrections as provided by NASA's global differential GPS system. While the dual-frequency user has the ability to eliminate the ionosphere error by taking a linear combination of observables, the single-frequency user must remove or calibrate this error by other means. To remove the ionosphere error we take advantage of the fact that the magnitude of the group delay in range observable and the carrier phase advance have the same magnitude but are opposite in sign. A way to calibrate this error is to use a real-time database of grid points computed by JPL's RTI (Real-Time Ionosphere) software. In both cases we evaluate the positional accuracy of a kinematic carrier phase based point positioning method on a global extent.

  3. A motion-based integer ambiguity resolution method for attitude determination using the global positioning system (GPS)

    NASA Astrophysics Data System (ADS)

    Wang, Bo; Deng, Zhihong; Wang, Shunting; Fu, Mengyin

    2010-06-01

    Loss of the satellite signal and noise disturbance will cause cycle slips to occur in the carrier phase observation of the attitude determination system using the global positioning system (GPS), especially in the dynamic situation. Therefore, in order to reject the error by cycle slips, the integer ambiguity should be re-computed. A motion model-based Kalman predictor is used for the ambiguity re-computation in dynamic applications. This method utilizes the correct observation of the last step to predict the current ambiguities. With the baseline length as a constraint to reject invalid values, we can solve the current integer ambiguity and the attitude angles, by substituting the obtained ambiguities into the constrained LAMBDA method. Experimental results demonstrate that the proposed method is more efficient in the dynamic situation, which takes less time to obtain new fixed ambiguities with a higher mean success rate.

  4. Investigation for improving Global Positioning System (GPS) orbits using a discrete sequential estimator and stochastic models of selected physical processes

    NASA Technical Reports Server (NTRS)

    Goad, Clyde C.; Chadwell, C. David

    1993-01-01

    GEODYNII is a conventional batch least-squares differential corrector computer program with deterministic models of the physical environment. Conventional algorithms were used to process differenced phase and pseudorange data to determine eight-day Global Positioning system (GPS) orbits with several meter accuracy. However, random physical processes drive the errors whose magnitudes prevent improving the GPS orbit accuracy. To improve the orbit accuracy, these random processes should be modeled stochastically. The conventional batch least-squares algorithm cannot accommodate stochastic models, only a stochastic estimation algorithm is suitable, such as a sequential filter/smoother. Also, GEODYNII cannot currently model the correlation among data values. Differenced pseudorange, and especially differenced phase, are precise data types that can be used to improve the GPS orbit precision. To overcome these limitations and improve the accuracy of GPS orbits computed using GEODYNII, we proposed to develop a sequential stochastic filter/smoother processor by using GEODYNII as a type of trajectory preprocessor. Our proposed processor is now completed. It contains a correlated double difference range processing capability, first order Gauss Markov models for the solar radiation pressure scale coefficient and y-bias acceleration, and a random walk model for the tropospheric refraction correction. The development approach was to interface the standard GEODYNII output files (measurement partials and variationals) with software modules containing the stochastic estimator, the stochastic models, and a double differenced phase range processing routine. Thus, no modifications to the original GEODYNII software were required. A schematic of the development is shown. The observational data are edited in the preprocessor and the data are passed to GEODYNII as one of its standard data types. A reference orbit is determined using GEODYNII as a batch least-squares processor and the

  5. Point measurements of mass balance of the Greenland Ice Sheet using precision vertical Global Positioning System (GPS) surveys

    NASA Astrophysics Data System (ADS)

    Hamilton, Gordon S.; Whillans, Ian M.

    2000-07-01

    Rates of ice sheet thickening or thinning in Greenland are measured using the coffee-can technique. This entails computing the difference in the vertical velocity of markers anchored in firn and the long-term rate of snow accumulation. The velocities are obtained from repeat surveys using the Global Positioning System (GPS). With corrections for densification and along-slope flow, this difference is the local mass balance. For two sites in western Greenland (Camp Century and a site just south of the EGIG line (Crawford Point)) results show ice sheet thinning. A third west Greenland site (inland from Upernavik) is close to balance. Two sites, Dye-2 in western Greenland and Summit, are thickening slowly.

  6. Precise Point Positioning Based on BDS and GPS Observations

    NASA Astrophysics Data System (ADS)

    Gao, ZhouZheng; Zhang, Hongping; Shen, Wenbin

    2014-05-01

    BeiDou Navigation Satellite System (BDS) has obtained the ability applying initial navigation and precise point services for the Asian-Pacific regions at the end of 2012 with the constellation of 5 Geostationary Earth Orbit (GEO), 5 Inclined Geosynchronous Orbit (IGSO) and 4 Medium Earth Orbit (MEO). Till 2020, it will consist with 5 GEO, 3 IGSO and 27 MEO, and apply global navigation service similar to GPS and GLONASS. As we known, GPS precise point positioning (PPP) is a powerful tool for crustal deformation monitoring, GPS meteorology, orbit determination of low earth orbit satellites, high accuracy kinematic positioning et al. However, it accuracy and convergence time are influenced by the quality of pseudo-range observations and the observing geometry between user and Global navigation satellites system (GNSS) satellites. Usually, it takes more than 30 minutes even hours to obtain centimeter level position accuracy for PPP while using GPS dual-frequency observations only. In recent years, many researches have been done to solve this problem. One of the approaches is smooth pseudo-range by carrier-phase observations to improve pseudo-range accuracy. By which can improve PPP initial position accuracy and shorten PPP convergence time. Another sachems is to change position dilution of precision (PDOP) with multi-GNSS observations. Now, BDS has the ability to service whole Asian-Pacific regions, which make it possible to use GPS and BDS for precise positioning. In addition, according to researches on GNSS PDOP distribution, BDS can improve PDOP obviously. Therefore, it necessary to do some researches on PPP performance using both GPS observations and BDS observations, especially in Asian-Pacific regions currently. In this paper, we focus on the influences of BDS to GPS PPP mainly in three terms including BDS PPP accuracy, PDOP improvement and convergence time of PPP based on GPS and BDS observations. Here, the GPS and BDS two-constellation data are collected from

  7. Networked differential GPS system

    NASA Technical Reports Server (NTRS)

    Mueller, K. Tysen (Inventor); Loomis, Peter V. W. (Inventor); Kalafus, Rudolph M. (Inventor); Sheynblat, Leonid (Inventor)

    1994-01-01

    An embodiment of the present invention relates to a worldwide network of differential GPS reference stations (NDGPS) that continually track the entire GPS satellite constellation and provide interpolations of reference station corrections tailored for particular user locations between the reference stations Each reference station takes real-time ionospheric measurements with codeless cross-correlating dual-frequency carrier GPS receivers and computes real-time orbit ephemerides independently. An absolute pseudorange correction (PRC) is defined for each satellite as a function of a particular user's location. A map of the function is constructed, with iso-PRC contours. The network measures the PRCs at a few points, so-called reference stations and constructs an iso-PRC map for each satellite. Corrections are interpolated for each user's site on a subscription basis. The data bandwidths are kept to a minimum by transmitting information that cannot be obtained directly by the user and by updating information by classes and according to how quickly each class of data goes stale given the realities of the GPS system. Sub-decimeter-level kinematic accuracy over a given area is accomplished by establishing a mini-fiducial network.

  8. GPS and Glonass Combined Static Precise Point Positioning (ppp)

    NASA Astrophysics Data System (ADS)

    Pandey, D.; Dwivedi, R.; Dikshit, O.; Singh, A. K.

    2016-06-01

    With the rapid development of multi-constellation Global Navigation Satellite Systems (GNSSs), satellite navigation is undergoing drastic changes. Presently, more than 70 satellites are already available and nearly 120 more satellites will be available in the coming years after the achievement of complete constellation for all four systems- GPS, GLONASS, Galileo and BeiDou. The significant improvement in terms of satellite visibility, spatial geometry, dilution of precision and accuracy demands the utilization of combining multi-GNSS for Precise Point Positioning (PPP), especially in constrained environments. Currently, PPP is performed based on the processing of only GPS observations. Static and kinematic PPP solutions based on the processing of only GPS observations is limited by the satellite visibility, which is often insufficient for the mountainous and open pit mines areas. One of the easiest options available to enhance the positioning reliability is to integrate GPS and GLONASS observations. This research investigates the efficacy of combining GPS and GLONASS observations for achieving static PPP solution and its sensitivity to different processing methodology. Two static PPP solutions, namely standalone GPS and combined GPS-GLONASS solutions are compared. The datasets are processed using the open source GNSS processing environment gLAB 2.2.7 as well as magicGNSS software package. The results reveal that the addition of GLONASS observations improves the static positioning accuracy in comparison with the standalone GPS point positioning. Further, results show that there is an improvement in the three dimensional positioning accuracy. It is also shown that the addition of GLONASS constellation improves the total number of visible satellites by more than 60% which leads to the improvement of satellite geometry represented by Position Dilution of Precision (PDOP) by more than 30%.

  9. Determination of locational error associated with global positioning system (GPS) radio collars in relation to vegetation and topography in north-central New Mexico

    SciTech Connect

    Bennett, K.; Biggs, J.; Fresquez, P.R.

    1997-02-01

    In 1996, a study was initiated to assess seasonal habitat use and movement patterns of Rocky Mountain elk (Cervus elaphus nelsoni) using global positioning system (GPS) radio collars. As part of this study, the authors attempted to assess the accuracies of GPS (non-differentially corrected) positions under various vegetation canopies and terrain conditions with the use of a GPS ``test`` collar. The test collar was activated every twenty minutes to obtain a position location and continuously uplinked to Argos satellites to transfer position data files. They used a Telonics, Inc. uplink receiver to intercept the transmission and view the results of the collar in real time. They placed the collar on a stand equivalent to the neck height of an adult elk and then placed the stand within three different treatment categories: (1) topographical influence (canyon and mesa tops), (2) canopy influence (open and closed canopy), and (3) vegetation type influence (ponderosa pine and pinion pine-juniper). The collar was kept at each location for one hour (usually obtaining three fixes). In addition, the authors used a hand-held GPS to obtain a position of the test collar at the same time and location.

  10. 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).

  11. GPS (Grammar Positioning System)

    ERIC Educational Resources Information Center

    Blaauw-Hara, Mark; Anderson, Andy

    2007-01-01

    In this Cross Talk, Mark Blaauw-Hara, the author of "Mapping the Frontier: A Survey of Twenty Years of Grammar Articles in 'TETYC,'" and one of the manuscript's reviewers, Andy Anderson, engage in a brief conversation about the essay, its content, and the processes of writing, reviewing, and revising. This article is presented in three sections:…

  12. Using GPS To Teach More Than Accurate Positions.

    ERIC Educational Resources Information Center

    Johnson, Marie C.; Guth, Peter L.

    2002-01-01

    Undergraduate science majors need practice in critical thinking, quantitative analysis, and judging whether their calculated answers are physically reasonable. Develops exercises using handheld Global Positioning System (GPS) receivers. Reinforces students' abilities to think quantitatively, make realistic "back of the envelope" assumptions, and…

  13. Compensating user position for GPS ephemeris error

    NASA Technical Reports Server (NTRS)

    Wu, J. T.

    1990-01-01

    A method for canceling the effect of GPS ephemeris error on user position is proposed. In this method, the baseline vectors from the reference stations to the user are estimated without adjusting the GPS ephemeris. The user position is computed by adjustment using differenced data from the user and each station separately and averaging the results with weights inversely proportional to the lengths of the baselines. Alternatively, the differenced data can be averaged in a similar manner before the user position is estimated. The averaging procedure cancels most of the ephemeris error because the error is proportional to the length of the baseline. A numerical simulation is performed to demonstrate and evaluate the method. Two reference stations with perfectly known locations are assumed to be placed several hundred kilometers apart. A user receiver with a poorly known location is located between the stations. The user positions are first estimated separately using data from the user and each station and then averaged. The averaging reduces the error by about one order of magnitude.

  14. 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

  15. GPS

    NASA Technical Reports Server (NTRS)

    Webb, Frank H.

    2006-01-01

    Geodetic networks support the TRF requirements of NASA ESE missions. Each of SLR, VLBI, GPS substantially and uniquely contributes to TRF determination. NASA's SLR, VLBI, and GPS groups collaborate toward wide-ranging improvements in the next 5 years. NASA leverages considerable resources through its significant activity in international services. NASA faces certain challenges in continuing and advancing these activities. The Terrestrial Reference Frame (TRF) is an accurate, stable set of positions and velocities. The TRF provides the stable coordinate system that allows us to link measurements over space and time. The geodetic networks provide data for determination of the TRF as well as direct science observations.

  16. Precise Positioning of Ships for Maritime Disasters Prevention Using GPS

    NASA Astrophysics Data System (ADS)

    Ha, J.; Heo, M.; Chun, S.; Park, S.; Cho, D.

    2010-12-01

    Most ships use the marine DGPS (Differential Global Positioning System) service to know position information in the sea. In Korea, the Ministry of Land Transport and Maritime Affairs (MLTM) provides the nationwide DGPS (NDGPS) service to users trying to secure the safety of traffic of ships. The precision of ship position information obtained by the MLTM NDGPS system is about 1-2m. When ships pass through courses under bridges, ship collisions can occur with the bridges because of the few meter-level precision of position information. In this study, as a feasibility test, we estimated positions of ships at sea to predict the collisions between ships and bridges using DGPS, carrier phase DGPS (CDGPS), and precise point positioning (PPP) techniques were used. We conducted ship borne GPS observations in the south sea of Korea. To process the GPS data, GIPSY-OASIS (GPS Inferred Positioning System-Orbit Analysis and Simulation Software) developed by the Jet Propulsion Laboratory and CDGPS MATLAB program developed by Korea Space Research Institute were used. Antenna phase center variations, ocean tidal loading displacements, and azimuthal gradients of the atmosphere were corrected or estimated as standard procedures of high-precision GIPSY-OASIS data processing. As a result, the position precision decreased to decimeter-level with increasing the quantity of motion such as velocity, pitch and roll of the ship and buoys.

  17. Improvements in Accurate GPS Positioning Using Time Series Analysis

    NASA Astrophysics Data System (ADS)

    Koyama, Yuichiro; Tanaka, Toshiyuki

    Although the Global Positioning System (GPS) is used widely in car navigation systems, cell phones, surveying, and other areas, several issues still exist. We focus on the continuous data received in public use of GPS, and propose a new positioning algorithm that uses time series analysis. By fitting an autoregressive model to the time series model of the pseudorange, we propose an appropriate state-space model. We apply the Kalman filter to the state-space model and use the pseudorange estimated by the filter in our positioning calculations. The results of the authors' positioning experiment show that the accuracy of the proposed method is much better than that of the standard method. In addition, as we can obtain valid values estimated by time series analysis using the state-space model, the proposed state-space model can be applied to several other fields.

  18. Architecture and performance of a new GPS time transfer and positioning receiver

    NASA Technical Reports Server (NTRS)

    Kido, T. I.; Ould, P. C.; Vanwechel, R. J.

    1983-01-01

    This paper describes the Interstate Electronics 4200 GPS Receiver System that has been developed for time transfer and low dynamic positioning applications. The receiver employs the NAVSTAR Global Positioning System (GPS) l sub 1 C/A code and has three optional solution modes fo the clock/navigation state estimation.

  19. The Effects of L2C Signal Tracking on High-Precision Carrier Phase GPS Positioning: Implications for the Next Generation of GNSS Systems

    NASA Astrophysics Data System (ADS)

    Blume, F.; Berglund, H.; Estey, L.

    2012-12-01

    In December 2005, the L2C signal was introduced to improve the accuracy, tracking and redundancy of the GPS system for civilian users. The L2C signal also provides improved SNR data when compared with the L2P(Y) legacy signal. However, GNSS network operators have been hesitant to use the new signal as it is not well determined how positions derived from L2 carrier phase measurements are affected. L2C carrier phase is in quadrature with L2P(Y); some manufacturers correct for this when logging L2C phase while others do not. In cases where both L2C and L2P(Y) are logged simultaneously, translation software must be used carefully in order to select which phase is used in positioning. Modifications were made to UNAVCO's teqc pre-processing software to eliminate confusion, however GNSS networks such as the IGS still suffer occasional data loss due to improperly configured GPS receivers or data flow routines. To date L2C analyses have been restricted to special applications such as snow depth and soil moisture using SNR data, as some high-precision data analysis packages are not compatible with L2C. We use several different methods to determine the effect that tracking and logging L2C has on carrier phase measurements and positioning for various receiver models and configurations. Twenty-four hour zero-length baseline solutions using L2 show sub- millimeter differences in mean positions for both horizontal and vertical components. Direct comparisons of the L2 phase observable from RINEX files with and without the L2C observable show sub-millicycle differences. The magnitude of the variations increased at low elevations. The behavior of the L2P(Y) phase observations or positions from a given receiver were not affected by the enabling of L2C tracking. We find that the use of the L2C-derived carrier phase in real-time applications can be disastrous in cases where receiver brands are mixed between those that correct for quadrature and those that do not (Figure 1). Until

  20. 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

  1. Airborne GPS kinematic positioning and its application to oceanographic mapping

    NASA Astrophysics Data System (ADS)

    Han, Shaowei; Rizos, Chris

    2000-10-01

    Precise, long-range, airborne GPS kinematic positioning requires the use of carrier phase measurements, the data processing of which suffers from the technical challenges of "on-the-fly" ambiguity resolution and cycle slip repair. In this paper the authors describe how the combination of an `ambiguity recovery' technique and a `linear bias correction' method has been used to support oceanographic mapping in Australian waters, together with the augmentation from the Laser Airborne Depth Sounder (LADS) system. Two experiments, carried out on the 4th December 1997 in the Torres Strait between Papua New Guinea and Australia, and on the 20 May 1998 at Lake Argyle in Australia, were analysed. The results indicate that the topography of the water surface can be obtained with sub-decimetre accuracy, with a spatial resolution of a few metres. The main errors are attributable to multipath interference of the GPS signals at the antennas from the aircraft surface.

  2. 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.

  3. GPS-based certification for the microwave landing system

    NASA Technical Reports Server (NTRS)

    Thornton, C. L.; Young, L. E.; Wu, S. C.; Thomas, J. B.

    1984-01-01

    An MLS (microwave landing system) certification system based on the Global Positioning System (GPS) is described. To determine the position history of the flight inspection aircraft during runway approach, signals from the GPS satellites, together with on-board radar altimetry, are used. It is shown that the aircraft position relative to a fixed point on the runway at threshold can be determined to about 30 cm vertically and 1 m horizontally. A requirement of the system is that the GPS receivers be placed on each flight inspection aircraft and at selected ground sites. The effects of different error sources on the determination of aircraft instantaneous position and its dynamics are analyzed.

  4. A Lane-Level LBS System for Vehicle Network with High-Precision BDS/GPS Positioning

    PubMed Central

    Guo, Chi; Guo, Wenfei; Cao, Guangyi; Dong, Hongbo

    2015-01-01

    In recent years, research on vehicle network location service has begun to focus on its intelligence and precision. The accuracy of space-time information has become a core factor for vehicle network systems in a mobile environment. However, difficulties persist in vehicle satellite positioning since deficiencies in the provision of high-quality space-time references greatly limit the development and application of vehicle networks. In this paper, we propose a high-precision-based vehicle network location service to solve this problem. The major components of this study include the following: (1) application of wide-area precise positioning technology to the vehicle network system. An adaptive correction message broadcast protocol is designed to satisfy the requirements for large-scale target precise positioning in the mobile Internet environment; (2) development of a concurrence service system with a flexible virtual expansion architecture to guarantee reliable data interaction between vehicles and the background; (3) verification of the positioning precision and service quality in the urban environment. Based on this high-precision positioning service platform, a lane-level location service is designed to solve a typical traffic safety problem. PMID:25755665

  5. A lane-level LBS system for vehicle network with high-precision BDS/GPS positioning.

    PubMed

    Guo, Chi; Guo, Wenfei; Cao, Guangyi; Dong, Hongbo

    2015-01-01

    In recent years, research on vehicle network location service has begun to focus on its intelligence and precision. The accuracy of space-time information has become a core factor for vehicle network systems in a mobile environment. However, difficulties persist in vehicle satellite positioning since deficiencies in the provision of high-quality space-time references greatly limit the development and application of vehicle networks. In this paper, we propose a high-precision-based vehicle network location service to solve this problem. The major components of this study include the following: (1) application of wide-area precise positioning technology to the vehicle network system. An adaptive correction message broadcast protocol is designed to satisfy the requirements for large-scale target precise positioning in the mobile Internet environment; (2) development of a concurrence service system with a flexible virtual expansion architecture to guarantee reliable data interaction between vehicles and the background; (3) verification of the positioning precision and service quality in the urban environment. Based on this high-precision positioning service platform, a lane-level location service is designed to solve a typical traffic safety problem. PMID:25755665

  6. 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.

  7. 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.

  8. Characteristics of atmospheric gravity waves observed using the MU (Middle and Upper atmosphere) radar and GPS (Global Positioning System) radio occultation

    PubMed Central

    TSUDA, Toshitaka

    2014-01-01

    The wind velocity and temperature profiles observed in the middle atmosphere (altitude: 10–100 km) show perturbations resulting from superposition of various atmospheric waves, including atmospheric gravity waves. Atmospheric gravity waves are known to play an important role in determining the general circulation in the middle atmosphere by dynamical stresses caused by gravity wave breaking. In this paper, we summarize the characteristics of atmospheric gravity waves observed using the middle and upper atmosphere (MU) radar in Japan, as well as novel satellite data obtained from global positioning system radio occultation (GPS RO) measurements. In particular, we focus on the behavior of gravity waves in the mesosphere (50–90 km), where considerable gravity wave attenuation occurs. We also report on the global distribution of gravity wave activity in the stratosphere (10–50 km), highlighting various excitation mechanisms such as orographic effects, convection in the tropics, meteorological disturbances, the subtropical jet and the polar night jet. PMID:24492645

  9. Characteristics of atmospheric gravity waves observed using the MU (Middle and Upper atmosphere) radar and GPS (Global Positioning System) radio occultation.

    PubMed

    Tsuda, Toshitaka

    2014-01-01

    The wind velocity and temperature profiles observed in the middle atmosphere (altitude: 10-100 km) show perturbations resulting from superposition of various atmospheric waves, including atmospheric gravity waves. Atmospheric gravity waves are known to play an important role in determining the general circulation in the middle atmosphere by dynamical stresses caused by gravity wave breaking. In this paper, we summarize the characteristics of atmospheric gravity waves observed using the middle and upper atmosphere (MU) radar in Japan, as well as novel satellite data obtained from global positioning system radio occultation (GPS RO) measurements. In particular, we focus on the behavior of gravity waves in the mesosphere (50-90 km), where considerable gravity wave attenuation occurs. We also report on the global distribution of gravity wave activity in the stratosphere (10-50 km), highlighting various excitation mechanisms such as orographic effects, convection in the tropics, meteorological disturbances, the subtropical jet and the polar night jet. PMID:24492645

  10. Ambiguity resolved precise point positioning with GPS and BeiDou

    NASA Astrophysics Data System (ADS)

    Pan, Li; Xiaohong, Zhang; Fei, Guo

    2016-07-01

    This paper focuses on the contribution of the global positioning system (GPS) and BeiDou navigation satellite system (BDS) observations to precise point positioning (PPP) ambiguity resolution (AR). A GPS + BDS fractional cycle bias (FCB) estimation method and a PPP AR model were developed using integrated GPS and BDS observations. For FCB estimation, the GPS + BDS combined PPP float solutions of the globally distributed IGS MGEX were first performed. When integrating GPS observations, the BDS ambiguities can be precisely estimated with less than four tracked BDS satellites. The FCBs of both GPS and BDS satellites can then be estimated from these precise ambiguities. For the GPS + BDS combined AR, one GPS and one BDS IGSO or MEO satellite were first chosen as the reference satellite for GPS and BDS, respectively, to form inner-system single-differenced ambiguities. The single-differenced GPS and BDS ambiguities were then fused by partial ambiguity resolution to increase the possibility of fixing a subset of decorrelated ambiguities with high confidence. To verify the correctness of the FCB estimation and the effectiveness of the GPS + BDS PPP AR, data recorded from about 75 IGS MGEX stations during the period of DOY 123-151 (May 3 to May 31) in 2015 were used for validation. Data were processed with three strategies: BDS-only AR, GPS-only AR and GPS + BDS AR. Numerous experimental results show that the time to first fix (TTFF) is longer than 6 h for the BDS AR in general and that the fixing rate is usually less than 35 % for both static and kinematic PPP. An average TTFF of 21.7 min and 33.6 min together with a fixing rate of 98.6 and 97.0 % in static and kinematic PPP, respectively, can be achieved for GPS-only ambiguity fixing. For the combined GPS + BDS AR, the average TTFF can be shortened to 16.9 min and 24.6 min and the fixing rate can be increased to 99.5 and 99.0 % in static and kinematic PPP, respectively. Results also show that GPS + BDS PPP AR outperforms

  11. Navstar/Global Positioning System

    NASA Technical Reports Server (NTRS)

    Ananda, M.

    1982-01-01

    The Global Positioning System (GPS) was developed to provide highly precise position, velocity, and time information to users anywhere in the area of the Earth and at any time. The GPS, when fully operational, will consist of 18 satellites in six orbital planes. Any GPS user, by receiving and processing the radio signals from the satellite network can instantaneously determine navigation information to an accuracy of about 15 m in position and 0.1 m/s in velocity. The GPS is compared with other systems such as Loran-C, Omega, TACAN and Transit.

  12. Signal quality monitoring for GPS augmentation systems

    NASA Astrophysics Data System (ADS)

    Mitelman, Alexander Michael

    Civilian applications of the Global Positioning System have grown rapidly over the past decade. One of the most significant examples is guidance for aviation. In conjunction with specially designed equipment on the ground, GPS can provide precision approach and landing capability for aircraft. As with other safety-critical aviation applications, GPS-based landing systems must meet stringent accuracy, safety, and availability requirements set by the Federal Aviation Administration. Currently, compliance with FAA requirements is ensured by a host of monitors including the Signal Quality Monitor, a module specifically tasked with continuously observing raw GPS signals for interference and distortion. This dissertation focuses on several theoretical and practical aspects of SQM design. The discussion begins with in-depth analysis of the seminal event in SQM, a significant anomaly on GPS space vehicle 19 initially observed in 1993. At the time, a tenfold increase in vertical position error was reported when this satellite was in view. Little consensus was initially reached about the exact origin, nature, or magnitude of the distortion; this section considers these effects in detail. The analysis is then extended to compute a rigorous upper bound for differential error. Starting with the architecture of a basic landing system, a theoretical worst-case is derived that maximizes user error while defying detection by the ground station. A simplified distortion model, adopted by the International Civil Aviation Organization in response to the worst-case analysis, is also described. The discussion then describes the design and construction of an arbitrary GPS generator. Essential features include architecture, shielding, independent signal and noise levels, and fast switching between two input channels. Two example applications are presented to illustrate the instrument's utility. A theoretical analysis of the ICAO model is validated by measuring the spectra of generated

  13. 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

  14. The performance analysis of a real-time integrated INS/GPS vehicle navigation system with abnormal GPS measurement elimination.

    PubMed

    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

  15. Global positioning system missile test range applications

    SciTech Connect

    Partridge, M.E.

    1986-06-01

    Using the Global Positioning System (GPS), a missile under test could transmit its own position, reducing radar tracking requirements while still providing three-dimensional position and velocity data with the required accuracy. This study investigated minimum package size requirements for GPS implementation on the SRAM II missile as part of the joint test assembly telemetry system. Reported GPS missile test range applications are reviewed. The two missile tracking system implementations considered are a complete GPS package onboard the missile and onboard frequency translator that retransmits the GPS satellite signals. Accuracy and operation of the two methods are compared. A functional description of the GPS is provided.

  16. Improved positioning by addition of atmospheric corrections to local area differential GPS

    NASA Astrophysics Data System (ADS)

    Singh, Malkiat; Reilly, Michael H.

    2006-10-01

    A local area differential GPS (DGPS) method applies corrections from a reference GPS receiver to improve positioning accuracy for a roaming GPS receiver. Increasing separation between reference and roaming receivers dilutes this improvement, largely because ionospheric and tropospheric effects differ between their two locations. We correct differential corrections for this difference and determine the improvement with this "atmospheric" DGPS method at roaming receiver positions that are separated from a Coast Guard reference receiver at Annapolis, Maryland, by 44, 67, and 228 km. For ionospheric corrections we use our Raytrace-Ionospheric conductivity and electron density-Bent-Gallagher ionospheric propagation model with driving parameters obtained from two-frequency data of surveyed reference GPS receivers. For tropospheric corrections we use the Hopfield model and weather station data for surface temperature, pressure, and relative humidity. Internet delivery of atmospheric differential corrections is used to avoid blockage or range cutoff of radio transmissions. Some comparisons are made with Wide Area Augmentation System GPS receiver performance.

  17. DARPA looks beyond GPS for positioning, navigating, and timing

    SciTech Connect

    Kramer, David

    2014-10-01

    Cold-atom interferometry, microelectromechanical systems, signals of opportunity, and atomic clocks are some of the technologies the defense agency is pursuing to provide precise navigation when GPS is unavailable.

  18. The GPS integrated navigation and attitude-determination system (GINAS)

    NASA Astrophysics Data System (ADS)

    Lucas, R.; Martin-Neira, M.

    When the European Columbus Free-Flying Laboratory is orbiting the earth at a speed of 7 km/s, the Global Positioning System (GPS) will allow its instantaneous position to be determined on-board, independently of the ground, to an accuracy of better than 100 m. When the European spaceplane Hermes and the Columbus elements are performing rendezvous maneuvers, they will also be relying on GPS measurements to compute the remaining distance to contact. For the first flight of Hermes itself, there will be no pilot on board and GPS-based navigation will be used for this first mission and the landing. This paper describes the results of GPS field-measurement experiments conducted at ESTEC's radio-navigation testbed laboratory, including a novel 'GPS integrated navigation and attitude-determination system'.

  19. GPS and odometer data fusion for outdoor robots continuous positioning

    NASA Astrophysics Data System (ADS)

    Pozo-Ruz, Ana; Garcia-Perez, Lia; Garcia-Alegre, Maria C.; Guinea, Domingo; Ribeiro, Angela; Sandoval, Francisco

    2002-02-01

    Present work describes an approximation to obtain the best estimation of the position of the outdoor robot ROJO, a low cost lawnmower to perform unmanned precision agriculture task such are the spraying of pesticides in horticulture. For continuous location of ROJO, two redundant sensors have been installed onboard: a DGPS submetric precision model and an odometric system. DGPS system will allow an absolute positioning of the vehicle in the field, but GPS failures in the reception of the signals due to obstacles and electrical and meteorological disturbance, lead us to the integration of the odometric system. Thus, a robust odometer based upon magnetic strip sensors has been designed and integrated in the vehicle. These sensors continuosly deliver the position of the vehicle relative to its initial position, complementing the DGPS blindness periods. They give an approximated location of the vehicle in the field that can be in turn conveniently updated and corrected by the DGPS. Thus, to provided the best estimation, a fusion algorithm has been proposed and proved, wherein the best estimation is calculated as the maximum value of the join probability function obtained from both position estimation of the onboard sensors. Some results are presented to show the performance of the proposed sensor fusion technique.

  20. An investigation of airborne GPS/INS for high accuracy position and velocity determination

    SciTech Connect

    Sun, H.; Cannon, M.E.; Owen, T.E.; Meindl, M.A.

    1993-12-31

    An airborne test using a differential GPS-INS system in a Twin Otter was conducted by Sandia National Laboratories to assess the feasibility of using the integrated system for cm-level position and cm/s velocity. The INS is a miniaturized ring-laser gyro IMU jointly developed by Sandia and Honeywell while the GPS system consists of the NovAtel GPSCard{trademark}. INS position, velocity and attitude data were computed using Sandia`s SANDAC flight computer system and logged at 4 Hz and GPS data was acquired at a 1 Hz rate. The mission was approximately 2.5 hours in duration and the aircraft reached separations of up to 19 km from the base station. The data was post-processed using a centralized Kalman filter approach in which the double differenced carrier phase measurements are used to update the INS data. The INS position is in turn used to detect and correct GPS carrier phase cycle slips and also to bridge GPS outages. Results are presented for the GPS-only case and also for integrated GPS/INS.

  1. The Global Positioning System

    USGS Publications Warehouse

    U.S. Geological Survey

    1999-01-01

    The Global Positioning System (GPS) is a constellation of navigation satellites called Navigation Satellite Timing And Ranging (NAVSTAR), maintained by the U.S. Department of Defense. Many outdoor enthusiasts recognize that a handheld GPS receiver can be an accurate tool for determining their location on the terrain. The GPS receiver helps determine locations on the Earth's surface by collecting signals from three or more satellites through a process called triangulation. Identifying a location on the Earth is more useful if you also know about the surrounding topographic conditions. Using a topographic map with the GPS receiver provides important information about features of the surrounding terrain and can help you plot an effective route from one location to another.

  2. Seasonal GPS Positioning Errors due to Water Content Variations in Atmosphere

    NASA Astrophysics Data System (ADS)

    Tian, Y.

    2013-12-01

    There are still non-tectonic signals, e.g. the seasonal variations and common-mode errors (CME), in Global Positioning System (GPS) positioning results derived using the state-of-the-art software and models, which blurs the detection of transient events. Previous studies had shown that there are also seasonal variations in the GPS positioning accuracy, i.e., the scattering degree of GPS positions in the summer is larger than that in the winter for some regional networks. In this work, a consistent reprocessing of historical data for global GPS stations is done to confirm the existence of such variations and figure out its spatial characteristics at the global scale. It is found that GPS stations in the north hemisphere have larger positioning error in the summer than in the winter; and contrarily the south hemisphere stations have larger errors in the winter than in the summer. Results for several typical stations are shown in Fig. 1. After excluding several possible origins of this phenomenon, it is found that the variation of precipitable water vapor (PWV) content in the atmosphere is highly correlated with this kind of seasonal positioning errors of GPS (Fig. 2). Although it currently cannot be validated that the GPS positioning accuracy will increase by eliminating PWV effect thoroughly in the rainy days during the GPS observation data processing step, it is most likely that this phenomenon is caused by the water vapor content in the troposphere. The solving of this problem will surely enhance our ability to detect weak transient signals that are blurred in the continuous GPS positions. Fig. 1 Position time series deprived of CME for BJFS (left), HRAO (middle), and WTZR (right). BJFS and WTZR are located in the north hemisphere where positions are much scattered in the summer; the situation is the contrary at HRAO which is seated in the south hemisphere. Fig. 2 GPS positioning errors (represented here by the one-way postfit residuals (OWPR) from GAMIT solution

  3. A novel fusion methodology to bridge GPS outages for land vehicle positioning

    NASA Astrophysics Data System (ADS)

    Chen, Wei; Li, Xu; Song, Xiang; Li, Bin; Song, Xianghui; Xu, Qimin

    2015-07-01

    Many intelligent transportation system applications require accurate, reliable, and continuous vehicle position information whether in open-sky environments or in Global Positioning System (GPS) denied environments. However, there remains a challenging task for land vehicles to achieve such positioning performance using low-cost sensors, especially microelectromechanical system (MEMS) sensors. In this paper, a novel and cost-effective fusion methodology to bridge GPS outages is proposed and applied in the Inertial Navigation System (INS)/GPS/ compass integrated positioning system. In the implementation of the proposed methodology, a key data preprocessing algorithm is first developed to eliminate the noise in inertial sensors in order to provide more accurate information for subsequent modeling. Then, a novel hybrid strategy incorporating the designed autoregressive model (AR model)-based forward estimator (ARFE) with Kalman filter (KF) is presented to predict the INS position errors during GPS outages. To verify the feasibility and effectiveness of the proposed methodology, real road tests with various scenarios were performed. The proposed methodology illustrates significant improvement in positioning accuracy during GPS outages.

  4. Fault tolerant GPS/Inertial System design

    NASA Astrophysics Data System (ADS)

    Brown, Alison K.; Sturza, Mark A.; Deangelis, Franco; Lukaszewski, David A.

    The use of a GPS/Inertial integrated system in future launch vehicles motivates the described design of the present fault-tolerant system. The robustness of the navigation system is enhanced by integrating the GPS with an inertial fault-tolerant system. Three layers of failure detection and isolation are incorporated to determine the nature of flaws in the inertial instruments, the GPS receivers, or the integrated navigation solution. The layers are based on: (1) a high-rate parity algorithm for instrument failures; (2) a similar parity algorithm for GPS satellite or receiver failures; and (3) a GPS navigation solution to monitor inertial navigation failures. Dual failures of any system component can occur in any system component without affecting the performance of launch-vehicle navigation or guidance.

  5. Impact of Ionization DEPLETIONS/TEC Bite-Outs of Equatorial Plasma Structures on Transionospheric Satellite Signals Using Global Positioning System (GPS)

    NASA Astrophysics Data System (ADS)

    Das, Tanmay

    2016-07-01

    This paper represents the impact of ionization depletions/TEC bite-outs of equatorial plasma structures on transionospheric satellite signals received from Calcutta (latitude: 22.58oN, longitude: 88.38oE geographic; 32oN magnetic dip) is situated near the northern crest of the equatorial ionization anomaly (EIA) in the Indian longitude sector, using Global Positioning System (GPS) during the equinoctial months of February-April 2011, August-October, 2011 and February-April 2012. It is observed that when a bubble moves across a satellite link, scintillations and ionization are usually encountered. The apparent duration of the bite-outs may be different from the true east-west duration, as observed with geostationary links, because of the presence of a relative velocity between the irregularity cloud and the satellite. The trajectory of a GPS satellite plays a vital role in observing the bubble characteristics. The distributions of amplitude and the parameters characterizing the ionization depletions, namely, the duration, depth and the leading and trailing edge slopes of the bubbles have been obtained during the same equinoctial months of 2011 and 2012. It is evident that the range error, extent of the bubble and ionization gradients measured in these equinoctial months of the equatorial region provides the worst case figures for system designers. The high range error (~ 3-4 m) is observed during these equinoctial months. The statistical distribution of the TEC depletions showed some significant results. Out of 29 bite-outs in February-April, 2011 equinox, the maximum amplitude was found to be about 23.25 TECU with a median depletion of about 5.92 TECU. The maximum amplitude corresponds to a range error of about 3.7 m at GPS L1 frequency. The majority of the bubbles were found to have observed duration between 10-20 minutes with a maximum of 28.14 minutes. The median value of actual duration 2.37 minutes translates to nearly 150sec of possible satellite signal

  6. Performance of Taiwan Ionospheric Model (TWIM) in Single-Frequency Differential GPS Positioning

    NASA Astrophysics Data System (ADS)

    Macalalad, Ernest; Chih Tsai, Lung; Wu, Joz; Liu, Chao Han

    2014-05-01

    Differential Global Positioning System (DGPS) is one of the common techniques using GPS positioning. One of its main advantages is the removal of clock biases of GPS satellites which greatly improves position accuracy. With this, only differential atmospheric (ionospheric and tropospheric) errors, receiver clock biases and measurement noise mainly remain and can be removed using various models. This study focuses on the differential ionospheric delay and the effect of its correction to DGPS positioning. Being the major source of error in GPS L1 pseudorange, this ionospheric delay is determined using a three-dimensional phenomenological ionospheric model called the TaiWan Ionospheric Model (TWIM). TWIM is derived from GPS radio occultation measurements of the Formosat3/COSMIC program. This error is removed from the pseudorange observations, which is then used to perform single-difference DGPS positioning. A network of 10 GPS receivers across Taiwan is used as both test and reference receivers in doing the differential positioning. The network has a maximum horizontal baseline of 400 km. It has been shown that TWIM can provide sub-meter positioning and can provide better positioning than other models such as Klobuchar and GIM. TWIM can also reduce the dependence of positioning accuracy to baseline length and solar flux for a 24-hour survey.

  7. Assessing the role of GPs in Nordic health care systems.

    PubMed

    Quaye, Randolph K

    2016-05-01

    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. PMID:27198702

  8. Combined GPS + BDS for short to long baseline RTK positioning

    NASA Astrophysics Data System (ADS)

    Odolinski, R.; Teunissen, P. J. G.; Odijk, D.

    2015-04-01

    The BeiDou Navigation Satellite System (BDS) has become fully operational in the Asia-Pacific region and it is of importance to evaluate what BDS brings when combined with the Global Positioning System (GPS). In this contribution we will look at the short, medium and long single-baseline real-time kinematic (RTK) positioning performance. Short baseline refers to when the distance between the two receivers is at most a few kilometers so that the relative slant ionospheric and tropospheric delays can be assumed absent, whereas with medium baseline we refer to when the uncertainty of these ionospheric delays can reliably be modeled as a function of the baseline length. With long baseline we refer to the necessity to parameterize the ionospheric delays and (wet) Zenith Tropospheric Delay (ZTD) as completely unknown. The GNSS real data are collected in Perth, Australia. It will be shown that combining the two systems allows for the use of higher than customary elevation cut-off angles. This can be of particular benefit in environments with restricted satellite visibility such as in open pit mines or urban canyons.

  9. A Demonstration of GPS Landslide Monitoring Using Online Positioning User Service (OPUS)

    NASA Astrophysics Data System (ADS)

    Wang, G.

    2011-12-01

    Global Positioning System (GPS) technologies have been frequently applied to landslide study, both as a complement, and as an alternative to conventional surveying methods. However, most applications of GPS for landslide monitoring have been limited to the academic community for research purposes. High-accuracy GPS has not been widely equipped in geotechnical companies and used by technicians. The main issue that limits the applications of GPS in the practice of high-accuracy landslide monitoring is the complexity of GPS data processing. This study demonstrated an approach using the Online Positioning User Service (OPUS) (http://www.ngs.noaa.gov/OPUS) provided by the National Geodetic Survey (NGS) of National Oceanic and Atmospheric Administration (NOAA) to process GPS data and conduct long-term landslide monitoring in the Puerto Rico and Virgin Islands Region. Continuous GPS data collected at a creeping landslide site during two years were used to evaluate different scenarios for landslide surveying: continuous or campaign, long duration or short duration, morning or afternoon (different weather conditions). OPUS uses Continuously Operating Reference Station (CORS) managed by NGS (http://www.ngs.noaa.giv/CORS/) as references and user data as a rover to solve a position. There are 19 CORS permanent GPS stations in the Puerto Rico and Virgin Islands region. The dense GPS network provides a precise and reliable reference frame for subcentimeter-accuracy landslide monitoring in this region. Our criterion for the accuracy was the root-mean-square (RMS) of OPUS solutions over a 2-year period with respect to true landslide displacement time series overt the same period. The true landslide displacements were derived from a single-baseline (130 m) GPS processing by using 24-hour continuous data. If continuous GPS surveying is performed in the field, then OPUS static processing can provide 0.6 cm horizontal and 1.1 cm vertical precision with few outliers. If repeated

  10. Solar system positioning system

    NASA Technical Reports Server (NTRS)

    Penanen, Konstantin I.; Chui, Talso

    2006-01-01

    Power-rich spacecraft envisioned in Prometheus initiative open up possibilities for long-range high-rate communication. A constellation of spacecraft on orbits several A.U. from the Sun, equipped with laser transponders and precise clocks can be configured to measure their mutual distances to within few cm. High on-board power can create substantial non-inertial contribution to the spacecraft trajectory. We propose to alleviate this contribution by employing secondary ranging to a passive daughter spacecraft. Such constellation can form the basis of it navigation system capable of providing position information anywhere in the soIar system with similar accuracy. Apart from obvious Solar System exploration implications, this system can provide robust reference for GPS and its successors.

  11. Precise point positioning with quad-constellations: GPS, BeiDou, GLONASS and Galileo

    NASA Astrophysics Data System (ADS)

    Cai, Changsheng; Gao, Yang; Pan, Lin; Zhu, Jianjun

    2015-07-01

    Multi-constellation GNSS precise point positioning (PPP) first became feasible back to 2007 but with only two constellations, namely GPS and GLONASS. With the availability of more satellites and precise orbit and clock products from BeiDou and Galileo, it is possible now to investigate PPP with four constellations, namely GPS, BeiDou, GLONASS and Galileo. This research aims at investigating the quad-constellation PPP for position determination and analyzing its positioning performance. A quad-constellation PPP model is developed to simultaneously process the observations from all the four GNSS systems. The developed model is also applicable to the PPP processing with observations from single, dual or triple constellations. The analysis on PPP accuracy and convergence time is conducted based on data processing results from both static and kinematic tests of single-constellation and multi-constellations. The three-hour static positioning results indicate that the BeiDou-only PPP accuracy is worse than the GPS-only PPP. The RMSs of position errors for BeiDou-only PPP are 5.2 cm, 2.7 cm and 8.3 cm in east, north and up directions while the ones for GPS-only PPP are 3.9 cm, 1.6 cm and 5.7 cm. The GPS/BeiDou PPP improves the positioning accuracy by 28%, 6% and 7% and reduces the convergence time by 26%, 13% and 14% over the GPS-only PPP in three coordinate components, respectively. The GPS/GLONASS PPP achieves slightly better performance than the GPS/BeiDou PPP. The triple-constellation PPP further increases the positioning accuracy and decreases the convergence time over the dual-constellation PPP. The improvement of positioning performance is not significant after adding Galileo due to currently limited number of satellites. Similar to the static positioning, the quad-constellation kinematic PPP also significantly improves the positioning performance in contrast with single-constellation and dual-constellations. The time varying characteristics of the time differences

  12. Modeling and Assessment of GPS/BDS Combined Precise Point Positioning.

    PubMed

    Chen, Junping; Wang, Jungang; Zhang, Yize; Yang, Sainan; Chen, Qian; Gong, Xiuqiang

    2016-01-01

    Precise Point Positioning (PPP) technique enables stand-alone receivers to obtain cm-level positioning accuracy. Observations from multi-GNSS systems can augment users with improved positioning accuracy, reliability and availability. In this paper, we present and evaluate the GPS/BDS combined PPP models, including the traditional model and a simplified model, where the inter-system bias (ISB) is treated in different way. To evaluate the performance of combined GPS/BDS PPP, kinematic and static PPP positions are compared to the IGS daily estimates, where 1 month GPS/BDS data of 11 IGS Multi-GNSS Experiment (MGEX) stations are used. The results indicate apparent improvement of GPS/BDS combined PPP solutions in both static and kinematic cases, where much smaller standard deviations are presented in the magnitude distribution of coordinates RMS statistics. Comparisons between the traditional and simplified combined PPP models show no difference in coordinate estimations, and the inter system biases between the GPS/BDS system are assimilated into receiver clock, ambiguities and pseudo-range residuals accordingly. PMID:27455278

  13. Modeling and Assessment of GPS/BDS Combined Precise Point Positioning

    PubMed Central

    Chen, Junping; Wang, Jungang; Zhang, Yize; Yang, Sainan; Chen, Qian; Gong, Xiuqiang

    2016-01-01

    Precise Point Positioning (PPP) technique enables stand-alone receivers to obtain cm-level positioning accuracy. Observations from multi-GNSS systems can augment users with improved positioning accuracy, reliability and availability. In this paper, we present and evaluate the GPS/BDS combined PPP models, including the traditional model and a simplified model, where the inter-system bias (ISB) is treated in different way. To evaluate the performance of combined GPS/BDS PPP, kinematic and static PPP positions are compared to the IGS daily estimates, where 1 month GPS/BDS data of 11 IGS Multi-GNSS Experiment (MGEX) stations are used. The results indicate apparent improvement of GPS/BDS combined PPP solutions in both static and kinematic cases, where much smaller standard deviations are presented in the magnitude distribution of coordinates RMS statistics. Comparisons between the traditional and simplified combined PPP models show no difference in coordinate estimations, and the inter system biases between the GPS/BDS system are assimilated into receiver clock, ambiguities and pseudo-range residuals accordingly. PMID:27455278

  14. 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.

  15. GPS & GLONASS mass-market receivers: positioning performances and peculiarities.

    PubMed

    Dabove, Paolo; Manzino, Ambrogio M

    2014-01-01

    Over the last twenty years, positioning with low cost Global Navigation Satellite System (GNSS) sensors have rapidly developed around the world at both a commercial and academic research level. For many years these instruments have only acquired the GPS constellation but are now able to track the Global'naja Navigacionnaja Sputnikovaja Sistema (GLONASS) constellation. This characteristic is very interesting, especially if used in hard-urban environments or in hard conditions where satellite visibility is low. The goal of this research is to investigate the contribution of the GLONASS constellation for mass-market receivers in order to analyse the performance in real time (Network Real Time Kinematic-NRTK positioning) with post-processing approaches. Under these conditions, it is possible to confirm that mass-market sensors could be a valid alternative to a more expensive receiver for a large number of surveying applications, but with low cost hardware the contribution of the GLONASS constellation for fixing ambiguities is useless, if not dangerous. PMID:25429405

  16. GPS & GLONASS Mass-Market Receivers: Positioning Performances and Peculiarities

    PubMed Central

    Dabove, Paolo; Manzino, Ambrogio M.

    2014-01-01

    Over the last twenty years, positioning with low cost Global Navigation Satellite System (GNSS) sensors have rapidly developed around the world at both a commercial and academic research level. For many years these instruments have only acquired the GPS constellation but are now able to track the Global’naja Navigacionnaja Sputnikovaja Sistema (GLONASS) constellation. This characteristic is very interesting, especially if used in hard-urban environments or in hard conditions where satellite visibility is low. The goal of this research is to investigate the contribution of the GLONASS constellation for mass-market receivers in order to analyse the performance in real time (Network Real Time Kinematic—NRTK positioning) with post-processing approaches. Under these conditions, it is possible to confirm that mass-market sensors could be a valid alternative to a more expensive receiver for a large number of surveying applications, but with low cost hardware the contribution of the GLONASS constellation for fixing ambiguities is useless, if not dangerous. PMID:25429405

  17. 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

  18. Real Time GPS Positioning and Data Transmission For Rescue Services

    NASA Astrophysics Data System (ADS)

    Cefalo, R.; Degrassi, F.; Manzoni, G.; Moro, A.; Martinolli, S.; Pagurut, R.; Piemonte, A.; Sluga, T.

    Real time differential and interferential kinematic GPS positioning are under test for accurate rescue services by using DARC radio data transmission for RTCM messages from a reference station to the users and by SMS via GSM or GLOBALSTAR from the users to a control centre. EGNOS is under test too. The results of several experi- ments are shown. Problems, advantages and possible improvements with map on line availability and updating are discussed.

  19. 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

  20. A Kalman filter implementation for precision improvement in low-cost GPS positioning of tractors.

    PubMed

    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

  1. Precise Point Positioning for the Efficient and Robust Analysis of GPS Data from Large Networks

    NASA Technical Reports Server (NTRS)

    Zumberge, J. F.; Heflin, M. B.; Jefferson, D. C.; Watkins, M. M.; Webb, F. H.

    1997-01-01

    Networks of dozens to hundreds of permanently operating precision Global Positioning System (GPS) receivers are emerging at spatial scales that range from 10(exp 0) to 10(exp 3) km. To keep the computational burden associated with the analysis of such data economically feasible, one approach is to first determine precise GPS satellite positions and clock corrections from a globally distributed network of GPS receivers. Their, data from the local network are analyzed by estimating receiver- specific parameters with receiver-specific data satellite parameters are held fixed at their values determined in the global solution. This "precise point positioning" allows analysis of data from hundreds to thousands of sites every (lay with 40-Mflop computers, with results comparable in quality to the simultaneous analysis of all data. The reference frames for the global and network solutions can be free of distortion imposed by erroneous fiducial constraints on any sites.

  2. Precise Point Positioning for the Efficient and Robust Analysis of GPS Data From Large Networks

    NASA Technical Reports Server (NTRS)

    Zumberge, J. F.; Heflin, M. B.; Jefferson, D. C.; Watkins, M. M.; Webb, F. H.

    1997-01-01

    Networks of dozens to hundreds of permanently operating precision Global Positioning System (GPS) receivers are emerging at spatial scales that range from 10(exp 0) to 10(exp 3) km. To keep the computational burden associated with the analysis of such data economically feasible, one approach is to first determine precise GPS satellite positions and clock corrections from a globally distributed network of GPS receivers. Then, data from the local network are analyzed by estimating receiver specific parameters with receiver-specific data; satellite parameters are held fixed at their values determined in the global solution. This "precise point positioning" allows analysis of data from hundreds to thousands of sites every day with 40 Mflop computers, with results comparable in quality to the simultaneous analysis of all data. The reference frames for the global and network solutions can be free of distortion imposed by erroneous fiducial constraints on any sites.

  3. A New Centimeter-Level Real-Time Global Navigation and Positioning Capability with GPS

    NASA Technical Reports Server (NTRS)

    Bar-Sever, Yoaz

    2001-01-01

    NASA/JPL has developed a new, precise, global, GPS-based capability for real-time terrestrial and space platform navigation. It has been demonstrated on Earth's surface and is 10 times more accurate than other real-time GPS-based systems. The new system poses certain advantages for Earth science remote sensing, including: the onboard generation of science data products in real-time, sensor control and reduction of data transmission bandwidth, improved environmental forecasting, autonomous and intelligent platform control, operations cost savings, and technology transfer and commercial partnership opportunities. The system's measurement capabilities and applications, demonstrated orbit accuracies, and precision LEO and spacecraft positioning and timing are highlighted.

  4. Huber's M-estimation in relative GPS positioning: computational aspects

    NASA Astrophysics Data System (ADS)

    Chang, X.-W.; Guo, Y.

    2005-08-01

    When GPS signal measurements have outliers, using least squares (LS) estimation is likely to give poor position estimates. One of the typical approaches to handle this problem is to use robust estimation techniques. We study the computational issues of Huber’s M-estimation applied to relative GPS positioning. First for code-based relative positioning, we use simulation results to show that Newton’s method usually converges faster than the iteratively reweighted least squares (IRLS) method, which is often used in geodesy for computing robust estimates of parameters. Then for code- and carrier-phase-based relative positioning, we present a recursive modified Newton method to compute Huber’s M-estimates of the positions. The structures of the model are exploited to make the method efficient, and orthogonal transformations are used to ensure numerical reliability of the method. Economical use of computer memory is also taken into account in designing the method. Simulation results show that the method is effective.

  5. Combined constellations GPS and Galileo systems

    NASA Astrophysics Data System (ADS)

    Januszewski, Jacek

    As for the users of satellite navigation systems the actual slogan is GPS and Galileo the advantages and disadvantages of different combined constellations of these systems must be taken into account. The distributions (in per cent) of the numbers of satellites visible by the observer at different latitudes situated in open and restricted (urban canyon) area for different masking elevation angles (Hmin) for two combined constellations GPS + Galileo systems (I - 29 GPS satellites + 27 Galileo satellites, II - 29 GPS + 30 Galileo) are presented in this paper. In addition to it the detailed distributions for the observer at latitudes 50-60° for other constellations & elevation angles are demonstrated. For the first constellation the difference between the number of GPS satellites visible by the observer above horizon (Hmin = 0°) at latitudes 50-60° and the number of Galileo satellites visible by the same observer at the same time can be equal each number between plus 7 and minus 7. This fact must be taken into account in the production and the determination of the number of channel of GPS-Galileo integrated receivers.

  6. 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

  7. GPS/GLONASS Combined Precise Point Positioning with Receiver Clock Modeling.

    PubMed

    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

  8. Integration of GPS Precise Point Positioning and MEMS-Based INS Using Unscented Particle Filter

    PubMed Central

    Abd Rabbou, Mahmoud; El-Rabbany, Ahmed

    2015-01-01

    Integration of Global Positioning System (GPS) and Inertial Navigation System (INS) integrated system involves nonlinear motion state and measurement models. However, the extended Kalman filter (EKF) is commonly used as the estimation filter, which might lead to solution divergence. This is usually encountered during GPS outages, when low-cost micro-electro-mechanical sensors (MEMS) inertial sensors are used. To enhance the navigation system performance, alternatives to the standard EKF should be considered. Particle filtering (PF) is commonly considered as a nonlinear estimation technique to accommodate severe MEMS inertial sensor biases and noise behavior. However, the computation burden of PF limits its use. In this study, an improved version of PF, the unscented particle filter (UPF), is utilized, which combines the unscented Kalman filter (UKF) and PF for the integration of GPS precise point positioning and MEMS-based inertial systems. The proposed filter is examined and compared with traditional estimation filters, namely EKF, UKF and PF. Tightly coupled mechanization is adopted, which is developed in the raw GPS and INS measurement domain. Un-differenced ionosphere-free linear combinations of pseudorange and carrier-phase measurements are used for PPP. The performance of the UPF is analyzed using a real test scenario in downtown Kingston, Ontario. It is shown that the use of UPF reduces the number of samples needed to produce an accurate solution, in comparison with the traditional PF, which in turn reduces the processing time. In addition, UPF enhances the positioning accuracy by up to 15% during GPS outages, in comparison with EKF. However, all filters produce comparable results when the GPS measurement updates are available. PMID:25815446

  9. Integration of GPS precise point positioning and MEMS-based INS using unscented particle filter.

    PubMed

    Abd Rabbou, Mahmoud; El-Rabbany, Ahmed

    2015-01-01

    Integration of Global Positioning System (GPS) and Inertial Navigation System (INS) integrated system involves nonlinear motion state and measurement models. However, the extended Kalman filter (EKF) is commonly used as the estimation filter, which might lead to solution divergence. This is usually encountered during GPS outages, when low-cost micro-electro-mechanical sensors (MEMS) inertial sensors are used. To enhance the navigation system performance, alternatives to the standard EKF should be considered. Particle filtering (PF) is commonly considered as a nonlinear estimation technique to accommodate severe MEMS inertial sensor biases and noise behavior. However, the computation burden of PF limits its use. In this study, an improved version of PF, the unscented particle filter (UPF), is utilized, which combines the unscented Kalman filter (UKF) and PF for the integration of GPS precise point positioning and MEMS-based inertial systems. The proposed filter is examined and compared with traditional estimation filters, namely EKF, UKF and PF. Tightly coupled mechanization is adopted, which is developed in the raw GPS and INS measurement domain. Un-differenced ionosphere-free linear combinations of pseudorange and carrier-phase measurements are used for PPP. The performance of the UPF is analyzed using a real test scenario in downtown Kingston, Ontario. It is shown that the use of UPF reduces the number of samples needed to produce an accurate solution, in comparison with the traditional PF, which in turn reduces the processing time. In addition, UPF enhances the positioning accuracy by up to 15% during GPS outages, in comparison with EKF. However, all filters produce comparable results when the GPS measurement updates are available. PMID:25815446

  10. Hydrologic applications of GPS site-position observations in the Western U.S

    NASA Astrophysics Data System (ADS)

    Ouellette, Karli J.

    Permanent Global Positioning System (GPS) networks have been established around the globe for a variety of uses, most notably to monitor the activity of fault lines and tectonic plate motion. A model for utilizing GPS as a tool for hydrologic monitoring is also developed. First, observations of the recent movement of the land surface throughout California by the Scripps Orbit and Permanent Array Center (SOPAC) GPS network are explored. Significant seasonal cycles and long term trends are related to historical observations of land subsidence. The pattern of deformation throughout the state appears to be caused by the occurrence of poroelastic deformation of the aquifer in the Central Valley, and elastic crustal loading by surface water and the winter snowpack in the Sierra Nevada Mountains. The result is a sort of teeter-totter motion between the Valley and the mountains where the Valley sinks in the dry season while the mountains lift, and the mountains sink in the wet season while the Valley lifts. Next, the elastic crustal deformation caused by the winter snowpack is explored more thoroughly at 6 high elevations throughout the Western United States. Expected annual deformation as a result of thermoelastic and snow water equivalent are calculated using SNOTEL observations and an elastic half-space model. The results demonstrate the dominance of snow loading on the seasonal vertical land surface deformation at all 6 GPS stations. The model is then reversed and applied to the GPS vertical site-position observations in order to predict snow water equivalent. The results are compared to SNOTEL observations of snow water equivalent and soil moisture. The study concludes that GPS site-position observations are able to predict variations in snow water equivalent and soil moisture with good accuracy. Then a model which incorporates both elastic crustal loading and poroelastic deformation was used to predict groundwater storage variations at 54 GPS stations throughout the

  11. 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

  12. GPS/GLONASS time offset monitoring based on combined Precise Point Positioning (PPP) approach

    NASA Astrophysics Data System (ADS)

    Huang, G.; Zhang, Q.; Fu, W.; Guo, H.

    2015-06-01

    A new strategy is proposed to monitor GPS/GLONASS time offsets for common navigation users using a combined GPS/GLONASS Precise Point Positioning (PPP) method based on the orbit and clock products of different time scales. The results of the inter-system GPS/GLONASS time offset, the user time offset and the inter-system device delay difference were obtained using the proposed method. The properties of these results were analyzed in terms of the stability, precision and variation characteristics. Moreover, the practicality of the time offset results in an actual navigation application was tested and demonstrated. The results indicate that the monitoring and prediction of the user time offset, but not the inter-system time offset, has important values for navigation users.

  13. Amazon river altimetry through satellite radar altimetry and GPS positionning

    NASA Astrophysics Data System (ADS)

    Kosuth, P.; Cazenave, A.; Blitzkow, D.

    2003-04-01

    Due to extremely poor road infrastructure and resulting difficulties in direct topographic levelling, Amazon river basin lacks a consistent topographical referential. Space based altimetric techniques appear to be the only feasible alternative to establish such a referential. Extensive processing of Topex/Poseidon satellite radar altimeter data upon continental open water bodies of the Amazon Basin over 1993-2000 period has been realised. Due to relatively poor reliability of Topex/Poseidon data at river low stage, processing focussed on maximum annual water levels. Such maximum annual water levels have been determined for more than 150 intersections between satellite ground traces and rivers, accuracy being improved by correlation analysis with continuous water level time series at closest gauging station. Results have been translated to a geoidal referential using EGM96 geoid model. Annual upper enveloppes of rivers longitudinal water profiles have been interpolated, allowing to quantify maximum annual water levels at existing gauging stations. Confrontation between satellite determined and field measured maximum water levels at these stations allowed to quantify the geoidal altitude of more than 80 stations with a decimetric accuracy (<0.5m). This method has been checked and validated through internal consistency analysis, hydrological consistency analysis and confrontation with bi-frequency GPS positionning measurement results at 22 stations. Mean difference between geoidal altitudes determined by satellite radar altimetry and bi-frequency GPS positionning for these 22 stations is +0.29 m +/- 0.63 m, GPS positionning results being lower than satellite radar altimetry ones. Till now about 30 000 km of Amazon Basin rivers over Brazil, Bolivia, Peru and Ecuador benefit from these altimetric references. This opens way for improved understanding of Amazon river dynamics and enlightens possible improvements in applying satellite radar altimetry techniques over

  14. An Effective Approach to Improving Low-Cost GPS Positioning Accuracy in Real-Time Navigation

    PubMed Central

    Islam, Md. Rashedul; Kim, Jong-Myon

    2014-01-01

    Positioning accuracy is a challenging issue for location-based applications using a low-cost global positioning system (GPS). This paper presents an effective approach to improving the positioning accuracy of a low-cost GPS receiver for real-time navigation. The proposed method precisely estimates position by combining vehicle movement direction, velocity averaging, and distance between waypoints using coordinate data (latitude, longitude, time, and velocity) of the GPS receiver. The previously estimated precious reference point, coordinate translation, and invalid data check also improve accuracy. In order to evaluate the performance of the proposed method, we conducted an experiment using a GARMIN GPS 19xHVS receiver attached to a car and used Google Maps to plot the processed data. The proposed method achieved improvement of 4–10 meters in several experiments. In addition, we compared the proposed approach with two other state-of-the-art methods: recursive averaging and ARMA interpolation. The experimental results show that the proposed approach outperforms other state-of-the-art methods in terms of positioning accuracy. PMID:25136679

  15. An effective approach to improving low-cost GPS positioning accuracy in real-time navigation.

    PubMed

    Islam, Md Rashedul; Kim, Jong-Myon

    2014-01-01

    Positioning accuracy is a challenging issue for location-based applications using a low-cost global positioning system (GPS). This paper presents an effective approach to improving the positioning accuracy of a low-cost GPS receiver for real-time navigation. The proposed method precisely estimates position by combining vehicle movement direction, velocity averaging, and distance between waypoints using coordinate data (latitude, longitude, time, and velocity) of the GPS receiver. The previously estimated precious reference point, coordinate translation, and invalid data check also improve accuracy. In order to evaluate the performance of the proposed method, we conducted an experiment using a GARMIN GPS 19xHVS receiver attached to a car and used Google Maps to plot the processed data. The proposed method achieved improvement of 4-10 meters in several experiments. In addition, we compared the proposed approach with two other state-of-the-art methods: recursive averaging and ARMA interpolation. The experimental results show that the proposed approach outperforms other state-of-the-art methods in terms of positioning accuracy. PMID:25136679

  16. Online monitoring of alpine slope instabilities with L1 GPS Real Time Kinematic Positions

    NASA Astrophysics Data System (ADS)

    Su, Zhenzhong; Geiger, Alain; Limpach, Philippe; Beutel, Jan; Gsell, Tonio; Buchli, Bernhard; Gruber, Stephan; Wirz, Vanessa; Sutton, Felix

    2014-05-01

    Real time (RT) monitoring the kinematic displacement of moving landforms is of great interest to geologists and geomorphologists. Differential GPS carrier phase processing is able to compute real time kinematic (RTK) positions with an accuracy of several centimeters. The accurate kinematic position means better temporal resolution compare to static daily solution. Cost-effective L1 GPS units make deployment of higher density network affordable, which means better spatial resolution. Moreover, the real time capability is critical in the context of early warning scenarios. In this work, we present an online system for monitoring of alpine slope instabilities developed in the framework of the X-Sense project. First, a short introduction about the system will be given, from RT data transfer to RT GPS data processing and the online visualization of results. Second, we demonstrate the real time solutions and we show that GPS signal delay induced by None-Line-of-Sight (NLOS) propagation (like diffraction and reflection delays) is the major error source degrading the accuracy of computed RTK positions in short baseline process. For static stations, we model the error based on the solutions of previous days, and use the model to correct present and future solutions. For stations in motion, we propose to make use of carrier-to-noise ratio (C/N0) to appropriate dilute or correct NLOS error. By doing so, the standard deviation and especially the maximum deviation of computed RTK positions are significantly reduced.

  17. An Interdisciplinary Approach at Studying the Earth-Sun System with GPS/GNSS and GPS-like Signals

    NASA Technical Reports Server (NTRS)

    Zuffada, Cinzia; Hajj, George; Mannucci, Anthony J.; Chao, Yi; Ao, Chi; Zumberge, James

    2005-01-01

    The value of Global Positioning Satellites (GPS) measurements to atmospheric science, space physics, and ocean science, is now emerging or showing a potential to play a major role in the evolving programs of NASA, NSF and NOAA. The objective of this communication is to identify and articulate the key scientific questions that are optimally, or perhaps uniquely, addressed by GPS or GPS-like observations, and discuss their relevance to existing or planned national Earth-science research programs. The GPS-based ocean reflection experiments performed to date have demonstrated the precision and spatial resolution suitable to altimetric applications that require higher spatial resolution and more frequent repeat than the current radar altimeter satellites. GPS radio occultation is promising as a climate monitoring tool because of its benchmark properties: its raw observable is based on extremely accurate timing measurements. GPS-derived temperature profiles can provide meaningful climate trend information over decadal time scales without the need for overlapping missions or mission-to-mission calibrations. By acquiring data as GPS satellites occult behind the Earth's limb, GPS also provides high vertical resolution information on the vertical structure of electron density with global coverage. New experimental techniques will create more comprehensive TEC maps by using signals reflected from the oceans and received in orbit. This communication will discuss a potential future GNSS Earth Observing System project which would deploy a constellation of satellites using GPS and GPS-like measurements, to obtain a) topography measurements based on GPS reflections with an accuracy and horizontal resolution suitable for eddy monitoring, and h) climate-records quality atmospheric temperature profiles. The constellation would also provide for measurements of ionospheric elec tron density. This is a good example of an interdisciplinary mission concept, with broad science objectives

  18. Development of an RTK-GPS positioning application with an improved position error model for smartphones.

    PubMed

    Hwang, Jinsang; Yun, Hongsik; Suh, Yongcheol; Cho, Jeongho; Lee, Dongha

    2012-01-01

    This study developed a smartphone application that provides wireless communication, NRTIP client, and RTK processing features, and which can simplify the Network RTK-GPS system while reducing the required cost. A determination method for an error model in Network RTK measurements was proposed, considering both random and autocorrelation errors, to accurately calculate the coordinates measured by the application using state estimation filters. The performance evaluation of the developed application showed that it could perform high-precision real-time positioning, within several centimeters of error range at a frequency of 20 Hz. A Kalman Filter was applied to the coordinates measured from the application, to evaluate the appropriateness of the determination method for an error model, as proposed in this study. The results were more accurate, compared with those of the existing error model, which only considered the random error. PMID:23201981

  19. Development of an RTK-GPS Positioning Application with an Improved Position Error Model for Smartphones

    PubMed Central

    Hwang, Jinsang; Yun, Hongsik; Suh, Yongcheol; Cho, Jeongho; Lee, Dongha

    2012-01-01

    This study developed a smartphone application that provides wireless communication, NRTIP client, and RTK processing features, and which can simplify the Network RTK-GPS system while reducing the required cost. A determination method for an error model in Network RTK measurements was proposed, considering both random and autocorrelation errors, to accurately calculate the coordinates measured by the application using state estimation filters. The performance evaluation of the developed application showed that it could perform high-precision real-time positioning, within several centimeters of error range at a frequency of 20 Hz. A Kalman Filter was applied to the coordinates measured from the application, to evaluate the appropriateness of the determination method for an error model, as proposed in this study. The results were more accurate, compared with those of the existing error model, which only considered the random error. PMID:23201981

  20. Impact of TEC Fluctuations on GPS Positioning During Halloween 2003 Storm

    NASA Astrophysics Data System (ADS)

    Sieradzki, R.; Krypiak-Gregorczyk, A.; Krankowski, A.

    2009-04-01

    With increasing reliance on space-based platforms for global navigation and communication, concerns about the impact of ionospheric scintillation and total electron content (TEC) fluctuations on these systems have became a high priority. In this paper, GPS trans-ionospheric signals have been used to study the development of ionospheric phase fluctuations observed at Antarctic (Mawson, Syowa, Vesleskarvet) and European (Ebre, Lamkówko, Cagliari, Hailsham, Potsdam, Wettzell) IGS permanent stations. The use of the multi-station, multi-path observations of the GPS beacons has allowed the study of the time development of irregularities of individual geomagnetic storms as a function of latitude and longitude. The basic storm studied here was this of October 29 - 31, 2003 (sum of Kp = 58). Over Europe, the ionospheric irregularities during this storm were analyzed on the base of TEC maps. Our estimation technique provided TEC maps with 15 min interval and with spatial resolution of 150 - 300 km. Over Antarctic region the rate of TEC (ROT) parameter was used to study the occurrence of TEC fluctuations. The results showed the unique nature of each storm. Fluctuation effects, causing dramatic changes in TEC, can have a different impact on GPS positioning accuracy (especially on phase ambiguity resolution). Bernese ver.5.0 software was used for the processing of the GPS permanent data from analized IGS stations. Two methods of GPS elaboration: relative and absolute (Precise Point Positioning - PPP) was applied to elaborate these data. The analyses rely on studying the repeatability of vector coordinates. The impact of TEC fluctuations at the high latitude ionosphere on GPS positioning accuracy has been discussed in terms of the total number of observations of double-differences (DD) and the ratio of the total number of all ambiguities to unresolved ones. For extremely disturbed conditions at high latitudes, the occurrence of medium and strong TEC fluctuations caused a

  1. Satellite emission radio interferometric earth surveying series - GPS geodetic system

    NASA Technical Reports Server (NTRS)

    Macdoran, P. F.

    1979-01-01

    A concept called SERIES (satellite emissions radio interferometric earth surveying) which makes use of GPS (global positioning system) radio transmissions without any satellite modifications, is described. Through the use of very long baseline interferometry (VLBI) and its calibration methods, 0.5 to 3 cm three dimensional baseline accuracy can be achieved over distances of 2 to 200 km respectively, with only 2 hours of on-site data acquisition. Attention is given to such areas as: the radio flux equivalent of GPS transmissions, synthesized delay precision, transmission and frequency subsystem requirements, tropospheric and ionospheric errors. Applications covered include geodesy and seismic tectonics.

  2. The Mathematics of the Global Positioning System.

    ERIC Educational Resources Information Center

    Nord, Gail D.; Jabon, David; Nord, John

    1997-01-01

    Presents an activity that illustrates the application of mathematics to modern navigation and utilizes the Global Positioning System (GPS). GPS is a constellation of 24 satellites that enables receivers to compute their position anywhere on the earth with great accuracy. (DDR)

  3. Instantaneous BeiDou+GPS RTK positioning with high cut-off elevation angles

    NASA Astrophysics Data System (ADS)

    Teunissen, P. J. G.; Odolinski, R.; Odijk, D.

    2014-04-01

    As the Chinese BeiDou Navigation Satellite System (BDS) has become operational in the Asia-Pacific region, it is of importance to better understand as well as demonstrate the capabilities that a combination of BeiDou with GPS brings to positioning. In this contribution, a formal and empirical analysis is given of the single-epoch RTK positioning capabilities of such a combined system. This will be done for the single- and dual-frequency case, and in comparison with the BDS- and GPS-only performances. It will be shown that with the combined system, when more satellites are available, much larger than the customary cut-off elevations can be used. This is important, as such measurement set-up will significantly increase the GNSS applicability in constrained environments, such as e.g. in urban canyons or when low-elevation multipath is present.

  4. RTK-GPS positioning by TV audio-MPX-data broadcast in Japan

    NASA Astrophysics Data System (ADS)

    Namie, Hiromune; Yasuda, Akio; Sasano, Koji

    2000-10-01

    RTK-GPS is a satellite positioning system which provides instant and accurate positions. The ranging error to the satellite from a user GPS antenna determined by the phase measurement of the carrier waves from the GPS satellites is of the order of mms. Thus an accuracy of a few cm can be easily obtained. The system is easier to operate than a traditional survey system such as the `Total Station'. Hence it has been used for many applications in Japan. It is necessary, however, to provide a fast data communication link for the transmission of carrier phase data from a reference station located at a known position, to a user receiver. A radio communication device with low power, is commonly used because it requires no license. However the data transmission area is generally limited to just several hundred meters in radius from the reference station. The authors have investigated RTK-GPS positioning with several different lengths of baseline using data transmission via TV audio-MPX-data broadcast, and evaluated its validity. The carrier phase data is transmitted from the reference receiver at the Tokyo University of Mercantile Marine, to the experimental station of the Asahi National Broadcasting Company, by public phone line with data rate 9,600 bps. The data, which when multiplexed into TV audio, was then disseminated with the rate of about 8 kbps from the Tokyo Tower. The data transmission delay in this system appeared random between 0.740 and 1.317 s, of which the difference (0.577 s) corresponds to the transmission time of 32 blocks of multiplexed data. Positioning was tried at several fixed points with different lengths of baseline (0-21 km). Tests proved that the accuracy became worse as the length of baselines became longer. The 2drms height are less than the 2.5 cm, and `Fix' solution success rates are more than 98%, for shorter baselines less than 10 km in length.

  5. An Integer Precise Point Positioning technique for sea surface observations using a GPS buoy

    NASA Astrophysics Data System (ADS)

    Fund, F.; Perosanz, F.; Testut, L.; Loyer, S.

    2013-04-01

    GPS data dedicated to sea surface observation are usually processed using differential techniques. Unfortunately, the precision of resulting kinematic positions is baseline-length dependent. So, high precision sea surface observations using differential GPS techniques are limited to coasts, lakes, and rivers. Recent improvements in GPS satellite products (orbits, clocks, and phase biases) make phase ambiguity fixing at the zero difference level achievable and opens up the observation of the sea surface without geographical constraints. This paper recalls the concept of the Integer Precise Point Positioning technique and discusses the precision of GPS buoy positioning. A sequential version of the GINS software has been implemented to achieve single epoch GPS positioning. We used 1 Hz data from a two week GPS campaign conducted in the Kerguelen Islands. A GPS buoy has been moored close to a radar gauge and 90 m away from a permanent GPS station. This infrastructure offers the opportunity to compare both kinematic Integer Precise Point Positioning and classical differential GPS positioning techniques to in situ radar gauge data. We found that Precise Point Positioning results are not significantly biased with respect to radar gauge data and that horizontal time series are consistent with differential processing at the sub-centimetre precision level. Nevertheless, standard deviations of height time series with respect to radar gauge data are typically [4-5] cm. The dominant driver for noise at this level is attributed to errors in tropospheric estimates which propagate into position solutions.

  6. A GPS measurement system for precise satellite tracking and geodesy

    NASA Technical Reports Server (NTRS)

    Yunck, T. P.; Wu, S.-C.; Lichten, S. M.

    1985-01-01

    NASA is pursuing two key applications of differential positioning with the Global Positioning System (GPS): sub-decimeter tracking of earth satellites and few-centimeter determination of ground-fixed baselines. Key requirements of the two applications include the use of dual-frequency carrier phase data, multiple ground receivers to serve as reference points, simultaneous solution for use position and GPS orbits, and calibration of atmospheric delays using water vapor radiometers. Sub-decimeter tracking will be first demonstrated on the TOPEX oceanographic satellite to be launched in 1991. A GPS flight receiver together with at least six ground receivers will acquire delta range data from the GPS carriers for non-real-time analysis. Altitude accuracies of 5 to 10 cm are expected. For baseline measurements, efforts will be made to obtain precise differential pseudorange by resolving the cycle ambiguity in differential carrier phase. This could lead to accuracies of 2 or 3 cm over a few thousand kilometers. To achieve this, a high-performance receiver is being developed, along with improved calibration and data processing techniques. Demonstrations may begin in 1986.

  7. Accuracy in GPS/Acoustic positioning on a moored buoy moving around far from the optimal position

    NASA Astrophysics Data System (ADS)

    Imano, M.; Kido, M.; Ohta, Y.; Takahashi, N.; Fukuda, T.; Ochi, H.; Hino, R.

    2015-12-01

    For detecting the seafloor crustal deformation and Tsunami associated with large earthquakes in real-time, it is necessary to monitor them just above the possible source region. For this purpose, we have been dedicated in developing a real-time continuous observation system using a multi-purpose moored buoy. Sea-trials of the system have been carried out near the Nanakai trough in 2013 and 2014 (Takahashi et al., 2014). We especially focused on the GPS/Acoustic measurement (GPS/A) in the system for horizontal crustal movement. The GPS/A on a moored buoy has a critical drawback compared to the traditional ones, in which the data can be stacked over ranging points fixed at an optimal position. Accuracy in positioning with a single ranging from an arbitrary point is the subject to be improved in this study. Here, we report the positioning results in the buoy system using data in the 2014 sea-trial and demonstrate the improvement of the result. We also address the potential resolving power in the positioning using synthetic tests. The target GPS/A site consists of six seafloor transponders (PXPs) forming a small inner- and a large outer-triangles. The bottom of the moored cable is anchored nearly the center of the triangles. In the sea-trial, 11 times successive ranging was scheduled once a week, and we plotted positioning results from different buoy position. We confirmed that scatter in positioning using six PXPs simultaneously is ten times smaller than that using individual triangle separately. Next, we modified the definition of the PXP array geometry using data obtained in a campaign observation. Definition of an array geometry is insensitive as far as ranging is made in the same position, however, severely affects the positioning when ranging is made from various positions like the moored buoy. The modified PXP array is slightly smaller and 2m deeper than the original one. We found that the scatter of positioning results in the sea-trial is reduced from 4m to 1

  8. Medium to Long Range Kinematic GPS Positioning with Position-Velocity-Acceleration Model Using Multiple Reference Stations

    PubMed Central

    Hong, Chang-Ki; Park, Chi Ho; Han, Joong-hee; Kwon, Jay Hyoun

    2015-01-01

    In order to obtain precise kinematic global positioning systems (GPS) in medium to large scale networks, the atmospheric effects from tropospheric and ionospheric delays need to be properly modeled and estimated. It is also preferable to use multiple reference stations to improve the reliability of the solutions. In this study, GPS kinematic positioning algorithms are developed for the medium to large-scale network based on the position-velocity-acceleration model. Hence, the algorithm can perform even in cases where the near-constant velocity assumption does not hold. In addition, the estimated kinematic accelerations can be used for the airborne gravimetry. The proposed algorithms are implemented using Kalman filter and are applied to the in situ airborne GPS data. The performance of the proposed algorithms is validated by analyzing and comparing the results with those from reference values. The results show that reliable and comparable solutions in both position and kinematic acceleration levels can be obtained using the proposed algorithms. PMID:26184215

  9. Medium to Long Range Kinematic GPS Positioning with Position-Velocity-Acceleration Model Using Multiple Reference Stations.

    PubMed

    Hong, Chang-Ki; Park, Chi Ho; Han, Joong-hee; Kwon, Jay Hyoun

    2015-01-01

    In order to obtain precise kinematic global positioning systems (GPS) in medium to large scale networks, the atmospheric effects from tropospheric and ionospheric delays need to be properly modeled and estimated. It is also preferable to use multiple reference stations to improve the reliability of the solutions. In this study, GPS kinematic positioning algorithms are developed for the medium to large-scale network based on the position-velocity-acceleration model. Hence, the algorithm can perform even in cases where the near-constant velocity assumption does not hold. In addition, the estimated kinematic accelerations can be used for the airborne gravimetry. The proposed algorithms are implemented using Kalman filter and are applied to the in situ airborne GPS data. The performance of the proposed algorithms is validated by analyzing and comparing the results with those from reference values. The results show that reliable and comparable solutions in both position and kinematic acceleration levels can be obtained using the proposed algorithms. PMID:26184215

  10. Real-time GPS sensing of atmospheric water vapor: Precise point positioning with orbit, clock, and phase delay corrections

    NASA Astrophysics Data System (ADS)

    Li, Xingxing; Dick, Galina; Ge, Maorong; Heise, Stefan; Wickert, Jens; Bender, Michael

    2014-05-01

    The recent development of the International Global Navigation Satellite Systems Service Real-Time Pilot Project and the enormous progress in precise point positioning (PPP) techniques provide a promising opportunity for real-time determination of Integrated Water Vapor (IWV) using GPS ground networks for various geodetic and meteorological applications. In this study, we develop a new real-time GPS water vapor processing system based on the PPP ambiguity fixing technique with real-time satellite orbit, clock, and phase delay corrections. We demonstrate the performance of the new real-time water vapor estimates using the currently operationally used near-real-time GPS atmospheric data and collocated microwave radiometer measurements as an independent reference. The results show that an accuracy of 1.0 ~ 2.0 mm is achievable for the new real-time GPS based IWV value. Data of such accuracy might be highly valuable for time-critical geodetic (positioning) and meteorological applications.

  11. Intelligent sensor positioning and orientation through constructive neural network-embedded INS/GPS integration algorithms.

    PubMed

    Chiang, Kai-Wei; Chang, Hsiu-Wen

    2010-01-01

    Mobile mapping systems have been widely applied for acquiring spatial information in applications such as spatial information systems and 3D city models. Nowadays the most common technologies used for positioning and orientation of a mobile mapping system include a Global Positioning System (GPS) as the major positioning sensor and an Inertial Navigation System (INS) as the major orientation sensor. In the classical approach, the limitations of the Kalman Filter (KF) method and the overall price of multi-sensor systems have limited the popularization of most land-based mobile mapping applications. Although intelligent sensor positioning and orientation schemes consisting of Multi-layer Feed-forward Neural Networks (MFNNs), one of the most famous Artificial Neural Networks (ANNs), and KF/smoothers, have been proposed in order to enhance the performance of low cost Micro Electro Mechanical System (MEMS) INS/GPS integrated systems, the automation of the MFNN applied has not proven as easy as initially expected. Therefore, this study not only addresses the problems of insufficient automation in the conventional methodology that has been applied in MFNN-KF/smoother algorithms for INS/GPS integrated systems proposed in previous studies, but also exploits and analyzes the idea of developing alternative intelligent sensor positioning and orientation schemes that integrate various sensors in more automatic ways. The proposed schemes are implemented using one of the most famous constructive neural networks--the Cascade Correlation Neural Network (CCNNs)--to overcome the limitations of conventional techniques based on KF/smoother algorithms as well as previously developed MFNN-smoother schemes. The CCNNs applied also have the advantage of a more flexible topology compared to MFNNs. Based on the experimental data utilized the preliminary results presented in this article illustrate the effectiveness of the proposed schemes compared to smoother algorithms as well as the MFNN

  12. PMMW/DGPS/GPS integrated situation awareness system

    NASA Astrophysics Data System (ADS)

    Tarleton, Norman G.; Symosek, Peter F.; Hartman, Randy

    1998-07-01

    Integrating Passive Millimeter Wave camera (PMMW), Global Positioning System (GPS), and Differential Global Positioning System (DGPS) provides a pilot with a visual precision approach and landing in inclement weather conditions conceivably down to CAT III conditions. A DARPA funded, NASA Langley managed Technology Reinvestment Program (TRP) consortium consisting of Honeywell, TRW, Boeing, and Composite Optics Corporations is demonstrating the PMMW camera. The TRW developed PMMW camera displays the runway through fog, smoke, and clouds in day or night conditions. The Global Air Traffic Program Office entered into a Cooperative Research and Development Agreement (CRDA) with Honeywell to demonstrate DGPS. The Honeywell developed DGPS provides precision navigational data to within 1 m error where GPS has 100 m of error. In inclement weather the runway approach is initiated using GPS data until a range where DGPS data can be received. The runway is presented to the pilot using the PMMW image viewed via a Heads Up Display (HUD) or Head Mounted Display (HMD). At a range where DGPS data is available, a precise runway and horizon symbology is computed in the Flight Display Computer and overlaid on the PMMW image. Image processing algorithms operate on the PMMW image to identify and highlight obstacles on the runway. The integrated system provides the pilot with an enhanced situation awareness of the runway approach in inclement weather. When a DGPS ground station is not available at the landing area, image processing algorithms (again operating on the PMMW image) generate the runway and horizon symbology. GPS provides the algorithm with initial conditions for runway location and perspective. The algorithm then locates and highlights the runway and any obstacles on the runway. Honeywell Technology Center is performing research in the area of integrating the PMMW, DGPS, and GPS technologies to provide the pilot with the most necessary features of each system; namely

  13. Delay/Doppler-Mapping GPS-Reflection Remote-Sensing System

    NASA Technical Reports Server (NTRS)

    Lowe, Stephen; Kroger, Peter; Franklin, Garth; LeBrecque, John; Lerma, Jesse; Lough, Michael; Marcin, Martin; Muellerschoen, Ronald; Spitzmesser, Donovan; Young, Lawrence

    2003-01-01

    A radio receiver system that features enhanced capabilities for remote sensing by use of reflected Global Positioning System (GPS) signals has been developed. This system was designed primarily for ocean altimetry, but can also be used for scatterometry and bistatic synthetic-aperture radar imaging. Moreover, it could readily be adapted to utilize navigation-satellite systems other than the GPS, including the Russian Global Navigation Satellite System GLONASS) and the proposed European Galileo system. This remote-sensing system offers both advantages and disadvantages over traditional radar altimeters: One advantage of GPS-reflection systems is that they cost less because there is no need to transmit signals. Another advantage is that there are more simultaneous measurement opportunities - one for each GPS satellite in view. The primary disadvantage is that in comparison with radar signals, GPS signals are weaker, necessitating larger antennas and/or longer observations. This GPS-reflection remote-sensing system was tested in aircraft and made to record and process both (1) signals coming directly from GPS satellites by means of an upward-looking antenna and (2) GPS signals reflected from the ground by means of a downward-looking antenna. In addition to performing conventional GPS processing, the system records raw signals for postprocessing as required.

  14. Flight evaluation of differential GPS aided inertial navigation systems

    NASA Technical Reports Server (NTRS)

    Mcnally, B. David; Paielli, Russell A.; Bach, Ralph E., Jr.; Warner, David N., Jr.

    1992-01-01

    Algorithms are described for integration of Differential Global Positioning System (DGPS) data with Inertial Navigation System (INS) data to provide an integrated DGPS/INS navigation system. The objective is to establish the benefits that can be achieved through various levels of integration of DGPS with INS for precision navigation. An eight state Kalman filter integration was implemented in real-time on a twin turbo-prop transport aircraft to evaluate system performance during terminal approach and landing operations. A fully integrated DGPS/INS system is also presented which models accelerometer and rate-gyro measurement errors plus position, velocity, and attitude errors. The fully integrated system was implemented off-line using range-domain (seventeen-state) and position domain (fifteen-state) Kalman filters. Both filter integration approaches were evaluated using data collected during the flight test. Flight-test data consisted of measurements from a 5 channel Precision Code GPS receiver, a strap-down Inertial Navigation Unit (INU), and GPS satellite differential range corrections from a ground reference station. The aircraft was laser tracked to determine its true position. Results indicate that there is no significant improvement in positioning accuracy with the higher levels of DGPS/INS integration. All three systems provided high-frequency (e.g., 20 Hz) estimates of position and velocity. The fully integrated system provided estimates of inertial sensor errors which may be used to improve INS navigation accuracy should GPS become unavailable, and improved estimates of acceleration, attitude, and body rates which can be used for guidance and control. Precision Code DGPS/INS positioning accuracy (root-mean-square) was 1.0 m cross-track and 3.0 m vertical. (This AGARDograph was sponsored by the Guidance and Control Panel.)

  15. Nutrigenomic targeting of carbohydrate craving behavior: Can we manage obesity and aberrant craving behaviors with neurochemical pathway manipulation by Immunological Compatible Substances (nutrients) using a Genetic Positioning System (GPS) Map?

    PubMed Central

    Downs, B. William; Chen, Amanda L.C.; Chen, Thomas J.H.; Waite, Roger L.; Braverman, Eric R.; Kerner, Mallory; Braverman, Dasha; Rhoades, Patrick; Prihoda, Thomas J.; Palomo, Tomas; Oscar-Berman, Marlene; Reinking, Jeffrey; Blum, Seth H.; DiNubile, Nicholas A.; Liu, H.H.; Blum, Kenneth

    2013-01-01

    SUMMARY Genetic mediated physiological processes that rely on both pharmacological and nutritional principles hold great promise for the successful therapeutic targeting of reduced carbohydrate craving, body-friendly fat loss, healthy body recomposition, and overall wellness. By integrating an assembly of scientific knowledge on inheritable characteristics and environmental mediators of gene expression, we review the relationship of genes, hormones, neurotransmitters, and nutrients as they correct unwanted weight gain coupled with unhappiness. In contrast to a simple one-locus, one-mechanism focus on pharmaceuticals alone, we hypothesize that the use of nutrigenomic treatment targeting multi-physiological neurological, immunological, and metabolic pathways will enable clinicians to intercede in the process of lipogenesis by promoting lipolysis while attenuating aberrant glucose cravings. In turn, this approach will enhance wellness in a safe and predictable manner through the use of a Genetic Positioning System (GPS) Map. The GPS Map, while presently incomplete, ultimately will serve not only as a blueprint for personalized medicine in the treatment of obesity, but also for the development of strategies for reducing many harmful addictive behaviors and promoting optimal health by using substances compatible with the body’s immune system. PMID:19450935

  16. Global Positioning System Instruction in Higher Education.

    ERIC Educational Resources Information Center

    Wikle, Thomas A.; And Others

    1996-01-01

    Provides an overview of satellite-based global positioning system (GPS) technology and includes some illustrations of how GPS is introduced in field-based exercises in the educational setting. Highlights forestry and geography classes, but also discusses archeology, geology, and wildlife science. Benefits include affordability, flexibility,…

  17. Local positioning system

    SciTech Connect

    Kyker, R.

    1995-07-25

    Navigation systems have been vital to transportation ever since man took to the air and sea. Early navigation systems utilized the sextant to navigate by starlight as well as the magnetic needle compass. As electronics and communication technologies improved, inertial navigation systems were developed for use in ships and missile delivery. These systems consisted of electronic compasses, gyro-compasses, accelerometers, and various other sensors. Recently, systems such as LORAN and the Global Positioning System (GPS) have utilized the properties of radio wave propagation to triangulate position. The Local Positioning System (LPS), described in this paper, is an implementation of a limited inertial navigation system designed to be used on a bicycle. LPS displays a cyclist`s current position relative to a starting location. This information is displayed in Cartesian-like coordinates. To accomplish this, LPS relies upon two sensors, an electronic compass sensor and a distance sensor. The compass sensor provides directional information while the distance sensor provides the distance traveled. This information yields a distance vector for each point in time which when summed produces the cyclist`s current position. LPS is microprocessor controlled and is designed for a range of less than 90 miles.

  18. The First Experiment with VLBI-GPS Hybrid System

    NASA Technical Reports Server (NTRS)

    Kwak, Younghee; Kondo, Tetsuro; Gotoh, Tadahiro; Amagai, Jun; Takiguchi, Hiroshi; Sekido, Mamoru; Ichikawa, Ryuichi; Sasao, Tetsuo; Cho, Jungho; Kim, Tuhwan

    2010-01-01

    In this paper, we introduce our GPS-VLBI hybrid system and show the results of the first experiment which is now under way. In this hybrid system, GPS signals are captured by a normal GPS antenna, down-converted to IF signals, and then sampled by the VLBI sampler VSSP32 developed by NICT. The sampled GPS data are recorded and correlated in the same way as VLBI observation data. The correlator outputs are the group delay and the delay rate. Since the whole system uses the same frequency standard, many sources of systematic errors are common between the VLBI system and the GPS system. In this hybrid system, the GPS antenna can be regarded as an additional VLBI antenna having multiple beams towards GPS satellites. Therefore, we expect that this approach will provide enough data to improve zenith delay estimates and geodetic results.

  19. Inertial and GPS data integration for positioning and tracking of GPR

    NASA Astrophysics Data System (ADS)

    Chicarella, Simone; D'Alvano, Alessandro; Ferrara, Vincenzo; Frezza, Fabrizio; Pajewski, Lara

    2015-04-01

    Nowadays many applications and studies use a Global Positioning System (GPS) to integrate Ground-Penetrating Radar (GPR) data [1-2]. The aim is the production of detailed detection maps that are geo-referenced and superimposable on geographic maps themes. GPS provides data to determine static positioning, and to track the mobile detection system path on the land. A low-cost standard GPS, like GPS-622R by RF Solutions Ltd, allows accuracy around 2.5 m CEP (Circular Error Probability), and a maximum update rate of 10 Hz. These accuracy and update rate are satisfying values when we evaluate positioning datum, but they are unsuitable for precision tracking of a speedy-mobile GPR system. In order to determine the relative displacements with respect to an initial position on the territory, an Inertial Measurement Unit (IMU) can be used. Some inertial-system applications for GPR tracking have been presented in recent studies [3-4]. The integration of both GPS and IMU systems is the aim of our work, in order to increase GPR applicability, e.g. the case of a GPR mounted on an unmanned aerial vehicle for the detection of people buried under avalanches [5]. In this work, we will present the design, realization and experimental characterization of our electronic board that includes GPS-622R and AltIMU-10 v3 by Pololu. The latter comprises an inertial-measurement unit and an altimeter. In particular, the IMU adopts L3GD20 gyro and LSM303D accelerometer and magnetometer; the digital barometer LPS331AP provides data for altitude evaluation. The prototype of our system for GPR positioning and tracking is based on an Arduino microcontroller board. Acknowledgement This work benefited from networking activities carried out within the EU funded COST Action TU1208 'Civil Engineering Applications of Ground Penetrating Radar. ' References [1] M. Solla, X. Núñez-Nieto, M. Varela-González, J. Martínez-Sánchez, and P. Arias, 'GPR for Road Inspection: georeferencing and efficient

  20. Evaluation of Mobile Phone Interference With Aircraft GPS Navigation Systems

    NASA Technical Reports Server (NTRS)

    Pace, Scott; Oria, A. J.; Guckian, Paul; Nguyen, Truong X.

    2004-01-01

    This report compiles and analyzes tests that were conducted to measure cell phone spurious emissions in the Global Positioning System (GPS) radio frequency band that could affect the navigation system of an aircraft. The cell phone in question had, as reported to the FAA (Federal Aviation Administration), caused interference to several GPS receivers on-board a small single engine aircraft despite being compliant with data filed at the time with the FCC by the manufacturer. NASA (National Aeronautics and Space Administration) and industry tests show that while there is an emission in the 1575 MHz GPS band due to a specific combination of amplifier output impedance and load impedance that induces instability in the power amplifier, these spurious emissions (i.e., not the intentional transmit signal) are similar to those measured on non-intentionally transmitting devices such as, for example, laptop computers. Additional testing on a wide sample of different commercial cell phones did not result in any emission in the 1575 MHz GPS Band above the noise floor of the measurement receiver.

  1. Software for a GPS-Reflection Remote-Sensing System

    NASA Technical Reports Server (NTRS)

    Lowe, Stephen

    2003-01-01

    A special-purpose software Global Positioning System (GPS) receiver designed for remote sensing with reflected GPS signals is described in Delay/Doppler-Mapping GPS-Reflection Remote-Sensing System (NPO-30385), which appears elsewhere in this issue of NASA Tech Briefs. The input accepted by this program comprises raw (open-loop) digitized GPS signals sampled at a rate of about 20 MHz. The program processes the data samples to perform the following functions: detection of signals; tracking of phases and delays; mapping of delay, Doppler, and delay/Doppler waveforms; dual-frequency processing; coherent integrations as short as 125 s; decoding of navigation messages; and precise time tagging of observable quantities. The software can perform these functions on all detectable satellite signals without dead time. Open-loop data collected over water, land, or ice and processed by this software can be further processed to extract geophysical information. Possible examples include mean sea height, wind speed and direction, and significant wave height (for observations over the ocean); bistatic-radar terrain images and measures of soil moisture and biomass (for observations over land); and estimates of ice age, thickness, and surface density (for observations over ice).

  2. Spaceborne Global Positioning System for Spacecraft

    NASA Technical Reports Server (NTRS)

    Dougherty, Lamar F. (Inventor); Niles, Frederick A. (Inventor); Wennersten, Miriam D. (Inventor)

    2001-01-01

    The spaceborne Global Positioning System receiver provides navigational solutions and is designed for use in low Earth orbit. The spaceborne GPS receiver can determine the orbital position of a spacecraft using any of the satellites wi thin the GPS constellation. It is a multiple processor system incorporating redundancy by using a microcontroller to handle the closure of tracking loops for acquired GPS satellites, while a separate microprocessor computes the spacecraft navigational solution and handles other tasks within the receiver. 'Me spaceborne GPS receiver can use either microcontroller or the microprocessor to close the satellite tracking loops. The use of microcontroller provides better tracking performance of acquired GPS satellites. The spaceborne GPS receiver utilizes up to seven separate GPS boards, with each board including its own set of correlators, down-converters and front-end components. The spaceborne GPS receiver also includes telemetry and time-marking circuitry. The spaceborne GPS receiver communicates with other spacecraft systems through a variety of interfaces and can be software-configured to support several different mission profiles.

  3. 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

  4. An Artificial Neural Network Embedded Position and Orientation Determination Algorithm for Low Cost MEMS INS/GPS Integrated Sensors.

    PubMed

    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

  5. Global Positioning System for the Geosciences: Summary and Proceedings of a Workshop on Improving the GPS Reference Station Infrastructure for Earth, Oceanic, and Atmospheric Science Applications

    NASA Technical Reports Server (NTRS)

    1997-01-01

    This report, which represents the results of the workshop, is divided into two sections. Section I includes an executive summary, a chapter introducing the reader to GPS and its usefulness for Earth, oceanic, and atmospheric research, and four chapters summarizing the themes of the workshop presentations, poster papers, and working group discussions. Section II contains the proceedings of the workshop and is divided into five chapters corresponding to the five categories of invited papers written by workshop speakers and authors of poster papers. The appendices contain additional information about the workshop and the Steering Committee.

  6. Brief report: Using global positioning system (GPS) enabled cell phones to examine adolescent travel patterns and time in proximity to alcohol outlets.

    PubMed

    Byrnes, Hilary F; Miller, Brenda A; Morrison, Christopher N; Wiebe, Douglas J; Remer, Lillian G; Wiehe, Sarah E

    2016-07-01

    As adolescents gain freedom to explore new environments unsupervised, more time in proximity to alcohol outlets may increase risks for alcohol and marijuana use. This pilot study: 1) Describes variations in adolescents' proximity to outlets by time of day and day of the week, 2) Examines variations in outlet proximity by drinking and marijuana use status, and 3) Tests feasibility of obtaining real-time data to study adolescent proximity to outlets. U.S. adolescents (N = 18) aged 16-17 (50% female) carried GPS-enabled smartphones for one week with their locations tracked. The geographic areas where adolescents spend time, activity spaces, were created by connecting GPS points sequentially and adding spatial buffers around routes. Proximity to outlets was greater during after school and evening hours. Drinkers and marijuana users were in proximity to outlets 1½ to 2 times more than non-users. Findings provide information about where adolescents spend time and times of greatest risk, informing prevention efforts. PMID:27214713

  7. 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

  8. Global Positioning System Satellite Selection Method

    NASA Technical Reports Server (NTRS)

    Niles, Frederick A. (Inventor)

    2001-01-01

    The satellite selection method as utilized by the spaceborne Global Positioning System receiver provides navigational solutions and is designed for use in low Earth orbit. The satellite selection method is a robust algorithm that can be used a GPS receiver to select appropriate GPS satellites for use in calculating point solutions or attitude solutions. The method is takes into account the difficulty of finding a particular GPS satellite phase code, especially when the search range in greatly increased due to Doppler shifts introduced into the carrier frequency. The method starts with an update of the antenna pointing and spacecraft vectors to determine the antenna backplane direction. Next, the GPS satellites that will potentially be in view of the antenna are ranked on a list, whereby the list is generated based on the estimated attitude and position of each GPS satellite. Satellites blocked by the Earth are not entered on this list. A second list is created, whereby the GPS satellites are ranked according to their desirability for use in attitude determination. GPS satellites are ranked according to their orthogonality to the antenna backplane, and according to geometric dilution of precision considerations. After the lists are created, the channels of the spaceborne GPS receiver are assigned to various GPS satellites for acquisition and lock. Preliminary Doppler frequencies for searching are assigned to the various channels.

  9. Performance Analysis of Several GPS/Galileo Precise Point Positioning Models.

    PubMed

    Afifi, Akram; El-Rabbany, Ahmed

    2015-01-01

    This paper examines the performance of several precise point positioning (PPP) models, which combine dual-frequency GPS/Galileo observations in the un-differenced and between-satellite single-difference (BSSD) modes. These include the traditional un-differenced model, the decoupled clock model, the semi-decoupled clock model, and the between-satellite single-difference model. We take advantage of the IGS-MGEX network products to correct for the satellite differential code biases and the orbital and satellite clock errors. Natural Resources Canada's GPSPace PPP software is modified to handle the various GPS/Galileo PPP models. A total of six data sets of GPS and Galileo observations at six IGS stations are processed to examine the performance of the various PPP models. It is shown that the traditional un-differenced GPS/Galileo PPP model, the GPS decoupled clock model, and the semi-decoupled clock GPS/Galileo PPP model improve the convergence time by about 25% in comparison with the un-differenced GPS-only model. In addition, the semi-decoupled GPS/Galileo PPP model improves the solution precision by about 25% compared to the traditional un-differenced GPS/Galileo PPP model. Moreover, the BSSD GPS/Galileo PPP model improves the solution convergence time by about 50%, in comparison with the un-differenced GPS PPP model, regardless of the type of BSSD combination used. As well, the BSSD model improves the precision of the estimated parameters by about 50% and 25% when the loose and the tight combinations are used, respectively, in comparison with the un-differenced GPS-only model. Comparable results are obtained through the tight combination when either a GPS or a Galileo satellite is selected as a reference. PMID:26102495

  10. Performance Analysis of Several GPS/Galileo Precise Point Positioning Models

    PubMed Central

    Afifi, Akram; El-Rabbany, Ahmed

    2015-01-01

    This paper examines the performance of several precise point positioning (PPP) models, which combine dual-frequency GPS/Galileo observations in the un-differenced and between-satellite single-difference (BSSD) modes. These include the traditional un-differenced model, the decoupled clock model, the semi-decoupled clock model, and the between-satellite single-difference model. We take advantage of the IGS-MGEX network products to correct for the satellite differential code biases and the orbital and satellite clock errors. Natural Resources Canada’s GPSPace PPP software is modified to handle the various GPS/Galileo PPP models. A total of six data sets of GPS and Galileo observations at six IGS stations are processed to examine the performance of the various PPP models. It is shown that the traditional un-differenced GPS/Galileo PPP model, the GPS decoupled clock model, and the semi-decoupled clock GPS/Galileo PPP model improve the convergence time by about 25% in comparison with the un-differenced GPS-only model. In addition, the semi-decoupled GPS/Galileo PPP model improves the solution precision by about 25% compared to the traditional un-differenced GPS/Galileo PPP model. Moreover, the BSSD GPS/Galileo PPP model improves the solution convergence time by about 50%, in comparison with the un-differenced GPS PPP model, regardless of the type of BSSD combination used. As well, the BSSD model improves the precision of the estimated parameters by about 50% and 25% when the loose and the tight combinations are used, respectively, in comparison with the un-differenced GPS-only model. Comparable results are obtained through the tight combination when either a GPS or a Galileo satellite is selected as a reference. PMID:26102495

  11. Low-cost inertial/GPS for ballistic missiles with application to unmanned systems

    NASA Astrophysics Data System (ADS)

    Roberts, Chris E.; Jenkins, Philip N.; Osborn, Charles T.

    1996-05-01

    Many advances in inertial navigation have been made over the last decade. Small, lightweight inertial measurement units (IMU) have been developed which provide suitable accuracy at a reasonable cost for many unmanned systems. Price has also dropped to previously unheard of levels (under 10,000 dollars for large buys). IMUs can be augmented with global positioning system (GPS) receivers to provide highly accurate and robust navigation capability. GPS receivers have also dropped in size and cost and are becoming an attractive option for coupling with an inertial system. GPS systems alone are vulnerable to jamming and are not a good choice for military applications where jamming is a consideration. Current Army policy is not to use GPS as a mission essential element. The focus of this paper will be on low cost IMUs with GPS and their application to unmanned vehicles. In particular, the program to add guidance to the multiple launch rocket system extended range rocket will be discussed.

  12. Autonomous reconfigurable GPS/INS navigation and pointing system for rendezvous and docking

    NASA Technical Reports Server (NTRS)

    Upadhyay, Triveni N.; Cotterill, Stephen; Deaton, A. Wayne

    1991-01-01

    This paper describes the results of an integrated navigation and pointing system software development effort sponsored by the NASA MSFC through a SBIR Phase 2 Program. The integrated Global Positioning System (GPS)/Inertial Navigation System (INS) implements an autonomous navigation filter that is reconfigurable in real-time to accommodate mission contingencies. An onboard expert system monitors the spacecraft status and reconfigures the navigation filter accordingly, to optimize the system performance. The navigation filter is a multi-mode Kalman filter to estimate the spacecraft position, velocity, and attitude. Three different GPS-based attitude determination techniques, namely, velocity vector matching, attitude vector matching, and interferometric processing, are implemented to encompass different mission contingencies. The integrated GPS/INS navigation filter will use any of these techniques depending on the mission phase and the state of the sensors. The first technique, velocity vector matching, uses the GPS velocity measurement to estimate the INS velocity errors and exploits the correlation between INS velocity and attitude errors to estimate the attitude. The second technique, attitude vector matching, uses INS gyro measurements and GPS carrier phase (integrated Doppler) measurements during a spacecraft rotation maneuver to determine the attitude. Both of these techniques require only one GPS antenna onboard to determine the spacecraft attitude. The third technique, interferometric processing, requires use of multiple GPS antennae. In order to determine 3-axis body attitude, three GPS antennae (2 no-coplanor baselines) are required.

  13. 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

  14. 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

  15. Accuracy of velocities from repeated GPS surveys: relative positioning is concerned

    NASA Astrophysics Data System (ADS)

    Duman, Huseyin; Ugur Sanli, D.

    2016-04-01

    Over more than a decade, researchers have been interested in studying the accuracy of GPS positioning solutions. Recently, reporting the accuracy of GPS velocities has been added to this. Researchers studying landslide motion, tectonic motion, uplift, sea level rise, and subsidence still report results from GPS experiments in which repeated GPS measurements from short sessions are used. This motivated some other researchers to study the accuracy of GPS deformation rates/velocities from various repeated GPS surveys. In one of the efforts, the velocity accuracy was derived from repeated GPS static surveys using short observation sessions and Precise Point Positioning mode of GPS software. Velocities from short GPS sessions were compared with the velocities from 24 h sessions. The accuracy of velocities was obtained using statistical hypothesis testing and quantifying the accuracy of least squares estimation models. The results reveal that 45-60 % of the horizontal and none of the vertical solutions comply with the results from 24 h solutions. We argue that this case in which the data was evaluated using PPP should also apply to the case in which the data belonging to long GPS base lengths is processed using fundamental relative point positioning. To test this idea we chose the two IGS stations ANKR and NICO and derive their velocities from the reference stations held fixed in the stable EURASIAN plate. The University of Bern's GNSS software BERNESE was used to produce relative positioning solutions, and the results are compared with those of GIPSY/OASIS II PPP results. First impressions indicate that it is worth designing a global experiment and test these ideas in detail.

  16. Study of GPS Position error during low solar activity period near the Crest of the Equatorial Ionization Anomaly

    NASA Astrophysics Data System (ADS)

    Trivedi, Richa; Gwal, Ashok Kumar; Jain, Sudhir

    In order to study GPS position error, the GPS Ionospheric Scintillation and TEC Monitor (GISTM) based GPS receiver was installed at an equatorial station, Bhopal (23.2° N, 77.4° E, Geomagnetic latitude 14.23˚ N), India. We analyzed the horizontal error and the level of confidence in terms of DRMS & CEP and positional error from fixed GPS point for year 2005-2006. In this paper we observed position error in both storm/disturb as well as quiet ionospheric condition. As the range of error is directly proportional to TEC along the ray path since 6.15 TEC units correspond to the range error of 1 m on L1 frequency, we observed that the change of VTEC is 60 TECU which correspond to 9.76 m for ionospheric disturb day May 15, 2005 (severe geomagnetic storm; SSC at 0239 UT). During the study no scintillation and loss of lock has been observed in both disturb and quiet day except on May 27, 2006 (quiet day). On May 27, 2006 the loss of lock in one satellite has been observed. In order to study the effect of storm/quiet ionospheric condition on GPS position errors, the latitudinal error and longitudinal error in meter is studied. The range of position error was about 2.5 meters during the quiet ionospheric conditions except on June 26, 2006(quite day). The situation became adverse during disturbed ionospheric conditions, with the error reaching up to 5-6 meters. During disturb and quiet ionospheric condition it was observed that the in most of the cases the error point’s lies out side the 95% error ellipse and elongation in the N-E direction. The results have been compared with the earlier ones and discussed in terms of possible source mechanism responsible for the position error at anomaly crest region. Keywords: Total Electron Contents (TEC); Equatorial Ionization Anomaly (EIA); Global Positioning System (GPS).

  17. Experimental validation of GPS-INS-STAR hybrid navigation system for space autonomy

    NASA Astrophysics Data System (ADS)

    Tanabe, Toru; Harigae, Masatoshi

    The experimental validation of the GPS-INS-STAR hybrid navigation system concept is performed. The hybrid navigation system combines the best features of employed sensors to improve total navigation performances. The GPS-INS-STAR hybrid navigation system consists of the three different sensors, a GPS receiver, an inertial navigation system and a STAR image sensor. In this concept, the system integrates a high positioning performance of the GPS system, an accurate attitude determination capability of the STAR image sensor and the INS signal with a wide bandwidth. It results in a complete 6-DOF (degrees of freedom) autonomous navigation system. The present paper shows the validation of the concept by the experiments using GPS, INS and STAR hardware systems. The experiments are divided into three steps. Firstly, the INS-STAR hybrid navigation system is constructed on the 3-axis motion table to verify the performances of its attitude loop. Secondly, the GPS-INS hybrid navigation system installed on the car shows the performance improvement in its translational loop. Finally, the full configuration of the GPS-INS-STAR hybrid navigation system is evaluated at night. Each experiment result is checked by the theoretical analysis. In the theoretical analysis, the concept of observability well explains the performances of the system. Its feasibility for space application is also evaluated in the point of existing hardware technology. It is concluded that the experiments vaidate the concept of the hybrid navigation system and confirm its capability to realize space autonomy.

  18. 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.

  19. Global Positioning System receiver evaluation results

    SciTech Connect

    Byrne, R.H.

    1993-09-01

    A Sandia project currently uses an outdated Magnavox 6400 Global Positioning System (GPS) receiver as the core of its navigation system. The goal of this study was to analyze the performance of the current GPS receiver compared to newer, less expensive models and to make recommendations on how to improve the performance of the overall navigation system. This paper discusses the test methodology used to experimentally analyze the performance of different GPS receivers, the test results, and recommendations on how an upgrade should proceed. Appendices contain detailed information regarding the raw data, test hardware, and test software.

  20. Uav Onboard Photogrammetry and GPS Positionning for Earthworks

    NASA Astrophysics Data System (ADS)

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

    2015-08-01

    Over the last decade, Unmanned Airbone Vehicles (UAVs) have been largely used for civil applications. Airborne photogrammetry has found place in these applications not only for 3D modeling but also as a measurement tool. Vinci-Construction-Terrassement is a private company specialized in public works sector and uses airborn photogrammetry as a mapping solution and metrology investigation tool on its sites. This technology is very efficient for the calculation of stock volumes for instance, or for time tracking of specific areas with risk of landslides. The aim of the present work is to perform a direct georeferencing of images acquired by the camera leaning on an embedded GPS receiver. UAV, GPS receiver and camera used are low-cost models and therefore data processing is adapted to this particular constraint.

  1. Kalman filtering for GPS/magnetometer integrated navigation system

    NASA Astrophysics Data System (ADS)

    Guo, Hang; Yu, Min; Zou, Chengwu; Huang, Wenwen

    2010-06-01

    This paper investigated the data processing method for a GPS/IMU/magnetometer integrated system with Kalman filtering (KF). As a result of GPS/IMU/magnetometer land vehicle system, dead-reckoning of magnetometer and accelerometer integrated subsystem bridged very well the GPS signal outage due to the trees on the two sides of the road. Both differential GPS data processing method and the carrier-phase method with magnetometers' outputs for predicting the car position, velocity, and acceleration (PVA) are presented. The results from DGPS with Kinematical Positioning (KINPOS) software shown that the averages of the north, east, and down direction standard deviation (short for "std") are 0.014, 0.010, and 0.018 m, respectively. The std of velocities and accelerations derived by the position and velocity differentiation are 10, 7, 13 mm/s, 7, 5, 9 mm/s 2, respectively. This method for getting velocities and accelerations requires higher accurate position coordinates. But the position accuracy has frequently been degraded in this case when the car drove under the trees or other similar kinematical environments. That caused the larger velocity and acceleration errors. While the results from the carrier-phase method are std of the velocities = 2.1 mm/s, 1.3 mm/s, 3.7 mm/s in north, east, down, and std of the accelerations = 1.5 mm/s 2, 0.9 mm/s 2, 2.3 mm/s 2 for the static test period; as compared with KINPOS software results, std of the velocity difference between the carrier-phase method and the DGPS method = 7 mm/s, 6.9 mm/s, 9.7 mm/s in north, east, down direction, and std of acceleration difference = 5.0 mm/s 2, 4.5 mm/s 2, 7.5 mm/s 2 in north, east, down direction for the kinematical test period. Obviously, errors come from both the carrier-phase method and DGPS velocity and acceleration results derived directly by the position differentiation. In addition, better accuracy of positions than that before KF has been got by means of velocities and accelerations derived

  2. 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.

  3. A Pseudolite-Based Positioning System for Legacy GNSS Receivers

    PubMed Central

    Kim, Chongwon; So, Hyoungmin; Lee, Taikjin; Kee, Changdon

    2014-01-01

    The ephemeris data format of legacy GPS receivers is improper for positioning stationary pseudolites on the ground. Therefore, to utilize pseudolites for navigation, GPS receivers must be modified so that they can handle the modified data formats of the pseudolites. Because of this problem, the practical use of pseudolites has so far been limited. This paper proposes a pseudolite-based positioning system that can be used with unmodified legacy GPS receivers. In the proposed system, pseudolites transmit simulated GPS signals. The signals use standard GPS ephemeris data format and contain ephemeris data of simulated GPS satellites, not those of pseudolites. The use of the standard format enables the GPS receiver to process pseudolite signals without any modification. However, the position output of the GPS receiver is not the correct position in this system, because there are additional signal delays from each pseudolite to the receiver. A post-calculation process was added to obtain the correct receiver position using GPS receiver output. This re-estimation is possible because it is based on known information about the simulated signals, pseudolites, and positioning process of the GPS receiver. Simulations using generated data and live GPS data are conducted for various geometries to verify the proposed system. The test results show that the proposed system provides the desired user position using pseudolite signals without requiring any modifications to the legacy GPS receiver. In this initial study, a pseudolite-only indoor system was assumed. However, it can be expanded to a GPS-pseudolite system outdoors. PMID:24681674

  4. A pseudolite-based positioning system for legacy GNSS receivers.

    PubMed

    Kim, Chongwon; So, Hyoungmin; Lee, Taikjin; Kee, Changdon

    2014-01-01

    The ephemeris data format of legacy GPS receivers is improper for positioning stationary pseudolites on the ground. Therefore, to utilize pseudolites for navigation, GPS receivers must be modified so that they can handle the modified data formats of the pseudolites. Because of this problem, the practical use of pseudolites has so far been limited. This paper proposes a pseudolite-based positioning system that can be used with unmodified legacy GPS receivers. In the proposed system, pseudolites transmit simulated GPS signals. The signals use standard GPS ephemeris data format and contain ephemeris data of simulated GPS satellites, not those of pseudolites. The use of the standard format enables the GPS receiver to process pseudolite signals without any modification. However, the position output of the GPS receiver is not the correct position in this system, because there are additional signal delays from each pseudolite to the receiver. A post-calculation process was added to obtain the correct receiver position using GPS receiver output. This re-estimation is possible because it is based on known information about the simulated signals, pseudolites, and positioning process of the GPS receiver. Simulations using generated data and live GPS data are conducted for various geometries to verify the proposed system. The test results show that the proposed system provides the desired user position using pseudolite signals without requiring any modifications to the legacy GPS receiver. In this initial study, a pseudolite-only indoor system was assumed. However, it can be expanded to a GPS-pseudolite system outdoors. PMID:24681674

  5. Integrated GPS/INS navigation system design for autonomous spacecraft rendezvous

    NASA Astrophysics Data System (ADS)

    Gaylor, David Edward

    2003-10-01

    The goal of the NASA Space Launch Initiative (SLI) program is to advance the technologies for the next generation reusable launch vehicle (RLV). The SLI program has identified automated rendezvous and docking as an area requiring further research and development. Currently, the Space Shuttle uses a partially manual system for rendezvous, but a fully automated system could be safer and more reliable. Previous studies have shown that it is feasible to use the Global Positioning System (GPS) for spacecraft navigation during rendezvous with the International Space Station (ISS). However, these studies have not accounted for the effects of GPS signal blockage and multipath in the vicinity of the ISS, which make a GPS-only navigation system less accurate and reliable. One possible solution is to combine GPS with an inertial navigation system (INS). The integration of GPS and INS can be achieved using a Kalman filter. GPS/INS systems have been used in aircraft for many years and have also been used in launch vehicles. However, the performance of GPS/INS systems in orbit and during spacecraft rendezvous has not been characterized. The primary objective of this research is to evaluate the ability of an integrated GPS/INS to provide accurate navigation solutions during a rendezvous scenario where the effects of ISS signal blockage, multipath and delta-v maneuvers degrade GPS-only navigation. In order to accomplish this, GPS-only and GPS/INS Kalman filters have been developed for both absolute and relative navigation, as well as a new statistical multipath model for spacecraft operating near the ISS. Several factors that affect relative navigation performance were studied, including: filter tuning, GPS constellation geometry, rendezvous approach direction, and inertial sensor performance. The results showed that each of these factors has a large impact on relative navigation performance. Finally, it has been demonstrated that a GPS/INS system based on medium accuracy aircraft

  6. The Impact on the Positioning Accuracy of the Frequency Reference of a GPS Receiver

    NASA Astrophysics Data System (ADS)

    Yeh, Ta-Kang; Chen, Chieh-Hung; Xu, Guochang; Wang, Chuan-Sheng; Chen, Kwo-Hwa

    2013-01-01

    Despite the pervasive use of the global positioning system (GPS) as a positioning technology for its high efficiency and accuracy, several factors reduce its performance. This study examines to which extent the frequency offset and the frequency stability of the internal quartz oscillator or of an externally supplied rubidium oscillator have an influence. Observations were made at the Taiwan Ching Yun University (TCYU) tracking station, where a quartz oscillator and a rubidium oscillator were applied alternatively on a monthly basis throughout a 16-month period. Moreover, the accuracy of the local oscillator used in this study was calibrated by the National Standard Time and Frequency Laboratory, Taiwan. The frequency offset and frequency stability calculated via the remote method at the TCYU station were compared with values (uncertainty is 3.0E-13) measured directly at the National Standard Time and Frequency Laboratory, Taiwan. Analytical results show that the two methods vary by 1.4E-10 in terms of frequency offset and by 6.5E-12 in terms of frequency stability, demonstrating that the remote method can yield computational results almost as accurate as direct measurement. Positioning precision results also show that rubidium oscillator accuracy improved by 5, 11, and 15 % for short-, medium-, and long-baseline positioning, respectively, indicating that clock quality is more influential for long-baseline GPS relative positioning and that the frequency stability of a receiver clock is far more critical than the frequency offset. On the other hand, the positioning performance noted is essentially independent (max. 15 % change) of the reference frequency stability, which indeed differed by 4 orders of magnitude.

  7. Precise Applications Of The Global Positioning System

    NASA Technical Reports Server (NTRS)

    Lichten, Stephen M.

    1992-01-01

    Report represents overview of Global Positioning System (GPS). Emphasizes those aspects of theory, history, and status of GPS pertaining to potential utility for highly precise scientific measurements. Current and anticipated applications include measurements of crustal motions in seismically active regions of Earth, measurements of rate of rotation of Earth and orientation of poles, tracking of non-GPS spacecraft in orbit around Earth, surveying, measurements of radio-signal-propagation delays, determinations of coordinates of ground stations, and transfer of precise time signals worldwide.

  8. Accuracy and reliability of multi-GNSS real-time precise positioning: GPS, GLONASS, BeiDou, and Galileo

    NASA Astrophysics Data System (ADS)

    Li, Xingxing; Ge, Maorong; Dai, Xiaolei; Ren, Xiaodong; Fritsche, Mathias; Wickert, Jens; Schuh, Harald

    2015-06-01

    In this contribution, we present a GPS+GLONASS+BeiDou+Galileo four-system model to fully exploit the observations of all these four navigation satellite systems for real-time precise orbit determination, clock estimation and positioning. A rigorous multi-GNSS analysis is performed to achieve the best possible consistency by processing the observations from different GNSS together in one common parameter estimation procedure. Meanwhile, an efficient multi-GNSS real-time precise positioning service system is designed and demonstrated by using the multi-GNSS Experiment, BeiDou Experimental Tracking Network, and International GNSS Service networks including stations all over the world. The statistical analysis of the 6-h predicted orbits show that the radial and cross root mean square (RMS) values are smaller than 10 cm for BeiDou and Galileo, and smaller than 5 cm for both GLONASS and GPS satellites, respectively. The RMS values of the clock differences between real-time and batch-processed solutions for GPS satellites are about 0.10 ns, while the RMS values for BeiDou, Galileo and GLONASS are 0.13, 0.13 and 0.14 ns, respectively. The addition of the BeiDou, Galileo and GLONASS systems to the standard GPS-only processing, reduces the convergence time almost by 70 %, while the positioning accuracy is improved by about 25 %. Some outliers in the GPS-only solutions vanish when multi-GNSS observations are processed simultaneous. The availability and reliability of GPS precise positioning decrease dramatically as the elevation cutoff increases. However, the accuracy of multi-GNSS precise point positioning (PPP) is hardly decreased and few centimeter are still achievable in the horizontal components even with 40 elevation cutoff. At 30 and 40 elevation cutoffs, the availability rates of GPS-only solution drop significantly to only around 70 and 40 %, respectively. However, multi-GNSS PPP can provide precise position estimates continuously (availability rate is more than 99

  9. A Micromechanical INS/GPS System for Small Satellites

    NASA Technical Reports Server (NTRS)

    Barbour, N.; Brand, T.; Haley, R.; Socha, M.; Stoll, J.; Ward, P.; Weinberg, M.

    1995-01-01

    The cost and complexity of large satellite space missions continue to escalate. To reduce costs, more attention is being directed toward small lightweight satellites where future demand is expected to grow dramatically. Specifically, micromechanical inertial systems and microstrip global positioning system (GPS) antennas incorporating flip-chip bonding, application specific integrated circuits (ASIC) and MCM technologies will be required. Traditional microsatellite pointing systems do not employ active control. Many systems allow the satellite to point coarsely using gravity gradient, then attempt to maintain the image on the focal plane with fast-steering mirrors. Draper's approach is to actively control the line of sight pointing by utilizing on-board attitude determination with micromechanical inertial sensors and reaction wheel control actuators. Draper has developed commercial and tactical-grade micromechanical inertial sensors, The small size, low weight, and low cost of these gyroscopes and accelerometers enable systems previously impractical because of size and cost. Evolving micromechanical inertial sensors can be applied to closed-loop, active control of small satellites for micro-radian precision-pointing missions. An inertial reference feedback control loop can be used to determine attitude and line of sight jitter to provide error information to the controller for correction. At low frequencies, the error signal is provided by GPS. At higher frequencies, feedback is provided by the micromechanical gyros. This blending of sensors provides wide-band sensing from dc to operational frequencies. First order simulation has shown that the performance of existing micromechanical gyros, with integrated GPS, is feasible for a pointing mission of 10 micro-radians of jitter stability and approximately 1 milli-radian absolute error, for a satellite with 1 meter antenna separation. Improved performance micromechanical sensors currently under development will be

  10. Path duplication using GPS carrier based relative position for automated ground vehicle convoys

    NASA Astrophysics Data System (ADS)

    Travis, William E., III

    A GPS based automated convoy strategy to duplicate the path of a lead vehicle is presented in this dissertation. Laser scanners and cameras are not used; all information available comes from GPS or inertial systems. An algorithm is detailed that uses GPS carrier phase measurements to determine relative position between two moving ground vehicles. Error analysis shows the accuracy is centimeter level. It is shown that the time to the first solution fix is dependent upon initial relative position accuracy, and that near instantaneous fixes can be realized if that accuracy is less than 20 centimeters. The relative positioning algorithm is then augmented with inertial measurement units to dead reckon through brief outages. Performance analysis of automotive and tactical grade units shows the twenty centimeter threshold can be maintained for only a few seconds with the automotive grade unit and for 14 seconds with the tactical unit. Next, techniques to determine odometry information in vector form are discussed. Three methods are outlined: dead reckoning of inertial sensors, time differencing GPS carrier measurements to determine change in platform position, and aiding the time differenced carrier measurements with inertial measurements. Partial integration of a tactical grade inertial measurement unit provided the lowest error drift for the scenarios investigated, but the time differenced carrier phase approach provided the most cost feasible approach with similar accuracy. Finally, the relative position and odometry algorithms are used to generate a reference by which an automated following vehicle can replicate a lead vehicle's path of travel. The first method presented uses only the relative position information to determine a relative angle to the leader. Using the relative angle as a heading reference for a steering control causes the follower to drive at the lead vehicle, thereby creating a towing effect on the follower when both vehicles are in motion. Effective

  11. Multivariate bootstrapped relative positioning of spacecraft using GPS L1/Galileo E1 signals

    NASA Astrophysics Data System (ADS)

    Buist, Peter J.; Teunissen, Peter J. G.; Giorgi, Gabriele; Verhagen, Sandra

    2011-03-01

    GNSS-based precise relative positioning between spacecraft normally requires dual frequency observations, whereas attitude determination of the spacecraft, mainly due to the stronger model given by the a priori knowledge of the length and geometry of the baselines, can be performed precisely using only single frequency observations. When the Galileo signals will come available, the number of observations at the L1 frequency will increase as we will have a GPS and Galileo multi-constellation. Moreover the L1 observations of the Galileo system and modernized GPS are more precise than legacy GPS and this, combined with the increased number of observations, will result in a stronger model for single frequency relative positioning. In this contribution we will develop an even stronger model by combining the attitude determination problem with relative positioning. The attitude determination problem will be solved by the recently developed Multivariate Constrained (MC-) LAMBDA method. We will do this for each spacecraft and use the outcome for an ambiguity constrained solution on the baseline between the spacecraft. In this way the solution for the unconstrained baseline is bootstrapped from the MC-LAMBDA solutions of each spacecraft in what is called: multivariate bootstrapped relative positioning. The developed approach will be compared in simulations with relative positioning using a single antenna at each spacecraft (standard LAMBDA) and a vectorial bootstrapping approach. In the simulations we will analyze single epoch, single frequency success rates as the most challenging application. The difference in performance for the approaches for single epoch solutions, is a good indication of the strength of the underlying models. As the multivariate bootstrapping approach has a stronger model by applying information on the geometry of the constrained baselines, for applications with large observation noise and limited number of observations this will result in a better

  12. Evaluating the velocity accuracy of an integrated GPS/INS system: Flight test results

    SciTech Connect

    Owen, T.E.; Wardlaw, R.

    1991-12-31

    Verifying the velocity accuracy of a GPS receiver or an integrated GPS/INS system in a dynamic environment is a difficult proposition when many of the commonly used reference systems have velocity uncertainities of the same order of magnitude or greater than the GPS system. The results of flight tests aboard an aircraft in which multiple reference systems simultaneously collected data to evaluate the accuracy of an integrated GPS/INS system are reported. Emphasis is placed on obtaining high accuracy estimates of the velocity error of the integrated system in order to verify that velocity accuracy is maintained during both linear and circular trajectories. Three different reference systems operating in parallel during flight tests are used to independently determine the position and velocity of an aircraft in flight. They are a transponder/interrogator ranging system, a laser tracker, and GPS carrier phase processing. Results obtained from these reference systems are compared against each other and against an integrated real time differential based GPS/INS system to arrive at a set of conclusions about the accuracy of the integrated system.

  13. A GPS Backpack System for Mapping Soil and Crop Parameters in Agricultural Fields

    NASA Astrophysics Data System (ADS)

    Stafford, J. V.; Lebars, J. M.

    Farmers are having to gather increasing amounts of data on their soils and crops. Precision agriculture metre-by-metre is based on a knowledge of the spatial variation of soil and crop parameters across a field. The data has to be spatially located and GPS is an effective way of doing this. A backpack data logging system with GPS position tagging is described which has been designed to aid a fanner in the manual collection of data.

  14. GPS-based orbit determination and point positioning under selective availability

    NASA Technical Reports Server (NTRS)

    Bar-Sever, Yoaz E.; Yunck, Thomas P.; Wu, Sien-Chong

    1990-01-01

    Selective availability (SA) degrades the positioning accuracy for nondifferential users of the GPS Standard Positioning Service (SPS). The often quoted SPS accuracy available under normal conditions is 100 m 2DRMS. In the absence of more specific information, many prospective SPS users adopt the 100 m value in their planning, which exaggerates the error in many cases. SA error is examined for point positioning and dynamic orbit determination for an orbiting user. To minimize SA error, nondifferential users have several options: expand their field of view; observe as many GPS satellites as possible; smooth the error over time; and employ precise GPS ephemerides computed independently, as by NASA and the NGS, rather than the broadcast ephemeris. Simulations show that 3D point position error can be kept to 30 m, and this can be smoothed to 3 m in a few hours.

  15. GPS-based orbit determination and point positioning under selective availability

    NASA Astrophysics Data System (ADS)

    Bar-Sever, Yoaz E.; Yunck, Thomas P.; Wu, Sien-Chong

    Selective availability (SA) degrades the positioning accuracy for nondifferential users of the GPS Standard Positioning Service (SPS). The often quoted SPS accuracy available under normal conditions is 100 m 2DRMS. In the absence of more specific information, many prospective SPS users adopt the 100 m value in their planning, which exaggerates the error in many cases. SA error is examined for point positioning and dynamic orbit determination for an orbiting user. To minimize SA error, nondifferential users have several options: expand their field of view; observe as many GPS satellites as possible; smooth the error over time; and employ precise GPS ephemerides computed independently, as by NASA and the NGS, rather than the broadcast ephemeris. Simulations show that 3D point position error can be kept to 30 m, and this can be smoothed to 3 m in a few hours.

  16. Observability and performance analysis of integrated GPS/INS navigation systems

    NASA Astrophysics Data System (ADS)

    Shao, Yunfeng

    This primary objective of this thesis is to analyze the performance and observability characteristics of integrated navigation systems which fuse the information from the Global Positioning System (GPS) and Inertial Navigation Systems (INS) of varying quality. It is shown that INS output error characteristics affect the notion of observability with these systems. More specifically; it is shown that when INS sensor quality is low, the traditional metrics of deterministic and stochastic observability are incomplete metrics to describe the system performance. Accordingly, a new metric as well as detailed trade study results that characterize the observability of GPS/INS fusion filter which use low quality inertial sensors is developed. A secondary objective of this thesis is to evaluate the use of an integrated GPS/INS system in two aviation applications of significant current interest. The first application is about monitoring and mitigating the impact of structural flexure of an aircraft carrier which is he host of the GPS-based landing system known as Joint Precision Approach and Landing Systems (JPALS). A mathematic error model is developed and validated using experimental ship motion data. The second application is that of checking the integrity of the GPS signal used in GPS-based landing systems such as JPALS and other landing systems envisioned for future use in commercial aviation. An inertial aided Receiver Autonomous Integrity Monitoring (RAIM) algorithm is designed and its performance improvements with inertial aiding are quantified.

  17. Geometric rectification of airborne sensor data using GPS-based attitude and position information

    SciTech Connect

    Wilson, A.K.; Mockridge, W.

    1996-11-01

    The geometric rectification of remotely sensed data, acquired using airborne platforms, is an essential prerequisite for quantitative processing and analysis, due to the complex distortions inherent in such imagery. The Natural Environment Research Council (NERC) has implemented an Integrated Data System (IDS) on-board its survey aircraft to derive both attitude and position for use in a parametric solution to the geometric correction of data from two airborne sensors. This paper describes the elements of the NERC IDS and the complementary ground data processing system that carries out navigation pre-processing and geometric resampling of the airborne data. Test flights have been flown and processed to demonstrate the potential of this completely GPS-based solution to providing high quality, spatially referenced, data for use in environmental monitoring applications. 6 refs., 5 figs., 1 tab.

  18. A method of undifferenced ambiguity resolution for GPS+GLONASS precise point positioning

    NASA Astrophysics Data System (ADS)

    Yi, Wenting; Song, Weiwei; Lou, Yidong; Shi, Chuang; Yao, Yibin

    2016-05-01

    Integer ambiguity resolution is critical for achieving positions of high precision and for shortening the convergence time of precise point positioning (PPP). However, GLONASS adopts the signal processing technology of frequency division multiple access and results in inter-frequency code biases (IFCBs), which are currently difficult to correct. This bias makes the methods proposed for GPS ambiguity fixing unsuitable for GLONASS. To realize undifferenced GLONASS ambiguity fixing, we propose an undifferenced ambiguity resolution method for GPS+GLONASS PPP, which considers the IFCBs estimation. The experimental result demonstrates that the success rate of GLONASS ambiguity fixing can reach 75% through the proposed method. Compared with the ambiguity float solutions, the positioning accuracies of ambiguity-fixed solutions of GLONASS-only PPP are increased by 12.2%, 20.9%, and 10.3%, and that of the GPS+GLONASS PPP by 13.0%, 35.2%, and 14.1% in the North, East and Up directions, respectively.

  19. The Ether Wind and the Global Positioning System.

    ERIC Educational Resources Information Center

    Muller, Rainer

    2000-01-01

    Explains how students can perform a refutation of the ether theory using information from the Global Positioning System (GPS). Discusses the functioning of the GPS, qualitatively describes how position determination would be affected by an ether wind, and illustrates the pertinent ideas with a simple quantitative model. (WRM)

  20. Global gravity field models from the GPS positions of CHAMP, GRACE and GOCE satellites

    NASA Astrophysics Data System (ADS)

    Bezděk, A.; Sebera, J.; Klokočník, J.; Kostelecký, J.

    2012-04-01

    The aim of our work is to generate Earth's gravity field models from the GPS positions of low Earth orbiters. We will present our inversion method and numerical results based on the real-world data of CHAMP, GRACE and GOCE satellites. The presented inversion method is based on Newton's second law of motion, which relates the observed acceleration of the satellite with the forces acting on it. The vector of the observed acceleration is obtained through a numerical second-derivative filter applied to the time series of the kinematic positions. Forces other than those due to the geopotential are either modelled (lunisolar perturbations, tides) or provided by the onboard measurements (nongravitational perturbations). Then the observation equations are formulated using the gradient of the spherical harmonic expansion of the geopotential. From this linear system the harmonic coefficients are directly obtained. We do not use any a priori gravity field model. Although the basic scheme of the acceleration approach is straightforward, the implementation details play a crucial role in obtaining reasonable results. The numerical derivative of noisy data (here the GPS positions) strongly amplifies the high frequency noise and creates autocorrelation in the observation errors. We successfully solve both of these problems by using the generalized least squares method, which defines a linear transformation of the observation equations. In the transformed variables the errors become uncorrelated, so the ordinary least squares estimation may be used to find the regression parameters with correct estimates of their uncertainties. The digital filter of the second derivative is an approximation to the analytical operation. We will show how different the results might be depending on the particular choice of the parameters defining the filter. Another problem is the correlation of the errors in the GPS positions. Here we use the tools from time series analysis. The systematic behaviour

  1. Solar System Modeler: A Distributed, Virtual Environment for Space Visualization and GPS Navigation

    NASA Astrophysics Data System (ADS)

    Williams, Gary E.

    1996-12-01

    The Solar System Modeler (SM) extends the Space Modeler developed in 1994. It provides a virtual environment enabling an explorer to dynamically investigate near Earth satellites, deep space probes, planets, moons, and other celestial phenomena. The explorer navigates the virtual environment via mouse selected options from menu panels while wearing a tracked, head mounted display (HMD). Alternatively, a monitor may replace the HMD and keyboard controls replace head tracking. The SM's functionality is extended by the ability to broadcast simulated GPS satellite transmissions in compliance with Distributed Interactive Simulation (DIS) protocol standards. The transmissions include information found in true GPS broadcasts that is required for a receiver to determine its location. The Virtual GPS Receiver (VGPSR) receives the GPS transmissions from the SM and computes the receiver's position with a realistic error based on numerous variables simulating those encountered in the real GPS system. The VGPSR is designed as a plug-in module for simulations requiring virtual navigation. The receiver's client application provides the VGPSR with the simulation time and the true position of the receiver. In return, the application receives a GPS indicated position.

  2. The time keeping system for GPS block IIR

    NASA Technical Reports Server (NTRS)

    Rawicz, H. C.; Epstein, M. A.; Rajan, J. A.

    1993-01-01

    The precision time keeping system (TKS) in the Global Positioning System (GPS), Block IIR satellites is designed to operate under severe natural and man made environmental conditions. The Block IIR TKS provides precise, autonomous time keeping for periods of up to seven months, without the intervention of the GPS Control Segment. The TKS is implemented using both linear and non-linear controls. The resulting TKS architecture uses a hybrid analog/digital phase locked loop (PLL). The paper provides details of the design and analysis of the TKS. The simulation techniques and the test bed activities used in performing the TKS design trade-offs are described. The effects of non-linear controls are analyzed using a TKS computer simulation of the PLL. The results from a hardware test bed are provided that verify desired TKS operation. The design criteria for the TKS computer simulation and the hardware test bed are indicated. The concepts for verification and testing of the TKS computer simulation and hardware test bed are presented.

  3. A GPS System-of-Systems for Science

    NASA Astrophysics Data System (ADS)

    Sherwood, R.; Mannucci, A.; Zuffada, C.; Heeg, C.

    2006-12-01

    The 2006 National Research Council (NRC) Decadal Report will stress that future directions for Earth science at NASA/NOAA will focus on achievement of a national strategy for the Earth Sciences that balances international economic competitiveness, protection of life and property, and stewardship of the planet for this and future generations. Because of the urgent need for climate measurements identified in the report, a small group from JPL was formed to explore the science benefits of maintaining GPS receivers in orbit for climate science. This is a particularly timely topic since 7 new GPS-science capable satellites were launched in 2006 (COSMIC 1-6, MetOp1), resulting in 10 GPS-science capable satellites in orbit (including CHAMP, SAC-C, GRACE). For this GPS System-of-Systems, we studied climate observations, ionosphere observations, and ocean science. For climate observations, we simulated a constellation of ten satellites in a configuration similar to COSMIC, and performed a multi-year analysis of how such a constellation would be able to characterize long-term trends in temperature. We find that such a constellation is adequate to compute zonally-averaged, monthly mean temperatures with a precision adequate to address expected climate trends of order ~0.1 K per decade. Such a constellation also has adequate local time coverage to avoid aliasing diurnal cycle trends with global climate trends. The high accuracy and consistency of GPS-based atmospheric retrievals suggests that continuously maintaining an operating constellation of such receivers is an important global observation asset for characterizing long-term climate trends. We also performed a series of simulations to determine the science returns that could be achieved with varying sizes of GPS receiver constellations. This study can be used to consider the advantages of including GPS science receivers on future satellites as dedicated constellations or constellations of opportunity. For ocean science

  4. 76 FR 31943 - Global Positioning System Directorate (Gpsd); Notice of Meeting

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-06-02

    ... Department of the Air Force Global Positioning System Directorate (Gpsd); Notice of Meeting ACTION: Notice of..., IS-GPS-705A, IS-GPS-800A). SUMMARY: This notice informs the public that the Global Positioning Systems (GPS) Directorate will be hosting a Public Interface Control Working Group (ICWG) meeting for...

  5. 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.…

  6. Influence of the TEC fluctuations in the polar region on precise GPS positioning.

    NASA Astrophysics Data System (ADS)

    Sieradzki, Rafal; Paziewski, Jacek; Wielgosz, Pawel

    2014-05-01

    The ionospheric delay is an atmoshperic effect influencing on Global Navigation Satellite System signals. On the one hand it is a factor limiting the accuracy of the GNSS positioning, and on the other it makes satellite observations a very good source of the information on the ionospheric conditions. The degradation of the relative positioning accuracy and reliability can be connected with high gradients of the total electron content or with the TEC fluctuations. The latter of these effects mainly occurs in the equatorial and polar regions. The ionosphere near the geomagnetic poles is characterized by relatively small TEC values in comparison to the other regions. However, the connection between the magnetosphere and ionosphere systems in the polar regions allows particle precipitation and leads to very strong ionospheric dynamics. In this work, performance of the GNSS precise relative positioning under disturbed ionospheric conditions in the northern polar region is studied. The test results are based on processing 24-hour data sets from the selected permanent GPS stations located in Greenland. The studies cover several days of high and low solar activity, and also periods of a geomagnetic storm characterized by intensive TEC fluctuations. The data processing was carried out in static and kinematic modes. The GINPOS software developed at the University of Warmia and Mazury in Olsztyn was used for positioning tests. The study confirms and presents the influence of the ionospheric and geomagnetic activity in the polar region on the results in coordinate and ambiguity domains.

  7. The future of GPS-based electric power system measurements, operation and control

    SciTech Connect

    Rizy, D.T.; Wilson, R.E.; Martin, K.E.; Litzenberger, W.H.; Hauer, J.F.; Overholt, P.N.; Sobajic, D.J.

    1998-11-01

    Much of modern society is powered by inexpensive and reliable electricity delivered by a complex and elaborate electric power network. Electrical utilities are currently using the Global Positioning System-NAVSTAR (GPS) timekeeping to improve the network`s reliability. Currently, GPS synchronizes the clocks on dynamic recorders and aids in post-mortem analysis of network disturbances. Two major projects have demonstrated the use of GPS-synchronized power system measurements. In 1992, the Electric Power Research Institute`s (EPRI) sponsored Phase Measurements Project used a commercially available Phasor Measurements Unit (PMU) to collect GPS-synchronized measurements for analyzing power system problems. In 1995, Bonneville Power Administration (BPA) and Western Area Power Administration (WAPA) under DOE`s and EPRI`s sponsorship launched the Wide Area Measurements (WAMS) project. WAMS demonstrated GPS-synchronized measurements over a large area of their power networks and demonstrated the networking of GPS-based measurement systems in BPA and WAPA. The phasor measurement technology has also been used to conduct dynamic power system tests. During these tests, a large dynamic resistor was inserted to simulate a small power system disturbance.

  8. Aircraft Positioning for Airborne Gravimetry: GRAV-D's 'Kinematic GPS Processing Challenge' (Invited)

    NASA Astrophysics Data System (ADS)

    Damiani, T.; Bilich, A. L.; Mader, G. L.

    2013-12-01

    The National Geodetic Survey's (NGS's) Gravity for the Redefinition of the American Vertical Datum (GRAV-D) program will collect airborne gravity data across the entire U.S. and its holdings by 2022 to support a new national vertical datum. By July 2013, >26% of data collection was complete. To achieve the best airborne gravity data accuracy possible, the GPS-derived position, velocity, and accelerations of the aircraft must also be highly accurate. In Fall 2010, NGS issued the 'Kinematic GPS Challenge', asking for kinematic GPS experts to voluntarily process dual-frequency GPS data from two 2008 GRAV-D flights over Louisiana. The Challenge data have: long baselines (> 500 km), high altitudes (35,000 ft), high speeds (280 kts), and difficult locations (half of each flight is over the Gulf of Mexico). For both flights, 1s GPS receiver data was available from: the aircraft, nearby CORS stations, and an NGS-run Ashtech GPS base station at the New Orleans airport. The goal of the Challenge was to compare the position results of a variety of methods, and to compare the airborne gravity calculated using each of those position solutions. In response to the Challenge, eighteen position results from twelve contributors (including two from NGS), using both differential and PPP methods, were submitted. Initial analysis of submitted solutions showed many of the position solutions were contaminated by a 'sawtooth' pattern. Eventually, the 'sawtooth' was attributed to problems with the Trimble receiver in the aircraft. Despite the receiver problem and after removal of two outlier solutions, the submitted position solutions were different by no more than +/- 0.25 m in X, Y, and Z. The differential and PPP solutions were indistinguishable from one another, even when the aircraft was over 500 km away from the airport. The two best gravity results came from position solutions that incorporated smoothing into their processing. For the high-noise flight, NGS' preferred GPS+IMU loosely

  9. 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

  10. Performance enhancement for GPS positioning using constrained Kalman filtering

    NASA Astrophysics Data System (ADS)

    Guo, Fei; Zhang, Xiaohong; Wang, Fuhong

    2015-08-01

    Over the past decades Kalman filtering (KF) algorithms have been extensively investigated and applied in the area of kinematic positioning. In the application of KF in kinematic precise point positioning (PPP), it is often the case where some known functional or theoretical relations exist among the unknown state parameters, which can be and should be made use of to enhance the performance of kinematic PPP, especially in an urban and forest environment. The central task of this paper is to effectively blend the commonly used GNSS data and internal/external additional constrained information to generate an optimal PPP solution. This paper first investigates the basic algorithm of constrained Kalman filtering. Then two types of PPP model with speed constraints and trajectory constraints, respectively, are proposed. Further validation tests based on a variety of situations show that the positioning performances (positioning accuracy, reliability and continuity) from the constrained Kalman filter are significantly superior to those from the conventional Kalman filter, particularly under extremely poor observation conditions.

  11. Environmental applications of GPS

    SciTech Connect

    Vigil, S.A.; Zueck, D.

    1999-07-01

    The use of the Global Positioning System (GPS) has revolutionized air travel, ocean navigation, land navigation, and the collection of environmental data. Although a basic civilian GPS receiver can be purchased for as little as $100, the receiver is only the tip of a 12 billion dollar iceberg. This paper will discuss the history and basic operation of the Global Positioning System, a satellite-based precision positioning and timing service developed and operated by the Department of Defense. It will also describe the accuracy limitations of the civil GPS service and how accuracy can be enhanced by the use of differential GPS (DGPS), using either the free National Differential GPS system, or commercial differential monitor stations. Finally, the paper will discuss the future accuracy upgrades of civil GPS as a result of recent federal policy decisions.

  12. A GPS/GNSS dense network used to monitor ionospheric positioning error

    NASA Astrophysics Data System (ADS)

    Wautelet, G.; Lejeune, S.; Warnant, R.

    2010-12-01

    GPS/GNSS networks are, for the last few years, quickly expanding their density all over the surface of the globe. The present idea is to use this density in order to assess the effect of ionospheric disturbances on relative positioning but also to monitor their propagation patterns. Local variability in the ionospheric electron density can dramaticaly affect the reliability of GPS/GNSS real time applications. In particular, Traveling Ionospheric Disturbances (TID's) or plasma instability due to geomagnetic storms can induce strong disturbances in relative positioning. It is therefore useful to develop an integrity monitoring service based on a GPS/GNSS dense network. To assess the effects of ionospheric activity on relative positioning, the SoDIPE-RTK software (Software for Determining the Ionospheric Positionning Error on RTK) has been developed at the Royal Meteorological Institute of Belgium. The approach consists in computing the positioning error due to the ionosphere and has been applied, as a proof of concept, on the Belgian dense network. This network called Active Geodetic Network (AGN) is composed of 66 GPS (dual-frequency) stations. In order to ensure a successful ambiguity resolution for both L1 and L2 carriers, baselines larger than 40 km are not taken into account in the analysis. In a first step, we assess the nominal RTK precision for each baseline during quiet ionospheric conditions (i.e. a background of low Total Electron Content (TEC) variability). The observed positioning accuracy is ~1 cm and depends mainly on baseline length and satellite geometry at the two considered stations. In a second step, the impact of two ionospheric events on positioning error (a medium scale TID and a powerful geomagnetic storm) is evaluated. As expected, the study demonstrates that the largest effects are observed during the occurrence of the geomagnetic storm with an ionospheric positioning error reaching 0.9 m. The maximal positioning error observed during the

  13. Multi-Flight-Phase GPS Navigation Filter Applications to Terrestrial Vehicle Navigation and Positioning

    NASA Technical Reports Server (NTRS)

    Park, Young W.; Montez, Moises N.

    1994-01-01

    A candidate onboard space navigation filter demonstrated excellent performance (less than 8 meter level RMS semi-major axis accuracy) in performing orbit determination of a low-Earth orbit Explorer satellite using single-frequency real GPS data. This performance is significantly better than predicted by other simulation studies using dual-frequency GPS data. The study results revealed the significance of two new modeling approaches evaluated in the work. One approach introduces a single-frequency ionospheric correction through pseudo-range and phase range averaging implementation. The other approach demonstrates a precise axis-dependent characterization of dynamic sample space uncertainty to compute a more accurate Kalman filter gain. Additionally, this navigation filter demonstrates a flexibility to accommodate both perturbational dynamic and observational biases required for multi-flight phase and inhomogeneous application environments. This paper reviews the potential application of these methods and the filter structure to terrestrial vehicle and positioning applications. Both the single-frequency ionospheric correction method and the axis-dependent state noise modeling approach offer valuable contributions in cost and accuracy improvements for terrestrial GPS receivers. With a modular design approach to either 'plug-in' or 'unplug' various force models, this multi-flight phase navigation filter design structure also provides a versatile GPS navigation software engine for both atmospheric and exo-atmospheric navigation or positioning use, thereby streamlining the flight phase or application-dependent software requirements. Thus, a standardized GPS navigation software engine that can reduce the development and maintenance cost of commercial GPS receivers is now possible.

  14. 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.

  15. Global Positioning System Simulator Field Operational Procedures

    NASA Technical Reports Server (NTRS)

    Kizhner, Semion; Quinn, David A.; Day, John H. (Technical Monitor)

    2002-01-01

    Global Positioning System (GPS) simulation is an important activity in the development or qualification of GPS signal receivers for space flight. Because a GPS simulator is a critical resource it is highly desirable to develop a set of field operational procedures to supplement the basic procedures provided by most simulator vendors. Validated field procedures allow better utilization of the GPS simulator in the development of new test scenarios and simulation operations. These procedures expedite simulation scenario development while resulting in scenarios that are more representative of the true design, as well as enabling construction of more complex simulations than previously possible, for example, spacecraft maneuvers. One difficulty in the development of a simulation scenario is specifying various modes of test vehicle motion and associated maneuvers requiring that a user specify some (but not all) of a few closely related simulation parameters. Currently this can only be done by trial and error. A stand-alone procedure that implements the simulator maneuver motion equations and solves for the motion profile transient times, jerk and acceleration would be of considerable value. Another procedure would permit the specification of some configuration parameters that would determine the simulated GPS signal composition. The resulting signal navigation message, for example, would force the receiver under test to use only the intended C-code component of the simulated GPS signal. A representative class of GPS simulation-related field operational procedures is described in this paper. These procedures were developed and used in support of GPS integration and testing for many successful spacecraft missions such as SAC-A, EO-1, AMSAT, VCL, SeaStar, sounding rockets, and by using the industry standard Spirent Global Simulation Systems Incorporated (GSSI) STR series simulators.

  16. Finding a Target with an Accessible Global Positioning System

    ERIC Educational Resources Information Center

    Ponchillia, Paul E.; MacKenzie, Nancy; Long, Richard G.; Denton-Smith, Pamela; Hicks, Thomas L.; Miley, Priscilla

    2007-01-01

    This article presents two target-location experiments. In the first experiment, 19 participants located a 25-foot chalk circle 93% of the time with a Global Positioning System (GPS) compared to 12% of the time without it. In a single-subject follow-up experiment, the participant came within 1 foot of the target on all GPS trials. Target-location…

  17. Estimating snow water equivalent from GPS vertical site-position observations in the western United States.

    PubMed

    Ouellette, Karli J; de Linage, Caroline; Famiglietti, James S

    2013-05-01

    [1] Accurate estimation of the characteristics of the winter snowpack is crucial for prediction of available water supply, flooding, and climate feedbacks. Remote sensing of snow has been most successful for quantifying the spatial extent of the snowpack, although satellite estimation of snow water equivalent (SWE), fractional snow covered area, and snow depth is improving. Here we show that GPS observations of vertical land surface loading reveal seasonal responses of the land surface to the total weight of snow, providing information about the stored SWE. We demonstrate that the seasonal signal in Scripps Orbit and Permanent Array Center (SOPAC) GPS vertical land surface position time series at six locations in the western United States is driven by elastic loading of the crust by the snowpack. GPS observations of land surface deformation are then used to predict the water load as a function of time at each location of interest and compared for validation to nearby Snowpack Telemetry observations of SWE. Estimates of soil moisture are included in the analysis and result in considerable improvement in the prediction of SWE. Citation: Ouellette, K. J., C. de Linage, and J. S. Famiglietti (2013), Estimating snow water equivalent from GPS vertical site-position observations in the western United States, Water Resour. Res., 49, 2508-2518, doi:10.1002/wrcr.20173. PMID:24223442

  18. Estimating snow water equivalent from GPS vertical site-position observations in the western United States

    PubMed Central

    Ouellette, Karli J; de Linage, Caroline; Famiglietti, James S

    2013-01-01

    [1] Accurate estimation of the characteristics of the winter snowpack is crucial for prediction of available water supply, flooding, and climate feedbacks. Remote sensing of snow has been most successful for quantifying the spatial extent of the snowpack, although satellite estimation of snow water equivalent (SWE), fractional snow covered area, and snow depth is improving. Here we show that GPS observations of vertical land surface loading reveal seasonal responses of the land surface to the total weight of snow, providing information about the stored SWE. We demonstrate that the seasonal signal in Scripps Orbit and Permanent Array Center (SOPAC) GPS vertical land surface position time series at six locations in the western United States is driven by elastic loading of the crust by the snowpack. GPS observations of land surface deformation are then used to predict the water load as a function of time at each location of interest and compared for validation to nearby Snowpack Telemetry observations of SWE. Estimates of soil moisture are included in the analysis and result in considerable improvement in the prediction of SWE. Citation: Ouellette, K. J., C. de Linage, and J. S. Famiglietti (2013), Estimating snow water equivalent from GPS vertical site-position observations in the western United States, Water Resour. Res., 49, 2508–2518, doi:10.1002/wrcr.20173. PMID:24223442

  19. SAR image registration in absolute coordinates using GPS carrier phase position and velocity information

    SciTech Connect

    Burgett, S.; Meindl, M.

    1994-09-01

    It is useful in a variety of military and commercial application to accurately register the position of synthetic aperture radar (SAR) imagery in absolute coordinates. The two basic SAR measurements, range and doppler, can be used to solve for the position of the SAR image. Imprecise knowledge of the SAR collection platform`s position and velocity vectors introduce errors in the range and doppler measurements and can cause the apparent location of the SAR image on the ground to be in error by tens of meters. Recent advances in carrier phase GPS techniques can provide an accurate description of the collection vehicle`s trajectory during the image formation process. In this paper, highly accurate carrier phase GPS trajectory information is used in conjunction with SAR imagery to demonstrate a technique for accurate registration of SAR images in WGS-84 coordinates. Flight test data will be presented that demonstrates SAR image registration errors of less than 4 meters.

  20. 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

  1. 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. PMID:22368460

  2. Seafloor horizontal positioning from a continuously operating buoy-based GPS-acoustic array

    NASA Astrophysics Data System (ADS)

    Chadwell, C. D.; Brown, K. M.; Tryon, M. D.; Send, U.

    2009-12-01

    Seafloor horizontal positions in a global frame were estimated daily from an autonomous buoy operating continuously over several months. The buoy (GEOCE) was moored offshore San Diego in 100-m-deep waters above an array of 4 seafloor transponders. Dual-frequency GPS data were collected at 1-Hz at a main antenna on the buoy and at 3 shore stations to provide continuous 2-3 cm positions of the buoy main antenna. Two single-frequency antennas on the buoy along with the main antenna were used to estimate the buoy attitude and short-term velocity. At one minute intervals the two-way acoustic travel time was measured between the buoy and transponders. During this few second span when transmitting and receiving acoustic signals, 10-Hz attitude and velocity were collected to locate the position of the transducer mounted approximately 2 m below the water line. The GPS and acoustic data were recorded internally and transmitted to shore over a cell-phone link and/or a wireless Ethernet. GPS data were combined with the acoustic data to estimate the array location at 1 minute intervals. The 1-minute positions are combined to provide a daily estimate of the array position. The buoy is autonomous, solar-powered and in addition to the GPS and acoustic data collects air pressure, temperature, wind speed/direction as well as water level at the surface and conductivity and temperature along the mooring line from near the sea surface to just above the sea floor. Here we report results from the horizontal positioning effort from Phase I of the project in shallow waters. The project also includes a vertical deformation sensor and physical oceanographic monitoring. A deep water (nominally 1000 m) test is planned for 2010. This work is supported by NSF-OCE-0551363 of the Ocean Technology and Interdisciplinary Coordination Program.

  3. Tractor-mounted, GPS-based spot fumigation system manages Prunus replant disease

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Our research goal was to use recent advances in global positioning system (GPS) and computer technology to apply just the right amount of fumigant where it is most needed (i.e., in a small target treatment zone in and around each tree replanting site) to control Prunus replant disease (PRD). We deve...

  4. 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.

  5. MicroBlaze implementation of GPS/INS integrated system on Virtex-6 FPGA.

    PubMed

    Bhogadi, Lokeswara Rao; Gottapu, Sasi Bhushana Rao; Konala, Vvs Reddy

    2015-01-01

    The emphasis of this paper is on MicroBlaze implementation of GPS/INS integrated system on Virtex-6 field programmable gate array (FPGA). Issues related to accuracy of position, resource usage of FPGA in terms of slices, DSP48, block random access memory, computation time, latency and power consumption are presented. An improved design of a loosely coupled GPS/INS integrated system is described in this paper. The inertial navigation solution and Kalman filter computations are provided by the MicroBlaze on Virtex-6 FPGA. The real time processed navigation solutions are updated with a rate of 100 Hz. PMID:26543763

  6. Key solutions to WEB-GIS based GPS vehicle monitoring system

    NASA Astrophysics Data System (ADS)

    Tan, Jian; Gao, Liang; Zhang, Jian Bing; Ren, Yingchao; Wu, Lei; Sheng, Lei

    2007-11-01

    Using Web-GIS to implement GPS monitoring is a promising implementation mode for public service and GPS monitoring in big organization. The critical bottle neck is the bandwidth, because both geographic maps and vehicle positioning data in the system are mass and they need to be transmitted frequently. In this paper, we illustrate five methods to solve this problem. The performances demonstrated in practicing application confirm the validity of these measures. Finally, the system achieves the balance between computational efficiency and transmission speed on internet and gains a nice user experience.

  7. Crop Dusting Using GPS

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Global Positioning System (GPS) receivers and GPS-based swath guidance systems are used on agricultural aircraft for remote sensing, airplane guidance, and to support variable-rate aerial application of crop inputs such as insecticides, cotton growth regulators, and defoliants. Agricultural aircraf...

  8. Supporting EarthScope Cyber-Infrastructure with a Modern GPS Science Data System

    NASA Astrophysics Data System (ADS)

    Webb, F. H.; Bock, Y.; Kedar, S.; Jamason, P.; Fang, P.; Dong, D.; Owen, S. E.; Prawirodirjo, L.; Squibb, M.

    2008-12-01

    Building on NASA's investment in the measurement of crustal deformation from continuous GPS, we are developing and implementing a Science Data System (SDS) that will provide mature, long-term Earth Science Data Records (ESDR's). This effort supports NASA's Earth Surface and Interiors (ESI) focus area and provide NASA's component to the EarthScope PBO. This multi-year development is sponsored by NASA's Making Earth System data records for Use in Research Environments (MEaSUREs) program. The SDS integrates the generation of ESDRs with data analysis and exploration, product generation, and modeling tools based on daily GPS data that include GPS networks in western North America and a component of NASA's Global GPS Network (GGN) for terrestrial reference frame definition. The system is expandable to multiple regional and global networks. The SDS builds upon mature data production, exploration, and analysis algorithms developed under NASA's REASoN, ACCESS, and SENH programs. This SDS provides access to positions, time series, velocity fields, and strain measurements derived from continuous GPS data obtained at tracking stations in both the Plate Boundary Observatory and other regional Western North America GPS networks, dating back to 1995. The SDS leverages the IT and Web Services developments carried out under the SCIGN/REASoN and ACCESS projects, which have streamlined access to data products for researchers and modelers, and which have created a prototype an on-the-fly interactive research environment through a modern data portal, GPS Explorer. This IT system has been designed using modern IT tools and principles in order to be extensible to any geographic location, scale, natural hazard, and combination of geophysical sensor and related data. We have built upon open GIS standards, particularly those of the OGC, and have used the principles of Web Service-based Service Oriented Architectures to provide scalability and extensibility to new services and capabilities.

  9. GPS Seismology: Using Precise Point Positioning for Resolving Surface Wave Displacements from Large Earthquakes

    NASA Astrophysics Data System (ADS)

    Dragert, H.; Henton, J. A.; Lahaye, F.; Kouba, J.; Larson, K. M.; Rogers, G. C.

    2010-12-01

    High-rate continuous GPS data can provide direct, high-quality measurements of surface wave displacements generated by large earthquakes (Larson et al., 2003; Bock et al., 2004; Larson, 2009). To achieve high precision, differential positioning is often used in the GPS analysis strategy with distant reference stations held fixed. In this presentation, we examine the use of the Precise Point Positioning (PPP) technique to estimate epoch-by-epoch positions at single stations. Specifically, we use the PPP software developed by Natural Resources Canada (Heroux and Kouba, 2001) to analyze high-rate (5 Hz) GPS data collected at stations of the Plate Boundary Observatory (PBO) in southern California at the time of the M7.2 El Mayor-Cucapah Earthquake of April 4, 2010. The hypocenter for this earthquake was located in northern Baja California, approximately 50 km south of Mexicali on the US-Mexico border, at a depth of ~10 km. Large horizontal displacements were observed at a number of PBO GPS sites, with the largest peak-to-peak displacements exceeding 90 cm in the east-west component for 10-sec period waves observed at El Centro, CA (P496), located about 70 km northeast of the epicenter. The PPP technique clearly resolved surface waves with 1 to 2 cm amplitudes at sites more than 800 km away from the epicenter, illustrating that surface waves eventually reach even distant reference sites within the period of interest and can thereby introduce artifacts for differential GPS positioning. Fine-tuning of PPP methodology revealed the following: 1) Since the quality of a PPP solution will not be optimal until the carrier phase ambiguities have converged (tens of minutes), it is best to begin the analyses well before the arrival of seismic waves. To reduce computations, the data for this convergence period need not be high-rate; 2) The use of 5-second precise satellite clock sampling instead of the nominal 30-second clock sampling minimized clock interpolation errors and

  10. A method of undifferenced ambiguity resolution for GPS+GLONASS precise point positioning.

    PubMed

    Yi, Wenting; Song, Weiwei; Lou, Yidong; Shi, Chuang; Yao, Yibin

    2016-01-01

    Integer ambiguity resolution is critical for achieving positions of high precision and for shortening the convergence time of precise point positioning (PPP). However, GLONASS adopts the signal processing technology of frequency division multiple access and results in inter-frequency code biases (IFCBs), which are currently difficult to correct. This bias makes the methods proposed for GPS ambiguity fixing unsuitable for GLONASS. To realize undifferenced GLONASS ambiguity fixing, we propose an undifferenced ambiguity resolution method for GPS+GLONASS PPP, which considers the IFCBs estimation. The experimental result demonstrates that the success rate of GLONASS ambiguity fixing can reach 75% through the proposed method. Compared with the ambiguity float solutions, the positioning accuracies of ambiguity-fixed solutions of GLONASS-only PPP are increased by 12.2%, 20.9%, and 10.3%, and that of the GPS+GLONASS PPP by 13.0%, 35.2%, and 14.1% in the North, East and Up directions, respectively. PMID:27222361