Abstract:
Employing the largest global real-time tracking network, the Global Differential GPS (GDGPS) System tracks the GPS civil signals on the L1 and L2 frequencies. Highly redundant satellite coverage (25 fold, on average) ensures seamless and robust global coverage. The raw measurements are streamed via redundant communication paths to multiple GDGPS Operation Centers (GOC) (3 centers as of October ... 2006). At the GOC the data is processed by the award-winning software, Real Time GIPSY (RTG), to derive the real-time differential corrections to the GPS orbit and clock states, as well as many by-products and services. Our state-space approach to orbit determination ensures that all the products are globally and uniformly valid.
The fundamental latency of the system is ~5 seconds from reception of the navigation signal by the tracking receiver to the production and dissemination of the differential corrections and the other real-time by-products. Lower latency for certain products, such as integrity monitoring, is supported.
The data products are disseminated to customers through a variety of channels. Customers are encouraged to access multiple GOCs and use multiple communications channels to ensure end-to-end redundancy for mission-critical products and services. Supported channels include: internet, VPN over internet, T1, Frame Relay, modems, and satellite broadcast.
Extremely high reliability has been accomplished through an extremely high level of end-to-end redundancy, without any single point of failure. Innovative software ensures automatic fault detection and seamless failover between various redundant components of the system, resulting in uninterrupted service to customers.
Name:
YOAZ
BAR-SEVER
Phone:
818-354-2665
Fax:
818-393-4965
Email:
yoaz.e.bar-sever at nasa.gov
Contact Address:
Mail Stop 238-600
4800 Oak Grove Drive City:
Pasadena
Province or State:
CA
Postal Code:
91109
Country:
USA
Personnel
YOAZ
BAR-SEVER Role:
TECHNICAL CONTACT
Phone:
818-354-2665
Fax:
818-393-4965
Email:
yoaz.e.bar-sever at nasa.gov
Contact Address:
Mail Stop 238-600
4800 Oak Grove Drive City:
Pasadena
Province or State:
CA
Postal Code:
91109
Country:
USA
TYLER
B.
STEVENS Role:
SERF AUTHOR
Phone:
(301) 614-6898
Fax:
301-614-5268
Email:
Tyler.B.Stevens at nasa.gov
Contact Address:
NASA Goddard Space Flight Center
Global Change Master Directory City:
Greenbelt
Province or State:
MD
Postal Code:
20771
Country:
USA
Publications/References
Development of a Real-Time Single-Frequency Precise Point Positioning System and Test Results Yang Gao and Kongzhe Chen The University of Calgary Describe the development of a real-time single-frequency PPP system using the ireal-time GPS orbit and clock products from the JPL GDGPS System. Report test results under road and marine conditions. ION GNSS 2006, Fort ... Worth, TX, USA, Sept.2005.
StarFire: A Global SBAS for Sub-Decimeter Precise Point Positioning Kevin Dixon Navcom Technology Inc. Describe the structure and performance of the Navcom differential system, which is based partially on JPL's Real Time GIPSY (RTG) software, and on the GDGPS tracking network. ION GNSS 2006, Fort Worth, TX, USA, Sept.2005.
Real-Time Precise Point Positioning (PPP) Using Single Frequency Data Kongzhe Chen and Yang Gao The University of Calgary Investigates PPP using single-frequency data and precise real-time orbits and clocks while comparing ionospheric correction methods: Klobuchar, GIM, GRAPHIC and ionospheric gradient estimation. Includes both static and kinematic airborne positioning results, contrasting the different modeling methods. ION GNSS 2005, Long Beach, CA, USA, Sept.2005.
Performance Evaluation of Global Differential GPS (GDGPS) for Single Frequency C/A Code Receivers Sundar Raman, and Lionel Garin SiRF Technology, Inc. Analyze the performance of GDGPS as a replacement for local differential GPS (LDGPS) for single-frequency users. ION GNSS 2005, Long Beach, CA, USA, Sept.2005.
Real-time Kinematic Positioning with NASA's Global Differential GPS System Kechine, M.O., C.C.J.M Tiberius, H. van der Marel University of Delft, The Netherlands Independent performance assessment of the GDGPS system for real-time kinematic positioning performed at University of Delft, The Netherlands. GNSS Conference, St. Petersburg, Russia, May 2004.
Real-Time Sub-cm Differential Orbit Determination of Two Low-Earth Orbiters with GPS Bias Fixing Sien Wu and Yoaz Bar-Sever Jet Propulsion Laboratory, California Institute of Technology An effective technique for real-time differential orbit determination of two low Earth orbiters with GPS bias fixing is formulated. With this technique, only moderatequality GPS orbit and clock states (e.g., as available in real-time from the NASA Global Differential GPS System with 1020 cm accuracy) are needed to seed the process. ION GNSS 2006, Fort Worth, TX, USA, Sept.2005.
The NASA Global Differential GPS System (GDGPS) and The TDRSS Augmentation Service for Satellites (TASS) Yoaz Bar-Sever, Larry Young, Frank Stocklin, Paul Heffernan and John Rush Jet Propulsion Laboratory, California Institute of Technology Status of the NASA GDGPS System and the newly developed TDRSS Augmentation Service for Satellites (TASS), with focus on space applications. Presentation at the ESA 2nd Workshop on navigation equipment, Noordwijk, The Netherlands, December 2004.
Real-Time Point Positioning Performance Evaluation of Single-Frequency Receivers Using NASA's Global Differential GPS System Muellerschoen, R., B. Iijima, R. Meyer, Y. Bar-Sever, E. Accad Jet Propulsion Laboratory, California Institute of Technology Techniques for precise real time positioning of single frequency users. Accuracy assessment of real-time global ionospheric maps produced by the GDGPS System. ION GNSS Meeting, Long Beach, CA, September 2004.
Toward Decimeter-level Real-Time Orbit Determination: a Demonstration Using the SAC-C and CHAMP Spacecraft Reichert, A., T. Meehan, and T. Munson Jet Propulsion Laboratory, California Institute of Technology Demonstration of onboard, autonomous, real-time orbit determination with JPL's Real Time GIPSY (RTG) software and analysis of the orbit determination capabilities of the GDGPS System ION GPS Meeting, Portland OR, September, 2002.
Demonstration of Decimeter-level Real-time Positioning of an Airborne Platform M. Armatys, R. Muellerschoen, Y. Bar-Sever, R. Meyer Jet Propulsion Laboratory, California Institute of Technology Proceedings,ION NTM-2003, Anaheim, CA
Orbit Determination With NASA's High Accuracy Real-Time Global Differential GPS System R. J. Muellerschoen, A. Reichert, D. Kuang, M. Heflin, W. I. Bertiger and Y. E. Bar-Sever GPS orbits and clocks are computed in real-time with data from NASA's global GPS network. The accuracy of the GPS orbits and reference frame alignment to ITRF'97 is discussed. The dissemination of the global correction message is over the Internet, and a signal-in-space (SIS) is provided by America's Inmarsat satellite. The SIS will soon expand for global coverage with Inmarsat's ASPAC (Asia/Pacific) and EMEA (Europe/Africa) satellites yielding coverage over the entire globe between +/-75 degrees in latitude. The inherent latency in providing the corrections to the user through the geosynchronous satellites is shown to have little impact on true real-time positioning. Orbit determination, post-processed but filtered as if in real-time, of a low-Earth orbiter's GPS data using the real-time orbit and clock products will be presented. Anticipated plans call for uploading the code to a space-qualified receiver and performing orbit determination with the GPS differential global corrections as transmitted by the Inmarsat beams. Proceedings of ION GPS-2001, Salt Lake City, UT, September 2001.
Results of an Internet-Based Dual-Frequency Global Differential GPS System R. J. Muellerschoen, W. I. Bertiger and M. F. Lough Observables from a global network of 18 GPS receivers are returned in real-time to JPL over the open Internet. Global GPS orbits accurate to 30-40 cms RSS and precise dual-frequency GPS clocks are computed in real-time with JPL's Real-Time Gipsy (RTG) software. Corrections to the broadcast orbits and clocks are communicated to the user over the open Internet via a TCP server. Tests of user positioning show real-time RMS accuracy of 8 cms RMS in horizontal and 20 cms RMS in the vertical. Proceedings of IAIN World Congress, San Diego, CA, June 2000
An Internet-Based Global Differential GPS System, Initial Results R. J. Muellerschoen, W. I. Bertiger, M. F. Lough, D. Stowers, D. Dong Using a network of 15 global GPS receivers, GPS data is returning to JPL via the open Internet to determine the orbits and clocks of the GPS constellation in real-time. Corrections to the broadcast orbits and clocks are currently communicated in real-time to the user over the open Internet via a TCP server. Tests of user positioning show real-time RMS accuracy of ~10 cms RMS in horizontal and < 20 cms RMS in the vertical. ION National Technical Meeting, Anaheim, CA, Jan, 2000
Flight Tests Demonstrate Sub 50 cms RMS Vertical WADGPS Positioning Wide Area Differential GPS (WADGPS) positioning is performed in real-time during NASA's DC-8 AirSAR flights. R. J. Muellerschoen, W. I. Bertiger and M. L. Whitehead The goal of the experiment is to demonstrate absolute positioning in earth-fixed coordinates to better than one meter in all components in real-time. Results show dual-frequency real-time RMS (root-mean-square) accuracy in the vertical to be 50-60 cms with an RMS horizontal accuracy of better than 40 cms. Proceedings of ION GPS-99, Nashville, Tenn., September 1999.
Incorporation of Orbital Dynamics to Improve Wide-Area Differential GPS J. Ceva, B. Parkinson, W. I. Bertiger, R. J. Muellerschoen, and T. P. Yunck Navigation, Summer 1997, Vol. 44, No. 2, pg. 171-180 Invited Contribution to Institute of Navigation "Red Books," Global Positioning System: Papers Published in Navigation, Vol. IV, 1999.
A Real-Time Wide Area Differential GPS System W. I. Bertiger, Y. E. Bar-Sever, B. J. Haines, B. A. Iijima, S. M. Lichten, U. J. Lindqwister, A. J. Mannucci, R. J. Muellerschoen, T. N. Munson, A. W. Moore, L. J. Romans, B. D. Wilson, S. C. Wu, T. P. Yunck, G. Piesinger, and M. L. Whitehead Invited Contribution to Institute of Navigation "Red Books," Global Positioning System: Papers Published in Navigation, Vol. IV, 1999 Navigation: Journal of the Institute of Navigation, Vol. 44, No. 4, 1998, pgs. 433-447
A Close Look at Satloc's Real-Time WADGPS System GPS Solutions M. L. Whitehead, G. Penno, W. J. Feller, I. C. Messinger, W. I. Bertiger, R. J. Muellerschoen, and B. A. Iijima GPS Solutions, Vol 2, No. 2, John Wiley & Sons, Inc., 1998. Invited Paper
Precise Real-Time Positioning Using Wide Area Differential GPS, Field Tests W. I. Bertiger, Y. E. Bar-Sever, T. J. Borden, B. A. Iijima, R. J. Muellerschoen, T. N. Munson, A. W. Moore, L. J. Romans, S. C. Wu, M. L. Whitehead, W. Feller, G. Penno Proceedings of the ION National Tech. Meeting, Long Beach, CA, Jan. 1998
Concept for a Wide-Area GPS Navigation System W. I. Bertiger, S. M. Lichten, A. J. Mannucci, R. J. Muellerschoen, S. C. Wu, and T. P. Yunck NASA Tech Brief, NPO-19625, June, 1997.
A Prototype Real-Time Wide Area Differential GPS System W. I. Bertiger, Y. E. Bar-Sever, B. J. Haines, B. A. Iijima, S. M. Lichten, U. J. Lindqwister, A. J. Mannucci, R. J. Muellerschoen, T. N. Munson, A. W. Moore, L. J. Romans, B. D. Wilson, S. C. Wu, T. P. Yunck, G. Piesinger, and M. L. Whitehead Proceedings of the ION National Technical Meeting, Santa Monica, CA, Jan. 1997.
Orbit and Troposphere Results of a Real-Time Prototype WADGPS System R. J. Muellerschoen, W. I. Bertiger, and L. J. Romans, Proceedings of the ION National Tech. Meeting, Santa Monica, CA, Jan. 1997.
A Prototype WADGPS System for Real Time Sub-Meter Positioning Worldwide T. P. Yunck, Y. E. Bar-Sever, B. A. Iijima, S. M. Lichten, U. J. Lindqwister, A. J. Mannucci, R. J. Muellerschoen, T. N. Munson, L. J. Romans, S. C. Wu Proceedings of the 9th International Technical Meeting of The Institute of Navigation, Kansas City, MO, September 17-20, 1996.
Creation and Review Dates
SERF Creation Date:
2009-06-16
SERF Last Revision Date:
2009-09-23
Links
