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.