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

Abstract:	In this paper we describe the system architecture, algorithms, and preliminary results from an operating prototype Wide Area Differential GPS (WADGPS) system spanning the continental US (CONUS). With dual- frequency GPS user equipment and improved positioning algorithms, real-time 3-D RMS user position accuracy is better than 50 cm. Single-frequency users can obtain comparable accuracy with the current ionospheric intensity. There may be some degradation in single- frequency positioning during solar maximum or during ionopheric storms. The system consists of 14 codeless dual-frequency geodetic quality receivers distributed over the CONUS returning real-time data at a l-Hz rate, and a central processing facility where WADGPS products are computed. These products include: real-time GPS satellite positions with a 3-D RMS accuracy of 1.3 meters; real-time zenith tropospheric delays (at each site) estimated from GPS measurements (surface meteorological data are not needed or used) to an RMS accuracy of about 1.5 cm; GPS fast range corrections (l-Hz rate) which are optimally extrapo- lated to the time of use using information from the phase data; and a grid of real-time ionospheric corrections for measurements at Ll produced every 5 minutes with a current vertical RMS accuracy of 20 cm The software for GPS data processing and computation of real-time WADGPS corrections is easily hosted on a single UNIX workstation. The full computation adds only about 3 msec latency for users of the corrections. Commercial availability of the single frequency system is scheduled for the 2nd quarter of 1997. The software for estimation of the WADGPS corrections is also being adapted for use in the Federal Aviation Administration’s (FAA) Wide Area Augmentation System (WAAS).
Published in:	Proceedings of the 1997 National Technical Meeting of The Institute of Navigation January 14 - 16, 1997 Loews Santa Monica Hotel Santa Monica, CA
Pages:	645 - 660
Cite this article:	Bertiger, W. I., Bar-Sever, Y. E., Haines, B. J., Iijima, B. A., Lichten, S. M., Lindqwister, U. J., Mannucci, A. J., Muellerschoen, R. J., Munson, T. N., Moore, A. W., Romans, L. J., Wilson, B. D., Wu, S. C., Yunck, T. P., "A Prototype Real-Time Wide Area Differential GPS System," Proceedings of the 1997 National Technical Meeting of The Institute of Navigation, Santa Monica, CA, January 1997, pp. 645-660.
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