GPS-Based Orbit Determination and Point Positioning Under Selective Availability

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

Abstract:	Selective availability, or SA, degrades the positioning accuracy for non-differential users of the GPS Standard Positioning Service (SPS). The often quoted SPS accuracy available under normal conditions is 100 m “ZDRMS”. 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. Here we examine SA error for point positioning and dynamic orbit determination for an orbiting user. To minimize SA error, non-differential 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 rn: and this can be smoothed to 3 m in a few hours.
Published in:	Proceedings of the 3rd International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GPS 1990) September 19 - 21, 1990 The Broadmoor Hotel Colorado Spring, CO
Pages:	255 - 263
Cite this article:	Bar-Sever, Yoaz E., Yunck, Thomas P., Wu, Sien-Chong, "GPS-Based Orbit Determination and Point Positioning Under Selective Availability," Proceedings of the 3rd International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GPS 1990), Colorado Spring, CO, September 1990, pp. 255-263.
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