The Statistics of Selective Availability and Its Effect on Differential GPS

Yi-chung Chao and Bradford W. Parkinson

Abstract:	Selective Availability (SA) is the most significant artitkid emr source for the stand-alone GPS users. It also a-eates extra error on Differential GPS (DGPS) under the effect of time latency. Therefore, the SA error is an impomnt factor to the accuracy of GPS service. In this paper, the effect of SA is analyzed by calculating the pseudo-range error (PRE), delta range error (DRE), and delta DRE (DDRE). The measurements of code and carrier phase from Trimble 4000 SST and SSE receivers were used for this study. ‘Ibe PRE, which can be treated effectively as the SA error, is separated from other errors, i.e., atmospheric delays, clock biases, etc. The ephemeris error has also been investigated by an independent approach. The statistics of SA on PRE, DRE and DDRE from past sixteen-month data collection are presented. The PRE provides the waveform of Sk In addition, the DDRE, which has unit of acceleration, gives the very important information for the design of the updating rate for DGPS correction signal. Furthmore, two estimation models for the latency effect on DGPS are discussed and compared. The first model is the simple RTCM-104 linear prediction. The second is the adaptive lattice auto-regressive model. The position error caused by the latency is about the same as using the simple formula IL? a P * PDUP. where a is the DDRE, and f is the time latency.
Published in:	Proceedings of the 6th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GPS 1993) September 22 - 24, 1993 Salt Palace Convention Center Salt Lake City, UT
Pages:	1509 - 1516
Cite this article:	Chao, Yi-chung, Parkinson, Bradford W., "The Statistics of Selective Availability and Its Effect on Differential GPS," Proceedings of the 6th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GPS 1993), Salt Lake City, UT, September 1993, pp. 1509-1516.
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