Effect of Weighting GPS Pseudoranges on RAIM Availability

Jizhang Sang and Kurt Kubik

Abstract:	This paper discusses the following three problems: the relationship between the accuracy of the GPS CIA pseudorange and satellite elevation; the effect of weighting the GPS pseudoranges on the GPS RAIM availability, and the RAIM availability considering the constellation state probabilities. By apply the variance component estimate technique to the GPS C/A pseudorange measurements, it shows that the variance component of the pseudorange measurements from satellites below than 20” is in the range 0.83 to 0.63, assuming the variance component of the measurements from satellites above 20” is 1. The variance component estimates are then used in the GPS RAIM availability evaluation, where all the sub-constellations of removing 1, 2 or 3 satellites from the GPS Primary Constellation are considered to result in an average RAIM availability for an area of 5” to 50” South latitude and 85” to 185” East longitude which covers the majority of the Australian Area of Interest. The paper concludes that the RAIM identification availability for the precision approach is severely affected by weighting the GPS pseudoranges and the constellation state probabilities must be taken into the RAIM availability evaluation.
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:	519 - 527
Cite this article:	Sang, Jizhang, Kubik, Kurt, "Effect of Weighting GPS Pseudoranges on RAIM Availability," Proceedings of the 1997 National Technical Meeting of The Institute of Navigation, Santa Monica, CA, January 1997, pp. 519-527.
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