GPS Availability of the Terrestrial Navigation

Elham Ghashghai

Abstract:	Global Positioning System (GPS) Operational Requirement Document (ORD’99) commits to the sustainment of the existing GPS-24 and its historical navigation accuracy. The validated-ORD’99 specifies the "availability of the GPS accuracy" at all latitudes and longitudes assuming no Selective Availability (SA) and a dual frequency operation while the SORD'90 specified globally averaged requirements. The availability threshold value is based on the availability of 95- percentile position accuracy (13.6m vertical and 6.3m horizontal) upon removing the worst two satellites from the 24-satellite constellation. This paper illustrates the balance between accuracy and availability given a range of assumptions including the ORD "worst case.” This paper also shows the sensitivity of accuracy and availability to a variety of possible configurations.
Published in:	Proceedings of the IAIN World Congress and the 56th Annual Meeting of The Institute of Navigation (2000) June 26 - 28, 2000 The Catamaran Resort Hotel San Diego, CA
Pages:	217 - 221
Cite this article:	Ghashghai, Elham, "GPS Availability of the Terrestrial Navigation," Proceedings of the IAIN World Congress and the 56th Annual Meeting of The Institute of Navigation (2000), San Diego, CA, June 2000, pp. 217-221.
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