RAIM Availability for Supplemental GPS Navigation

Karen L. Van Dyke

Abstract:	RTCA SC-159 has completed the Minimum Operational Performance Standards (MOPS) for supplemental GPS navigation and is now working on the MOPS for sole means navigation. The FAA plans to implement GPS as a supplemental navigation system when DOD declares the system operational, or possibly even before this occurs. GPS is expected to reach full operational capability (FOC) during the fourth quarter of 1993. This paper e xamines GPS Receiver Autonomous Integrity Monitoring (RAIbQ availability for supplemental navigation based on the approximate radial-error protection (ARP) method. This method, developed by R. Grover Brown of Iowa State University, applies ceiling levels for the ARP figure of merit to screen out bad detection geometries under worst case bias conditions. The ARP criterion for each phase of flight is based on the integrity specifications stated in the RTCA SC-159 supplemental MOPS for GPS. Applying the ARP criterion, extensive analysis was performed to determine the availability of RAIM over the CONUS, North Atlantic, Europe, Central East Pacific, and North Pacific during enroute, terminal, and nonprecision approach phases of flight. The 21 Primary, Optimal 21, and Optimized 21-r 3 GPS constellations were examined. The results demonstrate that RAIM is not available 100% of the time, even with 24 operational satellites. This is because there are times when only four satellites are visible, preventing RAIM detection altogether, and other times when the geometry of the visible satellites has an ARP which exceeds the ARP ceiling value.
Published in:	Proceedings of the 48th Annual Meeting of The Institute of Navigation (1992) June 29 - 1, 1992 ANA Westin Hotel Dayton, OH
Pages:	73 - 80
Cite this article:	Updated citation: Published in NAVIGATION: Journal of the Institute of Navigation
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