A Baseline RAIM Scheme and a Note on the Equivalence of Three RAIM Methods

R. Grover Brown

Abstract:	The RTCA GPS Minimum Operational Performance Standards (MOPS) has now been released, and airborne equipment manufacturers will be expected to meet the specifications given in the MOPS. A considerable portion of the MOPS is devoted to GPS integrity requirements and the associated receiver testing procedures. The GPS Integrity Channel (GIC) is still a few years away, so some form of Receiver Autonomous Integrity Monitoring (RAIM) must be relied upon in the interim period (and perhaps beyond). Many different RAIM schemes have been proposed over the past few years, each with its respective advantages and disadvantages. This paper proposes a baseline RAIM scheme that can serve as a standard for performance comparisons. The proposed scheme is a straight-forward, workable RAIM method that is easily understood by all. It is a good scheme, but there is no claim that it is optimal. The proposed standard RAIM scheme is based on a unified theory that says that under the condition of equal alarm rates, the least-squares-residuals, parity, and range-comparison RAIM methods all yield identical results. This is not generally recognized, so a justification of this three-way equivalence is given in the paper. The proposed standard scheme involves the formation of a simple scalar test statistic from the redundant measurements. This, in turn, is then compared with a precomputed threshold. A standard procedure for pruning out bad detection geometries is also given. This is an important aspect of any RAIM scheme and is necessary in order to achieve the desired detection probability. Preliminary estimates of RAIM availability are given.
Published in:	Proceedings of the 1992 National Technical Meeting of The Institute of Navigation January 27 - 29, 1992 Catamaran Resort Hotel San Diego, CA
Pages:	127 - 137
Cite this article:	Updated citation: Published in NAVIGATION: Journal of the Institute of Navigation
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