A Position-Domain RAIM Algorithm for Improved Safety and Availability

Paul Massatt, Elham Ghashghai

Abstract:	Currently, most RAIM algorithms are based on using the Square Sum Error (SSE) of the residuals as a decision metric for determining whether a flight operation is safe or not. The SSE is optimal for determining whether a bias exists. However, it is not optimal for determining whether a tunnel excursion may have occurred. This paper introduces a position-domain RAIM algorithm which is optimal for avoiding tunnel excursions. The new method increases flight safety because it assures that the detection probability is met for any satellite error bias based on the actual values of all of the observable residuals, and not simply based on the SSE of the residuals. It increases availability because the method is optimal relative to the desired performance objective -- avoiding tunnel excursions -- and not simply based on a related objective. Receiver implementation of the position-domain RAIM algorithm is straight-forward, and global availability analyses can be computed efficiently. Analyses of the application of RAIM for precision approach and nonprecision approach are included with RAIM calculations based on both the new algorithm and the algorithm currently approved by the RTCA.
Published in:	Proceedings of the 54th Annual Meeting of The Institute of Navigation (1998) June 1 - 3, 1998 The Adams Mark Hotel Denver, CO
Pages:	211 - 221
Cite this article:	Massatt, Paul, Ghashghai, Elham, "A Position-Domain RAIM Algorithm for Improved Safety and Availability," Proceedings of the 54th Annual Meeting of The Institute of Navigation (1998), Denver, CO, June 1998, pp. 211-221.
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