RAIM FDE Revisited: A New Breakthrough In Availability Performance With NIORAIM (Novel Integrity-Optimized RAIM)

Patrick Y. Hwang and R. Grover Brown

Abstract:	The major shortcoming of RAIM FDE is widely recognized to be its occasional lack of availability, in the sense that the integrity level it can protect in any given situation cannot always be smaller than the required alert limit for a given flight operation. Ever since the RAIM FDE algorithms were developed, accepted and published more than ten years ago, the system availability has been bound, by and large, to the limitations of its monitoring mechanism to be able to detect and exclude a single measurement fault. More recently, there has been a proposition that departs from conventional assumptions made in the standard RAIM-FDE by better balancing accuracy and integrity levels. This proposition results in the lowering of the horizontal integrity limit for all satellite measurement geometries, thereby improving system availability in the process. In this paper, we present a specific methodology called NIORAIM for accomplishing the balancing of position accuracy with integrity, and we also give an estimate of the improvement achieved with the method. The results in this paper show, for the NPA phase of flight where baroaiding is available, that 50% of the unavailable geometries derived using standard RAIM-FDE can be salvaged when using NIORAIM. The paper also shows the added complexity involved in computing the NIORAIM algorithm, but presents a design that is still amenable to real-time computation.
Published in:	Proceedings of the 2005 National Technical Meeting of The Institute of Navigation January 24 - 26, 2005 The Catamaran Resort Hotel San Diego, CA
Pages:	654 - 665
Cite this article:	Hwang, Patrick Y., Brown, R. Grover, "RAIM FDE Revisited: A New Breakthrough In Availability Performance With NIORAIM (Novel Integrity-Optimized RAIM)," Proceedings of the 2005 National Technical Meeting of The Institute of Navigation, San Diego, CA, January 2005, pp. 654-665.
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