CDGPS RAIM: Algorithm and Protection Radius Calculation

Jason F. Hunzinger, Salvatore D. Morgera, John Studenny

Abstract:	Carrier phase based differential GPS (CDGPS) allows high precision positioning to be accomplished. An effi-cient and numerically stable and accurate method of CDGPS positioning is to use a double difference measurement based recursive filter with triple difference based time propagation to compensate for highly dynamic receiver movement. This paper develops a Receiver Autonomous Integrity Monitoring (RAIM) algorithm to verify the solution given by such a positioning algorithm. The algorithm includes both Fault Detection and Exclu-sion (FDE) as well as calculation of the Horizontal Protection Level (HPL) ensured by the algorithm. The filter residuals are proposed as a logical basis for a detection test statistic instead of the standard snap-shot least squares residual. There are several problems associated with using double difference measurements for integrity and thus a means of deriving and using single difference residuals is developed. The basic FDE algorithm has been established but the HPL calculation has not been verified as yet. This paper makes use of some simplifying assumptions to derive a new fully analytic means of correctly calculating the HPL. The integrity algorithm is described in detail with key equations. Preliminary results show promise for the algorithms developed.
Published in:	Proceedings of the 10th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GPS 1997) September 16 - 19, 1997 Kansas City, MO
Pages:	1055 - 1064
Cite this article:	Hunzinger, Jason F., Morgera, Salvatore D., Studenny, John, "CDGPS RAIM: Algorithm and Protection Radius Calculation," Proceedings of the 10th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GPS 1997), Kansas City, MO, September 1997, pp. 1055-1064.
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