GPS Integrity Reasoning Using Dempster-Shafer Theory

Hanna Sairo, Jari Syrjarinne, Helena Leppakoski and Jukka Saarinen

Abstract:	An expert system for GPS signal integrity reasoning is created. This expert system reasons the level of integrity of the received pseudorange signals as seen by the GPS receiver. The reasoning is accomplished by the Dempster- Shafer theory. For the sake of comparison a reasoning system applying Bayesian theory is also created. Reasoning is based on various GPS data, for example user range accuracy (URA) values and carrier-to-noise values. The proposed approach is different from existing GPS integrity monitoring methods. RAIM methods detect only whether there is a failure or not after the position has already been calculated. The presented approach gives qualitative information about the integrity of the pseudoranges before they are used in the position solution. This approach does not need refined or preprocessed information to determine integrity. Measurement redundancy is not needed as in RAIM. Integrity reasoning is based on data that is always, or at least usually, available from the received satellite signals. Assisted GPS (AGPS) makes signal integrity reasoning even more necessary, because AGPS can survive in such noisy and attenuated urban environments where a traditional GPS receiver clearly can not. The reasoning system was implemented using Matlab. The results for pseudorange signal integrity were plausible. They state that the expert system gives refined information about the integrity level of signals and this information can be used for weighting the pseudorange measurements or picking the good and the bad satellites.
Published in:	Proceedings of the 14th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GPS 2001) September 11 - 14, 2001 Salt Palace Convention Center Salt Lake City, UT
Pages:	3029 - 3035
Cite this article:	Sairo, Hanna, Syrjarinne, Jari, Leppakoski, Helena, Saarinen, Jukka, "GPS Integrity Reasoning Using Dempster-Shafer Theory," Proceedings of the 14th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GPS 2001), Salt Lake City, UT, September 2001, pp. 3029-3035.
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