Ground Based GPS Integrity Monitoring in the Presence of SA: A Comparison of Two Statistical Tests

Lobe Rater and Moises Montez

Abstract:	The possible lack of GPS integrity monitoring by the GPS receivers planned for the Space Shuttle has led to the consideration of ground based monitoring. This paper examines the ability of a GPS receiver operated at a surveyed site to detect GPS satellite failure. The receiver is expected to remove the ionospheric delay leaving Selective Availability as the dominant source of error masking the bias in the GPS satellite signal. Receiver clock bias must be removed by measurement. Two methods of combining observations made by an all-in-view receiver at a given epoch will be compared for ability to detect bias. The first method employs a test of chi- square. The second method transforms the observations to a set of zero mean correlated variables which provide equal, maximum exposure to bias detection in all GPS satellites being observed. The second method is more sensitive to the presence of bias than the chi-square method when more than two GPS satellites are being observed. Discriminators and GPS satellite biases are tabulated as functions of the probability of false alarm and the probability of missed detection. For the second method probabilities of correct fault isolation are provided.
Published in:	Proceedings of the 1995 National Technical Meeting of The Institute of Navigation January 18 - 20, 1995 Disneyland Hotel Anaheim, CA
Pages:	621 - 629
Cite this article:	Rater, Lobe, Montez, Moises, "Ground Based GPS Integrity Monitoring in the Presence of SA: A Comparison of Two Statistical Tests," Proceedings of the 1995 National Technical Meeting of The Institute of Navigation, Anaheim, CA, January 1995, pp. 621-629.
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