Simplified GPS Integrity Checking With Multiple Satellites

Bradford W. Parkinson, Penina Axelrad

Abstract:	As the Global Position System nears its initial operational capability, there is growing interest within the user community in autonomous verification of GPS measurement integrity. A number of integrity checking techniques have been suggested which involve Kalman filtering or comparison of GPS measurements with data from a complementary navigation sensor. We propose a simpler scheme which relies on the redundant satellite coverage available under a full 24 satellite GPS constellation. The simplified algorithm allows a user with 6 or more satellites in view to recognize the presence of a degraded measurement, and in most cases to pinpoint its source. The performance of the algorithm strongly depends upon the number of satellites available and the assumed ratio between an unhealthy satellite range bias and the nominal random range error deviation. The performance is evaluated based on the probability of detection and identification of a degraded measurement, and the resulting position estimation errors. In 97% of the preliminary simulation runs, the algorithm successfully singled out the unhealthy satellite and estimated user position to accuracies better than 100 ft. It is anticipated that this integrity verification algorithm can provide the required navigation system reliability without placing a heavy burden on the user equipment computer. We believe it is this simplicity which is its greatest advantage.
Published in:	Proceedings of the 43rd Annual Meeting of The Institute of Navigation (1987) June 23 - 25, 1987 Dayton, Ohio
Pages:	78 - 83
Cite this article:	Parkinson, Bradford W., Axelrad, Penina, "Simplified GPS Integrity Checking With Multiple Satellites," Proceedings of the 43rd Annual Meeting of The Institute of Navigation (1987), Dayton, Ohio, June 1987, pp. 78-83.
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