A General RAIM Algorithm Based on Receiver Clock

P. Misra, M. Pratt, R. Muchnik, and B. Manganis

Abstract:	A new approach to receiver autonomous integrity monitoring (RAIM) is proposed. The basic idea is simple and intuitive: A measurement anomaly affecting position estimate will affect clock bias estimate too. A clock with predictable behavior can, therefore, provide a basis for detecting faulty measurements. A test would consist of (i) prediction of clock bias on the basis of past measurements, and (ii) comparison of the predicted value with the estimate obtained from the current snapshot of measurements. A discrepancy beyond that which can be accounted for would signal a measurement anomaly. That’s fault detection, without requiring redundant measurements. This approach offers 100% availability of the fault detection function for nonprecision approaches with the 24-satellite GPS constellation; availability of fault detection and exclusion exceeds 95%. Practicality of the proposed clock-based RAIM currently rests on our ability to model the receiver clock behavior accurately using GPS measurements. The basic requirement is that there be no significant, unpredictable change in the clock frequency, and the period of such stability be long enough to allow for the clock parameters to be estimated accurately. Laboratory and flight tests have shown the approach to be practical.
Published in:	Proceedings of the 8th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GPS 1995) September 12 - 15, 1995 Palm Springs, CA
Pages:	1941 - 1948
Cite this article:	Misra, P., Pratt, M., Muchnik, R., Manganis, B., "A General RAIM Algorithm Based on Receiver Clock," Proceedings of the 8th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GPS 1995), Palm Springs, CA, September 1995, pp. 1941-1948.
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