GPS Integrity Monitoring Using an AHRS as Reference

Sanjai Kohli

Abstract: GPS satellite signals may degrade between uploads causing erroneous position outputs. In order to detect such failures when redundant satellites are not present, the use of an Attitude Heading Reference System (AHRS) is explored. It is assumed that the AHRS and GPS are integrated. GPS outputs are assumed to be pseudo and delta ranges, corrupted by errors due to measurements and selective availability (SA). AHRS errors are due to instrument errors and GPS calibration residual errors. The integrity tests for GPS signals using AHRS are obtained by utilizing the delta range (DR) measurements. Two tests on the DR are analyzed. One test compares the DR with the AHRS velocity and the second test compares the DR difference with delta velocity. It is shown that the second test eliminates SA errors because of their large time constants and utilizes the very accurate delta velocity outputs. Numerical results are obtained in terms of probabilities of detection for various false alarm and failure rates. Finally the results are compared with FAA requirements for fault detection derived from position accuracy requirements in various phases of flight.
Published in: Proceedings of the 1987 National Technical Meeting of The Institute of Navigation
January 20 - 23, 1987
Anaheim, CA
Pages: 155 - 158
Cite this article: Kohli, Sanjai, "GPS Integrity Monitoring Using an AHRS as Reference," Proceedings of the 1987 National Technical Meeting of The Institute of Navigation, Anaheim, CA, January 1987, pp. 155-158.
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