Alarm Limits for Local-DGPS Integrity Monitoring

Ronald Braff

Abstract:	The standard ground-integrity monitoring procedure for landing systems has been to employ alarm limits on changes from the nominal course and the magnitude of certain signal characteristics. A similar procedure is applied to the integrity monitoring of local- Differential Global Positioning System (DGPS) that uses the coarse/acquisition (C/A) code for precision approach guidance. Since in DGPS the reference and the monitor perform the same signal processing function (both are receivers), the integrity monitoring examines consistency rather than absolute errors. The alarm limits are derived through the application of a Markov chain model with continuity requirements as a constraint. The Markov model accounts for integrity monitoring decisions as they evolve in time, and allowable malfunction warning delay. The alarm limits are then used as part of a total system error integrity algorithm that is exercised in the avionics. Using parameters estimated from flight test data, the vertical-performance analyses indicate the potential of the integrity method for Category (CAT) III approaches.
Published in:	Proceedings of the 1995 National Technical Meeting of The Institute of Navigation January 18 - 20, 1995 Disneyland Hotel Anaheim, CA
Pages:	387 - 399
Cite this article:	Braff, Ronald, "Alarm Limits for Local-DGPS Integrity Monitoring," Proceedings of the 1995 National Technical Meeting of The Institute of Navigation, Anaheim, CA, January 1995, pp. 387-399.
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