Autonomous Integrity Monitoring and Wide Area DGPS

Todd Walter, Boris Pervan, Per Enge, John Herendeen and Peter L. Levin

Abstract:	The Wide Area Differential GPS (WADGPS) concept has several layers of integrity monitoring built into it. A distributed network of reference stations measures the pseudorange residuals for all the GPS (or GNSS) satellites in view. These reference stations send their data to a central station which checks the validity of the measurements and forms a final correction message for each GPS satellite. The correction message is then uplinked to a geostationary satellite for broadcast to all users within its coverage footprint. In addition, a second “shadow” set of monitors apply the corrections and check the end-to-end function of the WADGPS system. These monitors are independent of the first set of monitors - the data from the second set is not used to form the differential corrections. Rather, they simply cause the system to send a “don’t use” message if the corrections suffer from excessive errors. Finally, the aircraft receiver also checks integrity autonomously. It applies the corrections from the geostationary satellite broadcast, and then applies a consistency check to the corrected pseudoranges. The availability of such an autonomous integrity check is improved, because the geostationary satellites provide additional ranging sources. This paper will describe the availability of this integrity check and new methods for providing integrity against ionospheric disturbances.
Published in:	Proceedings of the 1994 National Technical Meeting of The Institute of Navigation January 24 - 26, 1994 Catamaran Resort Hotel San Diego, CA
Pages:	155 - 163
Cite this article:	Walter, Todd, Pervan, Boris, Enge, Per, Herendeen, John, Levin, Peter L., "Autonomous Integrity Monitoring and Wide Area DGPS," Proceedings of the 1994 National Technical Meeting of The Institute of Navigation, San Diego, CA, January 1994, pp. 155-163.
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