Analysis of Coast Times Upon Loss of GPS Signals for Integrated GPS/Inertial Systems:

Y.C. Lee, S. Ericson

Abstract:	An inertial system may be integrated with the Global Positioning System (GPS) to work synergistically because of their complementary error characteristics: GPS has good long-term accuracy while an inertial system has almost no high frequency noise. These complementary characteristics can be exploited to allow the aircraft to coast even if GPS signals are lost due to intentional or unintentional interference. In case of an interferencecaused GPS outage affecting multiple aircraft, such a coasting capability would provide improved availability of RNP operations, bringing significant operational benefits. For this purpose, the FAA Satellite Operational Implementation Team (SOIT) Required Navigation Performance (RNP) Working Group (WG) asked the GPS/inertial WG of RTCA Special Committee (SC)-159 to determine the characteristics of coasting capability for aircraft equipped with a tightly-coupled GPS/inertial reference system (IRS). This paper analyzes coast times for both a looselycoupled GPS/IRS and a tightly-coupled GPS/IRS. The analysis is performed for a variety of conditions in terms of flight profile and user-to-satellite geometry conditions with a set of assumptions that the GPS/inertial WG established. The results are examined to determine if the GPS/IRSs can meet the requirements for three coasting scenarios provided by the FAA. The FAA believes that coasting can provide significant operational benefits in these scenarios.
Published in:	Proceedings of the 2003 National Technical Meeting of The Institute of Navigation January 22 - 24, 2003 Disneyland Paradise Pier Hotel Anaheim, CA
Pages:	417 - 428
Cite this article:	Lee, Y.C., Ericson, S., "Analysis of Coast Times Upon Loss of GPS Signals for Integrated GPS/Inertial Systems:," Proceedings of the 2003 National Technical Meeting of The Institute of Navigation, Anaheim, CA, January 2003, pp. 417-428.
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