On the Selection of a GPS Validity Indicator for Aircraft Navigation in the National Airspace System (NAS)

Dirk deDoes, Lawrence Lupash, Kenneth Rhoades, Jacques Beser

Abstract:	Use of GPS as sole means of navigation in the National Airspace System (NAS) requires that enroute, terminal and approach mode accuracy requirements be met. Should ‘GPS performance degrade beyond the specified limits, then a navigation invalid warning, with a confidence of 99.97%, must be issued to the flight crew. System anomalies such as poor dilution of precision (DOP) and substantial satellite clock errors can result in User equipment (UE) performance degradation. This paper identifies and evaluates two potential warning indicators and presents test data generated for a representative flight path, using a multichannel GPS signal generator and a Phase III airborne 5 channel receiver (RCVR3A). The scenario includes a wide range of satellite geometry DOPs and measurement errors. Statistical post processing, including regression analysis and confidence interval determination are then used to yield threshold values for each indicator and for each flight mode. In addition, the robustness of the indicator in the presence of GPS system anomalies is assessed. Finally, conclusions are drawn and a recommendation is made for a GPS Validity Indicator for aircraft operations in the NAS.
Published in:	Proceedings of the 1992 National Technical Meeting of The Institute of Navigation January 27 - 29, 1992 Catamaran Resort Hotel San Diego, CA
Pages:	147 - 157
Cite this article:	deDoes, Dirk, Lupash, Lawrence, Rhoades, Kenneth, Beser, Jacques, "On the Selection of a GPS Validity Indicator for Aircraft Navigation in the National Airspace System (NAS)," Proceedings of the 1992 National Technical Meeting of The Institute of Navigation, San Diego, CA, January 1992, pp. 147-157.
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