GPS Multipath on Large Commercial Air Transport Airframes

Tim Murphy, Robert Snow, Michael Braasch

Abstract:	Multipath is potentially the largest contributor to positioning error for differential GPS. Airborne receivers will be subject to multipath from the airframe and from the ground and other objects during precision approach. Multipath and the mitigation of multipath inducti error has been the subject of extensive investigations. The Boeing Commercial Airplane Group has performed extensive flight test of GPS receiver systems on the new Boeing 777. One of the characteristics of this new aircraft is its large wingspan, which may cause significant GPS multipath positioning errors. Experiments were carried out to quantify these effects under various flight regimes. The 777 flight test experimental set-up involved both narrow and standard cot-relator receivers, The data was analyzed and particular attention was given to assessing the multipath effects during precision approach. Flight test results for both types of receivers are presented. Boeing has also performed flight testing of GPS receivers on the 747400 and 737 to support certification of primary means RNP operations for enroute through non-precision approach. This data has also been analyzed to assess level of airframe mu1tipat.h. This paper compares the airframe multipath effects for 2 different commercial transport airframes, the 747400 and the 777. In addition, the flight test results are supported by theoretical analysis of multipath effects on ranging. The relative merits of narrow correlator technology compared to carrier smoothed standard correlator phase measurements are discussed. The results of this study may have significant ramifications towards the design of DGPS precision approach systems.
Published in:	Proceedings of the 1996 National Technical Meeting of The Institute of Navigation January 22 - 24, 1996 Loews Santa Monica Hotel Santa Monica, CA
Pages:	137 - 143
Cite this article:	Updated citation: Published in NAVIGATION: Journal of the Institute of Navigation
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