Results from the Program for the Investigation of Airborne Multipath Errors

Tim Murphy, Matt Harris, Janet Booth, Preston Geren, Tom Pankaskie, Barbara Clark, Jason Burns and Ted Urda

Abstract:	The development of Ground Based Augmentation Systems (GBAS) to support Category II/III approach and landing operations is underway. Given improvements in GBAS ground stations, airborne multipath is apparently the largest error source affecting the accuracy and integrity of GBAS. A previous paper described a program designed to investigate and quantify the effects of multipath from the airframe as well as from short delay ground bounce multipath during landing operations. The program includes development of an electromagnetic modeling capability which predicts amplitude, time delay and phase characteristics of airframe multipath. The program also includes the collection of a very large amount of GPS code and carrier phase measurement collected during flight testing of the 777-300ER and 737- NG airplanes. The flight test observations will ultimately be used to validate the modeling capability. Then, the modeling capability will be exercised to develop an Airborne Multipath Model (AMM) suitable for standardization. This paper presents the first results of the study described in the previous paper. These results include observations from the flight testing as well as predictions from the high fidelity electromagnetic modeling capability. A comparison of the predicted errors with the flight test observations is included in the results. Finally, the paper outlines the work remaining to be done to complete the program to develop an improved AMM. This program is expected to be an important step in the development of GBAS to support CAT II/III approach and landing operations. These initial results indicate that an improved model for the airborne contribution to the overall GBAS error budget is likely to be validated.
Published in:	Proceedings of the 2005 National Technical Meeting of The Institute of Navigation January 24 - 26, 2005 The Catamaran Resort Hotel San Diego, CA
Pages:	153 - 169
Cite this article:	Murphy, Tim, Harris, Matt, Booth, Janet, Geren, Preston, Pankaskie, Tom, Clark, Barbara, Burns, Jason, Urda, Ted, "Results from the Program for the Investigation of Airborne Multipath Errors," Proceedings of the 2005 National Technical Meeting of The Institute of Navigation, San Diego, CA, January 2005, pp. 153-169.
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