Using a Sky Projection to Evaluate Pseudorange Multipath and to Improve the Differential Pseudorange Position

Dana G. Hynes

Abstract:	In order to understand the nature of the pseudorange distortions seen in GPS receiver test results, software ha been developed that takes statistical results from the measurements of one or two receivers and maps them against the sky to create polar plot images. One statistic the standard deviation of the code minus carrier, can be used to create a picture of the pseudorange distortion usually multipath from a single receiver. This makes it useful for imaging the code distortion pattern of a single stationary antenna. The first part of this paper describes the method o creating the pseudorange multipath sky map and how it illustrates the way local site reflectors, the environment antenna design and antenna location affect measurements. The second part of this paper explores a method that uses this multipath sky map to improve the performance of a differential base station. Since the base receiver picture showed a repeatable image it seemed likely that not using data from areas of high pseudorange multipath would improve the accuracy of the rover position. The elevation cut-off for both receivers was set to the standard 15-degrees. Increasing amounts of-distortion cut-off-was applied to remove data from the areas of the image that showed higher pseudorange multipath. This experiment showed that a 15% improvement in the differential pseudorange position of the rover receiver could be achieved.
Published in:	Proceedings of the 2001 National Technical Meeting of The Institute of Navigation January 22 - 24, 2001 Westin Long Beach Hotel Long Beach, CA
Pages:	850 - 859
Cite this article:	Hynes, Dana G., "Using a Sky Projection to Evaluate Pseudorange Multipath and to Improve the Differential Pseudorange Position," Proceedings of the 2001 National Technical Meeting of The Institute of Navigation, Long Beach, CA, January 2001, pp. 850-859.
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