Detection and Estimation of Multipath Error in GPS Pseudorange Measurements using Signal-To-Noise Ratio in a Stationary Single-Frequency Receiver

Kjetil Breivik, Barje Forssell, Changdon Kee, Per Enge and Todd Walter

Abstract:	The focus in this paper is on multipath errors in the pseudorange measurements done by the Global Positioning System (GPS). By using Differential GPS (DGPS) it is possible to reduce clock, ephemeris, ionospheric and tropospheric errors to centimeter level. Multipath then becomes the major source of error in GPS pseudorange measurements. The errors can be at the level of several meters. An algorithm has been developed that can estimate these errors in real-time for a stationary single frequency receiver in the case of one, dominating specular reflected multipath signal. The estimation algorithm is based on hardware studies of a digital GPS receiver. From these studies a strong correlation between the Signal to Noise Ratio (SNR) measurements done by the receiver and the multipath errors in the pseudorange measurements was found. Theory behind the development of the algorithm will be shown, as well as measurements comparing this method to earlier methods using dual frequency receivers. A test of the performance of the algorithm using Differential GPS was also done. The results show that the estimation method has the potential of reducing both standard-deviation of errors and maximum errors in DGPS positioning by 40-50%.
Published in:	Proceedings of the 52nd Annual Meeting of The Institute of Navigation (1996) June 19 - 21, 1996 Royal Sonesta Hotel Cambridge, MA
Pages:	147 - 156
Cite this article:	Updated citation: Published in NAVIGATION: Journal of the Institute of Navigation
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