Low Cost Multipath Mitigation in a Single Frequency Environment for a DGPS Station

Greg Johnson and Dennis King

Abstract:	Multipath is the dominant error source in Code-Based DGPS ground stations. Narrow correlators and other code tracking technologies have been implemented in order to reduce multipath in the pseudorange measurement. Multipath error reduction can be obtained in a more cost effective manner by filtering the output of a standard correlator with the synergistic properties of pseudorange and carrier phase measurements. Carrier phase measurements have superior multipath and thermal noise rejection to pseudorange measurements. However, carrier phase ionospheric delay diverges from pseudorange ionospheric delay and carrier phase measurements have unknown integer ambiguities. Clearly, if the integer ambiguities and ionospheric group delay could be known, the carrier phase measurement could be substituted for the pseudorange measurement, effectively eliminating multipath. This paper presents a Kalman Filter that estimates the group delay of pseudorange ionospheric error with Ll only and the integer ambiguities of carrier phase measurements. This filter includes a bandwidth that will adapt to the environment of the pseudorange. Results show significant multipath reduction over carrier smoothed pseudoranges.
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:	899 - 904
Cite this article:	Johnson, Greg, King, Dennis, "Low Cost Multipath Mitigation in a Single Frequency Environment for a DGPS Station," Proceedings of the 1996 National Technical Meeting of The Institute of Navigation, Santa Monica, CA, January 1996, pp. 899-904.
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