Reliable Multi-Carrier Ambiguity Resolution in the Presence of Multipath

Sandra Verhagen and Dennis Odijk, Frank Boon and Jose Maria Lopez Almansa

Abstract:	In this contribution it will be shown that a correct stochastic model will dramatically improve the degraded performance of carrier-phase ambiguity resolution in the presence of biases. The focus in this paper is on code biases caused by multipath, as it is known to be a dominant error source in high-accuracy GNSS applications. A bias in the observations will propagate in the parameter estimates, which may cause severe positioning errors. Therefore, it is essential to use the a-priori knowledge about errors in the model if possible. With the APosteriori Multipath Estimation (APME) method this is done by applying corrections to the observations prior to the parameter estimation. With the APME technique the multipath error affecting the code tracking is estimated, and this estimated error is subtracted from the code-phase measurements. APME also provides the standard deviation of the multipath estimates, so that the stochastic model can be adapted. In this contribution we will specifically investigate whether APME and the improved stochastic model may improve the reliability of ambiguity resolution, and/or may serve as an indication that reliable ambiguity resolution is not feasible. In conclusion, it will be shown that a good error mitigation method together with a correct stochastic model will significantly improve the reliability of ambiguity resolution, and if Ratio Test Integer Aperture estimation is applied APME automatically provides an indication when reliable ambiguity resolution is not possible.
Published in:	Proceedings of the 20th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS 2007) September 25 - 28, 2007 Fort Worth Convention Center Fort Worth, TX
Pages:	339 - 350
Cite this article:	Verhagen, Sandra, Odijk, Dennis, Boon, Frank, Almansa, Jose Maria Lopez, "Reliable Multi-Carrier Ambiguity Resolution in the Presence of Multipath," Proceedings of the 20th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS 2007), Fort Worth, TX, September 2007, pp. 339-350.
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