GPS Carrier Phase Multipath Reduction Using SNR Measurements to Characterize an Effective Reflector

Angela Reichert and Penina Axelrad

Abstract:	A process was developed to use the GPS signal to noise ratio (SNR) to identify an effective reflector for a given antenna. This is termed an effective reflector because the reflector identified can account for a number of effects found in the signal, including such things as multiple reflectors, changes in reflectivity, and changes in signal phase upon reflection. A physical location is used simply as a means to represent the spatial correlation of the multipath. Once a effective reflector location has been found, a carrier phase correction profile is computed for that reflector. The measured carrier phase is then corrected by that amount and a new attitude solution is computed. Using this technique, results from ground tests show that the RMS differential phase residuals improved from 11.37 mm to 8.56 mm, corresponding to a 25% improvement. These results were found using only a batch estimator to identify an effective reflector. For the CRISTA-SPAS flight data the lack of knowledge of the antenna gain pattern limited the ability of the method to determine a reliable reflector solution. Some residual improvement was found for the data. One such pass had a residual improvement from 6.4 mm to 5.5 mm. However, for much of the data, an effective reflector that improved the phase residuals could not be identified.
Published in:	Proceedings of the 12th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GPS 1999) September 14 - 17, 1999 Nashville, TN
Pages:	1951 - 1960
Cite this article:	Reichert, Angela, Axelrad, Penina, "GPS Carrier Phase Multipath Reduction Using SNR Measurements to Characterize an Effective Reflector," Proceedings of the 12th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GPS 1999), Nashville, TN, September 1999, pp. 1951-1960.
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