High Accuracy Deformation Monitoring Via Multipath Mitigation by Day-To-Day Correlation Analysis

Robert S. Radovanovic

Abstract:	On baseline lengths commonly encountered in local GPS- based deformation surveys, multipath is the dominant error source, causing errors as large as 5 centimetres. Since multipath is caused by reflections in the receiver environment, it repeats under identical satellite geometries (assuming a static receiver), or once every 23 hr 56 rain. The magnitude of the day-to-day correlation is typically around 85% (Radovanovic et al, 1999), depending on how static the reflective environment is. The day-to-day repeatability of multipath can be exploited to improve positioning accuracies. Given known coordinates of a point on a given day, the multipath error at every epoch can be calculated from the collected phase data. This multipath signature can then be subtracted from data collected the subsequent day. Although this procedure increases the noise of the corrected measurements, it removes multipath almost completely. Furthermore, since multipath is a low-frequency phenomena, time-averaging of the multipath-free coordinate solutions is more effective. Tests performed on static and slowly deforming baselines indicate that this mitigation technique can improve epoch- to-epoch position accuracies by 35% or to the 5 mm (1~) level. By averaging corrected 1 Hz position estimates over 30 seconds, improvements in positioning accuracies of up to 50 % can be realised. Of course, the technique is only applicable under the constraint of slowly moving monitoring stations, which insures that multipath does not significantly spatially decorrelate.
Published in:	Proceedings of the 13th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GPS 2000) September 19 - 22, 2000 Salt Palace Convention Center Salt Lake City, UT
Pages:	35 - 44
Cite this article:	Radovanovic, Robert S., "High Accuracy Deformation Monitoring Via Multipath Mitigation by Day-To-Day Correlation Analysis," Proceedings of the 13th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GPS 2000), Salt Lake City, UT, September 2000, pp. 35-44.
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