Precise GPS Processing Algorithm for Short Observation Time-Span in Urban Area

Lawrence Lau, Esmond Mok

Abstract:	GPS surveying in urban area may face the problem of cy-cle slips and fewer observing satellites than usual. They are due to some satellites’ signals being obstructed by buildings. This problem may result in impossibility of ambiguity resolution and so incorrect position determina-tion. Besides, multipath error may be serious in urban area. This paper proposes a precise high-accuracy GPS proc-essing algorithm for short observation time-span, which is very useful for GPS positioning in urban area. The ob-servables are double-differenced C/A code with L1 carrier phase only or L1 and L2 carrier phases. The algorithm is based on Ambiguity Function Method (AFM) which is insensitive to cycle slips and ambiguities do not need to fix. Moreover, multipath error is mitigated by using sig-nal- to-noise ratio weighting. The algorithm is tested with data sets collected in com-mercial areas where the roving receiver is surrounded by tall buildings. The reliabilities and accuracies of the algo-rithm in different areas and observation time-spans are shown. The significance of this processing algorithm is that it makes GPS positioning in urban area possible. When sin-gle epoch data are used, the algorithm has potential for precise vehicle navigation in urban area.
Published in:	Proceedings of the 55th Annual Meeting of The Institute of Navigation (1999) June 27 - 30, 1999 Royal Sonesta Hotel Cambridge, MA
Pages:	533 - 540
Cite this article:	Lau, Lawrence, Mok, Esmond, "Precise GPS Processing Algorithm for Short Observation Time-Span in Urban Area," Proceedings of the 55th Annual Meeting of The Institute of Navigation (1999), Cambridge, MA, June 1999, pp. 533-540.
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