How Multipath Error Influences on Ambiguity Resolution

N. Kubo, A. Yasuda

Abstract:	It is known that both code and carrier-phase multipath is currently one of a few remaining obstacles against high precision real time positioning. It easily leads to incorrect ambiguity resolution and causes cm-order fluctuations of positioning. If the multipath error in pseudorange fluctuates largely, the initial ambiguity for the satellite is biased and its search space can be enlarged. As a result, a longer time is needed to resolve the ambiguity and the probability of successful integer ambiguity estimation decreases. The carrier phase, disturbed by multipath largely, leads to the incorrect ambiguity resolution and the fluctuation of the positions of a few cm even if the integer is estimated correctly. The more the available satellites, the more the robustness against multipath of the ambiguity resolution. This implies that combined receivers of GPS, Galileo, and QZSS (Quasi-Zenith Satellite System) is more robust against multipath, as they can remove the satellite, which is seriously contaminated by multipath, in the calculation of RTK positioning. This paper demonstrates the effects of multipath error on ambiguity resolution for short-baseline in both simulation and real data analyses. We have often found that the effects of multipath in both carrier phase and pseudorange measurements make it difficult to fix ambiguities correctly. On the other hand, we have also found that removing satellites of which signal is contaminated by multipath is effective in RTK-positioning. Current RTK system isn't perfect against the biases such as multipath and insufficient satellites. Because of this, the range of RTK data service is limited. We also showed one example of the ambiguity resolution under strong multipath and insufficient satellites conditions.
Published in:	Proceedings of the 16th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GPS/GNSS 2003) September 9 - 12, 2003 Oregon Convention Center Portland, OR
Pages:	2142 - 2150
Cite this article:	Kubo, N., Yasuda, A., "How Multipath Error Influences on Ambiguity Resolution," Proceedings of the 16th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GPS/GNSS 2003), Portland, OR, September 2003, pp. 2142-2150.
Full Paper:	ION Members/Non-Members: 1 Download Credit Sign In