Analysis and Correction of BDS Code Multipath Bias

In view of the problem of the long-term variation of code multipath error (called code multipath bias) in the IGSO and MEO satellite observable, code multipath bias of BDS is analyzed using iGMAS data of multiple earth stations. In addition, the GPS and BDS multipath error variation is analyzed comparatively. The results show that the variation of BDS multipath error is related to the elevation angle, satellite orbit type and carrier frequency, but independent with the location of the receivers. And for the carrier frequency B1, B2, and B3, the code multipath bias for MEO satellite is 1.66, 1.05 and 0.53 m, respectively. For IGSO satellite the code multipath bias is 0.65, 0.44, and 0.31 m accordingly, which are smaller than that reported by earlier papers. Especially, for IGSO at frequency B2 and B3, the code multipath bias is smaller than half of that reported earlier. At the same time, in order to reduce the multipath bias, a two-order polynomial fitting algorithm is proposed in this paper. The results show that: compared with the results of piecewise linear model with 10 correction parameters, the two-order polynomial correction algorithm with three correction parameters can correct the multipath error and reduce the RMS of the multipath error more effectively. The two-order polynomial model in this paper is more convenient considering broadcasting the correction information to the users.