Multipath mitigation in GNSS precise point positioning using multipath hierarchy for changing environments

Global navigation satellite system precise point positioning (PPP) technology can be significantly affected by multipath errors of code and phase observations. Previous studies using multipath hemispherical map (MHM) to mitigate multipath highly rely on stable surrounding environments, and limited work emphasizes multipath mitigation in changing environments (i.e., the surrounding environments are variable but the user maybe static). We propose a new multipath mitigation method using multipath hierarchy (MH) derived from the C/N0 discrepancy in azimuth and elevation grid in changing environments. The main processing procedures using MH in GNSS PPP are given. Two dedicated static datasets are collected to analyze the multipath discrepancy of normal MHM and further conduct the C/N0-based MH. The performance using MH is carefully analyzed in terms of positioning accuracy and residual reduction. Specifically, the normal MHM exhibits multipath discrepancy in changing environments; thus, the C/N0-based MH is of great necessity to further mitigate multipath. Compared to the normal MHM, the MH-corrected positioning errors are improved, especially at the initial epochs. By calculating the three-dimensional positioning accuracy of all epochs, the MH-corrected positioning accuracy can be improved by approximately 6 and 3 cm compared to the uncorrected and MHM-corrected results in centimeter-level PPP, respectively. Also, the standard deviations of MH-corrected code and phase residuals are smaller than MHM-corrected results for each satellite. In this sense, the proposed multipath mitigation method using MH is highly appreciated for the performance of positioning accuracy and residual reduction in changing environments.