Improved GPS position time series analysis from static PPP with the modeling of multipath effect

Multipath effect is a significant factor affecting positioning accuracy of Global Positioning System (GPS). Utilizing 4.5 years of measurements from 124 global stations of international GNSS service (IGS), we thoroughly assessed the impact of multipath on position time series, not only positioning accuracy, but also noise and seasonal signals. The influence of multipath on float precise point positioning (PPP) solutions is pronounced, with positioning discrepancy in the east, north, and vertical components of 2.4 mm, 0.6 mm, and 2.7 mm, respectively, even for 24-hour solution. The shortening 4-hour solutions further magnifies the impact of multipath correction, with discrepancy of 6.4 mm, 3.2 mm, and 9.3 mm. Accuracy of float PPP solutions is improved with multipath hemispherical map (MHM) correction, with more than 87.1 % of stations being better consistent with IGS products. In addition, MHM correction improves the ambiguity fixing rate by 1.1 %, 3.6 %, and 5.8 % for 24-hour, 8-hour, and 4-hour solutions, respectively. The advantages of MHM correction are also validated by the stacking solutions, and the white noise and colored noise for the 8-hour and 4-hour fixed PPP could be significantly reduced. Additionally, the amplitudes of the first ten GPS draconitic harmonics decrease by 26 % and 44 % for the 8-hour and 4-hour solutions, respectively, while the decrease for the 24-hour solutions is less than 1 %. The 68 % decrease in diurnal and semidiurnal amplitudes for 4-hour solutions with MHM correction indicates that the implementation of MHM correction for sub-daily geophysical loading studies requires further validation.