Precision Point Positioning Method with Galileo Broadcast Ephemeris for Grid Operations in Complex Environments

Precise Point Positioning (PPP) is a major technique for obtaining high-precision coordinates for grid operations in deep mountainous areas. However, the effects of extrapolation errors for broadcast orbits and clock offsets need to be carefully considered in PPP with broadcast ephemeris. We take the European Galileo Navigation Satellite System (Galileo) as an example, and the performance of its broadcast ephemeris from day of year (DOY) 161 to 190 in 2022 are analyzed. The evaluation results show that the overall orbital accuracy and the signal-in-space ranging error (SISRE) are up to 0.157 and 0.205 m, respectively. For carefully considering the effect of Galileo broadcast ephemeris SISRE, combined errors in the line-of-sight (LOS) direction for each visible satellite orbit and clock are introduced in the traditional BE-PPP function model. The static and kinematic experimental results of the global MGEX stations show that considering LOS combined error can effectively improve the positioning accuracy of BE-PPP. The mean three-dimensional (3D) positioning accuracies of the BE-PPP static/kinematic solution for 14 global MGEX stations with considering SISRE are 16.0 and 35.3 cm, which are improved by $39.4 \%$ and $25.7 \%$ relative to the traditional BE-PPP solution, respectively.