Objectives Tropospheric anisotropy is one of the important factors affecting the positioning accuracy of global navigation satellite system (GNSS). The existing real-time precision point positioning (RT-PPP) technology usually combines empirical models, projection functions, and parameter estimation methods to eliminate the influence of tropospheric delay, but does not consider the impact of tropospheric anisotropy on positioning results. Solar radiation is an important factor causing tropospheric anisotropy. Therefore, we propose a RT-PPP calculation method that considers the tropospheric anisotropy caused by solar radiation.
Methods We calculate the solar altitude angle based on the station position and local time and characterize the influence of solar radiation on GNSS signals. And we improve the existing wet projection function and stochastic model to construct RT-PPP function model and stochastic model that consider the anisotropy of troposphere. The proposed method is validated by selecting 7 days of GNSS observation data from 13 international GNSS service center stations.
Results The proposed RT-PPP method outperforms the traditional methods and improves positioning accuracy in the N, E, and U directions to some extent. In terms of convergence time, the improvement rates of convergence speed in the three directions are 1.42%, 0.69%, and 2.46%, respectively. The analysis shows that the proposed method has improved the positioning results and convergence speed of stations in different latitude intervals to a certain extent, indicating that the robustness of the proposed method.
Conclusions The proposed method considers the impact of solar radiation on satellite signals passing through the troposphere, filling the gap in the influence of tropospheric anisotropy on RT-PPP. It is of great significance for further improvement of the theory and methods of RT-PPP that takes tropospheric anisotropy into account.
DownLoad: