BDS/GPS Zenith Tropospheric Delay Estimation and Its Effect on Precise Point Positioning

The influence of zenith wet delay parameter estimation and horizontal troposphere gradient processing strategy on precise point positioning is studied, Six zenith tropospheric delay processing schemes were designed and experimented on the basis of the measured data from nine Multi-GNSS Experiment stations. The experimental results show that, during the 8 h observation period, it is not suitable to use the random walk model to deal with the horizontal troposphere gradient of the zenith wet delay in the BDS/GPS Precise Point Positioning mode; and the strategies of estimating the zenith wet delay parameter by random walk and handling the horizontal troposphere gradient without estimating or using the piecewise constant are relatively advantageous. The results of the dynamic and static precise point positioning show that the BDS/GPS strategy of estimating the zenith wet delay parameter and processing the horizontal troposphere gradient with piecewise constant or random walk is relatively superior, while the strategy of processing the horizontal troposphere gradient with random walk is slightly weaker. Overall, the zenith tropospheric delay and precise point positioning accuracy estimated by BDS is slightly weaker than that by GPS; the differences in the results of the six schemes around the ocean are larger than those of the inland stations. In the static Precise Point Positioning mode, with the increase of observation time, the trend of Precise Point Positioning errors of the six schemes tends to be the same, and the error size is basically within 2 cm. When the observation time is longer than 12 h, the strategy of estimating the zenith wet delay parameter by random walk and not considering the horizontal troposphere gradient is better overall.