Research on refinement of the empirical tropospheric models and enhanced precise point positioning

Through solving the difference between zenith tropospheric delay (ZTD) obtained from the empirical tropospheric model and real ZTD, this research determines a refined tropospheric model by utilizing the relationship between the foregoing difference and latitude and altitude. Moreover, the model proposed is introduced in the precise point positioning (PPP) for ZTD-constrained PPP, which reduces the convergence time of PPP while improving its positioning accuracy. Concurrently, this research selects the data from 180 IGS stations around the world on September 1st, 2015, to facilitate further positioning experiments. The experimental results reveal that the convergence of traditional PPP to 5 cm takes approximately 20 minutes and 18 minutes respectively for eastward and northward errors, whereas PPP constrained by the refined tropospheric model solely takes 15 minutes and 10 minutes. Additionally, regarding the elevation direction error, the convergence of traditional PPP to 10 cm takes 20 minutes, while that of troposphere-constrained PPP only takes 10 minutes.