Algorithm and Performance of Precipitable Water Vapor Retrieval Using Multiple GNSS Precise Point Positioning Technology

It is of great importance to estimate zenith tropospheric delay (ZTD) and retrieve precipitable water vapor (PWV) using ground-based GNSS remote sensing technology. At present, the ground-based GNSS technology is usually studied based on single GPS system. In this paper, the precise point positioning technology for combined multi-GNSS is carried out using the observation data of 30 MGEX tracking stations for one month. The ZTD and PWV results obtained from individual GNSS and multi-GNSS are carefully compared and analyzed. The performance of multi-GNSS data for ZTD/PWV retrieval is also assessed and the accuracy is verified by CODE tropospheric products and Radiosonde observations. The statistical results show that: (1) There are significant differences in the PPP ZTD results obtained by different navigation systems, and the more stable ZTD results can be obtained from the multi-GNSS observations. (2) The ZTD series obtained from single GNSS and multiple GNSS show good agreement with CODE ZTD series. Compared with that of GPS, GLONASS, Galileo and BDS, the solution precision of combined GNSS is the highest, which is improved by 10.91, 19.04, 33.21 and 70.16% respectively. (3) The accuracy of atmospheric vapor in the PPP data processing can reach the meteorological requirements such as numerical weather prediction model. The performance of combined GNSS compared with sounding data is the best, the accuracy of which is improved than that of GPS, GLONASS, Galileo and BDS by about 3.45, 16.16, 16.45 and 41.78% respectively. Furthermore, the results reveal that the multi-GNSS combined PPP technology can significantly improve the accuracy and reliability of ZTD/PWV series, which can support for meteorological applications such as weather monitoring and forecasting.