Multi-GNSS real-time tropospheric delay retrieval based on SSR products from different analysis centers

Abstract. The troposphere plays an important role in a range of weather and various climate changes. With the development of the Global Navigation Satellite System (GNSS), the zenith tropospheric delay (ZTD) inversion based on GNSS has become one of the common methods. Research on real-time precise point positioning (RT-PPP)-derived ZTD accuracies of SSR corrections from different Analysis Centers (ACs) is important for earth observation correction, meteorological disaster forecasting, and warning with the increasing abundance of state-space representation (SSR) products obtained by the International GNSS Service Analysis Center (IGS). Therefore, accuracies and availability of real-time orbits and clock errors obtained by the Chinese Academy of Sciences (CAS), GMV Aerospace and Defense (GMV), Centre National d’Etudes Spatiales (CNE) and Wuhan University (WHU) were evaluated, and the RT positioning performance and ZTD accuracies were analyzed for GPS, Galileo, BDS3. The results indicate that CAS has the higher satellite availability, providing SSR corrections for 82 GPS, Galileo, BDS3 satellites. The accuracies of GPS/Galileo/BDS3 orbits are best at WHU, CAS, WHU with values of 5.57/5.91/11.77 cm, respectively; the STDs of clock error are all better than 0.22/0.19/0.55 ns, and the RMSEs are better than 0.54/0.32/1.46 ns. CAS has the best Signal-In-Space Ranging Errors (SISRE), followed by WHU, while CNE and GMV are worse. In the RT-PPP test, convergence times for CAS and WHU are 14.9 minutes and 14.4 minutes, respectively, with 3D positioning accuracy both around 3.3 cm, which is better than CNE and GMV. Among them, WHU-SSR has the higher accuracy of RT-PPP-derived ZTD with an RMSE of 6.06 mm and desirable availability with a completeness rate of 89 %.