The Tropospheric Product Combination of iGMAS Analysis Centers and the Analysis of Their Precision

Several analysis centers (AC) and a product integration and service center (ISC) have been built by the international GNSS continuous Monitoring and Assessment System (iGMAS) currently. ISC analyzes the quality of product provided by ACs of iGMAS, and then reprocesses to generate a combined product. The tropospheric solution is the key product of ISC and important data for satellite navigation and precise point positioning (PPP). First of all, this paper introduces the method and theory of tropospheric product combination by means of weighted average based on robust estimation. Then, the precision of combined tropospheric product of ISC and the AC’s product with respect to the JPL final tropospheric delay is compared and analyzed. Furthermore, the tests of using iGMAS data are implemented to verify the accuracy and reliability of combined tropospheric solution. The results show that the RMS of the combined tropospheric solutions of IGS stations are better than those of most analysis centers, and meet the accuracy requirement of iGMAS. Finally, the precision of ACs’ tropospheric products of iGMAS stations with respect to the ISC final products is compared and analyzed.