GEOCOM has maintained an active GNSS Network for over 10 years, which primarily supports RTK positioning through a Multi-station NTRIP, in addition to storing raw GNSS observations in Trimble format from its own stations and some client stations. Accordingly, the continuous calculation of their positions is absolutely necessary due to various geodynamic effects that cause deformations on the Earth's crust, which is reflected in the coordinates of the GNSS antennas.
In total, 27 stations are processed, 15 of which belong to SIRGAS, obtaining their coordinates from the SIR20P2138 solution. The remaining 12 stations are those that require a coordinate determination.
For the calculation, observations are collected from various GNSS data servers such as CDDIS, CSN, RAMSAC, and SONEL, with the aim of having observations from active SIRGAS stations. Observations are downloaded specifically for January 1, 2021, associating the solution with GPS week 2138. For GEOCOM station observations, the T02 format is used to create 24-hour sessions.
Based on the above, 178 baselines are processed, yielding a total of 534 geocentric component observations. The linear combination used for processing is Melbourne-Wübbena, using precise MGEX orbits. Generally, the processed GNSS baselines range from approximately 32 km to 3460 km, achieving 95% average precisions of 8.9 mm and 24.9 mm for the horizontal and vertical components, respectively.
Once the baselines are processed, the network adjustment is performed, obtaining the network coordinates with an average 95% precision of 3.5 mm for X, 8.5 mm for Y, and 5.7 mm for Z.
Furthermore, for comparison, the adjusted coordinates are compared with the solution obtained by the USC Geodetic Processing and Analysis Center of the University of Santiago, Chile, yielding a root mean square error of 1.1 mm for the north component, 1.3 mm for the east component, and 5.4 mm for the vertical component.
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