The simulation of GTRF initial realization using GPS data

The GTRF initial realization and long-term maintenance follows the state of the art of TRF implementation. In this paper, the background of GTRF realization and the history of ITRF establishment were reviewed firstly. The precious experience gained from IERS activities is very helpful in GTRF realization, based on such situation, so the combined model and strategy for simulating GTRF initial realization by GPS data in the first stage of Galileo project were discussed and. And then 200 GPS Weeks data in SINEX format from three IGS analysis centers COD, ESA and GFZ was used as input data, we apply loose constraint, use the variance factor of weekly time series as apriori weight in the combination, and estimate station coordinate and 7 transformation parameters together. According to this simulation, the translation and scale parameters of three analysis centers are attained by weekly combined solution, while the rotation parameters are just estimated by the data from ESA. With these 7 transformation parameters, the GTRF can be initially realized by alignment to the ITRF by the GSS co-located with ITRF core stations.