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When using GNSS, the positions derived are automatically in the geocentric coordinate system the satellite orbits are computed in. GPS-satellite orbits are derived from a tracking network with given reference positions in a pre-defined coordinate system. This coordinate system might vary over time due to tectonic movements. The orbits are always computed in a system, called the “International Terrestrial Reference Frame” (currently ITRF2008), at the current epoch. However, regional coordinate systems do usually not follow tectonic movements.
Station coordinates in Trimble 4D Control Server depend on the coordinate system and the selected datum (reference frame and tectonic plate).