Description: Changing ice masses cause deformation of the solid Earth on different time scales. The classic view discriminates between elastic deformation and glacial-isostatic adjustment (GIA) due to present-day and past changes, respectively. The increasing availability of observational data and modelling advances allows our understanding of the complex pattern of solid Earth response to improve, including observation of rapid GIA.Geodetic GNSS provides a technique to directly observe bedrock motion. In Antarctica, several studies already utilized such GNSS data but were limited in time or to a specific region, or could use recordings of only a limited number of stations. Within the SCAR-endorsed project GIANT-REGAIN a reprocessing of all available Antarctic GNSS data was realized, comprising data acquired by episodic and permanent recordings at about 280 bedrock sites between 1995 and 2021. Special attention was given to metadata which are indispensable for a correct assignment of the hardware set-up. The four processing centres applied precise point positioning or differential GNSS using different scientific software. Time series of consistent point coordinates were generated as the major product.We will report on the comparison of the different solutions which allows to quantify time series analysis uncertainty. From the time series, coordinate velocities will be estimated. Here, we will discuss different aspects such as useful noise models, spatial correlations and suitable trajectory models. The treatment of the solid Earth response to ice-mass changes occurring over the last decades up to present day is currently under strong discussion and will be touched briefly.