Velocity estimation from permanent GPS stations coordinate time series: 5 tusaga-active stations in Marmara region

Among operating permanent stations in Türkiye,the network with the highest number of stations is the Turkish National Permanent GNSS Stations Network (CORS-TR) system.In this study, 5 continuous GPS stations (BURS, ISTN, BILE, IZMT and TEKR) with no data loss of the CORS-TR network in the Marmara Region were selected and analyzed daily for the years 2016-2020 using the data of 18 IGS stations selected around Türkiye. For the analysis, GAMIT/GLOBK software running on the Linux operating system was used. Coordinate time series were produced from 1827 daily loose solution files (h-file) created with the GAMIT module. Daily solutions, which are free of errors, are combined monthly to determine coordinates and velocities. Finally, position and velocity information for all stations is estimated from monthly solutions via the GLOBK module. In order to define the reference frame, datum transformation was performed in the ITRF14 reference system with the 6 parameter (3 Translation, 3 Rotation) Helmert transform using the coordinates and velocities of the IGS stations included in the analysis. Finally, the TUREF coordinates and velocities calculated within the scope of this study and the ones estimated by General Directorate of Mapping and published on the CORS-TR internet address were compared and the obtained differences were interpreted.