Deformation of static datum: Turkish CORS network (TUSAGA-Aktif) is considered

Abstract

The geocentric datum of Turkish CORS Network (TUSAGA-Aktif) is a semi-kinematic datum realized with respect to the International Terrestrial Reference Frame (ITRF 96) at the reference epoch of 1 January 2005 (2005.00). This realization was maintained by ITRF no net rotation (NNR) velocities of CORS stations. Up-to-date ITRF NNR velocities were determined by General Command of Mapping in Turkey using 7 years of CORS stations data from 2008 to 2015. In accordance with Turkish surveying regulation, there are two types of coordinate computation of the control points performed with Global Navigation Satellite System relative positioning technique based on the datum. Coordinates of the first-order and the second-order control points are computed in semi-kinematic datum, whereas the third-order control points are computed in static datum. Generally, CORS stations of TUSAGA-Aktif are used as fiducial stations for coordinate computation of these control points. In this study, baseline deformation effect of static datum on the three-dimensional position of the points are investigated. 20 CORS stations within TUSAGA-Aktif were chosen to simulate the rover and the fiducial stations. The results show that relative displacement from the reference epoch (2005.00) between the rover-fiducial stations at the measurement time and the positioning error of the rover station are in a good agreement. The differences are in the order of mm to cm level. The results also show that when more than one fiducial station used in static datum processing, mean relative displacement between the rover-fiducial stations at the measurement time and the positioning error of the rover are also in a good agreement. The results emphasized that, velocities of the fiducial stations should be known by the users for conducting static datum processing with minimum baseline deformation as much as possible.