Usability of Turkish National GNSS Permanent Network-Active Points for Detecting Deformations

Abstract

Measurement and analyzing of deformations are one of the important subjects of geodesy. The effects of possible damages can be decreased by determining the deformations on earth crust and engineering structures. Both to lower the operating expenditure and to be assumed that there is no deformation during the measurement period, deformation measurements should be performed in a short time. At the present time, GNSS technique is used commonly to determine the deformations. In this study, it was investigated the usability of the Turkish National GNSS Permanent Network-Active (TNGPN-Active) points to determine the deformations. For this purpose, a pillar was established on the garden of Kutahya Environment and Urban Ministry Provincial Directorate. A mechanism which is for creating virtual deformation on the pillar was produced in high accuracy by using CNC machining center. The GNSS receiver was placed on the levelled mechanism and shifted with 1 cm interval along 20 cm on East-West, North-South and vertical directions. The GNSS measurements which were collected for 24 hours on the mechanism were adjusted based on the TNGPN-Active points which names are HARC, BILE, KUTA, ESKS, EMR1, AFYN, USAK, DEIR by using Bernese v5.2 Scientific GNSS software. The GNSS data which were collected were separated 6, 12 and 24 hourly parts while it was being processed. For any situations, cartesian coordinates of the points (X, Y, Z) and their root mean square errors (rmse) were calculated. The deformation analyses were performed for each situation by using the cartesian coordinates and the rmse. At the end of the analyses; it was reached the consequences that by using 12 and 24 hourly data which have 30 seconds data record interval is able to determine for 1 cm deformation on horizontal direction, by using 24 hourly data is able to determine for 1 cm deformation on vertical direction. In addition, the cartesian coordinates were transformed to projection coordinates for the purpose of comparing the shifting amount with the value which was calculated with measurements, the amount which was calculated from coordinates had been compared with the amount which was given as virtualy. At the end of the comparing, it was seen that when the measurement time increases, the virtual shifting amounts and the calculated values get closer to each others.