Monitoring Koyulhisar landslide using rapid static GPS: a strategy to remove biases from vertical velocities

GPS is frequently used in the monitoring of natural hazards and other geophysical phenomena. Landslide monitoring is one such area in which various GPS methods are tested and various systematic error sources are introduced. In previous studies, one error source introduced on rapid static GPS was the effect of large height differences in GPS positions. In this study, we further investigate how GPS velocities/slip rates are affected by large station height differences when rapid static surveying is used. In order to demonstrate the influences, we used static GPS measurements from the Koyulhisar landslide in central Turkey. Comparison of rapid static GPS solutions with static GPS solutions using BERNESE 5.0 indicates that systematic biases occur in the estimated rapid static GPS deformation rates when the station height difference is large between baseline points. The effect is more significant on the vertical component, whereas it is negligible on the horizontal components. When reducing the height difference between the reference station and the rover stations, rapid static solutions from 15-min sessions show high correlation and similar deformation rates with static positioning solutions.