Combining GPS and InSAR Data to Improve the Accuracy of Dams Displacement Monitoring (Case Study: Givi Dam - Iran)

Landslides are one of the most common natural phenomena that cause subsidence as well as deformation and displacement. Due to this point, the importance of detecting displacement in sensitive areas such as the dam and the surrounding area increases. Radar interferometry is currently one of the best techniques for assessing ground deformation. But this method alone is not suitable for structures that have horizontal deformation and displacement. In this study, in order to increase the accuracy and efficiency in detecting unstable points, we have used a combination of radar images and GPS satellite observations on the Givi Dam area in the period 2017 to 2019. Using Small Baseline Subset (SBAS) analyses, point stability analysis by Iterative Weighted Similarity Transformation (IWST) method and classical adjustment method were found to be two excellent methods for detecting displaced points and validating the results. So that both methods identified the same points on the dam and the points outside the dam. Among these points in the area around dam GR4 has the highest displacement of 5.57 mm and in the direction of the satellite line of view obtained from radar interference -1.61 mm per year and point P9 on the dam has the highest displacement of 9.06 mm and in line with the line of sight of the satellite obtained from radar interferometry is 1.96 mm per year. Also, as the distance between GPS stations and pixel points decreases, accuracy increases dramatically.