Landslide Monitoring Using Hybrid Conventional and Persistent Scatterer Interferometry

The Kahroud region located in the Alborz Mountains, northern Iran is subject to landslide. In this paper, the impact of two different Persistent Scatterer Interferometry methods on the study area is examined. The standard Stanford method for Persistent Scatterer (StaMPS) was applied to 14 ENVISAT ASAR images spanning between 2006 and 2008, but it was found that the displacement was underestimated due to a high deformation rate. A hybrid method that is a combination of conventional and PSI methods was then applied to the study area. In this method, the deformation rate roughly estimated by stacking the coherent interferograms characterized by small baselines was estimated and subtracted from the wrapped phase. The residual phase was then unwrapped using the standard StaMPS. The estimated rate was finally added back to the unwrapped residual phase. The maximum Line-Of-Sight (LOS) deformation rate estimated from the hybrid method was 25 mm/year, belonging to an area located in the lower part of the landslide. The deformation time series of a couple of distinct points showed differing behavior in different time periods. However, the area was still found to be generally sliding toward the satellite. These results were validated with GPS measurements at 7 stations. The Root Mean Square Error (RMSE) between LOS GPS-derived rates and rates estimated from the hybrid method was estimated as 4 mm/year.