Detection of subsidence in Bad Frankenhausen with time series analysis of interferometric Radar

Abstract

The area of Bad Frankenhausen, a small city in Thuringia in central Germany is subject to land subsidence because of the occurrence of sinkholes. We use SAR interferometry (InSAR) time series analysis to monitor the subsidence in this area. All the available C-band Sentinel-1A data in both geometries of ascending and descending are collected in this study. We exploit Small BAseline Subset (SBAS) as a time series algorithm to derive the subsidence rate of the study area. The accuracy of the SBAS time series analysis could be affected by high rate of atmospheric artifacts especially over the humid area, therefore, selection of the appropriate method of the atmospheric correction is required. In this study, a statistical based atmospheric correction method is performed to decrease the atmospheric influence The time series analysis result in both geometries show a low rate of deformation signal along LOS directions with nearly negative sign corresponding subsidence phenomena. Availability of the InSAR time series results in both ascending and descending tracks enables us to estimate the horizontal and vertical displacement using the decomposition process.. The results show a very small rate of movement, almost zero, along with horizontal direction. Vertical displacements with a maximum subsidence rate of 1.4 mm/a$ are observed over the area. The results of the time series analysis are partially compared to GNSS and leveling data.