Multitemporal monitoring of Karvina subsidence troughs using Sentinel-1 and TerraSar-X interferometry

Abstract

Satellite SAR interferometry (InSAR) allows to observe borders of subsidence troughs created in undermined areas. There is a possibility to evaluate a subsidence velocity in the accuracy of a mm/year for the stable reflectors of the radio signal, e.g. buildings. We apply Permanent Scatterers (PS) and Quasi-PS (QPS) techniques for monitoring of mine-caused subsidence in the Karvina area situated in the Czech part of Upper Silesian Basin. We use PS technique as effective for observation of displacements of built structures (e.g. buildings) and QPS for monitoring of spatio-temporal development of subsidence troughs. The results reveal information valuable for an identification of deviations from expected effects of mining activities on the land surface and for the infrastructure which are potentially affected by the subsidence. We perform the processing of Sentinel-1 and high resolution TerraSAR-X to find how the lower spatial resolution of Sentinel-1 SAR affects the reliability of results. The assets of these new sensors, especially the short revisit time, can overcome the basic limits of InSAR methods connected with temporal lags between available SAR images. In previous Karvina area datasets (ERS, Envisat, Alos satellites) the basic temporal step used to be around one month. During such temporal length significant changes occured in vegetation cover or in cultivated soil causing a loss of coherence of radar measurements. In addition to this, the amount of subsidence of Karvina troughs has often exceeded detection limits of the SAR systems. A significant increase of the reliability of evaluated subsidence also in areas with a moderate vegetation cover is expected with the launch of Sentinel-1B since the short-term interferograms would not be affected by a full decorrelation.