DS-InSAR-based monitoring and analysis of a long time series of surface deformation in the fire area of the Wuda coal field

Coal fire not only wastes a lot of coal resources but also severely damages the ecological environment of the fire area. However, conventional monitoring methods suffer disadvantages such as a small scope, low frequency, high cost, and great danger. Therefore, this study developed a monitoring method of coal field fire based on the distributed scatterer interferometric synthetic aperture Radar (DS-InSAR) technology. This method successively selects homogeneous pixels using the fast statistically homogeneous pixels selection (FaSHPS) algorithm, optimizes the phases of these pixels using the eigenvalue decomposition method, obtains the final distributed targets based on the temporal coherence, and calculates the time-series surface deformation by combining the small baseline subsets (SBAS) InSAR technique. Taking 63 scenes of Sentinel-1A images from March 2017 to April 2019 as the data source, this study obtained the time series surface subsidence in the Wuda coal field using this method and then verified the reliability of the results by comparison with the monitoring results obtained using the temporarily coherent point interferometric synthetic aperture Radar (TCP-InSAR) technology. As a result, the correlation coefficient between the two methods was 0.84, but the density of monitoring sites obtained using the method proposed in this study was 1.24 times higher than that of TCP-InSAR. The monitoring results show that the surface of the Wuda coal field deforms severely, with a maximum deformation rate of -215 mm/a, and that the deformation occurs more rapidly during autumn and winter and has multiple extensional directions and multiple subsidence centers at varying degrees.