New approaches to urban area change detection using multitemporal RADARSAT-2 polarimetric synthetic aperture radar (SAR) data

Abstract

With the current pace of regional and global urbanization, change detection and monitoring of urban areas using multitemporal synthetic aperture radar (SAR) datasets is becoming an important research topic for SAR Earth observation. Many SAR change detection methods have been proposed, but the change detection methods based on full polarimetric SAR and polarimetric SAR interferometry have not been extensively studied. In addition, due to the complexity of urban environments, most of the change detection methods were focused on natural targets. In this study, three urban area change detection methods are proposed using multitemporal RADARSAT-2 polarimetric SAR datasets; the Stationary Index Method (SIM) of urban area change detection using polarimetric SAR interferometry, the Coherence Index Method (CIM) of urban area change detection using polarimetric SAR interferometry, and the Two Scattering Components Method (TSCM) of manmade target change detection using polarimetric SAR. Three methods were applied to detect changes in an urban area after the 2008 Wenchuan earthquake. Through filed observation and high-resolution optical datasets, the true positives ratio (the ratio between the number of correctly detected “changed” pixels and the number of “changed” pixels) of manmade targets of the SIM, CIM, and TSCM were 81.34%, 89.00%, and 78.75%, respectively. The true negatives ratio (the ratio between the number of correctly detected “unchanged” pixels and the number of “unchanged” pixels) of manmade targets of the SIM, CIM, and TSCM were 87.17%, 71.42%, and 74.89%, respectively. The true positives ratio of the crops field for the SIM and CIM were 75.87% and 97.02%, respectively. The results indicated that these three methods can be effectively used to detect urban area change and manmade target change, demonstrating that RADARSAT-2 multitemporal datasets have great potential for urban area change detection.