Intra-Year Urban Renewal in Metropolitan Cities Using Time Series SAR and Optical Data

The rapid urbanization process over metropolitan cities often came with the dramatic urban land transformation of different natural land cover types into urban impervious surfaces (UIS) or UIS back to natural land covers. However, most UIS mapping studies usually focus on inter-year variation, suggesting that the urbanization process is irreversible. The rapid intra-year urban reconstruction and urban renewal are under-explored. This study develops a new algorithm for intra-year urban renewal using all available Sentinel-1 and Sentinel-2. Time series SAR and optical data are utilized for intra-year UIS change detection, i.e., to detect the changes from UIS to other land cover types. Results showed that the urban renewal process occurred within the metropolitan area, i.e., UIS changed into the bare land or vegetation. The overall accuracy and kappa of urban renewal change detection are 72.79% and 0.4599, respectively.