Built-Up Area Identification in Suburban Region Using Modified PRISI Index of Sentinel-1 Data (Case Study: Surabaya-Sidoarjo, Indonesia)

Rapid urbanization in Indonesia has led to the emergence of suburban areas and the phenomenon of urban sprawl-characterized by uncontrolled city expansion into previously non-urban regions. A prime example of suburban development is the Surabaya Metropolitan Area (SMA), especially Sidoarjo Regency, which has far higher rates of population growth than Surabaya City. Synthetic Aperture Radar (SAR) technology is capable of monitoring densely populated areas, as it overcomes the limitations of optical imagery, such as interference from adverse weather, cloud cover, and dependence on daylight. This study proposes the use of the Modified Piecewise Radar Impervious Surface Index (PRISI) to analyze the spatial distribution and characteristics of built-up land in suburban environments. PRISI integrates radar backscatter intensity and interferometric coherence to enhance the extraction of impervious surfaces. Experimental results indicate that the highest impervious surface extraction occurs in the Waru sub-district of Sidoarjo Regency, with overall accuracy of 88.46% and a kappa coefficient of 0.77%. Furthermore, analysis of the results reveals that the total built-up area along the Surabaya-Sidoarjo border spans approximately 2,847 hectares, with dense development found in suburban districts such as Waru, Taman, and Sedati. These findings affirm modified PRISI's effectiveness in supporting impervious surface extraction from Sentinel-1 SAR data in suburban regions.