Analysis of Urban Areas with Built-up Land Index Using ALOS PALSAR-2 Satellite Imagery (Case Study: Surabaya City)

Surabaya, the largest metropolitan city in East Java Province, has experienced rapid urban growth driven by population increase, economic development, and migration from surrounding regions. This growth has accelerated the expansion of built-up areas, particularly in suburban zones that were previously dominated by productive land such as rice fields and forests. These land use changes present significant challenges for sustainable urban spatial management, highlighting the need for efficient and reliable monitoring techniques. This study employs Synthetic Aperture Radar (SAR) based remote sensing, which enables consistent data acquisition regardless of weather conditions or illumination. ALOS PALSAR-2 Single Look Complex (SLC) data were utilized and analyzed using the SAR-based Impervious Built-up Index (IBUIsar) method to identify and map built-up areas based on backscatter characteristics. The application of the IBUIsar method aims to produce an accurate spatial distribution map of built-up land in Surabaya. The results indicate that higher IBUIsar values are concentrated in the city center and areas with intensive development activities. This information is expected to support urban spatial planning and contribute to sustainable urban development strategies.