Urban Impervious Surfaces Estimation From Optical and SAR Imagery: A Comprehensive Comparison

Numerous studies have demonstrated the benefits of fusing optical and synthetic aperture radar (SAR) data for urban impervious surfaces estimation. Given the increasing availability of SAR satellite data, the synergized use of optical and SAR data is increasingly important. However, previous studies have focused primarily on a single scale. This study aims to evaluate the impervious surfaces estimation using different combinations of optical and SAR data, as well as to quantify the scale effects of combining optical and SAR data under various resolutions from 30 to 1050 m. Six combinations of optical and SAR data in three cities, Shenzhen, Mumbai, and São Paulo, were compared. Experimental results illustrated the effectiveness of using texture and SAR data in improving impervious surface estimation with producer's accuracy improvement of 5%, 0%, and 4% in Shenzhen, Mumbai, and São Paulo at 30 m. The correlation coefficient assessment between the estimated and referenced impervious surfaces at various scales demonstrated that TerraSAR-X data generally outperformed ENVISAT advanced SAR of impervious surface estimation. Estimation accuracy of impervious surfaces in Shenzhen had an improvement of 4% to 5%. Moreover, the texture information of SAR data was observed to provide positive contributions to the impervious surfaces estimation in three study cases at different scales.