Scattering of C-band RADARSAT signal on sloping Earth's surface affected by forest fire areas

Abstract

This study investigates the backscattering properties of C-band RADARSAT (SAR) signal over sloping mountainous areas, and evaluates the utility of RADARSAT in natural disaster areas (e.g., forest fires), geological mapping, monitoring of natural hazards, natural and associated Earths environmental changes. Conventional change detection techniques in remote sensing are adequate for most applications. However, the changes in backscattering coefficients (σ0) before and after, for example, forest fires are not apparent in certain cases, mainly because of the effects of steeply sloping target scattering surface areas. The slopes of a mountainous test site can be divided into two cases with respect to the incident SAR signal look direction: the front and back slopes, where local incidence angles can vary significantly. Depending on the slope of the scattering surface, the backscattering coefficient increases to the maximum of 3.3. dB in the front-slope, but decreases 4.5 dB in back-slope after forest fires. Forest fire burnt areas provide a good example of a natural sloping scattering surface, which exhibits subtle changes in backscattering coefficients similar to the lithological changes in nature. The April 2000 forest fire in Kangwon province, Korea, burned for several weeks and was one of the worst ones in recent years. Among several firedamaged sites, an area near Samchuk city was investigated in detail with a set of multi-temporal RADARSAT Synthetic Aperture Radar (SAR) data to estimate the fire damages as compared to the unburnt background.