A normalised difference alpha-angle approach to burn scar extraction on multiple-polarisation sar data

Wild fires are often disastrous events, damaging infrastructure and the environment. However, in fire-prone ecosystems, periodic fires are vital for ecosystem functioning. Fire managers in these regions seek to promote the optimal fire regime by managing fire season and fire frequency. For this purpose, detailed information on the extent and date of previous burns over large areas are required. This paper proposes a Normalised Difference α-Angle approach to burn scar mapping using α-angles derived from a pre-burn scene and a post-burn RADARSAT-2 scene. A threshold-based segmentation approach was used to extract the burnt-area extent while minimizing speckle effects. The results of the burn scar extraction were compared to the extent of a burn scar derived from Sentinel-2 data. The results suggest that, in general, a good agreement between the two approaches was obtained with an overall accuracy of 0.98 achieved. High errors of omission was associated with areas of high local incidence angle. In general, the result suggests that SAR data, analysed using the proposed approach, can be used in areas where persistent cloud cover or smoke from active fires prevents the use of conventional approaches.