Assessing the Use of Sentinel-2 in Burnt Area Cartography: Findings from a Case Study in Spain

Abstract

Remote sensing is increasingly being used as a cost effective and practical solution for the rapid evaluation of impacts from wildfires. The recent launch of the Sentinels offers a unique opportunity to assess the impacts of wildfires at both greater spatial and spectral resolutions provided by those Earth observing systems. In this study, an assessment of the Sentinels to map burnt areas is conducted by initially exploring the use of Sentinel-2 to detect burnt areas. The investigation attempted in particular to evaluate the use of different bands and derived indices that are commonly used to detect burnt areas. A range of spectral indices was used, including Normalized Difference Vegetation Index (NDVI) and Normalized Burn Ratio (NBR) for both the SWIR1 and SWIR2 por- tions of the EM spectrum. The three new Red Edge bands that come with the Sentinel-2A MSI sensor were also used. The Slope, Aspect, and Fractional Vegetation Cover and Terrain Roughness were all derived to produce environmental variables. The Copernicus Emergency Management Service has produced a grading map for the fire using 0.5 m resolution Pleiades imagery, which was used as reference. The visible part of the EM spectrum was not well suited to discern burned from unburned land cover. The NBRb12 (SWIR2) produced the best results for detecting burnt areas. The SAM classification resulted in a 73% overall accuracy. All in all, our study contrib- utes to the understanding of Mediterranean landscape dynamics. It also provides further evidence that use of Sentinel-2 technology, combined with GIS analysis techniques, can offer an effective tool in mapping wildfires. © 2020 John Wiley & Sons, Inc.