Mediterranean forests are every year affected by wildfires which have a significant effect on the ecosystem. Mapping
burned areas is an important field of application for optical remote sensing techniques and several methodologies have
been developed in order to improve mapping accuracy. We developed an automated procedure based on spectral indices
and fuzzy theory for mapping burned areas from atmospherically corrected Landsat TM images. The algorithm proved to
provide consistent accuracy over Mediterranean areas. We further tested algorithm’s performance to assess the influence
of the atmospheric correction on the accuracy of burned areas. In particular, we ran the Second Simulation of a Satellite
Signal in the Solar Spectrum (6S) code with different Atmospheric Optical Thickness (AOT) levels and two aerosol
models (continental and maritime) on one TM image acquired over Portugal (12/08/2003). Burned area maps derived
from atmospherically corrected images and from the non corrected image (Top Of Atmosphere, TOA) have been
analyzed. In the output burned areas maps the omission error varies in the range 4.6-6.5% and the commission error
fluctuates between 11.9 and 22.2%; the highest omission (commission) errors occur with the continental (maritime)
model. The accuracy of burned area maps derived from non corrected image is very low, with omission error greater than
90%. These results show that, although atmospheric correction is needed for the application of the algorithm, the AOT
value does not significantly affect the performance.
Large wildfires in forests of southern European countries such as Portugal, Spain, Greece, France and Italy are one key
ecological disturbance of the Mediterranean environment. Optical data have been largely used for burned area mapping and literature provides an extensive reference for the typical spectral signal of burns and the methodologies applied to extract burn perimeters. However, optical remote sensing techniques have the major limitation of a reduced frequency of clear images due to cloud cover; moreover, for the specific application of burned area mapping, unburned targets such as shadows, can be spectrally confused and misclassified as burns. For this reason radar images could be integrated as an additional source of information. We developed an approach for mapping burned areas in Mediterranean regions based on Landsat TM/ETM+ data and vegetation indices that provided satisfactory results. However, we are currently working for further improving our approach by exploiting the synergy between optical and radar data. In this paper we present the first results of the analysis of the SAR backscatter over burned areas for future integration into the formal framework previously developed. Although results are preliminary, they encourage us to test the approach over different regions of the Mediterranean environment to evaluate its robustness.
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