Burnt area mapping by remote

Burnt area mapping by remote sensing is mostly done through measuring the changes of the reflectance of surface objects after the fire that occur mainly in the reflective part (0.45�C3.0 ��m) of the electromagnetic spectrum. This is because a fire alters the spectral response of the land surface by selleckchem reducing the fractional cover, density, greenness and water content of vegetation by partially or completely removing surface litter, exposing and altering simultaneously the colour and brightness of the soil [6]. These changes in the surface properties result to a strong contrast of the fire-affected areas with the surrounding environment [7,8].Generally, remote sensing-based methods employed today differ with regards to the number of the satellite scenes used and the type of processing carried out in the analysis.

Regarding the number of images employed in the analysis, methods are separated into single-image methods if one post-fire image is used, and bi-temporal methods when more than one image (usually one image before and one after the fire) is used. Single-image approaches have important advantages over bi-temporal methods, mainly because they are more cost and time effective in processing and analysis, and they are less prone to potential processing errors [9]. In addition, these methods do not require registration and do not require correcting the satellite imagery for errors arising from sun�Csensor geometry, atmospheric effects or perhaps differences in sensor calibration [10].

Nonetheless, for this type of approach, satellite imagery has to be acquired very shortly after the suppression of the fire incident, as otherwise, the identification of the burnt areas becomes more difficult [11]. On the other hand, the main advantage of the multi-temporal approaches is that they reduce the confusion with the types of permanent cover [12]. In terms of the type of processing applied, methods employed vary from those based on the calculation of simple radiometric indices, such as the Normalised Difference Vegetation Index (NDVI) of [13] or the Normalised Burnt Ratio (NBR) of [14], to other more complex ones, such as image classification and sub-pixel analysis [15]. A few other studies have proposed the retrieval of burnt area from surface temperature derived from thermal bands of satellite sensors (e.g., [16]). Overviews on the different remote sensing-based approaches for burnt area mapping can be found in [17,18].Based on the available methods and satellite sensors in orbit, operational services have also been developed by international space agencies providing at multiple resolutions and spatial scales fire analysis data, including burnt area maps, often in the form of regional-scale products [19].

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