On a new coordinate system for improved discrimination of vegetation and burned areas using MIR/NIR information

A transformation defined on the near-infrared (NIR) and middle-infrared (MIR) space is presented that allows deriving a new coordinate system appropriate for vegetation and burned area discrimination. The transformation is based on the difference between MIR and NIR in conjunction with the distance from a convergence point in the MIR/NIR space, representative of a totally burnt surface. One of the derived coordinates presents a small scatter for pixels associated to vegetated surfaces (strict scale) whereas the other one covers a wide range of values (large scale) that suggest its use as a proxy of water content of vegetation. The strict scale character of the first coordinate together with the large scale character of the second one make the coordinate system especially adequate to discriminate vegetated surfaces and rank them according to the water content, from green and dry to burned vegetation. The performance of the new coordinate system is then assessed against than traditional ratio or modified ratio indices (namely the Vegetation Index, the Burned Area Index and the Global Environmental Monitoring Index, modified to the MIR/NIR space) and it is shown that the new coordinate system provides better information than traditional indices, opening interesting perspectives for burned area discrimination and other applications like drought monitoring. ► A new coordinate system is presented for vegetation/burned area discrimination. ► The coordinate system is defined in the near vs. middle infrared spectral space. ► MODIS imagery is used to assess the performance of the new coordinate system. ► The new coordinates provide better information than traditional indexes. ► The study opens new perspectives for burned area and drought monitoring.