Comparison of fire temperature retrieved from SWIR and TIR hyperspectral data

This paper addresses the problem of active-fire temperature retrieval from hyperspectral remotely sensed data. A simple theoretical model able to retrieve the temperature of burning objects employing spectral data collected in the short-wave infrared interval is described and analysed. This algorithm assesses hot-spot temperature by processing the finite difference of at-sensor spectral radiance between nearly local spectral channels, and it is not able to retrieve the temperature of warm or cold targets at standard environment conditions (e.g. T similar to 300 K). Spectral radiance finite difference is modelled by a power series stopped to the first order, the expression of which is further simplified by Wien's approximation. The model assumes that spectral emissivity change between the two selected wavelengths is negligible and it would be used with hyperspectral data by averaging the estimates obtained at several channel couples. Performance of the new algorithm is compared with that of the "Grey-Body-Emissivity method", which computes the pixel temperature from thermal infrared spectral radiance data. The paper shows results obtained applying the above discussed methods to hyperspectral images gathered by the airborne MIVIS spectrometer over a natural fire broken out in July 1999 over the Alps, Northern Italy. (C) 2004 Elsevier B.V. All rights reserved.