Anybody read... Mapping variations in weight percent silica measured from multispectral thermal infrared imagery—Examples from the Hiller Mountains, Nevada, USA and Tres Virgenes-La Reforma, Baja California Sur, Mexico, S.J. Hook et al. / Remote Sensing of Environment 95 (2005) 273–289 ...??? It mentions that "The weight percent silica value for a given pixel depends on wavelength position of the minimum of the best fit Gaussian to the emissivity spectrum." I'd like to apply this methodology to ASTER TIR data using ENVI, but I'm wondering; how exactly would one determine the "Gaussian minimum" of each spectra in an image?