Mineralogical characterization of tropical soils by hyperspectral remote sensing

AVIRIS (Airborne Visible/Infrared Imaging Spectrometer) data collected in B razil were used for the spectral characterization of a typical crop-pasture scene, and for the evaluation of the Spectral Feature Fitting (SFF) techni que for clay mineral identification in the image. A six-endmember linear sp ectral unmixing model was applied, consisting of green and senescent vegeta tion, water, and the soils Alfisol, Oxisol and Entisol. For mineral identif ication of kaolinite, montmorillonite and gibbsite in the AVIRIS image, ref erence spectra from the JPL/NASA spectral library were selected. Pixel and reference spectra were normalized by the continuum removal method, in the 2 ,100-2,330 nm interval, and then compared by the use of the SFF technique. Kaolinite is the dominant mineral in the scene, whose identification is dep endent on the soil type and on the spectral mixture at sub-pixel level. The best results were obtained for soils with intermediate to high overall ref lectance and for pixels with soil abundance values greater than 70%, due, r espectively, to the lower amount of opaque substances of these soils and to the reduction of spectral effects of the lignin-cellulose features. These factors tend to obliterate the absorption bands of clay minerals.