Abstract

Spectral reflectance in the visible and near-infrared wavelengths provides a rapid and inexpensive means for determining the mineralogy of samples and obtaining information on chemical composition. Absorption-band parameters such as the position, depth, width, and asymmetry of the feature have been used to quantitatively estimate composition of samples from hyperspectral field and laboratory reflectance data. The parameters have also been used to develop mapping methods for the analysis of hyperspectral image data. This has resulted in techniques providing surface mineralogical information (e.g., classification) using absorption-band depth and position. However, no attempt has been made to prepare images of the absorption-band parameters. In this paper, a simple linear interpolation technique is proposed in order to derive absorption-band position, depth and asymmetry from hyperspectral image data. AVIRIS data acquired in 1995 over the Cuprite mining area (Nevada, USA) are used to demonstrate the technique and to interpret the data in terms of the known alteration phases characterizing the area. A sensitivity analysis of the methods proposed shows that good results can be obtained for estimating the absorption wavelength position, however the estimated absorption-band-depth is sensitive to the input parameters chosen. The resulting parameter images (depth, position, asymmetry of the absorption) when carefully examined and interpreted by an experienced remote sensing geologist provide key information on surface mineralogy. The estimates of depth and position can be related to the chemistry of the samples and thus allow to bridge the gap between field geochemistry and remote sensing.

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