An advanced method for mineral mapping applicable to hyperspectral images: the composite MSAM

摘要

We developed a new method for mineral mapping based on the continuum-removal Modified Spectral Angle Mapper (MSAM) method to distinguish minerals, such as calcite and chlorite, which have diagnostic spectral features in the visible near infrared (VNIR) and shortwave infrared (SWIR) regions. This method was applied to the reflectance data obtained by HyMap, a hyperspectral airborne sensor with 126 spectral bands (0.44-2.48 mu m) in Cuprite, Nevada, USA. Reflectance spectra in the VNIR and SWIR regions are characterized by a convex background (continuum). Continuum-removal processing results in emphasis of the shape and location of absorption peaks in reflectance spectra, and thus in recognition of the chemical species which are causing the absorption spectrum. On the other hand, the broad features in continuum spectra contain essential information for mineral classification as well. Therefore, we produced mineral index maps from both the continuum and continuum-removed images based on the MSAM method and then combined them to generate a mineral distribution map. This composite MSAM method was applied to remotely sensed hyperspectral data for the first time. It was confirmed that our mineral index maps were consistent with the existing mineral maps. We can conclude that the composite MSAM method has a great advantage over our previously developed method in discrimination between calcite and chlorite, in particular.