ASTER User's Guide - NASA

ASTER Users HandbookFigure 17: Cuprite Mining District, displayed with SWIR bands 4-6-8 as RGB composite.(Note: Area covered is 15 x 20 km)Red-pink areas mark mostly opalized rocks with kaolinite and/or alunite; the white area isStonewall Playa; green areas are limestones, and blue-gray areas are unaltered volcanics.Data from the SWIR region were processed to surface reflectance by LP-DAAC and imagespectra were examined for known targets at Cuprite. Evidence of SWIR crosstalk was apparent,making the data difficult to use for spectral analysis using direct comparisons with library orfield spectra. To reduce the cross-talk artifacts, a spectrum of Stonewall Playa was used as abright target, resampled to the ASTER wavelengths, and divided into the SWIR reflectance data.Library spectra were compiled for minerals known to occur at Cuprite; they were then resampledto ASTER SWIR wavelengths. These spectra were used with a supervised classificationalgorithm, Spectral Angle Mapper, to map similar spectral occurrences in the SWIR data. Theresult of this classification is shown in Figure 18.42