REMOTELY SENSING LA REFORMA CALDERA BY APPLYING ENVI PROCESSING TO ASTER IMAGE DATA

La Reforma Caldera, located on the eastern shore of Baja California Peninsula, Mexico, is the site of a spectral analysis of ASTER (Advanced Spaceborne Thermal Emission and Reflection Radiometer) image data utilizing ENVI digital processing software. The lack of vegetation in the desert terrain creates optimal conditions for remote geologic mapping. These Plio-Quaternary volcanics are composed mainly of a calco-alkaline series with an alkaline rich pyroclastic flow and some peralkaline basaltic cones. Processing reflectance spectra from ASTER image data in combination with previously assembled geologic maps enables production of a new geologic map. Each raw ASTER data package consisted of fourteen bandwidths ranging from visible to infrared wavelengths. Resizing the data to 15 meter/ pixel resolution allows for the combination of files and improved efficiency of computer processing. The full Reforma Caldera area of interest requires the combination of two 3600 square km data sets. Each pixel was geo-referenced for assimilation to a global network. Spectral-response curves based on percent reflectance and wavelength distinguish lithologic regions of different chemical composition. These regions were compared to existing geologic maps and sorted based on their spectral reflectance signature. This comparison shows the effectiveness of this remote sensing method in the interpretation of lithologic units.