Utilization of Landsat ETM+ data for mineral-occurrences mapping over Dalma and Dhanjori, Jharkhand, India: an Advanced Spectral Analysis approach

Abstract

The Advanced Spectral Analysis (ASA) technique, one of the most advanced remote-sensing tools, has been used as a possible means of identifying mineral occurrences over Dalma and Dhanjori. The ASA technique is a sixfold tool, which includes the continuous processes of (1) the reflectance calibration of Landsat Enhanced Thematic Mapper (ETM+) images of the study area, (2) the generation of minimum noise fraction (MNF) transformation, (3) the calculation of the pixel purity index (PPI), (4) the n-dimensional visualization and extraction of endmember spectra, (5) the identification of endmember spectra for mineral occurrences and (6) the mapping of mineral occurrences. The identification of the extracted endmember spectra is obtained by comparing it with available pre-defined library spectra (United States Geological Survey (USGS), John Hopkins University (JHU) and Jet Propulsion Laboratory (JPL) spectral libraries) using the Spectral Analyst tool of ENVI 4.1 software (Research Systems Inc., Boulder, CO, US), which provides scores of matching. Three techniques, namely Spectral Feature Fitting (SFF), Spectral Angle Mapping (SAM) and Binary Encoding (BE), are used for identification of the collected endmember spectra to produce a score between 0 and 1, where the value of 1 equals a perfect match showing the exact mineral type. A total of six endmember spectra are identified and extracted in the study area. Mapping of mineral occurrences is carried out using the Mixture-Tuned Matched Filtering (MTMF) technique over the study area on the basis of collected and identified endmember spectra. Results of the present study using the ASA technique ascertain that Landsat ETM+ data can be used to generate valuable mineralogical information.