عنوان مقاله [English]
Endmember detection in remote sensing is one of the significant factors to enhance the accuracy of spectral unmixing procedures. Because of highly mixed pixels in the case of mineral detection studies, the ordinary methods based on pure pixel occurrence assumption is not always applicable. The aim of this research is to detect the endmembers of Hyperion data using the ORASIS method in Agh-Dagh region of Ardebil, Iran and to compare the results with Pixel Purity Index method. ORASIS is a collection of algorithms that work together to produce a set of endmembers that are not necessarily inside the data set, therefore the pixel purity assumption is not vital for accurate results. Applying the consecutive algorithms of the ORASIS method on the Hyperion data of the study area has been generated 23 virtual endmembers. Spectral plots of these unknown endmembers were then compared to the USGS spectral library using SAM and SFF techniques; which resulted in recognition of ten minerals including alunite, kaolinite, hornblende, arsenopyrite, vermiculite, gypsum, lepidolite, chert, limonite and malachite, while the PPI method represented only 5 mineralogical compositions including kaolinite/smectite, clinoptilolite, celsian, muscovite and montmorillonite. Abundance maps of the detected minerals were generated by Linear Spectral Unmixing (LSU) technique for both ORASIS and PPI data. The results of ORASIS showed much better and reasonable coincidence with the geological settings according to the available exploration reports and direct field observations in the study area.