Use of spectral analysis for detection of alterations in ETM data, Yazd, Iran
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ORIGINAL PAPER
Use of spectral analysis for detection of alterations in ETM data, Yazd, Iran Rashed Poormirzaee & Majid Mohammady Oskouei
Received: 22 November 2009 / Accepted: 27 June 2010 / Published online: 13 August 2010 # The Author(s) 2010. This article is published with open access at Springerlink.com
Abstract Spectral analysis methods were used for detection of mineralogical features on a set of Enhanced Thematic Mapper Plus data of Behabad zone, central Iran. Several indicative minerals for hydrothermal alterations were identified in the study area. The spectra of unknowns were determined by comparing to USGS mineral spectral library. Different pre-processings and processings were performed to achieve the highest possible accuracy. These are the minimum noise fraction, the pixel purity index analysis, spectral feature fitting, spectral angle mapper and binary encoding. The results of spectral analysis, as a map of minerals abundances, along with the results of other Image processing methods such as least square fit, and Crosta method were integrated within ArcGIS Software to achive a potential map of hydrothermal alterations. The minerals: allanite, magnetite, alunite, clay minerals, and muscovite were therefore detected and mapped in this study. The detected alterations here highly match to the mineral concentrations which are formerly found and measured in the study area that emphasizes the reliability of the applied method. Keywords Remote sensing . GIS . Spectral analysis . Multispectral analysis . Mineral detection Alteration mapping
Introduction A diversity of previous researches has proved the reliability of multispectral data analysis in the field of alteration R. Poormirzaee (*) : M. M. Oskouei Sahand University of Technology, Tabriz, Iran e-mail: [email protected]
detection. Among them, Landsat data are important because of their broad coverage and popularity. On the other hand, Improvements in design of sensors and precise spectrometers helped researchers to measure different laboratory spectra. This advances spectral analysis as a quantitative method for applied remote sensing. The foundation for quantitative analysis of remote sensing data through spectral analysis is reflectance spectroscopy. Reflectance is generally defined as the ratio of the intensity of the electromagnetic radiation scattered from a surface to the intensity of the radiation incident upon it. When measured as a function of wavelength, reflectance spectra exhibit specific albedo, continuum, and absorption features which are a function of material properties of the surface measured. The absorption features are related to the chemical composition and mineralogy of the surface, while the continuum and overall albedo are a function of nonselective absorption and scattering as well as broad wavelength selective absorption (Rencz 1999). Spectral analysis, one of the most advanced remote sensing techniques, were used as a possible means of identifying the mineralogy of the clay fractions in the Kuchuk, Izmir, Turkey.
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