Using Principal techniques on ETM+ 2002 for arid and semi-arid environment Central IranGholamreza Mirzavand Civil Engineering Department, Islamic Azad University Dezful Branch, Dezful Iran Gholamreza Mirzavand mirzavand@yahoo.com Abstract Principal component analysis is a well known method of orthogonalizing data. It converges very fast and the theoretical method is well understood. Basically image processing is used for extraction of required information. The present study begins with remote sensing techniques and PCA applying on enhance thematic mapper (ETM+) satellite image dated 2002 for central of Iran, west Esfahan city. The study presents two methods of enhancing igneous body consists of amphibolites and volcanic using optimum index factor (OIF) and Crosta. In this study the optimum index factor allows to use the multi-spectral data for understanding the best false color composite (FCC) image. It is also highlighted the required spectral range (bands) for classification of image to enhance the igneous bodies. The Crosta technique is based on PCA using eigenvector, enhanced the spectral behavior of minerals. The objects on the image are enhanced in terms of black and white with respect to eigenvector loading. 27 FCC images are produced and analyzed using OIF. It is seen that the classification on FCC images for bands 741 and 541 of Infra-red and FCC images for band 654 and 641 of Thermal infra-red are the most accurate composite color images to enhance igneous body, amphibole and clay minerals. The study reveals that the PC3 is increasing the enhancement for reorganization of amphibole minerals in orthoamphibolite rocks. It also shows that PC5 has suitable enhancement to identify the clay minerals in granite rocks. However the study also indicates the use of optimum index factor for identification of spectral bands to give more information about minerals on the image using classification techniques in arid and semi-arid environment where vegetation cover is scanty. This study also represents the use of remote sensing techniques for exploration. 1. Introduction Principal component analysis is a linear procedure to find the direction in input space where most of the energy of the input lies. In other words, PCA performs feature extraction. The projections of these components correspond to the eigenvalues of the input covariance matrix. The principal component analysis is performed first, and then the eigenvector loading is trained to generate image that give the information of spectral bands for easy interpretation. The reason for this is that the PCA faster since eigenvalues are stable. Natural color and especially standard false color infrared images don't show much variation in rock colors. It is often difficult to discern rock contacts, let alone identify the rock type. Various computer based techniques have been developed that allow a greater variation in the observed colors in non-standard false-color renditions. Many workers have used OIF method such as Hunt and et al (1978), Abrams et al (1983), Duchscherer(1982), Srivastar and et al ( 1998) and Ranjbar and Honarman (2004). One of the statistical methods is optimum index factor (OIF) described by Chavez and et al, (1984). Landsat ETM+ data have been subjected to Crosta and OIF analysis. Igneous body, amphibole and clay minerals in images have been prepared according to OIF and crosta methods. The Crosta technique is based on PCA. Through the analysis of eigenvector values (Crosta and et al 1989), it allows identification of principal components that contain spectral information about specific minerals as well as contribution of each of the original bands to the components in relation to spectral response of the material interest. The PCA transformation (eigenvector and eigenvalues) is applied six ETM+ bands Viz. 1,2,3, 4,5 and 7 in table 3 for the study to enhance the spectral variability of content on the image. The purpose to use OIF and Crosta methods in the present study is: 1- to identify the suitable composite color to generate FCC that can enhance the igneous bodies and mineral content on the image, 2- to emphasize the suitable spectral range (bands) for classification on the image and 3- impact of environmental condition on the igneous body and its associated ecosystem. 2. Study area The study area lies between latitudes 32º 33' 00" N to 32 º 42' 44" N and longitudes 50 º 52' 30" E to 51º 42' 00" E (Fig 1). It lies in 65 km west of Esfahan city and south of Tiran city. The Zayandeh river is a perennial and flowing north to south direction. The sinuosity or meandering is high in the southern part of the study area. The area has variable topography and geomorphological features, with gentle to moderate slope. Environmentally, the area lies in arid and semi-arid region with seasonal rain fall and some times snow fall during winter period. The area is having scanty vegetation cover except along the river course. 2.1. Geological settings The pioneer workers are divided Iran into ten regions of different history, structures and sedimentation ( Berberian 1976, Colman-Sadd 1978, Darvishzadeh 1992, Ali and Pirasteh 2004, Pirasteh et al, 2004). Ali and Pirasteh 2004 stated that the Zagros Mountains comprises five litho-tectonic units from northeast to southwest, are Urumieh Dokhtar Arc (UDA), Sanandaj Sirjan Zone (SSZ), Imbricate Zone (IZ), Zagros Fold Belt (ZFB) and Molasse Cover Sequences (MCS). Geologically, the study area belongs to Sanandaj Sirjan Zone which consists of igneous-metamorphic rocks, volcanics and sedimentary from Precambrian to Recent in age (Fig. 1). Structurally, the area is complex with almost rugged topography, that is due to tectonic activities and erosion processes (Pirasteh and Ali, 2005). The area is uplifted with fault zones in Sanandaj Sirjan Zone. It comprises alternative metamorphic rocks of Precambrian age and undergone to younger sedimentary and Paleozoic rocks. Alternative metamorphic rocks consists of phylite rocks, schists and igneous bodies ( meta basaltic and granodiorite). Structurally, the trend of these outcrops follow the Zagros Mountains direction ( north west to south east). Meta-igneous rocks are consists of green schists with schistosity, light gray schists and ortho-amphibolite in dark color with coarse texture and non-schistosity. Granodioritic series are cut by ortho-amphibolite rocks in the area. They generally are comprise medium grained to coarse alkali feldspar and plagioclase with some quarts grained. Due to weathering feldspar minerals are converted to clay minerals.  Fig.1. Geological map of the study area
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