Urban Orthoimage Analysis Generated from Ikonos Data

Due to the increasing demand and use of digital spatial information, the interest is being drawn to the generation of digital orthophotos, which is the most accurate and reliable source of spatial information. The subject of this project is the generation of orthoimages as well as the further processing of these orthoimages for the full exploitation of their spectral and spatial information. The imagery data used are a panchromatic image of one-meter spatial resolution and a multispectral image of four-meter spatial resolution, both acquired from Ikonos-2 satellite over the extended region of the city of Thessaloniki. The orthorectification of the images involved the establishment of the interior and exterior orientation through the Rational Function coefficients, a number of ground control points, and a Digital Terrain Model (DTM). Following the orthorectification, the panchromatic orthoimage was fused with the multispectral orthoimage to produce a pan-sharpened image with the method Principal Components Transformation. At this point the spectral quality and the spatial accuracy of the pan-sharpened image were assessed by certain criteria, as it is very significant for the sharpened image to maintain the spectral and the spatial information of the original data. In order to produce an image containing thematic information a supervised classification pan-sharpened was realised. Finally the products of the analysis of the pan-sharpened orthoimage were used for the visualization of the study area.