The lack of adequate maps is one of the critical issues to be handled in developing countries. The main problem is the rapid development of urban areas, so that maps are out of date very fast. Consequently, nearly all these maps have to be revised and updated as soon as possible. Recently, due to the improvement in satellite technology, remote sensing data is applied for mapping and map updating at different scales. On April 17, 2007 the first Egyptian earth observation satellite Egypt Sat-1 was launched. The available images from Egypt Sat-1 satellite provides valuable source of remote sensing data in Egypt. This paper aims to evaluate the potential of Egypt Sat-1 images versus other satellite images for maps updating. Data used in this study are satellite images from Egypt Sat-1, SPOT 4, IKONOS and topographic map at scale 1:25,000. The methodology focuses on visual comparison of the images over the test area for specific features such as roads, railways, watercourses and boundaries of urban areas. After that an investigation is carried out for the potential of the information content in Egypt Sat-1 images, for updating 1:25,000 map. The results of these evaluations show that Egypt Sat-1 images, from the point of geometric accuracy, have the capability of 1:25,000 scale maps revision. Also, from the point of information content, it have the capability of revision of the main features such as building blocks, roads and vegetation cover. Revision of other objects in Egyptian 1:25,000 scale maps that are problematic in their identification and extraction from Egypt Sat-1 images can be completed using other mapping methods.
Digital orthoimages are proving to be suitable for a variety of mapping, Geographic Information Systems (GIS) and environmental monitoring tasks. The quality of the extracted data from orthoimages depends mainly on the accuracy of the input data and the used mathematical models. The availability of the Egypt Sat-1 satellite images provide valuable source of remote sensing data in Egypt. Egypt Sat-1 is the first Egyptian earth observation satellite which was successfully put in orbit on 2007. The main aim of this research is to represent a rigorous sensor model approach applied to Egypt Sat-1 image for orthoimage productions. For this study an image level 1A from Egypt Sat-1 satellite captured in 2009 and a topographic map, dated 1991, at scale 1:25,000 of the region of Assiut city and the surrounding are used. Orthoimage are generated in two parallel stages. The first stage is generation of Digital Elevation Model (DEM) and the second stage is developing mathematical model for an image-to-object relationship. The results of these two stages are integrated to generate the orthoimage proposed in two steps. The first step is the determination of image coordinates (in the original image plane) corresponding to the DEM grid points. The second step is assigning a gray value for these pixels. The results of this study demonstrate the possibility to orthorectify Egypt Sat-1 images to sub-pixel accuracy. Orthoimages that were generated from Egypt Sat-1 satellite images can contribute significantly to image map production and to GIS applications.
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