Document Type : Research Paper

Author

• Saeed Sadeghian

Ph.D. Student of Photogrammetry, University of Tehran

Abstract

Data related to features of the earth’s surface have applications in many activities concerning planning, control and management of ground resources and man-made features. Data of this type are usually displayed on maps that show information on a reference plane. It is highly necessary that data be ground-based, because it makes matching and combination of different sets of data possible.
A satellite image or photo provides an excellent outlook of a broad area of earth, thus presenting a comprehensive view of important physical and cultural features. Such images can be the best available data about many inaccessible areas of earth for which there are yet no reliable maps. However, a crude satellite image has defects such as distortion due to change of altitude, position of sensors, differences of altitude, earth’s spherical shape and lack of display of all features important for users. Consequently, in order to make best use of satellite images, data must be processed to remove distortions, extract three-dimensional information and practice interpretation of images for determination of type and use of features. Information obtained from other sources make completion of maps possible. Furthermore, by creating a network for displaying information system of national coordinates, the necessary consistency between the produced maps and other digital maps and data such as those available in a geographic information system can be realized.