ASSESSMENT OF THE PLANIMETRIC ACCURACY FOR SPOT SATELLITE IMAGERY

Abstract

Topographic maps are of fundamental importance for economic development and resource management in any country. So, it is necessary to increase the rate of mapping and map updates. At the moment, it seems that one way of doing this is to utilize the capabilities of remote sensing technology with its repeated coverage of_. the earth's surface.

The motivation for mappmg from space images is given by the fact that past conventional mapping techniques have not been able to provide adequate mapping coverage at the required scale or even update existed topographic maps at a proper rate. Moreover, the new generation of high resolution remote sensing and the modem techniques in image processing gave a new trend ofproducing large-scale maps from space imagery.

Raw digital images contain geometric distortions that make them unsatisfactory for use as maps. These geometric distortions have been classified into systematic and non-systematic distortions. In order to make remote sensing data useful for resource and environmental managers, it must be geometrically corrected. The goal of geometric correction is to correct raw images from distortions in order to produce an image, with the geometric integrity of a map.

The purpose of this research is to determine the planimetric accuracy of SPOT images, obtained using the low-order polynomials as a transformation model. Toe purpose is extended to investigate the influence of the number, the distribution, and the accuracy of ground control points on the planimetric accuracy of SPOT images. Moreover, the effect of the measuring accuracy of image coordinates of control points on the obtained accuracy was also studied.

This study involved the implementation of SPOT satellite imagery in Egypt. Two subscenes cut out from two SPOT (panchromatic and multispectral) images acquired on August 1 I, 1995 with image processing level IA were used.