On the Extraction of Elevation Information from SPOT Imagery

This paper has analysed theoretically the problems at the key link sin the procedure for elevation exfraction using SPOT imagery by means of fully digital approach and the proposed methods which are necessary and flexible. The mathematieal model of time-sequantial exterior to the geometric characteristics of SPOT imagery. It is very important to chose the precise control points and the reasonable preliminary value of exterior orientation elements of central line and to calculate the equivalent focal length. The iterations for calculating the elements must be performed for the solutions of linear elements in one time and angular elements in other time, i. e. no solutions for both at the same time, just as the case in aerophotogrammetry. New approaches should be taken for data organization, avoiding the loss of precision during the interpolation of elevation after automatic correlatcins. According to satellite image characteristics,a strategy of multi-level matching are realized to improve the precision and the reliability, for which it is important to introduce the modified high accuracy least square matching algorithm. The results of the DEM generation using SPOT image windows in Marseille area show us that they can reach the elevation accuracy of 10m when the image quality can be assured.