Generation of DEM by the Method of Correcting the Elevations of Ground Control Points Using System Corrected SPOT Data

Abstract

A method of generating Digital Elevation Model (DEM) automatically from system corrected SPOT data using at least 3 Ground Control Points (GCPs) of different elevations was developed. An area surrounding the Central Alps of Japan was selected as the test site and a pair of images (stereo registered images) of the test site which are registered to be available for computing the elevation, was produced using only 3 GCPs of different elevations. A method of correcting the elevations of the GCPs in producing the stereo registered images was proposed. The corresponding points between the stereo registered images were searched using an automatic image matching technique and three dimensional positions of the corresponding points were directly computed in the Earth Center Rotation (ECR) coordinate. The computing accuracy, examined by 36 check points, was 39.9 m, 71.7 m and 30.3 m (rms error) respectively in the direction of X, Y of an UTM and the elevation. The error of the elevation was 15.3 m and the errors of X, Y of the UTM were not changed when 3 GCPs of a same elevation were used. Many points of abnormal elevations whose elevations are abnormally different from their surroundings could be found in the first computed output, but most of them could be eliminated by post processings. A DEM generated by this method agreed generally very well with a DEM produced from 1 : 25000 scale geographical maps.