DTM generation using ground control points extracted from SAR image

Ground control points(GCPs) can be extracted from SAR data given precise orbit for DTM generation using optic images. In this study, we extract GCPs from ERS SAR data and SRTM DEM. Although it is very difficult to identify GCPs in ERS SAR image, the geometry of optic image is able to be corrected and more precise DTM can be constructed from stereo optic images. Twenty GCPs were obtained from the ERS SAR data with precise Delft orbit information. After the correction was applied, the mean values of planimetric distance errors of the GCPs were 3.7m, 12.1 and -0.8m with standard deviations of 19.9m, 18.1, and 7.8m in geocentric X, Y, and Z coordinates, respectively. The geometries of SPOT stereo pair were corrected by 13 GCPs, and r.m.s. errors were 4.5m, 7.5m and 8.6m in northing, easting and height direction, respectively. A DTM, through a method of area based matching with pyramid images, was generated by SPOT stereo images. Comparison between points of the obtained DTM and points estimated from a national 1:5,000 digital map was performed and the mean values of distance errors in northing, easting and height direction were respectively -7.6m, 9.6m and -3.1m with standard deviations of 9.1m, 12.0m and 9.1m. These results met the accuracy of DTED level 2.