Orientation of SPOT stereopairs by means of matching a relative DEM and the SRTM DEM (original) (raw)

This paper presents a methodology to obtain an accurate exterior orientation of SPOT stereopairs using as ground control only the SRTM 3 arc second DEM. The method is based on the extraction of a relative DEM from the stereopair, after a relative orientation. This DEM is then matched to the SRTM DEM by correlation. Small portions of the extracted DEM are adjusted, leading to corrections of the geolocation of the stereopair. A set of ground control points are simulated in order to enter a standard procedure for image orientation. The method was tested with two stereopairs, from Portugal and France. The accuracy of the exterior orientation obtained is similar to what is achieved with GCPs measured in maps of scale 1:25,000. The method can be largely automated and may be useful to make a better use of many thousands of stereopairs available in the SPOT archive, although only for areas with some relief. Another application is the extraction of data to fill SRTM void pixels, especially in mountains.