A Comparative Study on the Production of Satellite Orthoimagery for Geological Remote Sensing

In many geological applications of Earth Obervation (EO) data over mountainous regions little attention is given to orthorectification, mainly because of the large spatial errors that can be tolerated (often many times the original pixel size). In most times a least‐squares polynomial fit serves the purpose of image georeferencing. In this paper two procedures for optical EO data orthorectification are presented which differ on the extraction of the Digital Elevation Model (DEM). The procedures run on a commercial software package (EASI PACE v6.2.2 for Windows NT). The high‐resolution DEM can be either supplied by automated stereomatching of SPOT PAN 1A imagery or by in‐house digitising of l :50,000 contour maps. A SPOT DEM has been produced for a mountainous region in central Evia (Greece) and its comparison with the reference DEM yielded satisfactory results. That ensures the fast production of accurate orthoimages for geological mapping.