Photogrammetric approach to automated checking of DTMs

Geometrically accurate digital terrain models (DTMs) are essential for orthoimage production and many other applications. Collecting reference data or visual inspection are reliable but time consuming and therefore expensive methods for finding errors in DTMs. In this paper, a photogrammetric approach to automated checking and improving of DTMs is evaluated. Corresponding points in two overlapping orthoimages are found by means of area based matching. Provided the image orientation is correct, discovered displacements correspond to DTM errors. Improvements of the method regarding its reliability are discussed. Thresholds for image matching parameters are applied. A topographic database can be used for eliminating areas where mismatches might occur. Experimental results based on coloured aerial images at the scale of 1:25 000 and DTM derived from 5 m contour lines are reported.