International Archives of Photogrammetry & Remote Sensing, 32(2):136-139 TESTS ON AUTOMATIC DEM GENERATION IN A DIGITAL PHOTOGRAMMETRIC WORKSTATION

The massive introduction of modern digital photogrammetric workstations into routine mapping activities has obviously changed the tools and context of photogrammetric practice. Notably, DEM generation by image matching has become a standard softcopy photogrammetric technique. Énevitably, however, new questions have also arisen, often perplexing users, regarding geometric accuracy and success rates or expediency of user-defined matching strategies and suitable tuning of numerous parameters. In this contribution, tests on automatic DEM generation with the SoftPlotter system of Vision International are reported, employing several possibly “representative” DEM patches. The matching results were assessed against manual measurement (the precision of which was estimated as better than 0.1‰H). A basic finding was that, consistently, 20% of raw DEM nodes had elevations significantly different from those measured manually. In fact, 60% of nodes were correctly found directly by correlation (the remaining 20 % were interpolated elevations), which is an indication for the actual “intrinsic” success rate of matching encountered here.