Accuracy of automated aerotriangulation and DTM generation for low textured imagery

The Nasca-Project at ETH Zurich aims for a GIS-based analysis of the topography and the geoglyphs carved into the ground by the ancient Nasca (200 B.C. – 600 A.C.) in the desert region of Nasca/Palpa, about 500 km south-east of Lima, Peru. In 1998, three blocks of aerial images have been acquired during a photoflight. Two of these blocks (about 400 images, scale 1:7.500) were processed using an analytical plotter Wild S9 during 4 years of manual measurements, resulting in a high resolution DTM and 3Dvectors of the geoglyphs as well as topographic elements (rivers, streets, houses). Especially aerotriangulation and DTMmeasurements have been time-consuming processes. For the third block of Nasca imagery (about 400 images at a scale of approximately 1:9100) we aim for an automated processing (Aerotriangulation and DTM generation) to provide accurate data as a basis for terrain analysis (visibility studies, surface calculation etc.) in relation to the geoglyphs (Grun et al., 2003). Actual digital photogrammetric stations (DIPS) are examined for this case of low textured imagery due to the desertous characteristic of the landscape. Aerial triangulation and DTMs generated using Z/I's Image StationTM modules ISDM and ISAE, version 4.00, and Supresoft Inc. VirtuozoTM versions 3.1 and 3.3 are compared to reference data measured on an analytical plotter Wild S9. The main focus of this paper is on DTM generation, as for aerial triangulation no strictly comparable results, produced fully automatically, could have been achieved.