In: Wagner W., Szekely, B. (eds.): ISPRS TC VII Symposium - 100 Years ISPRS, Vienna, Austria, July 5-7, 2010, IAPRS, Vol. XXXVIII, Part 7B 
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Figure 1. Workflow 
This DSM will be corrected and refined in second part. In the 
normal way, a minimum of 100 points per square meter can be 
taken for the calculation of the DSM. That’s an enormous 
pointcloud in comparison to the point density of a laser model. 
This process will be stated with a precision of Vi pixel 
resolution which is specified in the program design. At the end 
it will be a really accurate digital surface model with a 
resolution of 12cm, which is the optimal resolution for 
successive tasks. Assuming like it will be flight in this scale. 
The resolution can differ, depending on scale. Up to 8cm 
resolution can be achieved. 
This process needs a relativly long calculating time. 2000 
images needs circa 10 days for matching. 
Figure 3. DSM in 3D View 
In first step, the AT will be optimzed. That means insufficient 
tie points will be eliminated and the data, especially the 
coordinates and angles of the exterior orientation, will conform 
to an optimal and readable datastructure for the software. 
Figure 2. Tiepoints 
In the next step the generation of the surface model will be 
started. 
An automatic matching process goes over all images in the 
project. First it will produce a rough connection and a DSM. 
After that the images will be straightened and rectified by the 
DSM. Nadirs will be produced from individual images, which 
are the base for the true-orthophoto production. 
In connection with this step the nadirs will be connected to 
orthophotos with a special fading technique to guarantee an 
areacovered mosaic. 
Black areas, which become by the different perspectives and 
overlapping, will be filled automatically with overlapping 
images at the end. 
Figure 4. Trueorthophoto