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the difference in reflectance, elevation "texture", local variance 
of surface gradients, vertical structure (elevation), and shape of 
the object surfaces (Hug and Wehr, 1997). 
One possibility to find man-made objects is to search for regular 
structures. For this purpose, the elevation data is thresholded 
approximately 2m above the ground. The resulting binary 
segments are examined for compactness. In the contour of 
compact segments we search for basic right-angled structures. A 
model for composing basic right-angled structures is described 
in Stilla etal. (1998). 
6. CONCLUSIONS 
The proposed method can be applied to reconstruct complex 
roof shapes from maps and elevation data. The approach allows 
to recognize additional structures (e.g. superstructures), which 
can not derived from the building outlines shown in the map. 
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