Eberhard Steinle 
  
the dark elements the DEMs. It is obvious that in last pulse DEM buildings are systematically smaller than the 
corresponding CAD objects, while on the other hand nearly no vegetation is acquired. 
  
Figure 6: Superimposition of CAD models and first pulse and last pulse DEM respectively; the brighter silhouettes 
represent the CAD-models, the dark elements the DEMs 
3 EFFECTS ON BUILDING RECONSTRUCTION 
3.1 Recognition and reconstruction process of buildings 
For understanding the effects on building reconstruction a short description of the approach developed at IPF has to be 
given. This method is based on laser scanning elevation data (DEM) and spectral information (CIR aerial images). 
During preprocessing a stepwise elimination of objects which are not buildings is carried out. After geometrical 
rectification, vegetation areas are extracted in the CIR images by means of vegetation index (NDVI). A superimposition 
of these with the laser DEM enables the elimination of 3D vegetation objects like trees or bushes (Figure 7, right side). 
All remaining 3D objects are separated and for further processing regarded as building hypotheses. For each object, 
plane parts (e.g. roof planes) are extracted by a specific region growing algorithm. An intersection of these planes leads 
to contour lines and corner points of the object (e.g. as wireframe model). A detailed description of this method is given 
in (Vogtle & Steinle, 2000). 
  
862 International Archives of Photogrammetry and Remote Sensing. Vol. XXXIII, Part B3. Amsterdam 2000.