Claus Brenner 
  
(a) 
(b) 
(c) 
  
  
  
  
  
  
(1) (2) (3) (4) 
Figure 11: Results for several buildings (a—d). (1) Skeleton based on ground plan. (2) Segmented regions. (3) Selected 
regions from the rule-based approach overlaid with intersection segments. (4) Final reconstructed roof. 
process is divided into three stages. In the first stage, a segmentation is used in order to obtain roof surface primitives. 
In a second step, a rule-based approach decides which segments can be explained by the building model we have chosen. 
Finally, in the third stage, the roof is built from the primitives that have been accepted, closing any gaps that have been 
caused by the deletion of unexplainable regions. The algorithm discussed here is only one part of our ATOP (automated 
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
Interpretation Select 
DSM Module 1 , 
d — i 
Groundplan |——*|Segmentation ° Topology An Result 
p 9 e —»| Generation |——94—* ™ 
E | set = 
1! 1 >| Interpretation > Hr 
Medos: Module n 
  
  
  
Figure 12: Framework of the ATOP modelling approach. 
topology generation for polyhedral objects) modelling approach. In our opinion, past research has too much concentrated 
on designing single, monolithic systems which are able to reconstruct a wide range of buildings. This may be due to the 
limited variety of building types in the test datasets which have been widely distributed. In contrast, our goal in ATOP 
is to provide several “tailored” interpretation modules each of which accepts certain segmentation primitives according 
to specific rules (Fig. 12). The algorithm presented in this paper as “second stage” is one such interpretation module. 
Another may be designed exclusively to recover the structure of flat roofs. We can even think of an interpretation module 
which works according to a rectangle subdivision (Brenner, 1999) or a straight skeleton algorithm. Based on the deviation 
of the reconstructed surface from the DSM (or image data), the final step of the system consists in selecting the best 
solution. 
  
International Archives of Photogrammetry and Remote Sensing. Vol. XXXIII, Part B3. Amsterdam 2000. 91