ISPRS Commission III, Vol.34, Part 3A ,,Photogrammetric Computer Vision‘, Graz, 2002 
  
  
Figure 7-a. Border Points (Building 1) 
  
Figure 7-b. Border Points (Building 2) 
In order to convert the extracted roof border points 
into polygons we used the algorithm presented in Bimal and 
Kumar 1991 and Bimal and Kumar (1992). The basic idea is 
to go through all the border points and only retain those that 
that are significant, i.e. those that represent vertices. The 
elevations of the corner points are then computed from the 
refined DEM. Adjacent corner points are grouped to form 
the building wire-frames. Figure 8 shows the two resulting 
building wire-frames. 
  
A - 106 
  
Figure 8. Building Wire-Frames 
ACKNOWLEDGMENT 
The authors would like to thank the Army Research Office 
for sponsoring this work. We also would like to thank 
Professor Edward Mikhail for his help and advice. 
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