Zheng Wang 
  
USGS digital ortho of quarter quad (DOQQO) and is displayed in figure 4. In the aerial photo, buildings can be recognized 
and they match the rectangular humps in the elevation image. 
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Figure 3. An elevation image of the test LIDAR data set. Figure 4. An aerial photo of the test area. 
To obtain the best results, both edges and contours were generated from the test LIDAR data set. A comparison 
between edges and contours clearly indicated that the contours were in much better shape than the edges in terms of 
sharp right corners and straight segments. Because of this, contours were used for the rest of the test, see figure 5. 
     
  
   
    
  
  
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Figure 5. Contours generated from the elevation image. Figure 6. Contour classification results. Contours marked 
with * were the final building contours. 
There were total forty-one qualified contours and they were classified into building contours and non-building 
contours. Table 1 gives a statistics of all forty-one contours in six categories after symmetry and circularity 
classification. Of the total forty-one contours, sixteen of them were classified as building contours, see figure 6. The rest 
  
International Archives of Photogrammetry and Remote Sensing. Vol. XXXIII, Part B3. Amsterdam 2000. 961