The International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences. Vol. XXXVII. Part B4. Beijing 2008 
Figure 16. Boundaries of roof 6, 7, and 8 onto the orthophoto 
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connected through the vertical planes shared by them. The 
refined lines sharing the same vertical plane are recognized and 
utilized to derive an estimate of the vertical plane. Then, the 
lines are redefined based on the computed vertical plane. 
Finally, these lines are connected to construct a closed wire 
frame. Figure 12 displays the produced roof top wire frame 
through all the previous procedures. In addition, a 3D wire 
frame is generated using the average elevation of the ground 
around the buildings in Figure 13. 
Figure 14. Projected rooftop boundaries onto the orthophoto 
Figure 13. Constructed 3D wire frame 
3. DISCUSSIONS 
The performance of the proposed methodology has been 
visually evaluated by the projected DBM onto the orthophoto. 
Figure 14 shows the main buildings in the entire study area and 
their refined rooftop boundaries (shown as red lines) projected 
on the orthophoto. Most of roofs in the figure are reconstructed 
correctly in terms of completeness of the structural shape. 
Detailed investigation of each roof is conducted by taking a 
closer look at Figure 15 and 16. Roof 1, 2, 4, 5, 6, and 7, which 
include orthogonal lines are reconstructed correctly in most 
parts. All the boundaries of roof 3, which are relevant to three 
different sloping planes, are well detected. Moreover, the non- 
orthogonal lines on roof 8 are reconstructed quite well. 
However, some of small details, which are enclosed by white 
solid circles, are lost on roof 2, 4, 5, and 6 due to the occlusion 
in the LiDAR data, inaccurate initial boundaries, and small 
structures on the roof. 
Figure 15. Boundaries of roof 1, 2, 3, 4, and 5 on orthophoto. 
Figure 12. Refined rooftop boundaries.