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The International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences. Vol. XXXVII. Part B5. Beijing 2008 
140 -I 
120 - I 
0 0,8 1,6 2,4 3,2 4 4,8 5,6 6,4 7,2 8 
Distance in m 
Figure 10. Distribution of the horizontal (dashed line) and 
vertical (solid line) distances of the graph edges. 
The final graph can be used in different ways to aid in the 
retrieval of replacement patches. For one it can be used to 
determine standard values for floor height and horizontal 
separation of façade elements. To do so we detect the peaks in 
the histogram of vertical and horizontal edge lengths. Figure 10 
shows such a plot. We can read a clear peak of about 3.3 m in 
horizontal distance. A peak of 5.1 m denotes the vertical 
separation of the floor levels. Both values were verified in the 
original point cloud. The graph is further used to reduce the 
template search for substituting defect areas. Instead of a global 
search, we only have to search at the vertices of the sub-graph, 
which has a vertex closest to the defect area. 
6. SUMMARY 
We have presented our strategy on adding façade detail to 
existing building models using ground-based LiDAR. A typical 
problem which occurs in street-level data acquisition is 
incomplete data. We have shown approaches on how to handle 
such cases. We have shown that the representation of façade 
detail in a LASERMAP is advantageous, since it allows the use 
of sophisticated image processing algorithms. Such algorithms 
can be used to substitute defective areas of the LASERMAP, 
caused by missing data. Our graph-based representation scheme 
reduces the number of comparisons needed to find suitable 
matches. 
ACKNOWLEDGEMENT 
We acknowledge the work of Angelos Tsakiroglou, Thanasis 
Georgantas and Christos Stamatopoulos of the Aristotle 
University of Thessaloniki, who have acquired the laser data set 
during their stay in Stuttgart in the ERASMUS exchange 
program. 
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