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International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences, Vol XXXV, Part B5. Istanbul 2004 
  
  
  
  
  
  
Figure 7. The building facade 
  
  
  
  
  
  
  
  
  
  
  
  
  
  
Figure 8. Targets acquired in both scans 
Nine targets have been positioned on the facade (Figure 7). 
Two scans have been carried out. Four targets are present in 
both scans (Figure 8). 
The coordinates of the targets have been also measured through 
a topographic survey, to obtain the orientation, using a Leica 
TC 2002 total station. 
For the test, the Laser Scanner Cyrax 2500 has been used. Its 
main characteristics are: 
- single-point range accuracy 
- angular accuracy 
- beam spot size 6mm at 50m range 
- capture speed up to 1,000 points/sec 
- minimum point-to-point spacing |. 0.25mm at 50m 
- horizontal and vertical FOV 40? 
+/- 4mm 
+/- 60 micro-radians 
The targets has been scanned, using the minimum point to point 
spacing. 
5. FIRST RESULTS 
To evaluate the effectiveness of the proposed method, the 
distances among the common targets, obtained using thc 
different scans, have been compared. In the Tables 9 and 10 the 
distances among the common targets, obtained with the first 
and the second scan are reported. 
Table 11 shows the differences between the distances obtained 
from scans 1 and 2. 
We can observe that the average difference is about 1 mm, 
whilest the maximum difference is about 2 mm, less than the 
scanner accuracy. 
A second comparison has been performed: the distances among 
the 9 targets obtained using the scans data, have been compared