International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences, Vol XXXV, Part B5. Istanbul 2004 
  
points are of about 2 m! 
The registration of a long chain of scans can be see as the 
problem of the photogrammetric triangulation of a single 
strip. In these cases a series of control points, referred to an 
external reference system, must be provided. 
In order to define the minimum control point needed, some 
tests have been performed. At least one control point each 
three adjacent scans must be provided avoiding the alignment 
of them. Using a minimum overlap of 30% the final precision 
is compatible with the range accuracy of the used laser 
scanner. 
  
   
  
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Figure 8. Example of a laser alignment with small 
overlapping area - before the triangulation process (left) and 
after a triangulation operation (right). 
In order to reach the expecting precision, a rigorous 
adjustment can be performed. Each scan has been considered 
as a separate object and tie points and control points have 
been considered with different weights (w = 1 the tie points 
and w = 2 the control points). 
All the fitting parameters can be calculated and all the points 
of the scans can be transformed in the external reference 
system. 
The good results can be justified if one consider that in 
independent model photogrammetric triangulation the 
adjacent model overlap is of about 10% but the projection 
centre of the common photo with the usual tie-points on the 
models give a good configuration of the points to be used for 
the registration. In the case of the laser scans only tie-points 
can be used but the minimum overlap of 30% recovers the 
lack of control information.[Bornaz, 2003]. 
3.6 | Management of the digital images and creation of 
the Solid Image 
À digital photo image can be considered, with a good 
approximation, as a central perspective of the acquired 
object. If the internal and external orientation parameters of 
the camera are known, it is possible to establish the direction 
in the space of each point of the object which is represented 
by a pixel in the image. 
Using a dense digital surface model (DDSM) of the acquired 
object each pixel (and therefore each direction in the space) 
can be associated to the distance value between the centre of 
perspective and the point of the object that is represented by 
the pixel itself. In this way each pixel can be made to the 3D 
position of the corresponding point of the object in an 
appropriate reference system 
The integration of the DDSM geometric data with the image 
radiometric data allows the new concept of the solid image to 
be obtained [Bornaz, 2003]. 
Solid images can be used in architectural, archaeological and 
land surveying applications to determine, in real time, the 
position of any point in a 3D reference system, using a 
common PC or to carry out correct. three-dimensional 
measurements (lines, areas, volumes, angles, ...), by just 
selecting some points on the image. 
Oriented images and related DDSM allow one to 
automatically produce artificial stereoscopic pairs and 3D 
colour model. 
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Figure 9. The LSR 2004 software — Solid Image of the 
Tetrarchi statue in Venice. 
Using LSR 2004 software it is possible to import and manage 
digital images, calculate their calibration and orientation 
parameters and create the Solid Image and their related 
products [Bornaz, 2003] 
4 EXAMPLES OF TERRESTRIAL LASER DATA TREATMENTS 
All the described procedure has been performed on different 
objects acquired with laser scanner devices. Some examples 
are shown: 
  
  
  
  
  
  
Figure 10. Trappistes (CH) — A rocks slope during pre- 
treatment phases. 
The following figures show the use of the L.S.R. 2004 
software during the management of all of the pre-treatment 
phases. 
  
    
  
    
    
   
    
   
     
       
    
     
     
   
  
    
   
    
   
   
   
  
  
    
   
  
  
  
    
   
   
  
  
  
  
  
  
     
   
      
  
  
    
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