10 
In 
I 
20 
21 
se horizontal axis of t 90", so that vertical views, up and down 
oriented can be obtained. 
With a few exceptions, stereometric cameras are rigidly mounted 
on a base with optical axes parallel to each other and perpendi- 
cular to the base, while in our case the projector axis is free 
to rotate relative to the base So that. convergent views. can. be 
carried. out and. the whole surface, onto. which. the reticle is pro 
jected, can be taken. 
3. The Acquisition Process 
A typical procedure followed in raster photogrammetry is shown 
in fig, 
  
  
    
SCENE 
ES x 
NN 
/ > x 
/ N X 
^ S 
/ p “ \ 
/ 1 f = \ 
L./ SN 
LE NEN 
did RETICLE 
Camera Projector 
| 
| 
| 
| 
| 
| 
| 
| 
  
  
s o asd IMAGE DIGITAL 
P 3 =A SCANNER | COMPUTER 
  
  
  
  
  
  
  
  
  
Fig.3: Acquisition procedure in raster photogrammetry 
Firstly a bright reticle is projected by the projector P onto 
the object to be analyzed, and a photogram of the scene is obta 
ined by using the camera C; the photogram is then digitized by 
a scanning device, so that a matrix is obtained whose elements 
are associated to the image pixels: this matrix (digital image)