International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences, Vol XXXV, Part B5. Istanbul 2004 
  
  
       
       
     
       
      
       
Correspondence between digital image 
and photographic image 
  
Determination of the inner parameters 
of the camera 
  
/ m TEES 
Relation between digital and fiducial 
coordinate systems 
  
( - . 
Projection of the DTEM to the fiducial 
coordinate system 
  
Transformation of the DTEM 
coordinates from the fiducial system to 
the digital system 
  
  
Correspondence betwen the DTEM 
resolution and the digital image 
resolution. 
       
      
       
      
        
  
  
Determination of the gray levels for each 
band of the orthophoto. 
  
Computing the horizontal paralaxes of 
the DTEM. 
  
Transformation of the DTEM subcells 
to the stereomate. 
  
Determination of the grav tone for each 
stereomate band. 
Figure |. Procedure scheme 
2.1 Correspondence between the digital image and 
photographic image 
The relationship between the digital image coordinates and the 
analogical image is determined from the calibration results of the 
scanner used. Digital image coordinates are referenced to 
coordinates system of the scanner, corresponding with its columns 
and rows. The analogical image coordinates are referenced to an 
orthogonal axes system (x,y). The relationship between the digital 
image and photographic image is established through an affine 
transformation, thus obtaining the coordinates of the control 
points in the system of photography. 
2.2 Determination of the internal parameters of photographic 
camera 
From the terrain coordinates of the control points and its 
coordinates in the photographic image, the internal parameters of 
camera using the procedure of Linear Direct Transformation 
(DLT) (Gamal, 2002) are determined. Having the parameters f,, 
fs XosŸo, the coordinates of the control points of the photographic 
image in the fiducial system are computed. 
2.3 Transformation of the DTEM from the terrain system to 
the fiducial system 
The DTEM nodes are projected to the analogical image system by 
means of the colinearity equations. This is performed in two 
phases: First, the parameters of transformation between the terrain 
system and the fiducial system are determined using the control 
points. Second, with these parameters the coordinates of the nodes 
DTEM are transformed to the fiducial system. 
The representation of a ground point on the negative plane of the 
image is done by means of the projective line that starts from the 
point, passing through the projection centre O up to its 
intersection with this negative plane, as shown in the Figure 2.. 
The length of the line L is determined from the altimetric 
information provided by the DTEM. The projective line is 
represented by the colinearity equations (Eq 1). 
X X- Xo 
y |ekrAfslya v, (1) 
a 7-2, 
where x , y, -c = image point coordinates referenced in the 
fiducial system. 
c = principal distance of the camera 
X, Y,Z = point coordinates in the terrain system 
X0» Yos20= coordinates of projection centre O referenced 
in the terrain system 
k = scale factor between the vector I and the vector L 
for each point 
A= rotation matrix defined by the angles ©, ¢ and ka 
round the X, Y and Z, respectively 
  
  
Figure 2. Reconstruction of projective ray 
     
   
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Figure 3,