during the shooting of a photogram, the indications of mark-time are record 
ed on the margin of the photogram itself. To each point observed on the pho 
togram, the two observed values x*, y* and the time At* of the impression, 
which will be introduced in the equations of the space resection, are given 
together with the corresponding ground coordinated. 
The parameter /|t* in effect comes to be & geometrical parameter since 
it indicates the distance on the photogram between the mark tine signal 
which corresponds to the considered image and the mark-time signal which 
corresponds to the instant of reference t . In the hypothesis of uniform ro 
tation of the device which accomplishes the scanning, this parameter is pet 
fectly equivalent to angle of scanning computed with respect to a reference 
position. We can therefore take as an independent variable the scanning an 
gle where the angle Y= O corresponds to the instant of maximum velocity of 
the IMC and to the above mentioned t instant. 
In the absence of both the recording of the scanning angle Y^ and the 
mark-time signals, the angle f, which will be used in the formulas, has 
both significances of indipendent variable and of parameter locating the i 
mage on the photogram. On the other hand the angle X is. perfectly equiva 
lent to the angle B when the adjustment conditions are satisfied. 
3.2 — DESCRIPTION OF THE ORIENTATION PARAMETERS. EXTERNAL REFERENCE SYSTEMS. 
We decided to assume the scanning angle X as an independent variable. 
The scanning angle is assumed variable from - Y to + 4, with reference to 
the value y - O when the IMC reaches the maximum speed. : 
We assume as a reference time t , the time corresponding to the posi 
tion y. Cet the IMC. Let us consider the following rectangular ldthhanded 
systems (see figure 5), to which the control points are referred: 
The system XY 5 has the plane X,Y, tangent to the ellipsoid in a 
point T near the at ot point N of the photogram and the axis Y, tangent 
to the meridian. This system is called the "Eulerian system". T 
The system X Y Z is rotated with respect to the preceding, around the 
axis Z2 of an angle & 3; the Xn axis is oriented on the approximated aximuth 
of flight A,» so that 
NK U 
pm, nm 
The system XYZ is rotated by an angle & around Z , SO the angle & is 
the angle that the actual direction of the flight forms with the approxi 
mated direction. The system XYZ has therefore the plane XZ parallel to the 
direction of the velocity V of the aircraft during the shooting time. 
For the moment we can say that the position of the plane X IN? Or, 
which is the same thing, the geographical coordinates of T , are easily 
indicated by the data which oan be inferred from informations on the flight, 
since the tangent point of the plane X Y, can be far from the nadiral point 
: NN 
of the photogram even for a few miles. 
Analogous indications on the flight enable an evaluation of €, . The 
determination of the angle « is instead, entrusted to the computation of 
  
  
  
   
  
  
  
  
  
  
  
  
   
   
  
  
  
  
   
     
    
   
  
    
   
  
   
  
  
   
   
  
   
  
  
   
   
   
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