elements cannot 
ystematie para] 
The relative Orientation 
any required degree of 
"ientation of the Camera 
is not the Case: In the 
°curacy is reacheq, This 
ble to reduce the Number 
cost of photogrammetyie 
be considerably cheaper 
' is simpler, It therefore 
neil of Canada a method 
» the Ferranti electronie 
ow be described in some 
ding points on a stereo 
oint as the origin of à 
ral types of errors, 
À grid plate is placed 
me of exposure. The c- 
the nearest grid inter- 
d co-ordinates of thes 
S. The radial distortion 
correction for radial 
1 can be measured and 
rtion if the photographs 
umptions may be found 
tria IX 1952—53 Nr. 3. 
is eliminated by radial 
vertieal photographs. 
h curvature: 
e strip to a plane. For 
'h as one tenth of à 
btained, the map co- 
n is most conveniently 
n. An arbitrary initial 
€ mage 
aXes are 
The second type of condition concerns ground control points. 
Jusly exceed the capacity of a medium sized electronic computer 
lie first photograph of a strip and to compute the absolute orientati 
jq. Generally more points will be measured in eac 
\inecessary to establish the orientation. This will be 
Jutly to increase the accuracy. 
Jmarately. 
{imltaneously, using all available heights. 
Tri 
{al trangulation has been developed and applied to instrumental triangulation. This 
     
   
  
  
   
   
   
   
  
  
   
   
   
  
   
  
   
   
  
   
  
  
  
   
     
   
   
  
  
   
   
  
  
  
  
  
   
  
  
    
  
  
    
   
   
   
  
    
    
  
   
  
  
   
   
  
   
  
  
  
  
  
  
   
  
  
   
  
   
   
   
    
  
3 
im mày be chosen. In this system the absolute orientation of each photograph is 
gs 
ge Bp orientation is expressed by six elements, e.g. the three rectangular co- 
mates of its projection centre and three rotations that give the position of the photo- 
ym o with respect to the axes of the co-ordinate System. 
p six elements must be determined from the conditions which 
ssonding image points must fulfill There are two types 
onem ding image points in two photographs must i 
m corresponding image points in three photographs 
ga the rays through 
of conditions. Firstly rays 
ntersect. This implies that 
must intersect in one point. 
The given co-ordinates of a 
mind control point must satisfy the equations of the rays through the corresponding 
image points. 
Conditions of the first type express relations. between orientat 
sve photographs. Therefore, they determine primaril 
slows that the absolute orientation of e 
ndependently. 
To determine the absolute orientation either one of two me 
The theoretically best method is to compute the elements of absolute orientation of all 
doographs directly and simultaneously. If a redundant number of co-ordinate readings 
: available a rigorous method of adjustment such as the method of least squares can be 
gplied. This method involves the simultaneous solution of as many equations as there 
me elements of absolute orientation, ie. six times the number of photographs. Even in 
mil mapping projects this will amount to a few hundred equations or more. This may 
or else require an 
is method does not seem practical yet. 
lowed is to assume an arbitrary absolute orientation for 
on of each following 
e relative orientation 
ion elements of suc- 
y their relative orientation. It 
ach separate photograph can not be established 
thods may be followed. 
winate amount of computing time. Therefore th 
The alternative that must be fol 
ibtograph in succession. This absolute orientation is established by th 
tech photograph to the preceding one and scaling of the resulting model. The relative 
mentation may be established by making five pairs of corresponding rays intersect. The 
muting model is then scaled to the preceding one by making one height in the two models 
h overlap than the minimum that 
done partly as a check on errors, 
The relative orientation and the Scale are then adjusted 
The six elements of absolute orientation can also be computed simultaneously. Four 
Tuis of corresponding rays may then be made to intersect each other, two of which at 
tights determined in the preceding model. If more than four p 
airs of corresponding 
mage points have been measured an adjustment is carried out 
for all six elements 
This method has its disadvantages. Errors 
readings result in errors in the relative orientation and thus in 
kormation of the model. If two or more heights established in the preceding model are 
il, the relative orientation will also be affected by errors in this model. This will 
rease the accuracy. Also the triangulation result will depend on the model used to 
I the co-ordinate 
J'ut the triangulation. 
The method of independent relative orientation and scaling should therefore be used. 
After orientation of the photographs, co-ordinates of the measured points are computed 
nersecting rays from corresponding image points. Finally these strip co-ordinates are 
lansformed to the required terrestrial or map co-ordinate system. 
As yet no possibility of adjusting the strip-triangulation as a whole has been provided. 
I the Photogrammetric section of the National Research Council an airborne method of