obvious that although this method may give a solution for the determination 
of the outer orientation of photographs, the direct method with the gyroscope 
will be more economical, 
Aerial Triangulation in Space, 
This method is applied by the Survey Department of the Ministry of 
Public Works at Delft and by K.L.M, Aerial Surveys. The former use Zeiss 
Stereoplanigraph and Wild A 5 and A 6. K.L.M. Aerial Surveys use both 
Wild instruments. 
The method of aerial triangulation in use in the Netherlands has not 
changed in principle. For details about the work carried out during these four 
years see page 25 of the present report of Commission III. 
For the relative orientation, the method with computation of the elements 
from the adjustment of the measured parallaxes is mainly used on those instru- 
ments where the reading of the elements of orientation is possible, viz. the 
Wild A 5. The advantages indicated by the author on page 22 of "Photo- 
grammetria" 1940 are now generally recognized. 
In particular the homogeneous results are of the utmost importance. 
The methods of computation of these precision triangulations are ap- 
proximately the same as those mentioned in the preceding National Report. 
It may be mentioned that aerial triangulation has also been applied to 
large-scale mapping in the Netherlands itself. In such cases parallel strips 
have been computed independently of each other and the results of adjoining 
strips have been compared. Ín those triangulations only x and y co-ordinates 
have been determined, because the necessary precision of determination of 
altitude in our flat country is so high that it can only be provided by levelling. 
The number of control points in these areas has been about two points on 
each fifth photograph. 
K.L.M. Aerial Surveys applied the aerial triangulation in a Wild A 5 to 
a large mapping work of 86,000 sq.km. A controlled mosaic had to be made of 
this area from photographs on a scale of 1:40,000. A rectangular framework 
of triangulation strips, the length of which was about 80 km., was triangulated 
in the A 5. In all corners of this framework an astronomical ground station 
was determined and a base length of between 4 and 8 km. was measured in 
order to provide the computation of the triangulation strips at both ends of the 
80 km. with exact control data for scale, azimuth and co-ordinates. Some of 
the strips in the flattest part of this area were measured in the radial triangula- 
tor. The filling strips within this framework were determined on the original 
scale of the photograph by the slotted template method. Each lay-out within 
a quadrangle was tied in between the four sides of each quadrangle. This 
method has given satisfactory results . 
    
  
  
  
  
  
  
   
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
    
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