Number of restituted models 
  
  
  
  
  
  
  
  
  
  
  
AT A8 | C8 SIV  |siiH 
group of flight |gr.of|gr.of| group of |gr.of 
Country Centre | flight flight, flight flight Toto! 
|1|N,nmimmi|:lisiuim 
Switzerland |ETH Zurich | 12 | 13 | 9 | | 34 
Germany TH Stuttgart | | 24 | 24 
IfAG Frankfrt. | 12 12 
ZA Oberkochen | | |L 2 
Austria |BA.f.E.u.V.W. 4 | 4 2 9 1 | 13 
Italy IEIRA | | 14 à} 2 | 18 
Netherlands ITC | 45 5 2| 4 10 2 | 8 
16 | 32 | 16 14 | 12 
64 3 {24 2% 4 | 141 
  
  
  
  
  
Restitution in group of flight I: 58 
  
» » » » » II: 46 
» » » » » II: 37 
Total 141 
According to the “Directives of restitution work” that machine scale should be chosen 
which the institute considers as the most suitable for each particular instrument. The 
Centres have so far applied the greatest possible scale of the model. The German Centres 
for instance have used in their Stereoplanigraph C8 for the restitution of standard angle 
photograps (Aviotar) scales of model between 2,2 and 2,5 X the scale of the photographs. 
The EIRA had used in the Stereocartograph IV machine scales varying between 2,2 and 
2,6 X the photo-scale. In order to restitute the wide-angle photographs (Aviogon f — 100 
mm) on the Stereocartograph IV and on the Stereosimplex III, the EIRA has applied 
a 3,5 X enlargement on the machines. 
The Centres were free in their choice of method of relative orientation. According to 
the reports established so far, the following methods have been applied: the optical- 
mechanical, the symmetric procedure according to von Gruber and the numerical method 
with six control points; in all cases each Centre has only employed one method. In general 
the residual parallaxes amounted to 0,01 in the plane of the negative; some Centres have 
reported small, purely local parallaxes in some isolated points, amounting to twice the 
value mentioned above. The Polytechnical College in Zurich has improved the relative 
orientation according to the known heights of the control points, whereas the other Cen- 
tres have not used the residual errors in the heights of the points obtained after the 
absolute orientation to improve the relative orientation. 
The time necessary for the relative and absolute orientation varies between 2 and 6 
hours. It depends amongst other factors on the particularities of the method of the 
absolute orientation and on the difficulties arising during this orientation of certain 
models. For more details please see the Special Reports of the Centres. 
The opinions of the Centres regarding the identification of the different forms of 
signals may be given as follows: 
Signals of class d) (whitewashed tops of boundary stones of 12 X 12 cm) are only 
recommended for photo-scales of up to 1:6000—1 : 7000; they are, however, in general 
still visible in smaller scales, for instance 1 : 12500, but their identification then becomes 
difficult or uncertain.