are to be plotted, a greater investment will be advisable. On the »Stereotop II" the 
aerial photographs are positioned on metal boards and connected to the stereoscope 
by a parallel guide. The r.h. picture holder may be displaced micrometrically 
  
  
Fig. 6b. New mirror stereoscope equipment “Stereotop III”. The warping relief displacements 
resulting from tip and tilt of the model can be eliminated automatically during the 
plotting process. 
with reference to the Lh. picture holder. The latter may be connected to a drawing 
pencil or the tracing pencil of a pantograph. 
When transforming the measured parallactic values into elevations, it must 
be assumed that the normal condition of stereophotogrammetry is fulfilled. It 
must therefore be assumed that exact verticals are available taken from the same 
flight altitude. If the pictures should contain minor tilt errors and variations of the 
flight altitude, the optical relief model is warped and tilted. It is therefore desirable 
to compensate a mean value of relief inclinations and displacements by additional 
expedients. Formerly, this was usually done by a complicated modification of the 
plotting process. In the ,,Stereotop III” this job is done entirely and automatically 
by the instrument. The basic idea of the instrument was evolved by Dr. Ing. 
Szczepanski. Since the Stereotop III embodies all attachments of Model I and II, 
a reference to Fig. 6b and 7 in the description of the basic principles of Model III 
will be sufficient. 
The mirror stereoscope has been intentionally designed with a base of 390 mm 
so as to facilitate the plotting of large pictures. We have adopted a concept which 
has given good results in the design of modern microscopes, namely that prolonged 
observation through vertically arranged eyepieces is inconvenient and therefore 
unsatisfactory. Hence, provision has been made for oblique oculars. A spindle 
permits the adjustment of the interpupillary distance. The telescopic lenses describ- 
  
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