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«334 
Use of the automatic image correlation devices, 
  
As has been proven using a suitable technique, 
a very fast and a fully automatic process of production 
of orthophotos is possible (at least for an average terrain). 
Since time is often a more important consideration than 
the cost, an automatic image correlation technique is 
an: important factor, particularly if the production cost 
is also favourable. 
The limitation of an automatic process however 
is the inability. of recognizing the terrain coverage 
(trees, vegetation, buildings) from the actual ground 
surface. As the result, the elevations (profiles, contour 
lines) derived by an automat are wrong with the exception 
when the terrain is bare. This in turn has an effect 
on the planimetric accuracy, when the: automatically 
produced profiles or elevations are used for the production 
of: the orthophotos. This latter effect is felt more 
strongly in the orthophotos at larger scales, to the 
extent that it precludes the use of the automatic methods. 
Also, there is an inherant difficulty in automatic 
processing of photographs of a rugged terrain. 
In view, of the foregoing, there are opinions, 
that the superior solution from the operational and the 
general economic point of view is the combination of 
manually produced profiles or contours with a suitable 
orthophoto printing process. In this approach, the elevation 
information which. is precise, could be used for any other 
mapping purposes, and could be stored as a permanent 
information in a land inventory system. 
In my own opinion there is an ample space for both 
approaches as there is no single solution which could 
satisfy all requirements and specific conditions. 
Scale of original orthophotos. 
  
  
Eventually the orthophoto product must be at 
some precise scale. This is one of the basic requirements 
and characteristics of an orthophoto product. Obviously 
there is a distinct advantage if the instrument used 
permits a precise choice of the most suitable scale, 
which usually is the final scale of the orthophoto 
map. This seems to be recognized by the majority of the 
manufacturers of orthophoto equipment, who provide quite 
a wide range of ratios between the scale of photographs 
and the scale of original orthophotos.