Introduction: 
The orthophoto technique is the youngest one in the 
arsenal of photogrammetric and mapping tools. It has ex- 
panded however to formidable dimensions and a medium size 
book would be necessary to cover it adequately. However 
since this invited paper is meant as a basis for a general 
discussion and should provide only essential information 
on existing methods and instruments, an extensive treatise 
would not fulfil the purpose. Therefore a very condensed 
presentation is being attempted with stress on features 
that in the author's opinion are of primary importance. 
This approach seems to be justified also by the fact that 
in photogrammetric literature one can easily find more 
detailed information on the subject. Among others, the 
220 page issue of March 1968 of "The Canadian Surveyor" is 
a kind of compendium on orthophoto technique. 
For the sake of clarity a classification of instru- 
ments and methods is desirable. This could be done in a 
variety of ways. For instance one could follow the chron- 
ological development and there are very strong arguments 
for this approach. One could also base the classification 
on the mode of operation (manual or automatic), type of 
image transfer, rectification technique, accuracy and other 
characteristic of final products, intended application, 
etc. The author decided that classification according to 
the mode of operation and image transfer mav be the most 
suitable for the purpose of this review, It follows to a 
certain degree the chronological development but at the 
same time introduces the intended application as an import- 
ant and often deciding factor into the discussion. 
As usually, before an International Photogramme- 
tric Congress, the manufacturers of photogrammetric equip- 
ment make a concentrated effort to surprise the photogram- 
metric community (and the competitors) with new or modi- 
fied solutions, They are therefore rather hesitant to 
disclose detailed and up to date information on their new 
developments which may not be even completed when the re- 
view is prepared. The reader should appreciate this sit- 
uation and must expect, that at the time this text will 
reach him, the actual equipment may contain features not 
described in the text. 
On the whole however, the author experienced very 
friendly and prompt cooperation from the instruments manu- 
facturing industries, which he wishes to acknowledge. 
In this paper, the Russian orthophoto-equipment 
will not be discussed because of the difficulities in 
establishing direct contact and obtaining reliable information. 
  
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