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23 
The last company is offering the production of orthophotos 
rather than orthophoto equipment. It seems that only the 
system developed by Hobrough is used in civilian operations 
and consequently we should give a brief description of it 
here. 
a. Hobrough Ltd. - Gestalt Photo "Mapper: 
The system consists of an analytical plotter, auto- 
matic image “correlation module, ‘orthophoto printer and the 
console containing television type monitor, and other con- 
trol electronics, The operator carries out the preparatory 
steps (about Í hour) and assists the system in establish- 
ing proper relative and absolute orientation. Once orien- 
tations are completed the automatic correlation and the 
printing of the orthophoto can begin. The operator is 
watching the performance of the system - intervening only 
when necessary. 
  
Fig.16 Gestalt Photo Mapper 
A new system of automatic correlation has been 
introduced. A hexagonal patch of approximately 48 mm 2 
is used as an elementary area in correlation and in recti- 
fication. Since ‘this is quite a sizable area and ‘it way 
contain varied topography, it is suitably transformed 
before being printed in the rectification process, by 
using a special transformation matrix of up to 1000 ele- 
ments. The correlation, transformation and the print is 
carried out at a stationary position of diapositives 
and film to avoid any undesirable effect of motion.