- Dio 
3. Orthophoto systems with automatic image correla- 
tors and an electronic image transfer. 
  
  
We can mention only briefly these very complex 
and powerful systems. They are designed for the pro- 
duction of orthophotos at small scales. Some of these 
systems were developed in view of military requirements. 
The introduction of an automatic image correlator 
permits much faster scanning of stereopairs than is possi- 
ble in manual operation. In consequence, much smaller 
area elements can be used in the production of orthophotos, 
whereby the accuracy of the final product can be made 
large independent of the topography of the terrain.  An- 
other approach is to üse a complex transformation of each 
single, larger area element involved in the rectification 
process, taking into account the topography within each 
area element. This is possible due to the extreme speed 
with which the necessary data can be gathered and process- 
ed using automatic image correlation and the analytical 
plotter principles. This leads to very fast systems, 
exemplified by the orthophoto equipment developed recently 
by Hobrough Ltd. in Canada. 
  
Unfortunately, at least at present, the automatic 
instruments cannot distinguish between the surface of ) 
the ground and buildings or trees and consequently these 
highly automatized and fast procedures must be restricted 
to the production of relatively small scale orthophotos 
where errors in the height of the projection plane 
caused by vegetation or buildings can be neglected. Also, 
the automatic image correlation proves difficult in very 
rugged terrain. 
Another restriction of these systems is the diffi- 
culty encountered in reproducing colour photographs. As 
is known, important areas of application of orthophotos 
are earth and environmental disciplines for which colour 
presentation of the terrain is of great interest and 
importance. 
In spite of these restrictions and its hígh cost, 
the automatic orthophoto equipment with electronic image 
transfer already constitutes an important component of 
modern mapping technology and its importance will grow 
with further scientific and technological advances. Its 
unique flexibility and its speed in handling suitable 
transformations of area elements to improve the geometri- 
cal quality of orthophotos and to speed up their product- 
ion are two strong points in its favour. | 
In this category belongs equipment built by OMI 
in Italy together with Bendix Co. in U.S.A., by Bunker- 
Ramo Co. which produced the UNAMACE (Universal Automatic 
Map Compilation Equipment), and by Hobrough Ltd. in Canada. 
  
The las 
rather 
system 
and con 
here. 
matic f 
console 
trol el 
steps ( 
ing pre 
tations 
printir 
watchir 
when ne 
  
introdi 
is usec 
ficatic 
contair 
before 
using e 
ments. 
carriec 
and fil