-3435 
Single orthophotos and stereo-orthophotos. 
  
A photographic picture of the earth's surface 
is not a map, even if the picture has the geometry of 
orthogonal projection. and is at.a specific,.uniform scale. 
A map-like product must have the desired information 
presented in a.clear,. unequivocal form. A great part of 
such information is visible.and directly recognizible 
in. single orthophotos, but another: is not and it must 
be found and suitably presented by using other means, 
usually conventional photogrammetric stereo-methods. 
In remote, unpopulated areas there are few details that 
require additional recognition and marking: accidental 
trails, outlines of marsh areas, courses of creeks 
covered by forest, and so.on..  . Obviously, the contour 
lines and the heights of characteristic terrain points 
must also be plotted. .1f this essential cartographic 
information is not carefully plotted and added, the value 
of the orthophoto product is. limited and. the products as 
such can easily fall in disrepute. 
The number of details that must be additionally 
plotted augments rapidly as the scale of the photomap 
grows. Furthermore special care must be taken to plot 
the relevant details in a position which coincides 
precisely with the photographic picture of the detail, 
since otherwise a serious confusion may result. One 
would also expect that in a large scale mapping work the 
topographical micro-features are included. All this work 
can not be done on single orthophotos since their 
readability is limited and they do not permit determination 
of elevations. 
To all these considerations is associated another 
one of extreme economic and technical importance: mapping 
needs outside of the conventional mapping field are 
enormous and rapidly growing. Not .only forestry and 
agriculture men, soil specialists, geologists, ecologists, 
geographers; but also business men, real estate people, 
administrators, engineers, planners and scores of others 
require their own maps, often of a very special nature, and 
perform all kind of measurements from aerial photographs 
and ‚do their own photointerpretation. Their disciplines 
and the associated requirements are highly specialized 
and therefore they must take care of their own requirements. 
Obviously, all these people contribute to the 
general land inventory system which is the goal towards 
which a modern country's mapping system must striye. 
It would seem, that an economic, very simple 
and at the same time technically superior tool for 
achieving this goal is the stereo-orthophoto technique 
[3,4]. As compared to the single orthophoto technique 
the stereo-orthophoto approach requires only minor 
instrumental adaptations. As has been demonstrated by 
  
  
SFMO so 
for the 
applyin 
method 
orthoph 
system, 
photogr 
The act 
classic. 
of the 
work or 
and abs: 
proceed 
choice, 
the Ste: 
stereo- 
line. dr. 
compile: 
includi: 
determi: 
these p: 
any fur 
nationa. 
up and i 
up poss: 
creatioi 
paper-l: 
be used 
course, 
as the 1 
this di: 
change 1 
product: 
Referent: 
[1] R 
[2] 0