S re- 
aerial 
ator in 
ortion 
ess of 
ator, 
partly 
ration 
t each 
dvanta- 
ystem 
care- 
veying 
and 
the 
erent 
map- 
l. topo- 
  
  
-29- 
graphical mapping at smaller scales and by an organization 
persuing a modern, economic integrated mapping system, in- 
cluding large scale cadastral mapping and land and resource 
inventory. The orthophoto technique provides a very power- 
ful tool in this regard. It can be very simple and vet 
efficient and it can satisfy the' simultaneous needs of 
many users, Particularly in young, developing countries, 
where lack of basic maps and land inventory hampers ration- 
al planning and development, orthophoto mapping provides an 
economic answer. There is another, strong technical and 
economic argument for using the orthophoto mapping approach 
in young countries with large, less developed areas. Such 
areas are ideally suited for orthophoto presentation be- 
cause of the small number of artificial terrain details, 
that must be symbolized and because an orthophoto map pre- 
sents the natural content of the terrain in a more meaning- 
ful and complete form than a conventional map. Of course 
one of the conditions is that the orthophoto maps also 
contain contour lines, which should be part of the ortho- 
photo process used, in order to save time and expense. 
Moreover the example of several European countries 
shows that orthophoto maps at large scales over densely 
populated areas are also very useful products if proper- 
ly integrated into the general surveying and mapping 
scheme, The most extreme example is probably that of 
France, where an essential part of urban mapping is based 
on the use of the orthophoto technique. Similarly in 
Morocco, a very modern and comprehensive cadastral survey 
including complete land inventory information and compu- 
tarized data bank is based on orthophotos. 
However we must warn potential users, that as in 
any other technique there are several pitfalls of an oper- 
ational nature. Before embarking on any larger ortho- 
photo mapping project one must study and lay out the 
whole procedure down to its smallest details. We receiv- 
ed reports from various places, that whole projects 
almost broke down because no proper consideration was 
given to the flight pattern or to the purely’ cartographic 
end of the projects. It is a relatively new technique 
which requires not only specific means but also modifi- 
cation and adaptation of existing’ procedures to the new 
technique and its products. 
As to the purely technical aspects of procedures 
and instruments, several questions remain to be answered 
in .a convincing way. In spite of rapid progress in var- 
ious areas of the orthophoto technique, we are far from 
reaching a more stationary stage of development, which 
would permit one to assess the available results and to 
draw more final conclusions for future work. May we out- 
line some of these questions, encouraging discussions 
which may clarify some points and bring to the focus 
others not ripe yet to be fully answered.