1at 
ATS 
Do 
aphical 
Oh 
Oh 
uipm. ) 
only as 
l maps 
he 
spect 
time 
refore 
hods 
the 
he 
een 
tical 
the 
he 
—13- 
The proposed system (including the refinements) may possibly not be much faster 
than the conventional system. It must be emphasised, however, that the intention 
was not in the first place to create a faster or a more economic mapping system, 
but to design a procedure whereby the need for a complete map coverage is 
fulfilled at an early stage of the mapping process and which adheres better to 
ihe special circumstances, prevailing in development countries. 
General discussion of the proposed mapping system 
  
À number of special features of the proposed system which, in the author's 
o 
Opinion, seem to adhere better to special requirements and environmental factors 
of developing countries are discussed in more detail: 
1) In the total mapping process, two main phases with distinctively different 
properties can be distinguished: 
The first phase, involving the production of orthophotos and drop line 
charts from extreme small scale photography, results in a provisional map 
coverage of the total area at a very early stage of the total mapping 
programme, thereby satisfying all kinds of urgent requirements for develop- 
mente 
Although the cost of this phase represents only a small part of the total 
project cost and requires only a small number of man hours, it involves the 
use of relatively sophisticated methods and equipment. 
special approach in the overall planninge 
This will require a I 
The second phase, consisting of consecutive "perfections" of the first 
provisional product and resulting finally in & multi-colour topographic 
line-map, constitutes the bulk of the total work in terms of man hours. 
It, however, involves only unsophisticated methods and requires no photo- 
grammetric plotters or other expensive equipment, 
2) Instead of using one photographio coverage at a compromisory scale, aerial 
photography at two different scales is used whereby the smaller scale is 
designed to satisfy the metric specifications only (accuracy in planimetry 
and height), and the larger one to meet the requirements for adequate photo 
interpretationo 
In this way, the procedure becomes cheaper, because all photogrammetric 
sub-processes, whose costs depend on the number of photographs involved and 
therefore on the photoscale (e.g. aerial triangulation, orthophoto produc- 
tion) are carried out using the smaller scale photography. 
" can be flown at such a 
On the other hand, the "interpretation coverage 
large scale so as to obtain a optimum balance between the cost of aerial 
photography, the quality of the final result and the cost of the necessary 
field completion,