Fig. 9. Interpretation of aerial photograph of area shown in Fig. 1, with various locations and 
definite route. 
tion rate of 10,000 cubic metres per km. was arrived at. After the work had been 
completed it was found that the quantity of earth actually moved differed by 
less than 5°/o from the quantity originally budgeted for. 
The above examples will show that contour maps prepared from aerial photo- 
graphs can be very useful in the case of areas for which no suitable maps exist. 
Conclusion. 
In the foregoing pages we have considered the usefulness of the system only 
from the point of view of road projects. It is obvious that such maps will be just 
as useful when applied to other civil engineering works. Accordingly, it is not 
economical to attempt to make projects in undeveloped areas without first carry- 
ing out an aerial survey over the areas and preparing contour maps of those parts 
of them where any civil engineering projects have to be carried out. 
The writer hopes that this article may cause advisory experts and others 
responsible for the development of undeveloped tropical areas to commence opera- 
tions by studying the aerial photographs, if they exist, of the region under con- 
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