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GVII-I* ( Sup o ) 
carried out wherever possible in connection with structural 
geology (Pakistan, Iraq, Algeria, Montana, USA)® 
In many of these cases photogeological mapping provided 
far more detailed and more accurate information than any 
field-mapping could have done, though even then some doubt 
ful features would require a certain amount of field check 
ing« In igneous and metamorphic areas especially, photo 
interpretation is often confined to the delineation of the 
outcropping bed-rock, to some structural features and to 
quatenary and pleistocene deposits. 
Most of this work covers geologically unknown (or 
vaguely known) regions and no detailed geological field- 
maps were at hand for comparison (excepting France, Algeria, 
Switzerland). Some of the work is of potential interest to 
petroleum, mining, engineering and agricultural geologists, 
other work is more of scientific interest. 
In the Geological Section of the International Training 
Center for /erial Survey of the Netherlands, research work 
can only be done as a part-time job and consequently the 
output is very limited. 
Forestry 
During the last four years the International Training 
Center for Aerial Survey at Delft has, at the request of the 
Netherlands Government, prepared vegetation maps of various 
areas in New Guinea. The purpose of this was to obtain a 
general idea about the forest conposition in these regions. 
In this way a total surface of 10,000 sq. km. was mapped. 
The scale of the air photos used was lsU0,000o The air 
survey was carried out during 1935-1937 and the camera type 
employed was the RC7* The interpretation of the visible 
vegetation types was not checked with the actual terrain 
condition. It was according to the more important differences 
in vegetation, such as tidal forest, swamp forest, dry land 
forest and other types of vegetation that a distinction was 
made. Each of these main types was, as far as possible, 
again subdivided in subtypes according to crown diameter and 
closure of the crown canopy. 
The measuring of tree height was not possible owing 
to the density of the vegetation cover, which prevented the 
ground from being visible on the photograph. On account of 
crown diameter and crown density it was possible to make a 
rough estimate of the wood volume per unit area. 
The identification of the various tree species in the 
tropical forest appeared to be impossible without additional