GVII-5 (Sup«) 
terrain investigation, Also in those cases where terrain 
investigation was possible (Surinam) only a small percentage 
of the occurring tree species could be distinguished in the 
photograph. For such an investigation the photo-scale is 
very important, large-scale photographs are to be preferred. 
Also in Central Africa (Uganda), a forest area has been 
worked out. The total surface of this territory was about 
£00 sq. km. Though the photos were not of the best quality, 
it was still possible to distinguish the different vegetation 
types according to composition of species and to map them* 
It may be assumed that the forest composition in areas with 
a dry season is of a more uniform character as far as composi 
tion of species is concerned than in the areas with a more 
equal distribution of the rainfall over the whole year. 
Thus in the drier areas of the tropics the interpretation 
of air photos with respect to the composition of species of 
the tropical forest will in general be more successful than 
in humid regions. However, for an investigation of the 
composition of species of the tropical rain forest the use 
of the air photo is also of great significance, because 
with its aid the terrestrial reconnaissance can be executed 
more efficiently. 
Land Use and Soils Analysis 
During the past four years, photo interpreters of the 
International Training Center for Aerial Survey, in the 
Netherlands, have been developing the techniques of soil 
analysis from aerial photography. For various good reasons 
photo interpretation has not been, in the past, entirely 
accepted by soil scientists as a reliable working method for 
the survey of soils and soil conditions. Therefore new 
methods of application of aerial photographs have been 
developed in Delft. These methods meet all criticism and 
at the same time mean a great step forward in the speeding 
up of the work of these kinds of surveys since the intro 
duction of aerial photographs as field maps. 
These methods are based on photo-analysis, i.e., the 
analysis of all possible factors ruling the processes of 
soil formation and of all other phenomena indicating pos 
sible differences in soil condition. It is clear that this 
work cannot be done by beginners or laymen, but requires 
esqperience in soil science and surveying. This method has 
been developed by Buringh who has published many articles 
on this subject. The analysis is executed systematicallyp 
about a hundred factors or elements of different nature 
(pedological, agricultural, geological, geomorphological, 
geographical, archeological, etc.) are used. Approximately