required for special engineering projects. 
Type of Aerial Camera 
  
In areas of difficult weather conditions the choice 
of either wide angle or super-wide angle photography will 
depend to a large extent upon the number of photographic days 
available at different altitudes. It can be generally stated e e 
that in such areas photography from 4,000 meter altitude can 
be obtained on a greater number of days than photography from 
8,000 meter altitude. Under these conditions, the super-wide 
angle photography is preferable as it allows photography to be 
obtained at 1:50,000 from an altitude of 4,400 meters and, 
consequently, increases the number of photographic days 
available. If the area has considerable relief, then the 
forward and side overlap should be increased when super-wide e 9 
photography is used, in order to minimize areas obscured due 
to relief. 
Type of Emulsion 
  
Results obtained on projects in Africa and South 
America clearly show that infra-red photography is preferable 
to panchromatic photography. The aerial film used for this 
purpose is Kodak Infra-red Aerographic Type 5424. 
Increased contrast between water and land on inf:a- 
red photography exposes drainage in heavily forested areas as