aerial cameras depend on a number of factors. 
The requirements of a survey and mapping project 
regarding scale of aerial photography are often conflicting 
and a compromise must be found to satisfy all users. In order 
to minimize the cost of control surveys, photography should be 
obtained at as small a scale as possible, so that the project 
area is covered with a minimum number of pictures. However, 
the amount of details which must be interpreted on the aerial 
photographs and shown on the map, as well as the requirement 
that the photography should be suitable for other purposes 
than mapping (for instance, geological and forestry inter- 
pretations) calls for a reasonably large scale of photography. 
Weather conditions may not permit obtaining of 
aerial photography from higher altitudes and put a limiting 
factor on the scale. 
Experience indicates that the photography at a 
scale of 1:40,000, or 1:50,000 provides the best compromise. 
Photography at this scale permits compilation of topographical 
maps at reasonable cost and satisfies the needs of photo inter- 
preters investigating the forest resources, soils, hydrology 
or geological features. It can also be used for compilation 
of topographical maps at larger scales (1:10,000 or 1:5,000)