map compilation. These data are: 
(1) Basic geodetic control 
(2) Mapping control 
(3) Aerial photography. 
Consequently, the mapping system to be employed for acquisition 
of this data must be capable of: 
(a) Obtaining control needed for mapping without the 
necessity of costly and time consuming surveys on the 
ground. 
(b) Obtaining aerial photography under unfavourable weather 
conditions. 
(c) Permitting accurate navigation in areas where there 
are no maps. 
TYPES 'OF MAPS 
  
The scale, the contour interval, and the final 
presentation of the maps must satisfy the needs of a large 
variety of users. Consequently, the final product will be a 
compromise. The experience in providing maps which serve as 
a base for initial development planning indicate that the most 
suitable product is a topographic map at a scale of 1:50,000 
with contour intervals of 50 feet, or in countries which have 
adopted the metric system, with contour intervals of 10 or 20 
   
meters. Whether the maps are to be produced in single colour