STANDARD SCALES OF AERIAL PHOTOGRAPHY AND THEIR PROPOSED USE 
Scale of Aerial 
Photography 
Use 
i. 1:50,000 
(Coverage for the 
whole country) 
2 . 1 : 20,000 
(Covering selected 
areas, say 75 % to 
Q0% of 1:50,000 
coverage) 
3* 1:10,000 or 1:6,000 
(for special projects 
requiring very large 
scale maps) 
Revision of 1:250,000 surveys 
Planimetry on 1:15,000 and larger 
scales (Planimetry can be In 
the form of photo-image or 
plotted section) 
Contouring with 10 metres or 
larger vertical interval*. 
Mapping on 1:25,000 scale 
Planimetry upto 1:5,000 scale 
(line or photo image) 
Contouring with vertical interval 
of 2.5 to 10 metres 
Interpretation 
Cadastral and town surveys on 
1:5,000 scale 
Densification of ground control 
by photogrammetric methods (3) 
Very large scale surveys 
Contouring with very small vertic 
al intervals) 
In Indian conditions, the contour interval in engineering sur 
veys is small. For example, it is 1 metre in canal area surveys and 
25 cm in command area surveys. Photogrammetric method would entail 
large scale aerial photography resulting in innumerable models and 
considerable work, but still would be less expensive. Ground sur 
veys are costlier but they may be justifiably adopted in the socio- 
-economic conditions in India where there is a pressing need for 
providing jobs to the unemployed. However, as mentioned earlier, 
each survey project has to be planned after considering cost and 
time factors. The diagram below shows some of the various possible 
courses to do the job. 
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