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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