10
16 Components Sheets on 1;50,000 Scale
Fig* i Original Preparation/Revision of 1:250,000 Maps
(b) 1:50*000 Scale map series
All the 5016 maps of this series are likely to he published by
1980* Afterwards, the production task will be of revision only*
The revision cyole of this map series is 20-25 years. But in some
areas, because of rapid pace of development, this cycle is woefully
Inadequate to keep the maps reasonably uptodate* The Defence Forces
are the largest users of this map series*
\
Proposed System
The 1:50,000 latest photography should be used to produce photo
images-orthophoto or rectified print-of the relevant photographs.
The comparison of these photo images with the existing maps will
reveal the changes that are to be incorporated* This is the primary
scale of mapping for the whole of India and maps on this scale are
produced by rigorous surveys either toy ground or photogrammetrie
method* Some areas like high-hills can toe surveyed by normal photo*«
gramraetric plotting but very few changes in remote areas are ex
pected to occur. Here again, image-transferfing type of instruments.
(Zoom transferscope) are quite useful for limited revision in small
areas*
(c) 1:25,000 Scale map series (7j minutes x 7% minutes)
There will be about 20,000 sheets covering the whole of India*
The present policy is to do mapping of only selected areas on this
scale* This series, however, is likely to prove extremely popular
with engineers as they need maps on near about this scale* The
truth of the matter is that if maps of this series were readily
