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