– Brig A. K. Sinha
Kindly refer to the article titled ‘Restrictions on SURVEY OF INDIA Maps; LOGIC AND RATIONALE’ written by Shri S.M. Mathur, inserted in your journal [email protected], July-August, 1999, Vol. 3 No. 4. While dealing with restriction policy followed by Govt. of India on Survey of India Maps, the eminent author has generated lot of misconception in the minds of readers inside and outside India.
- The author has mentioned in his article (para three) “The Surveyor General’s Post is reserved for an officer of the rank of Brigadier or above”. This is incorrect. The Surveyor General’s post is never reserved. The Surveyor General of India is selected by Union Public Service Commission through open competition. Quite a number of civilian officers headed the Department in the immediate past. Even post- independent period saw a civilian officer Shri E.R.Wilson, heading this department.
- Again in the fourth paragraph, the author writes quote the hold of the Army is reflected on each map and publication of SoI by the pompous declaration printed on them. “Published by the order of (rank, name and string of degrees) Surveyor General of India”. The statement is distorted and contrary to the facts. I would like to mention here the correct procedure followed in the department. For departmental maps – the caption is “Published under the direction of —” and for extra-departmental maps it is “Published under the authority.” It is only for books and pamphlets, the caption is “Published by the order of —”, which are normally used in the department.
- In the tenth paragraph under the sub-heading “Restriction of Survey of India Maps”, the author writes about GPS procedures and accuracy achievable. He says positional accuracy achievable is one thousandth part, of minute i.e. 1/1000 x 60 = .06 sec =6 ft. (1″ sec arc measures 100 ft. approx.). This is incorrect in the present day context. At present, absolute accuracy achievable for position is ±100 metres. Measured distance by GPS observation can be accurate to the tune of ±4 to 5 cms.
- In the fifteenth paragraph, the author mentions about gridded topo-sheets of India being published by the US army service and are readily available. I think the eminent author has very faint idea of Grid and Grid projections as a whole. Which grid the esteemed author is talking about? What is its extent and coverage of that grid and where the origin is located? Does the author has any clue about scale error and its effect? If he had any, such statements would not have come from him. Those gridded maps only help a traveller to find his own distance with respect to or prominent landmark like those shown in city guide maps.
- In the last but one paragraph under the sub heading ‘NRSA’, while mentioning the spatial resolution of IRS-IC and IRS-ID satellites, the author has talked about American Satellite having resolution to the tune of 10 cms. My question to the author – “Is it available for any use to the common man?” The author should have gone through various reputed publications and articles by renowned persons on the potential of high resolution satellite data (even those with 4.5 metres resolutions). It is a myth that one can generate even a 1: 50,000 scale topo map with the best commercially available satellite data.
Finally, he compared the resolution of the American Satellite with that of a 1:25,000 scale topo maps. I think the learned author has very sketchy idea of the accuracy achievable from a topo map sheet on 1:25,000 scale and confused himself with the term “resolution”. For information of the readers, one ‘dot’, equivalent to one fourth of millimetre on a map of 1:25,000 scale represents 6.25 metres on the ground. Even a small Indian village consisting of a single family only, is represented by a single ‘Hut’ of one mm square and not by a dot as mentioned by the author.
- The author, should have confined himself to writing on matters pertaining to his field of specialisation rather than hobnobbing in the fields which are alien to him, thus making blunders and incorrect statements. I also have suggestions to the Editor of your esteemed journal – Please make your journal technically excellent in content, instead of publishing articles which are worthless and bordering on untruth and with zero technical control.
Brig. A. K. Sinha
Dy. Director (Sel.Gd), Digital Mapping Centre,
Survey of India, Uppal, Hyderabad.
Ph: 7150385, 7152006