THE INDIAN FOOT-METRE RATIO AND ITS ADOPTION IN THE INDIAN GEODETIC SYSTEM

ISSN： 1752-2706

Source： Survey Review, Vol.16, Iss.119, 1961-01, pp. : 13-18

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Abstract

The lengths of the old base-lines of the Indian triangulation, measured in the period 1831–69, are expressed in terms of Indian foot or tenths of the Indian Standard known as Indian 10-foot Bar A at 62°F., whereas the measurement of the new base-lines after 1930 was carried out by means of the invar wires compared with the International Metre Standard. There is thus the necessity for ascertaining the correct Indian foot-metre ratio for expressing the lengths of the new base-lines also in terms of the Indian foot so that the Indian triangulation system may be self-consistent and become comparable to geodetic systems of other countries. An attempt has therefore been made to obtain the most probable value for the Indian footmetre ratio as in the period 1831–69, which has, however, been found to differ from one adopted by Brig. Bomford in the conversion of the new base-lines, and the effect of this discrepancy in scale error has been discussed in detail.It has been found that the Indian foot-metre ratio as obtained here differs very slightly from one newly introduced in India as a result of the Standards of Weights and Measures Act, 1956, which is again identical with the International foot-metre ratio to be in force on and after July 1, 1959, and as such it is possible to adopt the International foot-metre ratio straight away in the Indian geodetic system without affecting the accuracy needed for topographical purposes, though in precise geodetic investigations, the error involved is quite appreciable and requires to be corrected with the help of the correction chart provided in this paper.