Establishment of north-south gravimetric calibration line in India

Abstract

Twenty-five gravity stations, based on Madison, Wisconsin (980.3689 gals), embracing a change of 1016 mgal along an approximately north-south line were established as a preliminary step in setting up a gravity standardization range in India. The instrument, a small LaCoste and Romberg geodetic gravimeter, model G-1-A, was transported mostly by air over a network between Trivandrum in the south and Srinagar in the north. Ten of the sites occupied are reoccupations of stations established earlier by the University of Wisconsin and the Survey of India, A comparison of the present results with the earlier measurements indicates either a tare or an elevation effect in one of the earlier sets of measurements which affects the previous connection to the national gravity base at Dehra Dun. The present connection to Dehra Dun gives a value of 979.0640 gals, which is 0.4 mgal higher than the earlier University of Wisconsin value and 0.8 mgal higher than the value used by the Survey of India.