It is among the lesser known facts of the history of science that one of the major scientific projects of the Nineteenth Century took place in India. This project was the measurement of the Great Indian Arc of the Meridian undertaken in 1802. It was the longest measurement of the Earth's surface ever to be attempted. It began at the turn of the Century lasted almost fifty years covered over 1600 miles cost more lives than are lost in wars and involved complex mathematical equations which would have given modern computers minor headaches. This project was undertaken by The Survey of India and was subsequently put under the charge of a separate institution created for this purpose called the Great Trigonometric Survey of India (GTS) . The film by Pankaj Butalia, 'Tracing The Arc' deals with the period associated with both Lambton and Everest. It looks at what motivated the British to undertake such extensive mapping of India in the first place. To what extent were these maps necessary for expansion of the empire, and to what extent were these devices with which to access remote areas of India to see what they had to offer which was of commercial benefit to the East India Company are questions the film addresses. The film also attempts to understand the extent to which our perceptions of ourselves as Indians originates with a conception of the geographical space that links us, as well as of the manner in which it links us. It touches upon the way in which imperialist / expansionist policies underlay the entire project - the way in which map making by the Survey of India went hand in hand with the measurement of the Great Indian Arc of the Meridian by the Great Trigonometric Survey of India. In a sense the history of Cartography was linked up to both the history of science as well as to the ideology of British India.