Great Trigonometric Survey of India

Index to the Great Trigonometrical Survey of India, from the Report of the Survey of India for 1921–22. Photograph: Shyamal (2013), Wikimedia Commons

A project undertaken by the British military under the East India Company between 1802 and 1871. It conducted a geographical and topological survey of the Indian subcontinent using scientific instruments and methods, including such features as the height of Himalayan mountain ranges and the expanse of the riverine plains.