The Great Trigonometrical Survey of India was a project that aimed to carry out a survey across the Indian subcontinent with scientific precision. It was begun in 1802 by the British infantry officer William Lambton, under the auspices of the East India Company. Under the leadership of his successor, George Everest, the project was made the responsibility of the Survey of India. Everest was succeeded by Andrew Scott Waugh, and after 1861, the project was led by James Walker, who oversaw its completion in 1871.

Lieutenant-Colonel William Lambton was a British soldier, surveyor, and geographer who began a triangulation survey in 1800-1802 that was later called the Great Trigonometrical Survey of India. His initial survey was to measure the length of a degree of an arc of the meridian so as to establish the shape of the Earth and support a larger scale trigonometrical survey across the width of the peninsula of India between Madras and Mangalore. After triangulating across the peninsula, he continued surveys northwards for more than twenty years. He died during the course of the surveys in central India and is buried at Hinganghat in Wardha district of Maharashtra. He was succeeded by his assistant George Everest.