The story
The history of the Survey of India dates back to the 18th century. "First modern scientific survey of India" was undertaken by John Mather in 1793–96 on instructions of Superintendent of Salem and Baramahal, Col. Alexander Read. The present Dharmapuri district, Krishnagiri district and North Arcot in western Tamil Nadu were then called Baramahal.
The Great Trigonometrical Survey (1802–1852) was started by British surveyor Col. William Lambton on 10 April 1802, heading from St. Thomas Mount in Chennai to the foothills of the Himalayas. 36 inch huge half ton weight Theodolite was used, which took 57 days to measure the 12-km base line. This 5-decade project was completed under Survey General Lt. George Everest in the year 1852. Pioneering mathematician and Surveyor Radhanath Sikdar measured Mount Everest in 1852, with a height of 29,002 feet. Modern measurements indicate the height is 29,037 feet. This is regarded as the beginning of a new age of systematic topographical mapping in India succeeding the classical age, and the founding of one of the oldest survey and mapping agencies in the world.
From Wikipedia’s article on Survey of India, shared under CC BY-SA 4.0.4