Great Trigonometrical Survey in the context of James Walker (Surveyor General)

Kangchenjunga is the third-highest mountain in the world. Its summit lies at 8,586 m (28,169 ft) in a section of the Himalayas, the Kangchenjunga Himal, which is bounded in the west by the Tamur River, in the north by the Lhonak River and Jongsang La, and in the east by the Teesta River. It lies in the border region between Koshi Province of Nepal and Sikkim state of India, with the West and Kangbachen peaks located in Nepal's Taplejung District and the Main, Central and South peaks directly on the border.

Until 1852, Kangchenjunga was assumed to be the highest mountain in the world. However, precise calculations and meticulous measurements by the Great Trigonometrical Survey of India in 1849 showed that Mount Everest, known as Peak XV at the time, is actually higher. After allowing for further verification of all calculations, it was officially announced in 1856 that Kangchenjunga is the third-highest mountain in the world.

Lieutenant-Colonel William Lambton FRS (c. 1753 – 20 or 26 January 1823) 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.

The Survey of India is India's central engineering agency in charge of mapping and surveying. Set up in 1767 to help consolidate the territories of the British East India Company, it is one of the oldest Engineering Departments of the Government of India. Its members are from Survey of India Service cadre of Civil Services of India. It is headed by the Surveyor General of India. At present, the Surveyor General is Hitesh Kumar S. Makwana.

Major General Sir Andrew Scott Waugh (3 February 1810 – 21 February 1878) was a British army officer and Surveyor General of India who worked in the Great Trigonometrical Survey. He served under Sir George Everest and succeeded him in 1843. Waugh established a gridiron system of traverses for covering northern India. Waugh is credited with naming the peak of Mount Everest.