Great Trigonometrical Survey

Last updated March 08, 2024

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.^[1] 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.

Among the many accomplishments of the Survey were the demarcation of the British territories in India and the measurement of the height of the Himalayan giants: Everest, K2, and Kangchenjunga. The Survey had an enormous scientific impact as well. It was responsible for one of the first accurate measurements of a section of an arc of longitude, and for measurements of the geodesic anomaly, which led to the development of the theories of isostasy.

The native surveyors made use of in the Himalayas, especially in Tibet (where Europeans were not allowed), were called pundits, who included the cousins Nain Singh Rawat and Krishna Singh Rawat.^[2]^[3]^[4]

History

From its inception in 1600 to its domination of the entire Indian subcontinent by the beginning of the nineteenth century, the British East India Company gained more and more territory.^[1] With the acquisition of new territory, it employed several explorers and cartographers to provide maps and other information on its territories, most notably James Rennell, from 1767 in Bengal. As Rennell proceeded to make maps, the lack of precise measurement was noticed.^[1] In 1800, shortly after the Company victory over Tipu Sultan, William Lambton, an infantry soldier with experience in surveying, proposed to remedy precisely that, through a series of triangulations, initially through the newly-acquired territory of Mysore, and eventually across the entire subcontinent.^[5]

The Great Trigonometrical Survey of India started on 10 April 1802 with the measurement of a baseline near Madras.^[1] Major Lambton selected the flat plains with St. Thomas Mount at the north end and Perumbauk hill at the southern end. The baseline was 7.5 miles (12.1 km) long. Lieutenant Kater was despatched to find high vantage points on the hills of the west so that the coastal points of Tellicherry and Cannanore could be connected. The high hills chosen were Mount Delly and Tadiandamol. The distance from coast to coast was 360 miles (580 km) and this survey line was completed in 1806.^[7] The East India Company thought that this project would take about five years, but it took nearly 70 years, well past the Indian Rebellion of 1857 and the end of company rule in India. Because of the extent of the land to be surveyed, the surveyors did not triangulate the whole of India but instead created what they called a "gridiron" of triangulation chains running from north to south and east to west.^[1] At times the survey party numbered 700 people.^[8]

The Trigonometrical Survey was conducted independently of other surveys, notably the topographical and revenue surveys. In 1875, the decision was taken that the Survey budget should be reduced from 240,000 to 200,000 pounds. This resulted in a reorganization under Surveyor-General Colonel J.T. Walker to amalgamate the Great Trigonometrical, Topographical and Revenue Surveys into the Survey of India.^[9]

Instruments and methods used

Triangulation surveys were based on a few carefully measured baselines and a series of angles. The initial baseline was measured with great care since the accuracy of the subsequent survey was critically dependent upon it. Various corrections were applied, principally temperature. An especially accurate folding chain was used, laid on horizontal tables, all shaded from the sun and with constant tension. The early surveys made use of large and bulky theodolites made by William Carey,^[10] a Zenith sector made by Jesse Ramsden and 100-foot (30 m) chains. Later surveys used more compact theodolites.

Accurate instruments could not always be purchased through the standard system of government contract, and Everest personally supervised the construction of instruments. He had a maker, Henry Barrow, set up an instrument company in Calcutta. Barrow was succeeded by Syed Mohsin from Arcot, Tamil Nadu, and after his death, the instruments were supplied by Cooke from York.^[11]^[12]

Correcting deviations

To achieve the highest accuracy a number of corrections were applied to all distances calculated from simple trigonometry:

Curvature of the Earth
The non-spherical nature of the curvature of the Earth
Gravitational influence of mountains on pendulums and plumb lines^[13]
Refraction
Height above mean sea level

Superintendents

1818–1823 – William Lambton
1823–1843 – Sir George Everest
1843–1861 – Andrew Scott Waugh
1861–1883 – James Thomas Walker
1884–1888 – Charles Thomas Haig
1888–1894 – George Strahan
1894–1899 – St George Corbet Gore
1899–1911 – Sidney Gerald Burrard
1912–1921 – Sir Gerald Ponsonby Lenox-Conyngham

Notes

↑ A boning telescope was a small, low-magnification telescope used to align the survey markers.^[6]

Related Research Articles

Surveying or land surveying is the technique, profession, art, and science of determining the terrestrial two-dimensional or three-dimensional positions of points and the distances and angles between them. These points are usually on the surface of the Earth, and they are often used to establish maps and boundaries for ownership, locations, such as the designed positions of structural components for construction or the surface location of subsurface features, or other purposes required by government or civil law, such as property sales.

<span class="mw-page-title-main">George Everest</span> British surveyor and geographer (1790–1866)

Sir George Everest, was a British surveyor and geographer who served as Surveyor General of India from 1830 to 1843.

<span class="mw-page-title-main">Theodolite</span> Optical surveying instrument

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<span class="mw-page-title-main">Nain Singh</span> Pundit who explored the Himalayas for the British

Nain Singh, also known as Nain Singh Rawat, was one of the first Indian explorers employed by the British to explore the Himalayas and Central Asia. He came from the Johar Valley in Kumaon. He surveyed the trade route through Ladakh to Tibet, determined the location and altitude of Lhasa in Tibet, and surveyed a large section of Brahmaputra. He walked "1,580 miles, or 3,160,000 paces, each counted."

A total station or total station theodolite is an electronic/optical instrument used for surveying and building construction. It is an electronic transit theodolite integrated with electronic distance measurement (EDM) to measure both vertical and horizontal angles and the slope distance from the instrument to a particular point, and an on-board computer to collect data and perform triangulation calculations.

Troughton & Simms was a British scientific instrument firm. It was formed when Edward Troughton in his old age took on William Simms as a partner in 1826. It became a limited company in 1915 and in 1922 it merged with T. Cooke & Sons to form Cooke, Troughton & Simms.

The Ramsden surveying instruments are those constructed by Jesse Ramsden and used in high precision geodetic surveys carried out in the period 1784 to 1853. This includes the five great theodolites—great in name, great in size and great in accuracy—used in surveys of Britain and other parts of the world. Ramsden also provided the equipment used in the measurement of the many base lines of these surveys and also the zenith telescope used in latitude determinations.

The Principal Triangulation of Britain was the first high-precision triangulation survey of the whole of Great Britain and Ireland, carried out between 1791 and 1853 under the auspices of the Board of Ordnance. The aim of the survey was to establish precise geographical coordinates of almost 300 significant landmarks which could be used as the fixed points of local topographic surveys from which maps could be drawn. In addition there was a purely scientific aim in providing precise data for geodetic calculations such as the determination of the length of meridian arcs and the figure of the Earth. Such a survey had been proposed by William Roy (1726–1790) on his completion of the Anglo-French Survey but it was only after his death that the Board of Ordnance initiated the trigonometric survey, motivated by military considerations in a time of a threatened French invasion. Most of the work was carried out under the direction of Isaac Dalby, William Mudge and Thomas Frederick Colby, but the final synthesis and report (1858) was the work of Alexander Ross Clarke. The survey stood the test of time for a century, until the Retriangulation of Great Britain between 1935 and 1962.

<span class="mw-page-title-main">Pundit (explorer)</span> Native explorers who assisted British surveys of Asia

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<span class="mw-page-title-main">Heliotrope (instrument)</span> Measuring instrument

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In surveying, triangulation is the process of determining the location of a point by measuring only angles to it from known points at either end of a fixed baseline by using trigonometry, rather than measuring distances to the point directly as in trilateration. The point can then be fixed as the third point of a triangle with one known side and two known angles.

Alexander Strange was a British army officer in India and took part there in the Great Trigonometrical Survey. After retirement from the army he settled in Britain; he supervised the construction of scientific instruments used in surveying, and supported scientific research.

References

1 2 3 4 5 Gill, B. (2001); "THE BIG MAN. Surveying Sir George Everest", in: Professional Surveyor Magazine, Vol. 21 Nr 2. Retrieved online Archived 10 February 2017 at the Wayback Machine 8 March 2016.
↑ Peter Hopkirk, 1982, "Trespassers on the Roof of the World: The Race for Lhasa", Oxford University Press.
↑ Derek J. Waller, 2004, "The Pundits: British Exploration of Tibet and Central Asia," University Press of Kentucky.
↑ Account of the Pundit's Journey in Great Tibet - Capt. H. Trotter, The Journal of the Royal Geographical Society (1877).
↑ Lambton, William (1811). "An account of the Trigonometrical Operations in crossing the peninsula of India, and connecting Fort St. George with Mangalore". Asiatic Researches; or Transactions of the Society Instituted in Bengal for Inquiring into the History and Antiquities: 290–384.
↑ "bone, v.3" . Oxford English Dictionary (Online ed.). Oxford University Press.(Subscription or participating institution membership required.)
↑ Markham, Clements (1878). A Memoir on the Indian Surveys (2 ed.). London. W H Allen And Co. p. 67 . Retrieved 1 March 2009.
↑ Bluesci: Cambridge university science magazine, 29 January 2011,"History: The Great Trigonometrical Survey" "BlueSci » History: The Great Trigonometrical Survey". Archived from the original on 27 July 2014. Retrieved 5 May 2013.{{cite web}}: CS1 maint: bot: original URL status unknown (link), Cambridge.
↑ Black, Charles E.D. (1891). A memoir of the Indian Surveys, 1875–1890. London: Secretary of State for India in Council. pp. 39–40.
↑ R., Ramachandran (2 June 2021) [Originally appeared in print version on April 27, 2002]. "Survey Saga". frontline.thehindu.com. Retrieved 26 December 2022.
↑ Strahan, C. (1903). "The Survey of India". Professional Papers of the Corps of Royal Engineers. 28: 141–171.
↑ Insley, Jane (1995). "Making mountains out of molehills? George Everest and Henry Barry, 1830–39" (PDF). Indian Journal of History of Science. 30 (1): 47–55. Archived from the original (PDF) on 25 January 2014.
↑ Pratt, John Henry (1855). "On the Attraction of the Himalaya Mountains, and of the Elevated Regions beyond Them, upon the Plumb-Line in India". Philosophical Transactions of the Royal Society of London. 145: 53–100. doi: 10.1098/rstl.1855.0002 . JSTOR 108510.