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# The Great Trigonometrical Survey of India

K. S. Sivasami
Professor, Centre for Study of Regional Development, School of Social Sciences, Jawaharlal Nehru University, New Delhi-110067
Tel: +91-116180244

Each millennium had thrown up passion for doing something unique. One such passion prevailed in the 19th through the 18th century was the accurate determination of the dimension of the earth and the location of important geographical features in terms of latitude and longitude. In the western world as well as in India this passion was pursued with great zeal by committed people in the field of survey. Col. Lambton, Sir George Everest, Col. Waugh and Col. Walker were the persons who pursued the measurement of the great meridional arc from Kanyakumari to Banog in the foothills of the Himalayas and covering a large part of India by Trignometrical Survey from 1800 to 1866. Their works attempted to provide an accurate base for systematic topographic and revenue surveys of India. Map using people of India, particularly the geographers, owe a great deal to the visionaries and dedicated persons who worked under very trying circumstances and completed a stupendous task. In the 200th year of the beginning of the Great Trigonometric Survey, it is worthwhile to recollect the splendid work done by the surveyors.

Measurement of arc of meridian
The trignometrical survey had its origin to an earlier related endeavour in measuring the arc of the meridian. The objective of the measurement of arc of a meridian was to determine the size of the earth.

The earliest attempt at computing arc distance was by a Greek scholar Eratosthenes, in around 250 B.C. He computed the arc distance between Alexandria and Syene in Egypt by measuring on a summer solstice the altitude of the noon sun at Alexandria and assuring from the travellers’ account that the sun is overhead at Syene. He found that the arc distance between the two cities as 7’12” which is 1/50th of the circumference of the earth. The estimated circumference of the earth as estimated by this method is 46,250 Km. or 28750 miles, which are only 15% larger to the present accepted value. After Eratosthenes, only in early 18th century, attempts were made to measure the arc of meridian. Eight such attempts are listed in table 1. From early 19th century onwards, more attempts were made to standardise ellipsoids in different countries.

Table 1: Meridional arc Measurements in 18th & 19th Centuries
 Year Observers Country Latitude of Middle arc O ’ “ Length of a degree In Kms Miles 1738 Maupertius Re-examined by Svanberg Lapland 1.31.08 N 111.49 69.28 Struve Russia 58.17.37 N 111.37 69.20 1802 Roy & Kater England 52.35.45 N 111.24 69.12 Lacaille France 46. 52.2 N 111.21 69.10 1790 Delambre & Mecham France 44.51.2 N 111.11 69.04 1755 Ruscovich Rome 42.59.0 N 111.03 68.99 1750 Abbe Lacaille Cape of Good Hope 33.18.30 S 110.87 68.89 1835 Everest India 16.8.22 N 110.66 68.76 1808 Lambton India 12.32.21 N 110.64 68.75 1735 Condamine & Bouguer Peru 1.31.08 N 110.58 68.71

. Table 2 lists out 11 computations of parameters of ellipsoids out of the twenty determinations since 1800. The Everest spheroid (ellipsoid?) is still used in India as well as in Pakistan, Nepal, Burma, Sri Lanka, Bangladesh, Bhutan, and other South East countries. Clarke (1866) ellipsoid has been used for mapping in North America until recently. Now gradually many countries are switching over to World Geodetic System 84 ellipsoid.

Table 2: Official Ellipsoids Equatorial
 Name Date Radius a (metres) Radius b (metres) Polar Flattening WGS 84 1984 6,378,137 6,356,752.3 1/298.257 GRS 80* 1980 ,, ,, ,, WGS 72 1972 6,378,135 6,356,750.5 1/298.26 Australian 1965 6,378,160 6,356,774.7 1/298.25 Krasovsky 1940 6,378,245 6,356,863 1/298.3 Internat’l 1924 6,378,388 6,356,911.9 1/297 Clarke 1880 6,378.249.1 6,356,514.9 1/293.46 Clarke 1866 6,378,206.4 6,356,583.8 1/294.98 Bessel 1841 6,377,397.2 6,356,079.0 1/299.15 Airy 1830 6,377,563.4 6,356,256.9 1/299.32 Everest 1830 6,377,276.3 6,356,075.4 1/300.8

*Geodetic reference system 1980, adopted by the International Association of Geodesy.
(Source: J. Snyder, Map Projections –A Working Manual)
Map 1: Places of importance in GTS

Beginning of Trigonometric Survey
The endeavours in computing the distance of the arc of meridian in order to determine the size of the earth naturally led to the idea of providing accurate position of fixed points with reference to latitude and longitude which may provide landmark for accurate survey by method of triangulation. William Roy in the 18th century and Michael Topping were two of the early advocates of triangulation. The idea of a trigonometrical survey was first conceived by General Watson in 1745. William Roy determined the longitudinal difference by geodetic survey between the royal observatories of Greenwich and Paris. Earlier, in 1784, Alexander Dalrymple suggested a triangulation along the eastern coast of India. These suggestions were followed by Michael Toppling’s appointment as Marine Surveyor in 1791 and Reuben Burrow’s attempt to measure an arc in Bengal in 1790-’91. In 1799, Col. William Lambton had proposed a plan of a “Mathematical and Geographical Survey” right across the peninsula. In his proposal, Lambton noted: ” In a former communication I took the liberty of stating…My idea of a survey to be extended from the Coromandal to the Malabar coast, with a view to determine the exact position of all the great objects that appeared best calculated to become permanent geographical marks…facilitating a general survey of the peninsula and particularly the territories conquered…During the late glorious campaign…The surveyors of particular districts will be spared much labour when they know the position of some leading points to which they can refer because, when these points are laid down in the exact situations in which they are upon the globe, all the other objects…will also have their situations true in Latitude and Longitude…I have now adduced…the principles of my intended survey… which…involve many more objects than what immediately appertain to Geography…Whenever a cooperation with Captain Mackenzie can be dispensed with, I shall direct my views to the General object of determining the geographical features of the Peninsula (Phillimore 1950:234)”(as quoted by Karpagam). The proposal also included measurement of meridional arc along 78 degree east from Cape Comorin in order to determine the size of the earth. Government approval was given in February 1800. In September 1800, Lambton did trial survey of a base line near Bangalore as complement of Mackenzie’s topographic survey in Mysore.

William Lambton was born in 1753. He served under General Harris in the war of Tippoo. During the war of Tippoo, the need for a systematic survey of the country was felt and a plan was mooted. Col. Mackenzie in 1800 commenced the topographical survey in Mysore and Kanara. Lambton started the trignometrical survey. The actual work of trignometrical survey was commenced on 10th April, 1802 by measurement of base line near Madras. The baseline was 10.8 kms. (8 miles) long on a flat plain with St. Thomas Mount near its northern and Perambalur hill near the southern end. From the Madras base line, a series of triangles were carried up to Mysore plateau and a second base was measured near Bangalore in 1804 by Lt. Warren. Lambton was also assisted by Lt. Kater. The series of triangles up to Malabar Coast was completed in 1806. Lambton called these triangles as Great Arc Series. He later extended the series towards Cape Comorin and a new base line was measured in Coimbatore in 1806, at Tanjore in 1808, at Tinnavelly in 1809 and the primary triangles were extended then to sea shore at Pernnal, located 12 kms. north-east of Cape Comorin. The arc series was then completed from Cape Comorin to Bangalore.

After completing the arc series from Cape Comorin to Bangalore in 1811, Lambton started the northward measurement. A base was measured at Gooty with triangles connecting it with that near Bangalore and other extending to Thungabhadra, thus forming a foundation of a series of triangles across the peninsula connecting Masulipatnam with Goa. In 1815, Lambton measured another baseline as a part of the Great Arc series in the vicinity of Bidar at a station called Dumargidala. (Map 1). Till this time, Lamton’s survey was variously referred to as his general, geographical, geodetic or astronomical survey. Only in 1818, 16 years after the beginning of survey, the Government named it as “Great Trignometrical Survey” (GTS).

In 1818, George Everest joined Col. Lambton. In 1822, Lambton continued the survey from Hyderabad towards Nagpur. But he died on the road at Hinjunghat on 20th January, 1823.

Lambton’s contribution is significant. He measured the arc of the meridian near to Equator and his measurement was used to deriving the ellipsoid of the earth. But his work did not receive the attention it deserved from the scientific community till the fag end of his career. The French recognised his work earlier than British. In 1817, Major Lambton became a corresponding member of the French Institute. In 1818, the Royal Society of London made him a member. After this recognition, the Governor General took the trigonometric survey under his control and named it “The Great Trigonometric Survey of India” and Col. Lambton was made the first Superintendent of the GTS. He completed the triangulation of 165,342 sq. miles in the peninsula at a cost of 83837 L.

After the death of Col. Lambton, Everest assumed the control of the Great Trigonometrically Survey. In spite of his serious illness, he continued the measurement of the arc and reached the Tropic of Cancer in May 1824 and Sironj where he measured another baseline of 38410 ft. and completed the astronomical observation at Kalianpura by November.

Along with the measurement of meridianal arc, a longitudinal series of triangles was extended from Sironj to Calcutta by Mr. Joseph Olliva and it was completed by July, 1832 covering a distance of 700 miles.

During the absence of Everest, who went on leave to London for medical treatment, no significant progress was made in the measurement of the Great Arc. After his return, Everest resumed the work on meridianal arc. Andrew Waugh and Renny joined Everest for completion of this work. A plan of work for the completion was made and 35 stations between Sironj and Dehradun were selected for measurement. Base line of northernmost base of the Great Arc was measured in an area around Dehradun in 1834-’35. An observatory was formed at Kaliana for making astronomical observations. The connection of the bases at Sironj and Dehradun was done by using innovative methods against great odds. Since most of the area was plain scaffolding masts, masonary towers rising to a height of 50 to 70 ft. were constructed. Everest developed ray tracing method of locating stations and introduced the grid iron system of triangulation coverage. Assisted by Waugh, Everest, by February, 1837 connected the Dehradun base with that of Sironj, 13 years after the first measurement made at the later place.

Accuracy was the obsession. It was claimed that the difference between the length of Dehradun base as measured and as completed by triangulation from Sironj base was only 7.2”. Everest Waugh and Walker continued the longitudinal series of the Great Trigonometrical survey and completed it in 1866. The conclusion made by Clement R. Markham, in his memoirs on GTS “The story of Great Trigonometrical Survey when fittingly told will form one of the proudest pages in the history of English domination in the east”.

If one looks back at GTS, 200 years after it was conceptualised and 135 years after its completion in part, certain interesting features emerge. The immediate task of the Great Trigonometrical Survey was the accurate determination of the position of important points over the country which form the basis for geographical and other surveys and maps. Lambton also wanted to determine, by actual measurement, the magnitude and figure of the earth, a contribution to the geodetic science He measured an arc of the meridian from Cape Comorin to 180 N, the longest geodetic arc ever measured so close to equator and he completed the results. Later Everest extended it up to Himalayas. These measurements did form the basis for the determination of the ellipsoids. The Everest spheroid is still used not only by India but also by Bangladesh, Bhutan, Burma, Nepal, Pakistan, Sri Lanka and other south-east Asian countries.

The other primary objective of GTS – the accurate determination of the position of important points over the country, which would form the basis of trigonometrical and other surveys – was never achieved. Mathew H. Edney in his excellent book ” Mapping an Empire – The Geographical construction of British India” outlines the reasons behind this shortcoming of GTS. A triangulation may be simple in concept, but its implementation has always been difficult. It is slow and costly. The relationship between a triangulation extent and its cost is non-linear. The governments can only undertake it. Every state failed to incorporate a cadastre into systematic topographic surveys – the cartographic ideal before 1880. The progress of the comprehensive mapping was quite irregular. The British surveys did not follow the proper sequence. The triangulation has to be completed, computed and corrected before any detailed surveys are begun.

Almost all topographical and cadastral surveys in India were undertaken before the general triangulation could reach respective region. But at that time, a single, coherent survey organisation that would properly implement a systematic survey did not exist. All British survey activities were supposedly unified in 1878 to form the Survey of India, of which the GTS became the “Geodetic Branch”. Subsequently, the Indian survey committee was convened in 1904-’05 to effect substantial reform in the various mapping activities. Later in the 19th century, much of the triangulation of GTS was resurveyed.

Although GTS was supported as a great scientific endeavour, the Government of India had other pragmatic interests. The administration needed geographic information and small-scale maps for ruling and exploiting the country. For this purpose, in the 1820s Atlas of India project was established. The project aimed at compilation of maps at medium scale of four miles which “would bring together all the topographic surveys and warp them to fit GTS in order to create a definite cartographic representation of India” (Mathew H. Edney p.30)…” “The Atlas embodied the British view of India in 1820, fixed, eternal, imperial and known to British through scientific observation”. This view continued through the 19th century into the 20th century. Even after independence the preparation of 1:250,000 maps was given due importance. According to Edney, “Map making was integral to British imperialism in India. The surveys and maps together transformed the subcontinent from exotic and largely unknown region into a well-defined and knowable geographial entity. The empire might have defied the map’s extent, but mapping defined the empire’s nature.”

The history of the Great Trigonometrical Survey is relevant at present when technological thrust replaces conventional map making methods. GTS was considered the best scientific way of mapping India. In spite of its ardent supporters from the highest eclon of British Empire, it could not fully satisfy the mapping requirement of India. As a concept it was ideal but in practice it was riddled with insurmountable problems. Now GIS and GPS throw up such great expectation as GTS did in the nineteenth century. Time alone will tell how well these expectations are fulfilled.

References

1. Edney , Mathew H. (1999) : Mapping an Empire : The Geogrphical Construction of British India, 1765-1843, Oxford University Press, New Delhi
2. Kalpagam, U. (1995):’ Cartography in Colonial India’ Economic and Political Weekly, vol. XXX no. 30 pp. 87-98.
3. Markham, Clement R (1871): A Memoir on the Indian Surveys, W. H. Allen and Company, London
4. Robinson, Arthue H. (1995): Elements of Cartography, 6 ed., John Wiley & Sons, New York.