THE GREAT TRIGONOMETRIC SURVEY

                This was perhaps one of the most ambitious and arduous project taken up by British Administrators in India.  The Great Trignometrical Survey was a mega project which took over 70 years, thousands of workers and many officials to have the work done. The survey of India gave the Britishers a complete picture of the enormous size of India, the countless provinces and her people. This in fact helped them greatly to understand the way to rule India, and for India it was also a boon. It was discovered that Mount Everest was the tallest peak in the world, and several other giants like K2, Kanchenjunga were also measured.  

Colonel Lambton

                This great dream first hatched in the mind of one Colonel Lambton who submitted a proposal of this enormous work with recommendations of Colonel Wellington (later Duke of Wellington) to Lord Clive (Edward Clive, 1st Earl of Powis) for sing off in 1799. Major Lambton supported his work by saying that, “the utility of such a work, and the advantage and the information which the Nation would derive from there from are so clearly understood that no argument is necessary to demonstrate its advantages.” During the 1800’s the company (East India Company) had annexed a large area in South India and also for other reasons that the company felt it immensely necessary to start such a survey to know the fullest extent and geography of her Empire in the East.

                The operation began with the measurement of base-line in the vicinity of Bangalore in the year 1800. The instruments that were supplied to Lambton, iron chains, and zenith sector were not sufficient for such a mega project. He had to order many types of equipment from England and by the time it reached India, he devoted himself to select stations from where the surveys would be conducted. So effectively the survey began from 1802 in this time some preliminary operations of survey had begun in the near about of Mysore and extended towards Madras. The chain he used initially was of 100 foot in length and with 40 links, of 2.5 feet each.  The chains were laid on coffers, long wooden boxes, and thermometer was kept to record the temperature so that expansion due to alteration of temperature can be corrected. 

One of the great works that Colonel Lambton devoted himself during the commencement of the survey was to calculate the factors which affect spherical excess.  The Spherical Excess is the amount by which the theoretical sum of the three angles of a spherical triangle exceeds 180 degrees.  When a small piece of land is measured the triangle taken is generally considered a plane triangle, but when a large triangle is considered then the concept of spherical triangle comes because Earth is an oblate spheroid.  Colonel Lambton was aware of this, and also knew the fact that Earth’s ellipticity has a role in it. Therefore he found a new value of Earth’s ellipticity which was about 1/310, which bettered Sir Isaac Newton’s value of 1/230.
    
        

               

                To understand this great survey and the amount of labor connected with it one needs to be familiar with some of the basics of trigonometrical survey.  In a trigonometrical survey one uses a series of triangles to measure a particular plot or area.   See the triangle above, here we have three sides, A, B and C, in this we got to measure the distance between A and B, and from these two points measure the angles made by ABC and BAC to complete the triangle. Once we know the two angles, the third can be known; it may also be cross checked. Therefore as you can understand that there needs three stations which are mutually visible. By employing trigonometric principles then one can find out all the sides of the triangle. One of such readings taken during the Great Trigonometrical Survey is given below.

                

 The  survey was carried out in the south by the instruments brought in from England, namely, the three feet high Theodolite made by Carry, an eighteen inch repeating theodolite by the same maker, two steel measuring chains by Ramsden, a standard brass scale by Carry, and several small scale theodolites by different makers for small scale uses.  During one surveying operation near Tanjore,  Colonel Lambton’s Great Theodolite meet with an accident which gravely injured the graduations in it. However he was able to restore it by ingenious means. After three years of his surveying Colonel Lambton was asked by the Government of Madras to furnish all the details that he has acquired by the surveying process regarding, “the appearance and resources of the country, its roads, its supply of water, and whether favorable for military movements, also to represent its general features such as rivers, valleys, passes, mountains etc.” 

The Great Theodolite

                By the 1814 he was able to supply a set of maps to the Madras Government, displaying all the prominent features of the Peninsula, from Goa in the West to Machilipatnam in the East. In 1818 George Everest joined Lambton to carry on the work of survey eastwards.  In doing this work Captain Everest mentions the places as, “dreadful wilderness”, a kind of region that, “no part of the Earth was more dreary, desolate and fatal”.  He faced enormous odds, as the rivers swelled up with heavy rains, making movement extremely difficult. Sometimes Everest and his men had to clear off a square mile of dense forest before commencing the survey. In one occasion the place where Everest and his men were carrying on work, a terrible fever broke out, which claimed number of lives, and help had to be sent from Hyderabad for their flight.  In all this Everest suffered so much that he had to take a break and go to Cape of Good Hope for a change, in there he stayed for a year. 

                Colonel Lambton was 47 when he commenced this great survey but he was a man of indomitable courage and spirit which is why he could push a good fifteen or fourteen years until 1819 when he ceased to take active part in this great Triangulation. Captain Everest returned from Cape of Good Hope in 1822, and after the death of the pioneer of the Great Survey in 1823, The Government entrusted the duty on to him. Captain Everest carried the great survey to the Northwards from Central India, and also introduced a number of reforms, one of which included the introduction of light signals in stations. Previously locating a station in hazy weather was difficult with the introduction of light signals this became quite easy.     Also to avoid the heat of the day working after sunset was much comfortable, and that was achieved by lighting bonfires in stations, as signals.

                George Everest refined the old system prevalent under Colonel Lambton and brought in some concepts like grid-iron system of measurement, wherein a grid-iron of chains of triangles was employed to cover large areas of land in between. Through this map you can well see in the difference between Lambton’s approach and Everest’s approach of surveying. In a way Everest made the work easier, cheaper without compromising with quality and accuracy. Everest introduced the compensation bars to negotiate the effect of temperature during the measurement of baselines. Everest brought this bars to India from England after initial testing at Lord’s Cricket Ground in April 1830!

Radhanath Sikdar

                A graduate of Hindu College (Presidency College) Radhanath Sikdar joined the Great Survey in 1840. A legend has it that one day Radhanath Sikdar stormed into the office of Andrew Waugh (Surveyor General of the GTS after Everest’s retirement in 1843) exclaiming, “Sir, I have discovered the highest mountain in the world”. The announcement was not made right away and was delayed until 1856 to recheck the value of peak XV and was found to be 29,000 feet.  His brilliance in mathematics especially in spherical trigonometry can be well perceived by the fact that the measurement is exceptionally close to today’s value of 29028 feet! Next was to find a suitable name for the peak and Andrew Waugh and company started calling it by the name of Mount Everest, to which George Everest himself opposed, saying that the native people wouldn’t be able to spell the name, but the Royal Geographical Society adopted this name and now it is famous by that.

George Everest

                This entire survey was one of a kind, at that time a survey of this magnitude was never done.  Mr. Markham a writer of that time said, “They must be animated by the noble devotion to the cause of science-these Indian geologists, for theirs is neither a safe nor an easy task. Out of the two dozen or so that have entered the survey since it commenced, thirty four percent have been struck down by death or incapacitating disease. The rest work on zealously and bravely ……by the results of their labors, extending the sum of human knowledge and doing much practically useful work. In spite of all difficulties of climate, inaccessibility of districts, and slowness of means of travels, they have examined an area about four times as large as Great Britain!”