The mapping of India is a tale that touches all strands of culture, history, science and politics ensuring that one cannot help but be fascinated. The feats and determination of the surveyors astounded me when I first undertook the study of cartography and their effort is entwined with our need for understanding our planet as well as the desire for ownership.
The first known map of the Indian subcontinent was created as early as the third century BC. Drawn by Eratosthenes the map was based upon a mix of information from Alexander's invasion, hearsay and myth. Little wonder that this was improved upon by the great Ptolemy, in the second century AD, who recognised the existence of the Himalayas and the Ganges and, incredibly, whose map was used until the 16th-17th century. Subsequent maps were produced through measured routes and astronomical calculations, but it was only when Arthur Wellesley (later to become the Duke of Wellington) destroyed the Tipu Sultan and took control of Mysore for the East India Company that accurate land surveys of India were undertaken. The resulting maps were to be used as tools for military intelligence as well as establishing effective trade routes and centres for imperial commerce
Wellesley had brought to India Captain William Lambton, who was to produce one of the most extraordinary feats of surveying, the creation of the Great Arc of India. The Great Arc was the longest measurement of the Earth's surface ever undertaken, one of 1,600 miles, with the dual purpose of mapping India and measuring the curvature of the Earth.
Lambton's extraordinary skills were honed in America. He was an ensign in the 33rd Regiment of Foot when they were called to fight in the American War of Independence. Taken prisoner almost immediately, he was to survey and delineate the boundary between British Canada and the USA. His surveying techniques were inspired by William Roy of the Ordnance Survey and the Cassinis in France.
The survey, begun in 1800, was based upon triangulation. In simplistic terms, a baseline is accurately measured and the angles of the triangle are calculated by sighting a point with a theodolite. Then one side of the calculated measurements of the first triangle is used as the base line for the next and so on. The end result is a web of triangles, the size of which can vary depending on where one can sight to. This, however, is complicated by the fact that the earth is uneven and round; angles of any triangle on this surface do not add to 180 degrees so spherical excess has to be calculated and removed. To make things worse the earth is not truly round, shaped more like a grapefruit (or more accurately, an oblate spheroid). The aim of Lambton's Great Arc was to enable the accurate measurement of the earth and the accurate calculation of the spherical excess. His Arc was created as a series of triangles that progressively moved towards the Himalayas.
Lambton never saw the conclusion of his master plan, the Arc took nearly fifty years and many lives as the Arc progressed through malarial and typhoid ridden territory. Lambton died in central India in 1821 (or 1823 according to some sources), halfway through his Arc, so the Arc was to be completed by his Welsh assistant, the man who was to give his name to the highest point on Earth, George Everest.
The tale of Everest's obsession with detail and mathematical accuracy as well as Lambton's undertaking of the Great Arc is documented in the book of the same title, The Great Arc by John Keay. The book provides the background to the two extraordinary men as well as the hardship they and their surveyors endured to achieve this incredible feat. For anyone with an interest in surveying, cartographic achievement and monumental effort, the book is an essential read. The book also documents the impact cultural differences had upon the survey as well as some of the more spurious scientific ideas of the 19th century.
Unfortunately, Everest must turn in his grave every time the mountain's name is mentioned. According to Keay, his name was pronounced as Eve-rest, not Ever-est, and he would have passionately disliked any mispronunciation of his family name.
Top image: George Everest.
Author: Donna Wright
Date: 1 October 2001