James Rennell was one of the first mapmakers working in Bengal, but it was in Madras that the origins of the trigonometrical survey were laid by William Lambton, a grammar-school boy who was commissioned into a British regiment. He was posted to India in 1796 and had the good luck to meet Colonel Arthur Wellesley two years later. Wellesley, later the Duke of Wellington, shared his Madras home with Lambton and both fought in the final Anglo-Mysore War, which led to the death of Tipu Sultan at Seringapatam.

The sultan’s death meant that the Company now had more land from which to collect revenue, and it appointed a surveyor, the engineer Colonel Colin Mackenzie, to produce topographical maps of the area. Lambton’s proposal, which was supported by Wellesley, was both more theoretical and more practical. Surveys had been carried out in France and Spain to establish the curvature of the earth in northern latitudes, and Lambton wanted to extend the survey to India. He planned to do so by plotting a giant grid of triangles in a straight line from Cape Comorin in the extreme south to Dehra Dun in the Himalayas, along what was called the Great Meridional Arc.

To the unscientific mind it sounded a mad venture, and to some extent it was. It was not completed until 1870, long after Lambton’s death in 1823. Much of the triangulation had to be re-surveyed because it was inaccurate. There were a number of false starts, and work had begun with a second-hand set of instruments intended initially as a gift to the emperor of China. But the endeavour epitomises the Enlightenment view that everything could be measured, catalogued, counted, numbered and rationally explained.

Map by Thomas Jefferys, and James Rennell, published by Robert Laurie and James Whittle

The GTS could be seen purely as a vast scientific experiment, although Lambton also emphasised its practical value in establishing the geographical co-ordinates of towns and points of interest. In a series of articles in Asiatick Researches, he explains his intention to “cross the peninsular of India” with trigonometrical operations, to connect Fort St George with Mangalore (he calculated a distance of
362 miles) and “to ascertain certain positions on the Coromandel and Malabar coasts and affix the latitudes and longitudes of all the principle places in the interior country within the extent of the operations for connecting the two seas”.

Page after page lists his calculations, the names of the sites grouped into threes where triangulation took place marked by flags and the position of the pole star. Lambton summarised his findings for the “general reader”, who he said may not have had the time or inclination to follow his findings in detail, but in truth there can have been very few such people who could have understood his complex calculations and probably even fewer among Company officials. Yet the idea of being able to capture even a small part of the Indian peninsula and reduce it systematically to the printed page was attractive.

Could this be applied to other areas of what often seemed like a vast and inchoate country in which the Company had only a tiny, but increasing, hold?

Lambton’s work was continued by his former assistant and successor George Everest, who had been trained at the Woolwich Academy and arrived in India as a cadet. In spite of later poor health, Everest carried out a number of surveys in Bengal. After spending some time in England recuperating, he returned and brought with him more accurate measuring tools, including “compensation bars”, so-called because they allowed and compensated for the expansion and contraction of metal measuring rods.

'A mapp of the greate river Ganges as it emptieth it selfe into the Bay of Bengala,' made by John Thornton, official hydrographer of the East India Company, 1680.

Apart from the charts and maps that were produced during the GTS, a physical reminder of the venture exists on the road from Calcutta to Barrackpore in the form of two remaining survey towers. Because this area is notably flat, it was not possible to establish a baseline to begin measurements. So the 75-foot-high towers were built and observations were taken from their rooftops. Unlike the round semaphore towers, with which they are sometimes confused, the survey towers are tapered square blocks with arrow-slit openings at intervals.

For 16 years the Madras Observatory ran a surveying school for orphaned European boys. Opened in 1794, the teenage boys were taught “practical” surveying for land revenue collection purposes. This was quite different from Lambton’s grand surveys but of equal, if not greater, importance to the Company, which depended on this form of taxation to administer the areas newly under its control. Colin Mackenzie’s topographical survey of Mysore would have noted, among other things, the amount of fertile land; how it was irrigated; which areas had fruit-bearing trees like banana, coconut and mulberry; and how much land was covered with jungle. All these were factors relevant in determining the amount of revenue to be paid.

The boys did not collect the revenue themselves; this was carried out by local men with armed sepoys. The surveying school was open to Europeans only, with Indians not admitted. Even the most unenlightened Company official in Fort St George had heard the stories of Indian surveyors measuring “rich people’s lands short and poor people’s long”, with the obvious connotation of bribery. (Whether European boys could be bribed was not discussed.) By 1813, after the closure of the Madras surveying school, the use of harkaras, or “native assistants”. for survey work was banned, “as Government were anxious to prevent the Natives from obtaining, or being taught, any knowledge of the kind”. However, it was soon found impracticable to attempt any kind of survey work without involving the people whose country was being surveyed. But the temporary restrictions, and tighter controls once they were lifted, meant that Company officials had to familiarise themselves with the local terms relating to land tenure and its complicated web of ownership, landholding, temporary grants of land (jagirs) and rents, systems that had developed during the Mughal period and in some cases even earlier.

Excerpted with permission from Empire Building: The Construction of British India 1690-1860, Rosie Llewellyn-Jones, Penguin India.