The Great Trignometrical Survey

Each millenium throws up a passion for doing something unique. One passion that prevailed throughout the 19th century was the accurate determination of the dimensions of the earth and the location of important geographical features in terms of latitude and longitude. After all, who we are, is intimately associated with where we are.

In April 1802, the relatively comfortable cool days of winter were giving way to rising temperatures and increasing humidity while the sultry Indian summer loomed endlessly ahead. As fellow British officers explored ways to escape the heat, Colonel William Lambton (who, with George Everest, has been recognized as the man that made the arc possible) made plans to walk the heart of the steaming land: on April 10 he carefully laid the baseline for the measurement of the length of a degree of latitude along a longitude in the middle of peninsular India, at St Thomas' Mount in Madras. His ambitious and seemingly impossible plan, was to measure the great meridonial arc, by trignometric survey. The plan succeeded, and today, 200 years later, we celebrate and acknowledge the creation of what has come to be known as The Great Arc, upon which, modern mapping and surveying of the Indian peninsula is still based.

The over 2,400km of inch-perfect survey was, and still remains, one of the greatest human endeavours ever undertaken. Braving forest, flood and fever the British surveyors and their Indian staff carried instruments weighing over half-a-ton to make possible the mapping of the entire Indian subcontinent. The nearly half-a-century of dedicated effort consumed the lives of more men than most contemporary wars. In 1818, the Government named the survey 'The Great Trignometrical Survey'.

The equations that laid down ground reality were more complex than any that had been formulated in the pre-computer age and have been likened to as much of a technological achievement, as man stepping foot on the moon in 1969. Precision was the mantra; and it was so rigorously maintained that even today, despite more sophisticated mapping equipment and survey methods, the values arrived at then, using those techniques, cannot be disputed.