Posted on: 8 January 2013

By R.Ramachandran
The Hindu - 2002

One of the most stupendous tasks in the history of science, started 200 years ago by William Lambton and completed four decades later by George Everest, resulted in the Great Indian Arc of the Meridian. It also established that the Himalayas constituted a mountain range and Mount Everest was the highest point on the earth.

TWO HUNDRED years ago, on April 10, 1802, the British surveyor Col. William Lambton began an ambitious, audacious and mathematically meticulous scientific odyssey at St. Thomas Mount in Madras (now Chennai). It took four decades to be completed. The project ended on the foothills of the Himalayas. Lambton carefully laid the baseline, which stretched across a distance of 12 kilometres between St. Thomas Mount and another hillock in the southern direction, for the "measurement of the length of a degree of latitude" along a longitude in the middle of peninsular India.

This 12-km-long horizontal at about sea level grew into what is known as the Great Indian Arc of the Meridian, a gigantic geometric web of 'triangulations' roughly along the 78° longitude across the entire length of the subcontinent covering a distance of about 2,400 km in the north-south direction. As a corollary, at the end of this massive and perilous exercise, which consumed "more lives than in most contemporary wars" and involved tomes of calculations and equations more complex than any in the pre-computer age, it was conclusively proved in 1843 that the Himalayas constituted a mountain range that was higher than the Andes, until then believed to be the highest. It also established the height of the highest point on the earth, what is now called Mount Everest.

Lambton had originally planned a short arc. It later grew in size and scale to become "one of the most stupendous works in the history of science", one of the greatest human endeavours ever undertaken. It involved, among other difficult aspects of the relentless journey of scientific discovery, moving across the subcontinent with diverse measuring instruments and other paraphernalia, including the massive 36-inch theodolite which weighed over half a tonne, to be carried by as many as 12 men to be placed at vantage points - from the tops of temple gopurams to 30-metre high bamboo structures - from where the crucial measurements of angles were made. The Great Arc became the longest measurement of the earth's surface ever to have been attempted. William Lambton's genius had conceived the idea of the Great Trigonometrical Survey (GTS) of the country with the Great Arc providing the skeletal framework for it. But he died to the cause at the age of 70, midway through his task, while surveying at a place called Hinganghat in Maharashtra, where is situated his uncared-for grave, today no more than a flat, weathered and battered piece of stone. The Great Arc was completed by George Everest, after whom the highest point on the earth is named.

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Wow... What amazing feat.... Can you imagine doing this in early 18oo's... What has not been able to be even reviewed in last 65 yrs... With all the modern gadgetry available today..... Even today there are villages in Raigad district, where the work left incomplete by the British, due to their unimportant value at the time, that have not been brought under survey settlement...!!!