Great Stamps on Trigonometric Survey

The question of the size of the earth continued to occupy the scientific minds of the 18th century, and soon after the measurement of the arc of a meridian by Delambre, Borda and Mechain in 1790, an even more ambitious project was conceived, this time in India. In 1799, Colonel William Lambton proposed a plan of a mathematical and geographical survey right across the subcontinent along the 78th E meridian, ostensibly to fix the location of some important points in the country, to aid surveyors in their work and to serve as reference points in a lattice for more detailed mapping. The method used was to be triangulation, and the survey was later called the Great Trigonometric Survey. Begun in 1802, by the time of Lambton's death in 1823 the Great Arc of the measured meridian extended for nearly 700 miles, or 10 degrees. Colonel George Everest took over the survey and completed the longitudinal aspects in 1866.

British interest in lands beyond the Indian borders resulted in surveys carried out by Indian surveyors trained by the British, since the border countries did not allow foreigners to enter. These native surveyors were known as pundits, or men of learning. Two such pundits are honored on the sheetlet comemmorating the Great Arc; they are Nain Singh, who explored and mapped the trade route between Nepal and Tibet and determined the altitude of Lhasa; and Radhanath Sidkar, who determined the altitude of the highest peak in the mountain range, which was later named Everest. The center stamp shows a series of stylized triangles covering the subcontinent.

Acknowledgment : http://library.buffalo.edu/libraries/asl/exhibits/stamps/instruments/
The opinion of this article is not my opinion.