Wednesday, April 30, 2008

The Great Arc

I read very few books these days, but I am glad that The Great Arc was one among the few. It is wonderful book written by John Keay, an Englishman, about one of the greatest scientific feats of the 19th century. Before you start thinking about mile-long bridges or sky-high buildings, hey... There are things in life that people rarely know about and the science(and art) of Surveying is one of them.

I am in fact gifted to have learned this subject as part of my curriculum, though I wonder how many of my classmates share my opinion. People have often asked me what Surveying is. I am no expert in it and therefore my explanation does not make any impact on them. I say,"It involves getting the measurements from ground about the features there and transferring it to a map." People say,"Oh great. Is that all? You study only that for a year at college?" The point is I would recommend to these people the book I just mentioned.

The book is about a series of measurements made by two Englishmen, William Lambton and George Everest, of the entire Indian subcontinent spanning a period of fifty years. They made what are called triangulations across the entire subcontinent in times when there were no lights, no telegraph, no telephone, etc. It was no simple feat. For example, the beginning of the series of triangulations, called the Great Indian Arc of the Meridian, was at St.Thomas Mount in Chennai. A baseline of 12 Km was measured for some 50 days. The presicion with which these measurements were made was phenomenal. In a distance of about 1 m, the error would not exceed 1 mm. (In today's measurement the tolerances are 1 um in 1 m !!!). This was a stupendous task for times when no modern equipment like GPS were available. The author of the book goes so far to say that the amount of computations performed by the surveyors back then would take several days to complete in a supercomputer today.

The measurements were made in the field for years together in places where tigers roamed free and malaria wrecked havoc. There are more things I would like to mention but might end up writing an entire book!

The second name is probably familiar to many, George Everest. You guessed it, Mt.Everest is named after him, but not because he measured its height but because of the services he rendered by looking after the Great Arc for 30 years. This comes to show the respect these two commanded for their feats. Had it not been for the Great Arc we would never have had maps of India and we would never have known the heights of the Himalayas.

I read the book twice, once in my III semester and once in my IV. I found that it complemented my Survey course. I understood it better when I read it for the second time, since I knew a lot about the instruments like theodolites, levels, chains, etc.

The Great Arc was also publicised as a documentary in NDTV's Documentary 24x7. But it did not go beyond what I read in that book. I hope that I have made a little effort in bringing some light to this mammoth event that took place 200 years ago.


Survey of India's Celebration


P.S.: I took the photograph of the book myself. One of my many efforts in photography.