Surveys old and new

snh-course-027.jpgWe had the first meeting to organise this year’s Haddington triathlon the other night.  With all the new building that has gone on in Haddington in recent years and associated changes to road layouts, we have decided to alter the run route this year to separate the cyclists and runners at a few dangerous bottlenecks.  One of our number is going to go out with my GPS to measure the proposed new route.

Coincidentally, I am currently reading The Great Arc by John Keay, the story of how India was mapped, the heights of mountains established, and Everest was named.  It’s fascinating but slow going, but then the survey of India didn’t happen overnight.  One of the first things that had to be done was to establish a baseline of known length and height above sea level for all the subsequent survey triangles and trigonometry.  In early 1800 it took a team of men 57 days and 400 individual measurements to measure the 7.5 miles of the baseline with a 100ft length of chain.  Temperature changes during the day had to be taken into account as a 1 degree change in temperature made a difference of 0.00742 of an inch in the length of the chain.  Lambton, who was the mastermind behind the survey, was concerned that local thermometers weren’t sufficiently accurate and so used a series of thermometers for each measurement.  A second chain was kept in a cool vault for calibration purposes and both chains were measured against a standard bar.  From this baseline, with an initial accuracy of 7/100ths of an inch, they established a chain of triangles running the length of India with subsidiary networks stretching out across the country.  The survey took most of the 19th century and cost a lot of lives. 

Flipping to the end of the book, I notice that George Everest, who took on the survey after Lambton, lived to the then ripe old age of 76 and was buried in Hove.  I wonder if the Geography teachers who Ollie has been working with this week, realised that Everest was buried so close to their meeting venue? 

It all seems a very long way from GoogleEarth, satellite technology and GPS.  And yet they are still arguing over the precise height of mountains in Scotland. And I am quite sure that the Haddington tri route won’t be measured to an accuracy of 7/100ths of an inch.

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