I'm on top of a hill, and like six thousand other hills and high places across the United Kingdom,
this one has one of these on top of it. A short squat pillar, made of concrete, about three feet high.
Now why would someone go to the trouble of building six thousand odd 'trig points' as they're known,
trigonometric stations, on high points, because getting there is incredibly difficult, you have to lug tools,
you have to lug the concrete, and you're building something, by the look of it,
that's gonna last for centuries, why would you do that?
Well the answer is mapping. In 1936, and continuing for a quarter of a century, Brigadier Martin Hotine,
and thousands of people, who worked for the Ordnance Survey, built these pillars, in an attempt to retriangulate
Great Britain, and produce the first truly accurate map of the country.
See, distance is incredibly hard to measure but angles, angles, you can do precisely.
On top of here, you've got some hooks, on which you can set down a 'theodolite', something to measure angles.
And then, you build these on hills, so that no matter where you are, if you're at a trig point,
you can see at least two other trig points. And if you can do that, and you know High School trigonometry,
Then you can take one precise baseline measurement across a heath somewhere, the angles you've measured,
and work out the distance across the entire United Kingdom.
Nowadays, GPS has taken over of course, they're little more than a landmark for hill-walkers,
but nevertheless, these trig points meant that we had a precise map of the United Kingdom,
with nothing more than a lot of angles, and a lot of maths.
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