High Point

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In the middle of the last century some long suffering professionals trudged up hill and down dale to create a measurement of the land by “triangulation” , now superseded by GPS – the global positioning system. They were masters of all they surveyed – they built concrete trig pillars. The pillar was devised to provide a solid base for the theodolites used by the Ordnance Survey teams and to improve the accuracy of their readings. Starting in 1936 they completed some 6,500 over time choosing the highest point in an area in line of sight with at least two other pillars to form a triangle. By 1962 the project was complete and the Ordnance Survey launched their seventh series of the one-inch-to-the-mile maps

A cartographic classic that turned a generation on to the great outdoors

So on a cold but bright November morning I set out for the Beacon with my current “Explorer” map in hand – that great hump of chalk overlooking the Vale of Aylesbury – to rediscover the landscape from my mind’s eye. The surveyors measured the hill at 230 meters or 755 feet in old money, and I could make out the adjacent trig points at Castle Hill Totternhoe at 160 meters and Southend Hill at Cheddington at 140 meters. But there was more – the Ordnance Survey showed a trig point to the south on Clipper Down. Retracing my steps I headed off to find this elusive pillar which was recorded at 249 meters, the highest point on the Estate – not many people would know that! And sure enough it was still there, but hemmed in by the trees of Crawley Wood. There are no tracks or paths to show its presence as it is rarely visited – a poor relation to the Beacon. Not surprisingly you could not see Cheddington or the Beacon from the pillar because of intervening trees which have grown up over time. It turns out that the surveyors used hurricane lamps in the darkness to locate adjacent trig points and do their measuring, so it would have been possible to have a line of sight through the trees in winter time!

Suddenly from inside the wood there was a burst of noise which I recognised – the loggers were in business – more work for the volunteers. Thinning out this mixed wood plantation is a priority for the Trust in line with their 20 year management plan published last January – a high point in the restoration of the Estate.
“Thinning will be undertaken on a cycle of five or 10 years. It will concentrate on the removal of suppressed or deteriorating trees and will look to increase the light levels reaching the forest floor increasing the sub and understorey to provide improved habitat for roosting and nesting birds.” Enclosed on three sides Crawley Wood is not a safe attraction for the deer population probably predating the new growth, so the recovery of the understorey should take place quickly.
I have taken the opportunity to correct the Trust on the accuracy of their document where it states….
“The Estate lies on the Chilterns escarpment that peaks at an altitude of 230m above sea level (ASL) at Ivinghoe Beacon towards the northern end of the Estate.”

Chris Skinner

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