From The Neolithic To The Sea::A Journey From The Past To The Present
Trig Points
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Trig Points or Triangulation Points are concrete pillars that were erected by the Ordnance Survey.
Trig points were placed on top of prominent hills and mountains from 1935 to enable the accurate triangulation of Great Britain. It was possible to see at least two other trig points from any one of these pillars and with careful measurements of the angles between the, the Ordance Survey could accuratley measure and map the entire country.
Trig points are truncated square concrete pyramids or obelisks around 4' high, tapering towards the top. On the top a brass plate with three arms and a central depression is fixed. A benchmark is set on the side, marked with the letters "O S B M" (Ordnance Survey Bench Mark) and the reference number of the trig point. Within the trig point, there are concealed mountings for a specialised theodolite, which was temporarily mounted on the trig point while measurements were taken. These are now a national monument.
Trig points were placed on top of prominent hills and mountains from 1935 to enable the accurate triangulation of Great Britain. It was possible to see at least two other trig points from any one of these pillars and with careful measurements of the angles between the, the Ordance Survey could accuratley measure and map the entire country.
Trig points are truncated square concrete pyramids or obelisks around 4' high, tapering towards the top. On the top a brass plate with three arms and a central depression is fixed. A benchmark is set on the side, marked with the letters "O S B M" (Ordnance Survey Bench Mark) and the reference number of the trig point. Within the trig point, there are concealed mountings for a specialised theodolite, which was temporarily mounted on the trig point while measurements were taken. These are now a national monument.