Trigpointing

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Trigpointing is a recreational activity or sport in which participants search for trig points and log their finds.

These trig points were initially established at known geographical locations for the purposes of surveying.

Trigpoints are the common name for "triangulation pillars". These are concrete pillars, about 4' tall, which were used by the Ordnance Survey in order to determine the exact shape of the country. They are generally located on the highest bit of ground in the area, so that there is a direct line of sight from one to the next. By setting a theodolite (an accurate compass built into a telescope) on the top of the pillar, accurate bearings to nearby trigpoints could be taken. This process is called "triangulation".

The pillar is the classic trig point. A concrete pillar about 4' high, with a flush bracket near the base and a circular plate on top with groves for mounting a theodolite. There are 6550 pillars listed in the T:UK database. Whilst most of them have fallen into disuse, about 184 of them are currently used in the Passive Station network.

This sport is similar to benchmarking and participants are often also interested in geocaching.