Triangulation Station

A triangulation station, also known as a triangulation pillar, trigonometrical station, trigonometrical point, trig station, trig beacon or trig point, and sometimes informally as a trig, is a fixed surveying station, used in geodetic surveying and other surveying projects in its vicinity. The names of triangulation stations vary regionally; they are generally known as trigonometrical stations in North America, trig points in the United Kingdom, New Zealand and Australia, and trig beacons in South Africa; triangulation pillar is the more formal term for the concrete columns found in the UK.

The station is usually set up by a government with known coordinate and elevation published. Many stations are located on hilltops for the purposes of visibility. A graven metal plate on the top of a pillar may provide a mounting point for a theodolite or reflector.

Trigonometrical stations are grouped together to form a network of triangulation. Positions of all land boundaries, roads, railways, bridges and many other infrastructures can be accurately located by the network.

Trigonometrical stations are essential to the construction of modern infrastructure. Apart from the known stations set up by government, some temporary trigonometrical stations are set up near construction sites for monitoring the precision and progress of construction.

Some trigonometrical stations are equipped with Global Positioning Systems which greatly improve their accuracy.

Although many stations are no longer required for surveying purposes, they remain useful to hikers as navigational aids when hill-walking.