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 and New Zealand, trig stations or points in Australia, and trig beacons in South Africa; triangulation pillar is the more formal term for the concrete columns found in the UK.