Erina Trig station is part of a national geodetic survey established during the 1970's. The 'Triangulation station' (aka trigonometrical or trig station) is a distinct marker which was once clear of trees and would have been visible for many kilometers in the area. There are many such trig stations around Australia, used to help in surveying. Each station has a know position and altitude which allows surveyors to use triangulation to determine another point's location. With advances in technology, these trig stations have been superseded and abandoned.