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How is trilateration different from triangulation in surveying?
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Figure 1: Photogrammetric photographs from two short, overlapping flight strips arranged for supplying mapping details. Photo-control points are shown on only one photograph; shading indicates a typical terrain feature such as a lake (see text).
In surveying and civil engineering, the primary difference between triangulation and trilateration lies in which components of a triangle are measured directly versus calculated.12
- Triangulation: This traditional method involves measuring one baseline distance and two angles of a triangle using a theodolite. The remaining sides and the third angle are then derived through plane trigonometry.23
- Trilateration: In this method, the lengths of all three sides of a triangle are measured directly, typically using electronic distance-measuring (EDM) devices. Once the side lengths are known, the angles are computed.13
While triangulation was historically preferred due to the difficulty of measuring distances, the development of EDM technology has made trilateration a common and often preferred system. Both methods rely on constructing a series of adjacent triangles to establish a survey framework, ensuring that ground features are accurately positioned.132