A surveying method used to measuring a large area of land by establishing a baseline from which a network of triangles is laid out. Triangulation is based on the laws of plane trigonometry, that if one side and two angles of a triangle are known, the other two sides and angle can be readily calculated. One side of the selected triangle is measured; this is the baseline. The two adjacent angles are measured by means of a surveying instrument (transit, theodolite), and the entire triangle is established. By constructing a series of such triangles, each adjacent to at least one other, values can be obtained for distances and angles not otherwise measurable. Triangulation can be used to plan features or significant finds whose exact position it is important to record.