Also covered are primary and secondary triangulation stations, types of signals used in marking triangulation stations, and checking for precision and locations of points. He keeps the triangulation notes and should be at the spot where any important measurement is made so that he can verify the readings personally. He is responsible for selecting triangulation stations and erecting triangulation signals and towers. He determines the degree of precision to be attained. He also performs the computations necessary to determine horizontal locations of the points in the triangulation system by bearing and distance.
Triangulation is used extensively as a means of control for topographic and similar surveys.
A triangulation system consists of a series of triangles. By using the triangulation method of control, you do not need to measure the length of every line. However, two lines are measured in each system one line at the beginning and one at the closing of the triangulation system. These lines are called base lines and are used as a check against the computed lengths of the other lines in the system. The recommended length of a base line is usually one sixth to one fourth of that of the sides of the principal triangles.