Baseline (surveying)

In surveying, a baseline is a line between two points of the earth's surface and the direction and distance between them. In a triangulation network, at least one baseline needs to be measured to calculate the size of the triangles by trigonometry.

In the United States Public Land Survey System, a baseline is the principal east-west line (i.e., a parallel) upon which all rectangular surveys in a defined area are based. The baseline meets its corresponding principal meridian at the point of origin, or initial point, for the land survey. For example, the baseline for Nebraska and Kansas is shared as the border for both states, at the 40th parallel north.