Page "Surveying" Paragraph 36

Triangulation is another method of horizontal location made almost obsolete by GPS.

With the triangulation method, distances, elevations and directions between objects at great distance from one another can be determined.

Since the early days of surveying, this was the primary method of determining accurate positions of objects for topographic maps of large areas.

A surveyor first needs to know the horizontal distance between two of the objects.

Then the height, distances and angular position of other objects can be derived, as long as they are visible from one of the original objects.

High-accuracy transits or theodolites were used for this work, and angles between objects were measured repeatedly for increased accuracy.

See also Triangulation in three dimensions.