Geographic Information Systems: An Introduction, 3rd Edition

10.1 Surveying

In surveying, measured angles at, and distances from, known points in a coordinate system are used to determine the positions of other points (Figure 10.1). Surveying field data are almost always set out in polar coordinates, which may be transformed to rectangular coordinates using the relationships

Heights are computed from horizontal or inclined distances (Figure 10.2). Vertical angles are computed from known points to new points, or vice versa. The corresponding transformations between polar and rectangular coordinates are

Surveying has traditionally produced numerical data in the form of angles measured by transits and theodolites and distances measured by tapes and chains. Starting in the 1950s, however, the traditional optical and mechanical tools of the surveying trade were gradually supplanted by more accurate electronic and electro-optical devices for measuring distances. Modern surveying is computerized: A total station theodolite, as illustrated in Figure 10.3, can now store and process digital measurement data either in the field or, subsequently, ...