surveying

Method of making relatively large-scale, accurate measurements of the earth's surfaces. Its principal modern uses are in the fields of transportation, building, land use, and communications. Surveying is divided into the categories of plane surveying (mapping small areas) and geodetic surveying (mapping large areas of the globe). The Romans are said to have used the plane table, which consists of a drawing board mounted on a tripod or other support and a straightedge along which lines are drawn. It was the first device capable of recording or establishing angles. With the publication of logarithmic tables in 1620, portable angle-measuring instruments, called topographic instruments, or theodolites, came into use; they included pivoted arms for sighting and could be used for measuring both horizontal and vertical angles. Two revolutionary 20th-century innovations were photogrammetry (mapping from aerial photographs) and electronic distance measurement, including the use of the laser.

Find more information on surveying. Upgrade to Britannica Online for more on surveying.