|Also called (in the US and Canada): transit a surveying instrument for measuring horizontal and vertical angles, consisting of a small tripod-mounted telescope that is free to move in both the horizontal and vertical planes|
|[C16: from New Latin theodolitus, of uncertain origin]|
|theodolite (thē-ŏd'l-īt') Pronunciation Key
An optical instrument used to measure angles in surveying, meteorology, and navigation. In meteorology, it is used to track the motion of a weather balloon by measuring its elevation and azimuth angle. The earliest theodolite consisted of a small mounted telescope that rotated horizontally and vertically; modern versions are sophisticated computerized devices, capable of tracking weather balloons, airplanes, and other moving objects, at distances of up to 20,000 m (65,600 ft).