Theodolite

A precision instrument that measures horizontal and vertical angles. Surveyors use these measurements to establish directions, map positions, and set out construction work.

Telescope: An optical instrument that gathers light to make distant objects appear clearer or larger. The theodolite’s telescope aims at a target whose direction is measured.
Surveying: The science and practice of determining positions, distances, and boundaries on or near Earth’s surface. Theodolites are instruments within the broader practice of surveying.
Topographic survey: A survey that maps terrain, elevations, and natural or constructed features. Angular observations help locate mapped features relative to survey control points.
Total station: A surveying instrument combining an electronic theodolite, distance measurement, and onboard computation. It extends theodolite angle measurement by measuring distances and calculating coordinates.
Horizontal circle: A graduated circular scale used to measure angles in a horizontal plane. It records azimuth changes as the instrument turns around its vertical axis.
Angle: The geometric measure of the separation between two intersecting lines or rays. Theodolite readings are measurements of horizontal and vertical angles.
Construction staking: The transfer of planned positions and dimensions from design documents to a construction site. Theodolites set out building lines and other directions from established control.
Transit (surveying instrument): A surveying telescope instrument designed to rotate fully in the vertical plane. The transit is a related design, often distinguished by its ability to reverse the telescope.
Vertical circle: A graduated circular scale used to measure angles above or below the horizontal plane. It measures the telescope’s elevation or depression toward a target.
Azimuth: A horizontal direction measured as an angle clockwise from a reference direction, commonly north. A horizontal-circle reading can express the direction from a survey station to a target.

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