theodolieten

Theodolieten, or theodolites, are precision surveying instruments designed to measure horizontal and vertical angles between points. They are mounted on a tripod and consist of a telescope that can rotate around a horizontal axis and a vertical circle, with graduated scales or digital readouts, plus a leveling base and a supporting trivet to keep the instrument stable. The main measurements are horizontal angles (bearings) and vertical angles (elevations or zenith angles). The instrument is aligned with a reference direction, often using a compass or meridian line, and readings are taken by rotating the telescope and reading the scales through the eyepiece. Modern theodolites may be digital or electronic and may incorporate an electronic distance measurement (EDM) unit; traditional instruments used verniers or micrometers for precise readings.

Theodolites are used in land surveying, construction, civil engineering, and mapping, for tasks such as triangulation, layout of structures, and alignment of roads and tunnels. They require careful setup: placed on a stable tripod, leveled with a circular spirit level, and accurately centered over a known point with a plumb line or optical plummet.

History and evolution: Theodolites emerged in the 17th century as refinements of earlier angle-measuring devices and were developed by instrument makers across Europe. They became standard surveying tools in the 18th and 19th centuries and remained widely used into the late 20th century, increasingly complemented or replaced in many applications by digital total stations that combine angle measurement with distance measurement and data processing.