Theodolite

This theodolite, kept at the KIT Geodetic Institute, represents here the activities of engineer Johann Gottfried Tulla (1770–1828). Tulla initiated the channelization of the Upper Rhine and founded a predecessor to the current KIT Department of Civil Engineering, Geodesy and Environmental Sciences. Surveying the course of the Rhine was a necessary precondition for its straightening, as was mapping the Grand Duchy of Baden for many road-building projects, which was carried out under his direction. Tulla recognized that a dedicated school was needed to train specialists for the state’s construction projects. This insight was behind the proposal first submitted in 1808 by a government commission with Tulla’s participation, to establish a polytechnical school in Karlsruhe. Initially, however, the engineers received their training in a separate school which had been set up at Tulla’s instigation in the Waterway and Road Building Office in 1807. After his death, this engineering school became an independent school within Karlsruhe Polytechnical College. Theodolites are used for measuring angles in land surveying. In a process known as triangulation, the surveyor begins by taking the angles formed between a measured straight distance on the terrain and the lines of sight to a third point, such as a church tower, extending from both ends of this distance. Using the measured distance and these two angles, the lengths of the sight lines can be calculated as the other sides of a triangle. Additional triangles can be drawn from these side lengths, their other side lengths calculated, and a successive network of triangles can be formed without taking any more length measurements. A repeating theodolite as shown here takes serial measurements of the same angle, and each value is added by advancing the ring-shaped movable graduated scale. The multiplied measurement value is then divided by the number of repetitions to achieve greater accuracy. kn