Angle measuring instruments

thumb|A sextant

thumb|A direct-readout theodolite, manufactured in the Soviet Union in 1958 and used for topographic surveying

thumb|Goniometer made by Develey le Jeune in Lausanne, late 18th–early 19th century

navigation instrument

measuring instrument used primarily in navigation; type of reflecting instrument

calibrated wooden rod with sliding crosspiece used for measuring the altitude of celestial bodies or the height of distant objects

thumb|Graphic reconstruction of the dioptra, by Venturi, in 1814. (An incorrect interpretation of Heron's description)

thumb|Butterfield compass graphometer thumb|A German graphometer in Göttingen, Stadtmuseum. The instrument is on its side. At the back, the socket for a Jacob's staff can be seen. The graphometer, semicircle or semicircumferentor is a surveying instrument used for angle measurements. It consists of a semicircular limb divided into 180 degrees and sometimes subdivided into minutes. The limb is subtended by the diameter with two sights at its ends. In the middle of the diameter a "box and needle" (compass) is fixed. On the same middle the alidade with two other sights is fitted. The device is mo

angle-measuring device used for astronomical purposes