The Chorobates or Chorobat (from Gr. Χωροβἀτης, from χῶρος chōros "place" and βἀτης bátēs " walker ") was a surveying instrument in ancient Rome . It can also be called a measuring beam and is an early form of a leveling device .
There is only one description of Vitruvius (Vitruvius: Ten books on architecture 8,5, 1–3), there are no sketches or even preserved finds. However, many considerations have been made about its appearance and mode of operation. B. by Leonardo da Vinci .
The chorobat consisted of a 20 foot long beam (wooden beam) with vertical supports (legs) at its ends. The chorobat was mostly made entirely of wood and was either leveled with plumb bobs or z. B. in the wind by observing the level in a water-filled channel on the carrier. The girder and its two vertical supports were also connected to one another by inclined struts on which markings were made, which served to align the device horizontally with the plumb bobs. In addition, contrary to previous assumptions, he had no sighting aid.
The name “Chorobates” (German: “On the floor walking along”), which comes from ancient Greek, already provides information about the use of the device: One set-up was lined up with the other, with the Chorobat used like a large spirit level and without a sighting aid for each The setup was rotated 180 ° and placed with the same leg on the last stake (intermediate point) of the previous setup. As a result of this rotation, all instrument errors caused by manufacturing inaccuracies were eliminated, since they entered the measurement with the opposite sign every second setup. This made the high-precision leveling of the Romans possible. With each set-up, the difference in height on one of the two Chorobates legs could be measured with a measuring stick and recorded. The record was omitted if you measured along a contour line. In addition, the entire length of the route could be derived from the length of the chorobat.
Use of the chorobat with sighting device as a kind of leveling device was unlikely because of the errors that occurred and the much more difficult and complex handling. A horizontal bearing on a special measuring stick with a movable target would have been necessary along the upper edge of the carrier or possibly attached sighting aids . In order to achieve a high level of accuracy, it would have required special precision in the manufacture of the device and, because of the remaining instrument errors, leveling with the same target distances. The idea of using a sighting aid was based on many attempts at reconstruction since Leonardo da Vinci, i.e. since the Renaissance , but these were essentially new developments in equipment.
- Klaus Grewe : Chorobat and Groma. New thoughts on the reconstruction and handling of the two most important measuring devices of ancient engineers , in: Bonner Jahrbücher , Vol. 209 (2009), pp. 109–128.
- Klaus Grewe: Aqueducts. Water for Rome's cities. The big overview - from the Roman Canal to the aqueduct marble. Regionalia Verlag, Rheinbach 2014, ISBN 978-3-95540-127-6 , p. 31 ff.
- Curt Fensterbusch : Vitruvius. Ten books on architecture. Latin and German. Translated and annotated by Curt Fensterbusch. 6th edition 2008. Wissenschaftliche Buchgesellschaft, Darmstadt, ISBN 978-3-534-21964-3 , p. 391 f.
- Klaus Grewe: Aqueducts. Water for Rome's cities. 2014, p. 35.
- See Klaus Grewe: Aqueducts. Water for Rome's cities. 2014, p. 31 ff.
- Flicker: Chorobates