Editing Odometer (section)

=== Classical Era ===
[[File:Vitruve's odometer, 1st century BC, Roma (reconstruction).jpg|thumb|Reconstruction of [[Vitruvius]]' odometer, 1st century BC, Roma, [[Thessaloniki Science Center and Technology Museum]]]]
[[File:Odometer of Archimedes, Kotsanas Museum of Ancient Greek Archaeology.jpg|left|thumb|A reconstruction of [[Hero of Alexandria|Hero]]' odometer, 1st century AD, Alexandria, in [[Museum of Ancient Greek Technology|Kotsanas Museum of Ancient Greek Technology]], Athens, Greece.]]
Possibly the first evidence for the use of an odometer can be found in the works of the ancient Roman [[Pliny the Elder|Pliny]] (NH 6. 61-62) and the ancient Greek [[Strabo]] (11.8.9). Both authors list the distances of routes traveled by [[Alexander the Great]] (r. 336-323 BC) as by his [[bematist]]s Diognetus and Baeton. However, the high accuracy of the bematists's measurements rather indicates the use of a mechanical device. For example, the section between the cities Hecatompylos and Alexandria Areion, which later became a part of the [[Silk Road]], was given by Alexander's bematists as 575 [[Roman mile]]s (529 [[Mile|English miles]]) long, that is with a deviation of 0.2% from the actual distance (531 English miles). From the nine surviving bematists' measurements in Pliny's ''[[Natural History (Pliny)|Naturalis Historia]]'' eight show a deviation of less than 5% from the actual distance, three of them being within 1%. Since these minor discrepancies can be adequately explained by slight changes in the tracks of roads during the last 2300 years, the overall accuracy of the measurements implies that the bematists already must have used a sophisticated device for measuring distances, although there is no direct mention of such a device.

An odometer for measuring distance was first described by [[Vitruvius]] during the 1st century BC. According to André Wegener Sleeswyk, the actual inventor may have been [[Archimedes of Syracuse]] (c. 287 BC – {{circa|212&nbsp;BC}}).<ref>{{Cite journal |last=Sleeswyk |first=André Wegener |date=1981 |title=Vitruvius' Odometer |url=https://www.jstor.org/stable/24964584 |journal=Scientific American |volume=245 |issue=4 |pages=188–201 |doi=10.1038/scientificamerican1081-188 |jstor=24964584 |bibcode=1981SciAm.245d.188S |issn=0036-8733}}</ref> However, this mention is unjustified and nothing concerns the odometer in the preserved treatises of Archimedes.<ref>{{Cite journal |first=Philippe |last=Fleury |title=Odomètre terrestre de Vitruve |newspaper=Le Plan de Rome, Maison de la Recherche en Sciences Humaines Université de Caen Normandie |date=2021 |url=https://rome.unicaen.fr/machine/odometreterrevitruve/ |accessdate=2025-05-07}}</ref> [[Hero of Alexandria]] (10 AD – 70 AD) describes a similar device in chapter 34 of his ''[[Dioptra]]''. The machine was also used in the time of Roman Emperor [[Commodus]] ({{circa|192&nbsp;AD}}), although after this point in time there seems to be a gap between its use in Roman times and that of the 15th century in Western Europe.{{sfn | Needham | 1965 | p=285}} Some researchers have speculated that the device might have included technology similar to that of the Greek [[Antikythera mechanism]].<ref name="autogenerated188">{{cite journal | bibcode=1981SciAm.245d.188S | title=Vitruvius' Odometer | date=October 1981 | last=Sleeswyk | first=André Wegener | journal=[[Scientific American]] | volume=245 | issue=4 | pages=188–200 | issn=0036-8733 | doi=10.1038/scientificamerican1081-188}}</ref>

The odometer of Vitruvius was based on chariot wheels of 4 Roman feet (1.18 m) diameter turning 400 times in one Roman mile (about 1,480&nbsp;m). For each revolution a pin on the axle engaged a 400-tooth cogwheel thus turning it one complete revolution per mile. This engaged another gear with holes along the [[circumference]], where pebbles (''[[Jeton#Roman calculi|calculus]]'') were located, that were to drop one by one into a box. The distance traveled would thus be given simply by counting the number of pebbles.<ref name="autogenerated188" /> Whether this instrument was ever built at the time is disputed. [[Leonardo da Vinci]] later tried to build it himself according to the description, but failed. However, in 1981 engineer Andre Sleeswyk built his own replica, replacing the square-toothed gear designs of Leonardo with the triangular, pointed teeth found in the ''Antikythera mechanism''. With this modification, the Vitruvius odometer functioned perfectly.<ref name="autogenerated188" />