Editing Inch (section)

==Related units==

===US survey inches===
The United States retained the {{sfrac|1|39.37}}-metre definition for surveying, producing a 2 millionth part difference between standard and [[United States customary units#Length|US survey]] inches.<ref name = Astin>A. V. Astin & H. Arnold Karo, (1959), [http://www.ngs.noaa.gov/PUBS_LIB/FedRegister/FRdoc59-5442.pdf ''Refinement of values for the yard and the pound''], Washington DC: National Bureau of Standards, republished on National Geodetic Survey web site and the Federal Register (Doc. 59-5442, Filed, 30 June 1959, 8:45&nbsp;am)</ref> This is approximately {{sfrac|1|8}}&nbsp;inch per mile; 12.7 kilometres is exactly {{Nts|500000}} standard inches and exactly {{Nts|499999}} survey inches. This difference is substantial when doing calculations in [[State Plane Coordinate System]]s with coordinate values in the hundreds of thousands or millions of feet.

In 2020, the [[National Institute of Standards and Technology]] announced that the U.S. survey foot would "be phased out" on 1 January 2023 and be superseded by the international foot (also known as the foot) equal to 0.3048&nbsp;metres exactly, for all further applications.<ref>{{Cite web|url=https://www.nist.gov/pml/us-surveyfoot|title=U.S. Survey Foot|last=Materese|first=Robin|date=26 July 2019|website=NIST|language=en|access-date=1 February 2020}}</ref> This implies that the survey inch was replaced by the international inch.

===Continental inches===
{{Main|Roman inch|French inch}}
Before the adoption of the metric system, several European countries had customary units whose name translates into "inch". The French ''[[pouce]]'' measured roughly 27.0&nbsp;mm, at least when applied to describe the calibre of artillery [[Cannon|pieces]]. The [[Dutch units of measurement|Amsterdam foot]] (''voet'') consisted of 11 Amsterdam inches (''duim''). The Amsterdam foot is about 8% shorter than an English foot.<ref>*{{cite book
|url = {{google book|id=XYVbAAAAQAAJ|page=166|plain-url=yes}}
|title = Allereerste Gronden der Cijferkunst
|first = Jacob
|last = de Gelder
|location = The Hague <!-- Dutch: 's Gravenhage and Amsterdam -->
|language = nl
|year = 1824
|pages = 166
|publisher = de Gebroeders van Cleef
|trans-title=Introduction to Numeracy
|access-date = 10 April 2022}}
</ref>

=== Scottish inch ===
The now obsolete [[Obsolete Scottish units of measurement|Scottish inch]] ({{langx|gd|òirleach}}), {{sfrac|12}} of a Scottish foot, was about 1.0016 imperial inches (about {{convert|1.0016|in|mm|disp=output only}}).<ref>{{cite web
|url =https://dsl.ac.uk/entry/snd/snds3729
|title = Dictionary of the Scots Language
|publisher = Scottish Language Dictionaries
|location = Edinburgh
|access-date =22 January 2020}}</ref>