Editing Fathom (section)

==Forms==
{{anchor|Greek|Orguia|Greek fathom|Greek fathoms}}<!--linked-->

===Ancient fathoms===
The [[Ancient Greek units of measurement|Ancient Greek measure]] known as the '''orguia''' ({{langx|grc|ὀργυιά}}, ''orgyiá'', <small>{{abbr|lit|literally}}.</small>{{nbsp}}"outstretched") is usually translated as "fathom".<ref>{{citation |contribution-url=http://biblehub.com/greek/3712.htm |contribution=3712. orguia |title=Bible Hub |date=2016 }}.</ref> By the [[Byzantine Empire|Byzantine period]], this [[Byzantine units of measurement|unit]] came in two forms: a "simple orguia" ({{lang|grc|ἁπλὴ ὀργυιά}}, ''haplē orguiá'') roughly equivalent to the old Greek fathom (6 [[Byzantine units#Length|Byzantine feet]], {{c.|1.87}}{{nbsp}}[[meter (unit)|m]]) and an "imperial" ({{lang|grc|βασιλικὴ}}, ''basilikē'') or "geometric orguia" ({{lang|grc|γεωμετρικὴ ὀργυιά}}, ''geōmetrikē orguiá'') that was one-eighth longer (6 feet and a [[palmspan|span]], {{c.|2.10}}{{nbsp}}m).<ref>{{Citation |last=Loizos |first=Demetris I. |title=Digital Humanities: Diophant Ancient Measures Converter |contribution-url=http://www.anistor.gr/history/Byzantine_Units.pdf |contribution=Byzantine Measures |date=2010 |access-date=6 April 2015 |pages=1–2 }}.</ref><ref>{{citation |last=Schilbach |first=E. |author2=A. Cutler |display-authors=1 | editor-first = Alexander | editor-last = Kazhdan |editor-link=Alexander Kazhdan |display-editors=0 | encyclopedia = [[The Oxford Dictionary of Byzantium]] | publisher = Oxford University Press | year = 1991 | isbn = 978-0-19-504652-6 | ref={{harvid|ODB}} |contribution=Orgyia |pages=1532–1533 }}.</ref>

=== International fathom ===
One  international fathom is equal to:
* 1.8288 [[metre]]s exactly (Official international definition of the fathom)<ref>{{cite book|title=Admiralty Manual of Seamanship|year=1995|publisher=[[HMSO]]|isbn=0-11-772696-6|page=1·19|chapter=Sea measures}}</ref>
=== British fathom ===
The [[British Admiralty]] defined a fathom to be a thousandth of an [[Nautical mile|imperial nautical mile]] (which was 6080&nbsp;ft) or {{convert|6.08|ft|m}}. In practice the "warship fathom" of exactly {{convert|6|ft|m}} was used in Britain and the United States.<ref name=Fenna/> No conflict between the definitions existed in practice,{{citation needed|date=July 2023}} since depths on imperial nautical charts were indicated in feet if less than {{convert|30|ft|m}} and in fathoms for depths greater than that. Until the 19th century in England, the length of the fathom was more variable: from {{frac|5|1|2}}&nbsp;feet on merchant vessels to either {{convert|5|or|7|ft|m}} on fishing vessels (from {{convert|5+1/2|to|5|or|7|ft|m|disp=output only}}).<ref name=Fenna>Fenna (2000: 88-89)</ref>

=== Other definitions ===
Other definitions of fathom include:
* 1.828804&nbsp;m (Obsolete measurement of the fathom based on the [[US survey foot]], only for use of historical and legacy applications)<ref>[https://www.nist.gov/physical-measurement-laboratory/nist-guide-si-appendix-b NIST Guide to the SI, Appendix B: Conversion Factors]</ref>
* 2 [[yard]]s exactly
* 18 [[Hand (unit)|hands]]

One metre is about 0.5468 fathoms

In the [[international yard and pound]] agreement of 1959 the [[United States]], [[Australia]], [[Canada]], [[New Zealand]], [[South Africa]], and the [[United Kingdom]] defined the length of the international yard to be exactly 0.9144 [[metre]]. In 1959 United States kept the US survey foot as definition for the fathom.

In October 2019, the [[U.S. National Geodetic Survey]] and the [[National Institute of Standards and Technology]] announced their joint intent to retire the U.S. survey foot, with effect from the end of 2022. The fathom in U.S. Customary units is thereafter defined based on the International 1959 foot, giving the length of the fathom as exactly 1.8288 metres in the United States as well.<ref>{{cite web |title=NGS and NIST to Retire U.S. Survey Foot after 2022 |url=https://www.ngs.noaa.gov/web/news/us-survey-foot.shtml |publisher=National Geodetic Survey |access-date=4 March 2020 |date=31 October 2019}}</ref><ref>{{cite web |title=U.S. Survey Foot: Revised Unit Conversion Factors |url=https://www.nist.gov/pml/us-surveyfoot/revised-unit-conversion-factors |publisher=NIST |access-date=4 March 2020 |date=16 October 2019}}</ref>