Editing Mile (section)

==US survey <span class="anchor" id="U.S. survey mile"></span>==
{{For|the detailed calculations of international miles to survey miles and feet (above)|#International}}
The '''US survey mile''' is 5,280 [[U.S. survey foot|US survey feet]], or 1,609.347 metres and 0.30480061 metres respectively.<ref>{{cite web |title=Appendix E. General Tables of Units of Measurement |url=https://www.nist.gov/document-2382 |access-date=14 January 2020}} (links to a Microsoft Word document)</ref> Both are very slightly longer than the [[international mile]] and [[international foot]]. In the United States, the term ''statute mile'' formally refers to the survey mile,{{sfnp|Thompson|2008|loc=B.6.}} but for most purposes, the difference of less than {{convert|1/8|in|mm}} between the survey mile and the international mile (1609.344&nbsp;metres exactly) is insignificant—one international mile is {{val|0.999998}} US survey miles—so ''statute mile'' can be used for either. But in some cases, such as in the US [[State Plane Coordinate System]]s (SPCSs), which can stretch over hundreds of miles,<ref name="NGS-FAQ">{{cite web | title = What are the 'official' conversions that are used by NGS to convert 1) metres to inches, and 2) metres to feet? | url = http://www.ngs.noaa.gov/faq.shtml#Feet | id = Frequently Asked Questions about the National Geodetic Survey | author = US National Geodetic Survey | access-date = 16 May 2009 | archive-date = 5 September 2015 | archive-url = https://web.archive.org/web/20150905054504/http://www.ngs.noaa.gov/faq.shtml#Feet | url-status = live }}</ref> the accumulated difference can be significant, so it is important to note that the reference is to the US survey mile.

The United States redefined its yard in 1893, and this resulted in US and Imperial measures of distance having very slightly different lengths.

The [[North American Datum]] of 1983 (NAD83), which replaced the NAD27, is defined in metres. State Plane Coordinate Systems were then updated, but the [[National Geodetic Survey]] left individual states to decide which (if any) definition of the foot they would use. All State Plane Coordinate Systems are defined in metres, and 42 of the 50 states only use the metre-based State Plane Coordinate Systems. However, eight states also have State Plane Coordinate Systems defined in feet, seven of them in US survey feet and one in international feet.<ref name="NGS-FAQ" />

State legislation in the US is important for determining which conversion factor from the metric datum is to be used for land surveying and real estate transactions, even though the difference (2&nbsp;[[Parts per million|ppm]]) is hardly significant, given the precision of normal surveying measurements over short distances (usually much less than a mile). Twenty-four states have legislated that surveying measures be based on the US survey foot, eight have legislated that they be based on the international foot, and eighteen have not specified which conversion factor to use.<ref name="NGS-FAQ" />

SPCS 83 legislation refers to state legislation that has been passed or updated using the newer 1983 NAD data. Most states have done so. Two states, [[Alaska]] and [[Missouri]], and two jurisdictions, [[Guam]] and [[Puerto Rico]], do not specify which foot to use.<ref name="NGS-FAQ" /> Two states, [[Alabama]] and [[Hawaii]], and four jurisdictions, [[Washington, DC]], [[United States Virgin Islands|US Virgin Islands]], [[American Samoa]] and [[Northern Mariana Islands]], do not have SPCS 83 legislation.<ref name="NGS-FAQ" />

In October 2019, [[US National Geodetic Survey]] and [[National Institute of Standards and Technology]] announced their joint intent to retire the US survey foot and US survey mile, as permitted by their 1959 decision, with effect on January 1, 2023.<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 |archive-date=27 May 2021 |archive-url=https://web.archive.org/web/20210527213329/https://www.ngs.noaa.gov/web/news/us-survey-foot.shtml |url-status=live }}</ref><ref>{{cite journal |title=U.S. Survey Foot: Revised Unit Conversion Factors |url=https://www.nist.gov/pml/us-surveyfoot/revised-unit-conversion-factors |journal=NIST |access-date=4 March 2020 |date=16 October 2019 |archive-date=2 March 2020 |archive-url=https://web.archive.org/web/20200302225408/https://www.nist.gov/pml/us-surveyfoot/revised-unit-conversion-factors |url-status=live }}</ref><ref>{{cite web | url=https://www.federalregister.gov/documents/2020/10/05/2020-21902/deprecation-of-the-united-states-us-survey-foot | title=Federal Register :: Request Access | date=5 October 2020 | access-date=5 July 2022 | archive-date=21 December 2022 | archive-url=https://web.archive.org/web/20221221184624/http://www.federalregister.gov/documents/2020/10/05/2020-21902/deprecation-of-the-united-states-us-survey-foot | url-status=live }}</ref>