chain (unit)

The UK statute chain is 22 yards, which is {{convert|66|feet|4}}. This unit is a statute measure in the United Kingdom, defined in the Weights and Measures Act 1985.

{{Cite web |title=Weights and Measures Act 1985 |url=http://www.legislation.gov.uk/ukpga/1985/72/schedule/1/part/VI |website=Legislation.gov.uk |access-date=25 September 2014 |at=Sch 1, Part VI }} One link is a hundredth part of a chain, which is {{convert| 7.92|inch|cm|4}}.

The surveyor's chain first appears in an illustration in a Dutch map of 1607,{{cite web |last1=Corneliisz van Alckmaer |first1=Pieter |title="Caerte vande gheleghentheyt van de Beemster met de landen die daeromme ende aengheleghen zijn, na rechte landmetersch conste op perfecte maet aldus ghestelt door Pieter Cornelisz. Cort van Alckmaer, ghesworen landmeter, anno 1607". Het Schermereiland met links een deel van de onbedijkte Schermer en rechts de onbedijkte Beemster. |url=https://www.regionaalarchiefalkmaar.nl/collecties/beelden/beelden-2/detail/9a5bede0-ce28-4584-9494-06c0abef1af9 |website=Regional Archive, Alkmaar |access-date=29 July 2018 |language=nl}} and in an English book for surveyors of 1610.{{cite encyclopedia |encyclopedia=Oxford English Dictionary |date=1933 |entry=Chain (5) |volume=2 |page=248 |url=https://archive.org/details/the-oxford-english-dictionary-1933-all-volumes/The%20Oxford%20English%20Dictionary%20Volume%202/page/248/mode/1up |quote=1610 W. F{{sc|olkingham}}, Art Survey. |title=The Oxford English Dictionary - 1933 - All Volumes }} In 1593 the English mile was redefined by a statute of Queen Elizabeth I as 5,280 feet, to tie in with agricultural practice. In 1620, the polymath Edmund Gunter developed a method of accurately surveying land using a surveyor's chain 66 feet long with 100 links.{{cite web |title=Gunter biography |url=http://www-history.mcs.st-andrews.ac.uk/Biographies/Gunter.html |website=www-history.mcs.st-andrews.ac.uk |access-date=21 July 2018}} The 66-foot unit, which was four perches or rods,{{cite web |last1=Slater |first1=Michael |last2=Saunders |first2=Ian |title=Rods, poles and perches |url=http://www.northcravenheritage.org.uk/nchtjournal/Journals/2006/RodsPolesPerches/RodsPolesPerches.html |website=www.northcravenheritage.org.uk |publisher=North Craven Heritage Journal |access-date=29 July 2018}} took on the name the chain. By 1675 it was accepted, and Ogilby wrote:

{{blockquote|

...a Word or two of Dimensurators or Measuring Instruments, whereof the most usual has been the Chain, and the common length for English Measures 4 Poles, as answering indifferently to the English Mile and Acre, 10 such Chains in length making a Furlong, and 10 single square Chains an Acre, so that a square Mile contains 640 square Acres...'{{cite book |title=Britannia |chapter=Preface |chapter-url=https://www.fulltable.com/vts/m/map/ogilby/a/SH947.jpg |date=1675 |via=Fulltable.com}} |source=John Ogilby, Britannia, 1675}}

From Gunter's system, the chain and the link became standard surveyors' units of length and crossed to the colonies. The thirteen states of America were expanding westward and the public land had to be surveyed for a cadastral. In 1784 Thomas Jefferson wrote a report for the Continental Congress proposing the rectangular survey system; it was adopted with some changes as the Land Ordinance of 1785 on 20 May the following year. In the report, the use of the chain as a unit of measurement was mandated, and the chain was defined.{{cite web |last1=Cazier |first1=Lola |title=Surveys and Surveyors of the Public Domain 1785-1975 |url=https://www.ntc.blm.gov/krc/uploads/538/Sur_Sur_Pub_Dom.pdf |publisher=US Government |access-date=29 July 2018 |id=Stock Number 024-041-00083-6 |page=22}}

{{blockquote|1=

The chain is the unit of linear measurement for the survey of the public lands as prescribed by law. All returns of measurement in the rectangular system are made in the true horizontal distance in links, chains, and miles. The only exceptions to this rule are special requirements for measurement in feet in mineral surveys and townsite surveys.

Linear Measurement

:1 Chain = 100 links or 66 feet

:1 Mile = 80 chains or 5,280 feet

Area Measurement

:1 Acre = 10 square chains or 43,560 square feet

:1 square mile = 640 acres

|source = Lola Cazier (1976), Surveys and Surveyors of the Public Domain 1785-1975, page 15}}

{{further|Milestone|Linear referencing}}

Image:Bridge miles and chains.jpg

In the United Kingdom, the chain is no longer used for practical survey work.Plane and Geodetic Surveying, A.L. Johnson (SPON) However, it is still used on the railways as a location identifier. When railways were designed, the location of features such as bridges and stations was indicated by a cumulative longitudinal "mileage", using miles and chains, from a zero point at the origin or headquarters of the railway, or the originating junction of a new branch line. Since railways are linear in topology, the "mileage" or "chainage" is sufficient to identify a place uniquely on any given route. Thus, a given bridge location may be indicated as 112 miles and 63 chains (181.51 km) from the origin. In the case of the photograph, the bridge is near Keynsham, which is that distance from London Paddington station. The indication "MLN" after the mileage is the Engineer's Line Reference describing the route as the Great Western Main Line, which is needed to uniquely determine the bridge, as there may be points at 112 miles 63 chains on other routes.

On new railway lines built in the United Kingdom such as High Speed 1, the position along the alignment is still referred to as "chainage", although the value is now expressed in metres.[http://assets.dft.gov.uk/publications/hs2-maps-20120110/hs2arp00drrw05022issue4.pdf HS2 proposed alignment with chainages expressed in metres]

The use of the chain was mandatory in laying out US townships. A federal law was passed in 1785 (the Public Land Survey Ordinance) that all official government surveys must be done with a Gunter's (surveyor's) chain. Chains and links are commonly encountered in older metes and bounds legal descriptions. Distances on township plat maps made by the US General Land Office are shown in chains.

Under the US Public Land Survey System, parcels of land are often described in terms of the section ({{convert|640|acre|ha|0|disp=or}}), quarter-section ({{convert|160|acre|ha|1|disp=or}}), and quarter-quarter-section ({{convert|40|acre|ha|2|disp=or}}). Respectively, these square divisions of land are approximately 80 chains (one mile or 1.6 km), 40 chains (half a mile or 800 m), and 20 chains (a quarter mile or 400 m) on a side.

The chain is still used in agriculture: measuring wheels with a circumference of 0.1 chain (diameter ≈ 2.1 ft or 64 cm) are still readily available in Canada and the United States. For a rectangular tract, multiplying the number of turns of a chain wheel for each of two adjacent sides and dividing by 1,000 gives the area in acres.

In Canada, road allowances were originally 1 chain wide and are now 20 metres.{{cite news |last1=Lakey |first1=Jack |title=Turns out there is a standard to determine where a homeowner's property ends: The Fixer |url= https://www.thestar.com/yourtoronto/the_fixer/2017/06/21/turns-out-there-is-a-standard-to-determine-where-a-homeowners-property-ends-the-fixer.html |access-date=22 June 2017 |work=Toronto Star |date=21 June 2017}}

The unit was also used in mapping the United States along train routes in the 19th century. Railroads in the United States have long since {{when|date=July 2018}} used decimal fractions of a mile. Some subways such as the New York City Subway and the Washington Metro were designed with and continue with a chaining system using the 100-foot engineer's chain.{{Cite web|url=https://issuu.com/erausa/docs/2017-01-bulletin|title=The ERA Bulletin 2017-01|date=January 18, 2017|website=Issuu|publisher=Electric Railroaders' Association|access-date=January 18, 2017}}

In the United States, the chain is also used as the measure of the rate of spread of wildfires (chains per hour), both in the predictive National Fire Danger Rating System as well as in after-action reports. The term chain is used by wildland firefighters in day-to-day operations as a unit of distance.[http://www.fs.fed.us/psw/publications/documents/psw_gtr090/psw_gtr090.pdf Documents]

In Australia and New Zealand, most building lots in the past were a quarter of an acre, measuring one chain by two and a half chains, and other lots would be multiples or fractions of a chain.{{cite book|author=George Seddon|title=Landprints: Reflections on Place and Landscape|url=https://books.google.com/books?id=ZIAR6EvER2AC&pg=PA151|access-date=28 May 2013|date=28 September 1998|publisher=Cambridge University Press|isbn=978-0-521-65999-4|pages=151–}} The street frontages of many houses in these countries are one chain wide—roads were almost always {{convert|1|chain|m|1}} wide in urban areas, sometimes {{convert|1.5|chain|m|1}} or {{convert|2.5|chain|m|1}}. Laneways would be half a chain (10.1 m). In rural areas the roads were wider, up to {{convert|10|chain|m|1}} where a stock route was required. {{convert|5|chain|m|1}} roads were surveyed as major roads or highways between larger towns, {{convert|3|chain|m|1}} roads between smaller localities,{{cite web|last=Lay|first=M. G.|title=Roads|url=http://www.emelbourne.net.au/biogs/EM01255b.htm|work=emelbourne the city past and present|publisher=School of Historical Studies Department of History, The University of Melbourne|access-date=28 May 2013|date=July 2008}} and {{convert|2|chain|m|1}} roads were local roads in farming communities. Roads named Three Chain Road etc. persist today.{{cite web |title=375 THREE CHAIN ROAD, Kilmore, Vic 3764 - Property Details |url=https://www.realestate.com.au/sold/property-livestock-vic-kilmore-7908210 |website=www.realestate.com.au |access-date=8 August 2018 |language=en-AU}}{{cite web |title=Map of Three Chain Road in Queensland - Bonzle Digital Atlas of Australia |url=http://www.bonzle.com/c/a?a=p&p=173789&cmd=sp |website=www.bonzle.com |access-date=8 August 2018}}

The "Queen's Chain" is a concept that has long existed in New Zealand, of a strip of public land, usually 20 metres (or one chain in pre-metric measure) wide from the high water mark, that has been set aside for public use along the coast, around many lakes, and along all or part of many rivers.{{cite web|url=https://en.oxforddictionaries.com/definition/queen%27s_chain|archive-url=https://web.archive.org/web/20180808172201/https://en.oxforddictionaries.com/definition/queen%27s_chain|url-status=dead|archive-date=August 8, 2018|access-date=4 July 2017|title=Queen's Chain|publisher=Oxford Dictionaries – oxforddictionaries.com}}{{cite web|url=http://www.nzherald.co.nz/nz/news/article.cfm?c_id=1&objectid=3517579|access-date=4 July 2017|title=Truth behind the Queen's Chain|date=12 August 2003|publisher=The New Zealand Herald }} These strips exist in various forms (including road reserves, esplanade reserves, esplanade strips, marginal strips and reserves of various types) but not as extensively and consistently as is often assumed.{{Cite web|url=http://www.teara.govt.nz/en/law-of-the-foreshore-and-seabed/page-3|title=Te Ara, Encyclopedia of New Zealand}}

The chain also survives as the length of a cricket pitch, being the distance between the stumps.{{cite web|url=https://www.espncricinfo.com/story/_/id/23233624/the-measurements-cricket |title=The measurements of cricket |work=ESPN Cricinfo |access-date=19 February 2020}}{{cite web|url=https://www.bbc.co.uk/bitesize/guides/zpcg4j6/revision/2 |title=Cricket - factfile |work=BBC Bitesize |access-date=19 February 2020}}

Civil engineers and surveyors use various instruments including chains to measure distance.{{cite book |last1=Punmia |first1=B. C. |last2=Jain |first2=A. K. |last3=Jain |first3=A. K. |year=2003 |title=Basic civil engineering |publisher=Laxmi Publications |location=New Delhi |isbn=9788170084037 |oclc=1006316184}} Other instruments used for measuring distance include tapes and bands. A steel band is also known as a "band chain".[https://theconstructor.org/surveying/types-of-chains-surveying/13889/ Types of Chains used in Surveying, Their Parts, Testing and Advantages]

{{main|Gunter's chain}}

{{anchor|Gunter's chain}}

In 1620, the polymath Edmund Gunter developed a method of accurately surveying land using a 100 link chain, 22 yards (66 feet) long, called the Gunter's Chain. Other surveyors chains have been used historically.

{{anchor|Ramsden's chain (engineer's chain)}}

{{main|Ramsden surveying instruments#Chains and rods}}

A longer chain of {{convert|100|ft|m|1}}, with a hundred {{convert|1|ft|mm|0}} links, was devised in the UK in the late 18th century by Jesse Ramsden, though it never supplanted Gunter's chain.{{cite book |author1=William John Macquorn Rankine |author-link=William John Macquorn Rankine |title=A Manual of Civil Engineering |date=1863 |publisher=Griffin Bohn & Company |location=London |pages=[https://archive.org/details/amanualcivileng05rankgoog/page/n38 18]–19 |edition=2nd |url= https://archive.org/details/amanualcivileng05rankgoog}} Surveyors also sometimes used such a device, and called it the engineer's chain.

In the Southwestern United States, the {{lang|es|vara}} chain also called the Texas chain, of 20 {{lang|es|varas}} ({{cvt|16.9164|m|ft|1}}) was used in surveying Spanish and later Mexican land grants, such as the major Fisher–Miller and Paisano Grants in Texas, several similarly large ones in New Mexico, and Ranchos of California.

Metric chains, of lengths 5 m, 10 m, 20 m and 30 m, are widely used in India. Tolerances are ±3 mm for 5 m and 10 m chains, ±5 mm for a 20 m chain, and ±8 mm for a 30 m chain.{{cite book |last=Bhavikatti |first=S. S. |year=2008 |title=Surveying and levelling |volume= 1 |publisher=IK International |location=New Delhi |isbn=9788190694209 |oclc=660131493 |chapter=Chain Surveying}}

In India, a revenue chain with 16 links and of length {{cvt|33|ft|disp=flip}} is used in cadastral surveys.[http://www.agriinfo.in/default.aspx?page=topic&superid=8&topicid=45 Instruments used in Surveying - Instruments Used for Measuring Distance]

Also in North America, a variant of the chain is used in forestry for traverse surveys.{{citation needed|date=July 2018}} This modern chain is a static cord (thin rope) 50 metres long, marked with a small tag at each metre, and also marked in the first metre every decimetre.{{citation needed|date=July 2018}} When working in dense bush, a short axe or hatchet is commonly tied to the end of the chain, and thrown through the bush in the direction of the traverse.{{clarify|date=July 2018|reason=What is it called?}}

Another version used extensively in forestry and surveying is the hip-chain: a small box containing a string counter, worn on the hip.{{citation needed|date=July 2018}} The user ties off the spooled string to a stake or tree and the counter tallies distance as the user walks away in a straight line. These instruments are available in both feet and metres.

The lyrics of Three Chain Road, by Lee Kernaghan, include the line "He lived out on the three chain road" which is the name of many Australian roads; referring to the width of the road reserve.[https://genius.com/Lee-kernaghan-three-chain-road-lyrics Lee Kernaghan - Three Chain Road lyrics]

{{Reflist}}

• {{usurped|1=[https://web.archive.org/web/20100618055137/http://pballew.net/arithm16.html#gunter Math Words]}}

{{Forestry tools}}

{{Imperial units}}

{{United States Customary Units}}

Category:Units of length

Category:Imperial units

Category:Surveying

Category:Customary units of measurement in the United States

Category:Forestry tools