Chain (unit)

Last updated
chain
Gunter's chain at Campus Martius Museum.JPG
The chain is based on the length of Gunter's chain, which is 66 feet (22 yd) long.
General information
Unit system Imperial/US  units
Unit of length
Symbolch
Conversions
1 ch in ...... is equal to ...
   Imperial/US units   22  yd , 66  ft , 100  links
    Metric (SI) units   20.1168  m

The chain (abbreviated ch) is a unit of length equal to 66 feet (22 yards), used in both the US customary and Imperial unit systems. It is subdivided into 100 links. [1] [2] There are 10 chains in a furlong, and 80 chains in one statute mile. [2] In metric terms, it is 20.1168  m long. [2] By extension, chainage (running distance) is the distance along a curved or straight survey line from a fixed commencing point, as given by an odometer.

Contents

The chain has been used since the early 17th century in England, and was brought by British settlers during the colonial period to other countries around the globe. In the United Kingdom, there were 80 chains to the mile, but until the early nineteenth century the Scottish and Irish customary miles were longer than the statute mile; consequently a Scots chain was about 74 (imperial) feet, [3] an Irish chain 84 feet. These longer chains became obsolete following the adoption of the imperial system of units in 1824. [4] In India, "metric chains" of exactly 20 metres (65.62 feet) are used, along with fractions thereof. [5]

Definition

The UK statute chain is 22 yards, which is 66 feet (20.1168 m). This unit is a statute measure in the United Kingdom, defined in the Weights and Measures Act 1985. [6] One link is a hundredth part of a chain, which is 7.92 inches (20.1168 cm). [7]

The surveyor's chain first appears in an illustration in a Dutch map of 1607, [8] and in an English book for surveyors of 1610. [9] 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. [10] The 66-foot unit, which was four perches or rods, [11] took on the name the chain. By 1675 it was accepted, and Ogilby wrote:

...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...' [12]

— 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. [13]

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. [13]

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
— Lola Cazier (1976), Surveys and Surveyors of the Public Domain 1785-1975, page 15


Modern use and historic cultural references

United Kingdom

Location marker painted on a British railway bridge, showing 112 miles and 63 chains; photograph taken August 2007 Bridge miles and chains.jpg
Location marker painted on a British railway bridge, showing 112 miles and 63 chains; photograph taken August 2007

In the United Kingdom, the chain is no longer used for practical survey work. [14] 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. [15]

North America

The use of the chain was mandatory in laying out US townships. [13] 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 (640 acres or 259 hectares), quarter-section (160 acres or 64.7 hectares), and quarter-quarter-section (40 acres or 16.19 hectares). 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. [16]

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? ] 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. [17]

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. [18]

Australia and New Zealand

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. [19] The street frontages of many houses in these countries are one chain wide—roads were almost always 1 chain (20.1 m) wide in urban areas, [19] sometimes 1.5 chains (30.2 m) or 2.5 chains (50.3 m). Laneways would be half a chain (10.1 m). In rural areas the roads were wider, up to 10 chains (201.2 m) where a stock route was required. 5 chains (100.6 m) roads were surveyed as major roads or highways between larger towns, 3 chains (60.4 m) roads between smaller localities, [20] and 2 chains (40.2 m) roads were local roads in farming communities. Roads named Three Chain Road etc. persist today. [21] [22]

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. [23] [24] 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. [25]

Cricket pitches

The chain also survives as the length of a cricket pitch, being the distance between the stumps. [26] [27]

Measuring instruments

Civil engineers and surveyors use various instruments including chains to measure distance. [5] Other instruments used for measuring distance include tapes and bands. A steel band is also known as a "band chain". [28]

Surveyors' chain (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.

Engineer's chain (Ramsden's chain)

A longer chain of 100 feet (30.5 m), with a hundred 1 foot (305 mm) links, was devised in the UK in the late 18th century by Jesse Ramsden, though it never supplanted Gunter's chain. [7] Surveyors also sometimes used such a device, and called it the engineer's chain.

Vara or Texas chain

In the Southwestern United States, the vara chain also called the Texas chain, of 20 varas (16.9164 m , or 55+1⁄2 ft) 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 over 200 smaller ranchos in California.

Metric chains

Metric chains, of lengths 5 m, 10 m, 20 m and 30 m, are widely used in India. [5] 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. [29]

Revenue chain

In India, a revenue chain with 16 links and of length 10 m (33 ft) is used in cadastral surveys. [30]

Other instruments

Also in North America, a variant of the chain is used in forestry for traverse surveys.[ citation needed ] 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 ] 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.[ clarification needed ]

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 ] 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. [31]

Related Research Articles

<span class="mw-page-title-main">Acre</span> Unit of area

The acre is a unit of land area used in the British imperial and the United States customary systems. It is traditionally defined as the area of one chain by one furlong, which is exactly equal to 10 square chains, 1⁄640 of a square mile, 4,840 square yards, or 43,560 square feet, and approximately 4,047 m2, or about 40% of a hectare. Based upon the international yard and pound agreement of 1959, an acre may be declared as exactly 4,046.8564224 square metres. The acre is sometimes abbreviated ac but is usually spelled out as the word "acre".

<span class="mw-page-title-main">Furlong</span> Unit of length equal to 660 feet or about 201 metres

A furlong is a measure of distance in imperial units and United States customary units equal to one-eighth of a mile, equivalent to any of 660 feet, 220 yards, 40 rods, 10 chains, or approximately 201 metres. It is now mostly confined to use in horse racing, where in many countries it is the standard measurement of race lengths, and agriculture, where it is used to measure rural field lengths and distances.

<span class="mw-page-title-main">Imperial units</span> System of measurements

The imperial system of units, imperial system or imperial units is the system of units first defined in the British Weights and Measures Act 1824 and continued to be developed through a series of Weights and Measures Acts and amendments.

<span class="mw-page-title-main">Mile</span> Unit of length

The mile, sometimes the international mile or statute mile to distinguish it from other miles, is a British imperial unit and United States customary unit of length; both are based on the older English unit of length equal to 5,280 English feet, or 1,760 yards. The statute mile was standardised between the Commonwealth of Nations and the United States by an international agreement in 1959, when it was formally redefined with respect to SI units as exactly 1,609.344 metres.

<span class="mw-page-title-main">Nautical mile</span> Unit of distance (1,852 m)

A nautical mile is a unit of length used in air, marine, and space navigation, and for the definition of territorial waters. Historically, it was defined as the meridian arc length corresponding to one minute of latitude at the equator, so that Earth's polar circumference is very near to 21,600 nautical miles. Today the international nautical mile is defined as exactly 1,852 metres. The derived unit of speed is the knot, one nautical mile per hour.

<span class="mw-page-title-main">Yard</span> Unit of length

The yard is an English unit of length in both the British imperial and US customary systems of measurement equalling 3 feet or 36 inches. Since 1959 it has been by international agreement standardized as exactly 0.9144 meter. A distance of 1,760 yards is equal to 1 mile.

<span class="mw-page-title-main">Surveying</span> Science of determining the positions of points and the distances and angles between them

Surveying or land surveying is the technique, profession, art, and science of determining the terrestrial two-dimensional or three-dimensional positions of points and the distances and angles between them. These points are usually on the surface of the Earth, and they are often used to establish maps and boundaries for ownership, locations, such as the designated positions of structural components for construction or the surface location of subsurface features, or other purposes required by government or civil law, such as property sales.

<span class="mw-page-title-main">Foot (unit)</span> Customary unit of length

The foot is a unit of length in the British imperial and United States customary systems of measurement. The prime symbol, ′, is commonly used to represent the foot. In both customary and imperial units, one foot comprises 12 inches, and one yard comprises three feet. Since an international agreement in 1959, the foot is defined as equal to exactly 0.3048 meters.

<span class="mw-page-title-main">Public Land Survey System</span> System of dividing land in the United States

The Public Land Survey System (PLSS) is the surveying method developed and used in the United States to plat, or divide, real property for sale and settling. Also known as the Rectangular Survey System, it was created by the Land Ordinance of 1785 to survey land ceded to the United States by the Treaty of Paris in 1783, following the end of the American Revolution. Beginning with the Seven Ranges in present-day Ohio, the PLSS has been used as the primary survey method in the United States. Following the passage of the Northwest Ordinance in 1787, the Surveyor General of the Northwest Territory platted lands in the Northwest Territory. The Surveyor General was later merged with the United States General Land Office, which later became a part of the U.S. Bureau of Land Management (BLM). Today, the BLM controls the survey, sale, and settling of lands acquired by the United States.

<span class="mw-page-title-main">Unit of length</span> Reference value of length

A unit of length refers to any arbitrarily chosen and accepted reference standard for measurement of length. The most common units in modern use are the metric units, used in every country globally. In the United States the U.S. customary units are also in use. British Imperial units are still used for some purposes in the United Kingdom and some other countries. The metric system is sub-divided into SI and non-SI units.

The rod, perch, or pole is a surveyor's tool and unit of length of various historical definitions. In British imperial and US customary units, it is defined as 16+1⁄2 feet, equal to exactly 1⁄320 of a mile, or 5+1⁄2 yards, and is exactly 5.0292 meters. The rod is useful as a unit of length because integer multiples of it can form one acre of square measure (area). The 'perfect acre' is a rectangular area of 43,560 square feet, bounded by sides 660 feet long and 66 feet wide or, equivalently, 40 rods by 4 rods. An acre is therefore 160 square rods or 10 square chains.

A system of units of measurement, also known as a system of units or system of measurement, is a collection of units of measurement and rules relating them to each other. Systems of measurement have historically been important, regulated and defined for the purposes of science and commerce. Instances in use include the International System of Units or SI, the British imperial system, and the United States customary system.

<span class="mw-page-title-main">Gunter's chain</span> Distance measuring device used for surveying

Gunter's chain is a distance-measuring device used for surveying. It was designed and introduced in 1620 by English clergyman and mathematician Edmund Gunter (1581–1626). It enabled plots of land to be accurately surveyed and plotted, for legal and commercial purposes.

<span class="mw-page-title-main">Link (unit)</span> Unit of length

The link, sometimes called a Gunter’s link, is a unit of length formerly used in many English-speaking countries. In US customary units modern definition, the link is exactly 66⁄100 of a US survey foot, or exactly 7.92 inches or 20.1168 cm.

<span class="mw-page-title-main">Metrication in the United Kingdom</span> Adoption of the metric system of measurements

Metrication is the act or process of converting to the metric system of measurement. The United Kingdom, through voluntary and mandated laws, has metricated most of government, industry, commerce, and scientific research to the metric system; however, the previous measurement system is still used in society. Imperial units as of 2024 remain mandated by law to still be used without metric units for speed and distance road signs, and the sizes of cider and beer sold by the glass, returnable milk containers and precious metals, and in some areas both measurement systems are mandated by law.

<span class="mw-page-title-main">Metrication in Ireland</span> Adoption of the metric system of measurements in Ireland

Metrication in the Republic of Ireland happened mostly in the 20th century and was officially completed in 2005, with a few exceptions.

<span class="mw-page-title-main">Measuring rod</span> Tool used to physically measure lengths

A measuring rod is a tool used to physically measure lengths and survey areas of various sizes. Most measuring rods are round or square sectioned; however, they can also be flat boards. Some have markings at regular intervals. It is likely that the measuring rod was used before the line, chain or steel tapes used in modern measurement.

Construction surveying or building surveying is to provide dimensional control for all stages of construction work, including the stake out of reference points and markers that will guide the construction of new structures such as roads, rail, or buildings. These markers are usually staked out according to a suitable coordinate system selected for the project.

<span class="mw-page-title-main">Hong Kong units of measurement</span>

Hong Kong has three main systems of units of measurement in current use:

<span class="mw-page-title-main">Imperial and US customary measurement systems</span> English (pre 1824), Imperial (post 1824) and US Customary (post 1776) units of measure

The imperial and US customary measurement systems are both derived from an earlier English system of measurement which in turn can be traced back to Ancient Roman units of measurement, and Carolingian and Saxon units of measure.

References

  1. ↑ James, Robert C.; James, Glenn (1992). Mathematics Dictionary. New York: Chapman & Hall. p. 453. ISBN   9780412990410.
  2. 1 2 3 "6 Tables of Interrelation of Units of Measurement". Units of Weight and Measure (United States Customary and Metric): Definitions and Tables of Equivalents (PDF). U.S. Department of Commerce, National Bureau of Standards. 1960. pp. 8–9. (PDF)
  3. ↑ Smeaton, John (1837). Reports of the Late John Smeaton, F.R.S. (2nd ed.). London: M Taylor. p.  308. Since the foregoing Report [on the best route for the Forth and Clyde Canal] ... was delivered ... , Mr Smeaton has discovered that, notwithstanding the care and pains he took to be correct, he has committed an error, in supposing the Scotch chain, with which the measures of the length of the tract of land were taken, to consist of seventy feet each, whereas, in reality, it consists of seventy-four
  4. ↑ William John Macquorn Rankine (1863). A Manual of Civil Engineering (2nd ed.). London: Griffin Bohn & Company. p.  3.
  5. 1 2 3 Punmia, B. C.; Jain, A. K.; Jain, A. K. (2003). Basic civil engineering. New Delhi: Laxmi Publications. ISBN   9788170084037. OCLC   1006316184.
  6. ↑ "Weights and Measures Act 1985". Legislation.gov.uk. Sch 1, Part VI. Retrieved 25 September 2014.
  7. 1 2 William John Macquorn Rankine (1863). A Manual of Civil Engineering (2nd ed.). London: Griffin Bohn & Company. pp.  18–19.
  8. ↑ Corneliisz van Alckmaer, Pieter. ""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". Regional Archive, Alkmaar (in Dutch). Retrieved 29 July 2018.
  9. ↑ "Chain (5)". The Oxford English Dictionary - 1933 - All Volumes. Oxford English Dictionary. Vol. 2. 1933. p. 248. 1610 W. FOLKINGHAM, Art Survey.
  10. ↑ "Gunter biography". www-history.mcs.st-andrews.ac.uk. Retrieved 21 July 2018.
  11. ↑ Slater, Michael; Saunders, Ian. "Rods, poles and perches". www.northcravenheritage.org.uk. North Craven Heritage Journal. Retrieved 29 July 2018.
  12. ↑ "Preface". Britannia. 1675 – via Fulltable.com.
  13. 1 2 3 Cazier, Lola. "Surveys and Surveyors of the Public Domain 1785-1975" (PDF). US Government. p. 22. Stock Number 024-041-00083-6. Retrieved 29 July 2018.
  14. ↑ Plane and Geodetic Surveying, A.L. Johnson (SPON)
  15. ↑ HS2 proposed alignment with chainages expressed in metres
  16. ↑ Lakey, Jack (21 June 2017). "Turns out there is a standard to determine where a homeowner's property ends: The Fixer". Toronto Star . Retrieved 22 June 2017.
  17. ↑ "The ERA Bulletin 2017-01". Issuu . Electric Railroaders' Association. January 18, 2017. Retrieved January 18, 2017.
  18. ↑ Documents
  19. 1 2 George Seddon (28 September 1998). Landprints: Reflections on Place and Landscape. Cambridge University Press. pp. 151–. ISBN   978-0-521-65999-4 . Retrieved 28 May 2013.
  20. ↑ Lay, M. G. (July 2008). "Roads". emelbourne the city past and present. School of Historical Studies Department of History, The University of Melbourne. Retrieved 28 May 2013.
  21. ↑ "375 THREE CHAIN ROAD, Kilmore, Vic 3764 - Property Details". www.realestate.com.au. Retrieved 8 August 2018.
  22. ↑ "Map of Three Chain Road in Queensland - Bonzle Digital Atlas of Australia". www.bonzle.com. Retrieved 8 August 2018.
  23. ↑ "Queen's Chain". Oxford Dictionaries – oxforddictionaries.com. Archived from the original on August 8, 2018. Retrieved 4 July 2017.
  24. ↑ "Truth behind the Queen's Chain". NZ Herald. 12 August 2003. Retrieved 4 July 2017.
  25. ↑ "Te Ara, Encyclopedia of New Zealand".
  26. ↑ "The measurements of cricket". ESPN Cricinfo. Retrieved 19 February 2020.
  27. ↑ "Cricket - factfile". BBC Bitesize. Retrieved 19 February 2020.
  28. ↑ Types of Chains used in Surveying, Their Parts, Testing and Advantages
  29. ↑ Bhavikatti, S. S. (2008). "Chain Surveying". Surveying and levelling. Vol. 1. New Delhi: IK International. ISBN   9788190694209. OCLC   660131493.
  30. ↑ Instruments used in Surveying - Instruments Used for Measuring Distance
  31. ↑ Lee Kernaghan - Three Chain Road lyrics
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