Gunter's chain
| Gunter's chain | |
|---|---|
 Gunter's chain at Campus Martius Museum | |
| General information | |
| Unit system | imperial/US units |
| Unit of | length |
| Conversions | |
| 1 gunter's chain in ... | ... is equal to ... |
| imperial/US units | 22 yd |
| metric (SI) units | 20.1 m |
| Gunter's link | |
|---|---|
| Unit system | imperial/US units |
| Unit of | length |
| Conversions | |
| 1 gunter's link in ... | ... is equal to ... |
| imperial/US units | 1/100 Gunter's chain 7.92 in |
| metric (SI) units | 200 mm |
Gunter's chain (also known as Gunter’s measurement) 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.
Gunter developed an actual measuring chain of 100 links. These, the chain and the link, became statutory measures in England[when?] and subsequently the British Empire[when?].
Description
The 66-foot (20.1 m) chain is divided into 100 links, usually marked off into groups of 10 by brass rings or tags which simplify intermediate measurement. Each link is thus 7.92 inches (201 mm) long. A quarter chain, or 25 links, measures 16 feet 6 inches (5.03 m) and thus measures a rod (or pole). Ten chains measure a furlong and 80 chains measure a statute mile.[1]
Gunter's chain reconciled two seemingly incompatible systems: the traditional English land measurements, based on the number four, and decimals based on the number 10. Since an acre measured 10 square chains in Gunter's system, the entire process of land area measurement could be computed using measurements in chains, and then converted to acres by dividing the results by 10.[2] Hence 10 chains by 10 chains (100 square chains) equals 10 acres, 5 chains by 5 chains (25 square chains) equals 2.5 acres.
Method
Unit of length
Although link chains were later superseded by the steel ribbon tape (a form of tape measure), its legacy was a new statutory unit of length called the chain, equal to 66 feet (or 100 links).[3] This unit still exists as a location identifier on British railways, as well as in some areas of America. In the United States (US), for example, Public Lands Survey plats are published in the chain unit to maintain the consistency of a two-hundred-year-old database. In the Midwest of the US it is not uncommon to encounter deeds with references to chains, poles, or rod units, especially in farming country. Minor roads surveyed in Australia and New Zealand in the 19th and early 20th centuries are customarily one chain wide.[4]
The length of a cricket pitch is one chain (22 yards).[5][6]
Similar measuring chains
A similar American system, of lesser popularity, is Ramsden’s or the engineer’s system, where the chain consists also of 100 links, each one foot (0.3048 m) long. The original of such chains was that constructed, to very high precision, for the measurement of the baselines of the Anglo-French Survey (1784–1790) and the Principal Triangulation of Great Britain.
The even less common Rathborn system, also from the 17th century, is based on a 200-link chain of two rods (33 feet, 10.0584 m) length. Each rod (or perch or pole) consists of 100 links, (1.98 inches, 50.292 mm each), which are called seconds (″), ten of which make a prime (′, 19.8 inches, 0.503 m).[7]
Vincent Wing made chains with 9.90-inch links, most commonly as 33-foot half-chains of 40 links. These chains were sometimes used in the American colonies, particularly Pennsylvania.[8]
In India, surveying chains 20 metres (65 ft 7.4 in) (occasionally 30 metres) in length are used.[9] Links are 200 millimetres (7.87 in) long.[10]
In France after the French Revolution, and later in countries that had adopted the Metric System, 10 metre (32 ft 9.7 in) chains, of 50 links each 200 millimetres (7.87 in) long were used until the 1950s.[11]
The fathom was a common measure used in English mines to describe depth and measure distances in some types of mine.[citation needed] Accordingly a 60 foot, 10 fathom chain was used.[citation needed] The chain consisted of 120 x 6 inch links with numbered tallies at each fathom (six feet).[citation needed]
See also
References
- ^ Slater; Saunders. "Rods, poles and perches". www.northcravenheritage.org.uk. Retrieved 22 July 2018.
- ^ John Love (1688). "VII : How to cast up the Contents of a Plot of Land". Geodaesia: or, The art of surveying and measuring land made easy : shewing, by plain and practical rules, how to survey, protract, cast up, reduce or divide any piece of land whatsoever : with new tables for the ease of the surveyor in reducing the measure of land. London: J. Taylor. p. 122.
- ^ Nesbit, Anthony (1847). A complete treatise on practical land-surveying, Ninth edition. Longman, Brown, Green and Longmans. London. p. 29. Retrieved April 7, 2009.
- ^ McKay, Donald F. (ed.) (2009). "Land Title Surveys in New Zealand" Archived 2015-05-23 at the Wayback Machine. Chapter 2, Section 8: Public Roads. New Zealand Institute of Surveyors.
- ^ Craven, Ian; Gray, Martin; Stoneham, Geraldine (1994). Australian Popular Culture. Cambridge University Press. p. 27. ISBN 0-521-46667-9.
- ^ MCC (2018). "Law 6 – the pitch". Retrieved 23 November 2018.
- ^ Zupko, Ronald Edward. A Dictionary of Weights and Measures for the British Isles
- ^ Denny, Milton. "The Colonial Surveyor in Pennsylvania", Surveyors Historical Society, 2013.
- ^ Instruments used in Surveying My Agriculture information bank
- ^ Surveying I - R. Gopalakrishnan, Sri Venkateswara College of Engineering (pdf)
- ^ Plomion, Charles. Arithmétique-Cours élémentaire, Librairie A. Hatier, Paris, 1925