Gunter's measurement
From Wikipedia, the free encyclopedia
| International units | |
|---|---|
| 0.201 m | 201.168×10−6 km |
| 201.168 mm | 2.012×109 Å |
| 1.345×10−12 AU | 21.263×10−18 LY |
| US customary / Imperial units | |
| 7.92 in | 0.66 ft |
| 0.22 yd | 125×10−6 mi |
Gunter’s measurement, sometimes Surveyor’s measurement, is a geodetic system, formerly popular in Britain and its (former) colonies. It was developed in the 17th century by Edmund Gunter and is still in use today in the United States of America.
Gunter used an actual measuring chain of 100 links. These, the chain and the link, have become units of their own.
A Gunter’s chain is 4 rods long, with the rod being a standardized measurement of 5 1/2 yards or 16 1/2 feet. This rod is also called a perch or a pole. The statute rod was codified in English law at least as early as Edward I, and possibly predates the Norman conquest.
Gunter’s chain is 22 yards, 66 feet, 20.1168 metres, or 80 to the mile. Also the rectangular area with edges of one chain and one furlong (10 chains) respectively, or ten square chains, is one acre, therefore the chain is sometimes called an acre-breadth.
Gunter’s link is 1 chain/100. Thus it is exactly 7.92 inches or 201.168 mm. A square link is exactly one hundred-thousandth of an acre and one ten-thousandth of one square chain or 0.0404685642 m². It is about 62¾ square inches.
In some places other lengths have been used, for example 8.928 inches (ca. 0.227 m) in Scotland and 10.08 inches (ca. 0.256 m) in Ireland.
Chain is usually abbreviated as 'ch.', whereas link becomes either 'l.', 'li.' or 'lnk.'.
An American, similar system of about the same age but lesser popularity is Ramden’s or the engineer’s system, where the chain consists also of 100 links, each one foot (0.3048 m) long. The even less common Rathborn system, also from the 17th century, is based on a chain of two rods (33 feet, 10.0584 m) length, which consists of 100 links, too (1.98 inches, 50.292 mm each), which are called seconds (″), ten of which make a prime (′, 19.8 inches, 0.503 m).
