Perches

A rod is a unit of length, equal to 11 cubits, 5.0292 metres or 16.5 feet. A rod is the same length as a perch and a pole. more...

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The lengths of the perch (one rod) and chain (four rods) were standardized in 1607 by Edmund Gunter.

The length is equal to the standardized length of the ox goad used by medieval English ploughmen; fields were measured in acres which were one chain (four rods) by one furlong (in the United Kingdom, ten chains).

Because the furlong was "One Plough's Furrow Long" and a furrow was the length a plough team was to be driven without resting, the length of the furlong and the acre vary regionally, nominally due to differing soil types. In England the acre was 4,840 square yards, but in Scotland it was 6,150 square yards and in Ireland 7,840 square yards. In all three countries, fields were divided in acres and thus the furlong became a measure commonly used in horse racing, archery, and civic planning.

Bars of metal one rod (16.5 feet) long were used as standards of length in surveying land in the past. One example of a surveyor's rod is a one piece metal bar encased in a cylindrical canvas tube (to keep the sun from heating it and making it increase in length) with a piece of the semiprecious gemstone jasper at each end of the rod (to prevent wear of the metal bar).

The rod is still in use as a unit of measure in certain specialised fields. In recreational canoeing, maps measure portages (overland paths where canoes must be carried) in rods. This is thought to persist due to the rod approximating the length of a typical canoe. In the United Kingdom, the sizes of allotment gardens continue to be measured in rods.

The rod was still in use as a common unit of measurement in the mid-1800s, when Henry David Thoreau used it frequently when describing distances in his work Walden.

Notes

↑  A perch is also a unit of area of land = 1 square rod, and a unit of cubic measure of stonework, usually = 16.5 feet by 1 foot by 1.5 feet = 24.75 cubic feet.;

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