A pole (more commonly called a perch or a rod) is a unit of length, equal to 5.5 yards or 16.5 feet (5.0292 metres in SI units).
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 England, 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.
The rod is still in use as a unit of measure in recreational canoeing. In particular, 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.
The lengths of the perch and chain were standardized in 1607 by Edmund Gunter.
trigonometry the " pole " of a circle on a sphere is the point where the diameter of the sphere perpendicular to the plane of the circle intersects the sphere.
In crystallography (q.v.) the " pole " of a face is the intersection of a line perpendicular to the face with the sphere of projection.
The " magnetic poles " of the earth are the points on the earth's surface where the dipping needle is vertical (see Terrestrial Magnetism); and the " poles " of a magnet are the points of the magnet where the magnetic intensity is greatest.
Pole vaulting is an athletics event where competitors use a long, flexible pole as an aid to leap over a bar, similar to the high jump, but at much greater heights.
Pole jumping competitions were known to the ancient Greeks, as well as the Cretans and Celts, but with these exceptions there is no record of its ancient practice as a sport.
Initially, vaulting poles were made from stiff materials such as bamboo or aluminium, until the introduction of flexible vaulting poles made from composites such as fiberglass or carbon fiber.
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