Earth's circumference mile in the seventeenth century and the metre in the eighteenth. Earth's polar circumference is almost exactly 40,000 km because the metre was originally calibrated on this measurement (1/10-millionth of the distance between the poles and the equator), which is almost exactly 21,600 nautical miles (being defined as one minute of a degree – i.e. 360 multiplied by 60). It has been described as "the single most important measurement" of the Earth, assuming the Earth to be a sphere (the Earth is an technically an ellipsoid, albeit with just 0.3% flattening). Earth's circumference lines are the foundation of the coordinate
Foot (unit) feet 4 inches is sometimes denoted as 2′−4″, 2′ 4″ or 2′4″. (See 'minute' for another case where prime and double prime symbols are used to denote first and second cuts in refining measurement.) In the United States, the foot was defined as 12 inches, with the inch being defined by the Mendenhall Order of 1893 by 39.37 inches = 1 m. In Imperial units, the foot was defined as yard, with the yard being realized as a physical standard (separate from the standard meter). The yard standards of the different Commonwealth countries were periodically compared with one another. The