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
Urban unit for the measurement of contiguously built-up areas. Other comparable units in other countries are the United States "Urbanized Area" and the "urban area" definition shared by the United Kingdom and Canada. Urban unit In France, an urban unit ("fr: "unité urbaine"") is a statistical area defined by INSEE, the French national statistics office, for the measurement of contiguously built-up areas. According to the INSEE definition , an "unité urbaine" is a commune alone or a grouping of communes which: a) form a single unbroken spread of urban development, with no distance between habitations greater than 200 m and b) have