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The radian is the standard unit of angular measure, used in many areas of mathematics. The length of an arc of a unit circle is numerically equal to the measurement in radians of the angle that it subtends; one radian is just under 57.3 degrees.
A angular mil is the unit of angular measurement equal to 1/6400 of a complete circle. At 1000 metres one mil subtends about one metre (~0,98 m). Also 1/6000 and 1/6300 are used in other countries.