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  2. Nautical mile - Wikipedia

    en.wikipedia.org/wiki/Nautical_mile

    A nautical mile is a unit of length used in air, marine, and space navigation, and for the definition of territorial waters. [2] [3] [4] Historically, it was defined as the meridian arc length corresponding to one minute (⁠ 1 / 60 ⁠ of a degree) of latitude at the equator, so that Earth's polar circumference is very near to 21,600 nautical miles (that is 60 minutes × 360 degrees).

  3. Foot (unit) - Wikipedia

    en.wikipedia.org/wiki/Foot_(unit)

    0.3048 m. 30.48 cm. 304.8 mm. The foot (standard symbol: ft) [1][2] is a unit of length in the British imperial and United States customary systems of measurement. The prime symbol, ′, is commonly used to represent the foot. [3] In both customary and imperial units, one foot comprises 12 inches, and one yard comprises three feet.

  4. Minute and second of arc - Wikipedia

    en.wikipedia.org/wiki/Minute_and_second_of_arc

    The physical group size equivalent to m minutes of arc can be calculated as follows: group size = tan(⁠ m / 60 ⁠) × distance. In the example previously given, for 1 minute of arc, and substituting 3,600 inches for 100 yards, 3,600 tan(⁠ 1 / 60 ⁠) ≈ 1.047 inches. In metric units 1 MOA at 100 metres ≈ 2.908 centimetres.

  5. 1 in 60 rule - Wikipedia

    en.wikipedia.org/wiki/1_in_60_rule

    Here is the breakdown: A circle of 60 NM radius has a circumference of: 2 x 60 x π = 376.99 NM. 376.99 divided by 360° produces: 376.99/360 = 1.047 NM (off by 4.7%) This rule is therefore very good approximation. As a coincidence, 1 NM is about 6,000 feet (6,076.1 feet) so we can use the 60:1 rule for this too.

  6. Earth's circumference - Wikipedia

    en.wikipedia.org/wiki/Earth's_circumference

    t. e. Earth's circumference is the distance around Earth. Measured around the equator, it is 40,075.017 km (24,901.461 mi). Measured passing through the poles, the circumference is 40,007.863 km (24,859.734 mi). [1] Measurement of Earth's circumference has been important to navigation since ancient times. The first known scientific measurement ...

  7. Mile - Wikipedia

    en.wikipedia.org/wiki/Mile

    nautical units. ≈ 0.868 98 nmi [n 1] The mile, sometimes the international mile or statute mile to distinguish it from other miles, is a British imperial unit and United States customary unit of length; both are based on the older English unit of length equal to 5,280 English feet, or 1,760 yards. The statute mile was standardised between the ...

  8. Metre sea water - Wikipedia

    en.wikipedia.org/wiki/Metre_sea_water

    U.S. customary. ≈ 0.444 44 psi. The metre (or meter) sea water (msw) is a metric unit of pressure used in underwater diving. It is defined as one tenth of a bar. [1][2] The unit used in the US is the foot sea water (fsw), based on standard gravity and a sea-water density of 64 lb/ft 3. According to the US Navy Diving Manual, one fsw equals 0. ...

  9. Rod (unit) - Wikipedia

    en.wikipedia.org/wiki/Rod_(unit)

    The rod, perch, or pole (sometimes also lug) is a surveyor's tool [1] and unit of length of various historical definitions. In British imperial and US customary units, it is defined as 16 + 1 ⁄ 2 feet, equal to exactly 1 ⁄ 320 of a mile, or 5 + 1 ⁄ 2 yards (a quarter of a surveyor's chain), and is exactly 5.0292 meters.