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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).
The nautical mile (nmi) was originally defined as the arc length of a minute of latitude on a spherical Earth, so the actual Earth circumference is very near 21 600 nmi. A minute of arc is π 10 800 of a radian . A second of arc, arcsecond (arcsec), or arc second, denoted by the symbol ″, [ 2] is 1 60 of an arcminute, 1 3600 ...
Conversion of units is the conversion of the unit of measurement in which a quantity is expressed, typically through a multiplicative conversion factor that changes the unit without changing the quantity. This is also often loosely taken to include replacement of a quantity with a corresponding quantity that describes the same physical property.
Speed of sound. The speed of sound is the distance travelled per unit of time by a sound wave as it propagates through an elastic medium. More simply, the speed of sound is how fast vibrations travel. At 20 °C (68 °F), the speed of sound in air is about 343 m/s (1,125 ft/s; 1,235 km/h; 767 mph; 667 kn ), or 1 km in 2.91 s or one mile in 4.69 s.
The knot ( / nɒt /) is a unit of speed equal to one nautical mile per hour, exactly 1.852 km/h (approximately 1.151 mph or 0.514 m/s ). [ 1][ 2] The ISO standard symbol for the knot is kn. [ 3] The same symbol is preferred by the Institute of Electrical and Electronics Engineers ( IEEE ), while kt is also common, especially in aviation, where ...
The original Naismith 's rule from 1892 says that one should allow one hour per three miles on the map and an additional hour per 2000 feet of ascent. [ 1][ 4] It is included in the last sentence of his report from a trip. [ 1][ 8] Today it is formulated in many ways. Naismith's 1 h / 3 mi + 1 h / 2000 ft can be replaced by:
If d is in nautical miles, and h in feet, the constant factor is about 1.06, which is close enough to 1 that it is often ignored, giving: d ≈ h {\displaystyle d\approx {\sqrt {h}}} These formulas may be used when h is much smaller than the radius of the Earth (6371 km or 3959 mi), including all views from any mountaintops, airplanes, or high ...
3.0976 × 106 sq yd. 640 acres. SI units. 2.59 × 106 m2. 2.59 km2. The square mile (abbreviated as sq mi and sometimes as mi2) [ 1] is an imperial and US unit of measure for area. One square mile is equal to the area of a square with each side measuring a length of one mile. [ 2]