what is the history of coming up with the knotical mile?

Answer 1

The nautical mile was historically defined as a minute of arc along a meridian of the Earth. It can therefore be used for approximate measures on a meridian as change of latitude on a nautical chart.

According to WGS84, radius of curvature in a meridian plane is 6 399 593.6258 meters at the poles and 6 335 439.3273 meters at the Equator. By the definition of geodetic latitude, length of the minute of arc depends on the radius of curvature; distance to the angle (1 minute, in this case), not to the Earth's center. This length equals to approx. 1861.57 meters at the poles and 1842.90 meters at the Equator.

Length of a minute of arc defined by the geocentric latitude depends on the distance from the Earth's center (and curvature). This length is greater at the Equator.

Other nations had different definitions of the nautical mile. International agreement was achieved in 1929, when the International Extraordinary Hydrographic Conference held in Monaco adopted a definition of one (1) international nautical mile as being equal to 1,852 metres exactly. This value is very close (within 0.01 percent) to the average length of one minute of latitude.

Since the 1929 agreement, all nations have now adopted the international definition.

In the United States, the nautical mile was defined in the nineteenth century as 6080.2 ft (1853.249 m). This was chosen by a measurement of the Earth made by an American. It adopted the international definition in 1954.

The precise definition of the foot varied slightly around the world until a standard definition of the international yard, always equal to exactly 3 feet, was agreed upon in 1959.

The British definition related to the length on the surface of the Earth just south of Great Britain. It was 6080 feet exactly (1853.184 metres). But it wasn't specified according to a calibrated measurement of the Earth, but chosen as exactly 800 feet longer than a statute mile. For disambiguation, this is sometimes called the "admiralty mile" after the British Admiralty. The Royal Hydrographic Office of the United Kingdom converted to the international definition in 1970.

As a simpler approximation, designers of radar systems for ballistic and cruise missiles for use by the US Navy in the 1950s would take 6000 feet as their equivalent of a nautical mile.

Answer 2

I hope it makes sense:

Nautical miles measure distance. 1 nautical mile is the angular distance of 1 minute of arc on the earth's surface. As these differ slightly (6108' at pole c.f. 6046' at equator) 6080 was adopted (this being it's approximate value in the English Channel). The International nautical mile is 1852 metres, so is very slightly different from the UK nautical mile.


1 UK nautical mile = 1.00064 international nautical miles
Now the International nautical mile is used throughout the UK, except in the Statutory Instrument 1995 No. 1804 which defines it as 1853 metres! If you want an irrelevant fact, one minute of arc on Mars is close to a kilometre (.987 km to be more accurate). Perhaps the French who defined the kilometre were really Martians!
A knot is a nautical measure of speed, one nautical mile per hour (or about 1.15 mph). The name comes from the knots tied in the log line used with the sand glass. The log line was thrown onto the sea and the knots in the line were counted as they ran out during the sand glass interval. The knot has been used since the 17c. It is sometimes called the sea mile. Again, the international knot is very slightly less than the UK knot.
I have been told by a correspondent "The knot : Two meanings. (Ignorance of this has led many "experts" into confusing others).
(a) Unit of speed = one nautical mile per hour. This is the normal definition today and comes, of course from the use of the Ship Log with its line marked (with a knot) every 47.3 ft or so and used with a sand glass.

Answer 3

the difference between ground speed and air speed in flying created a need for knots

Answer 4

do u mean NAUTICAL? something to do with seaman. were u raised out at sea?