The code name of "Knot" is English, which refers to the length of latitude 1 minute on the meridian of the earth. Because the earth is slightly ellipsoid, the radian of 1 minute at different latitudes is slightly different. On the equator 1 nautical mile is approximately equal to1843m; At latitude 45, it is approximately equal to1852.2m, and at the poles it is approximately equal to1861.6m.. 1929 International Hydrography Conference, adopted 1 minute average length 1 852m as1nautical mile.

/kloc-in the 9th century, in order to calculate the speed of a ship, sailors figured out a way to tie many knots on a long rope, and then put them down behind the ship, and calculate the speed of the ship by counting the number of knots washed away in a certain period of time.

The distance of each knot is 47 feet 3 inches (one hundredth of a nautical mile), and sailors will use a 30-second hourglass (currently 28 seconds is used because of international standards in the sea) to calculate the moving speed, and each knot is a knot.

Related conversion:

1, 1 nautical mile =1.852 kilometers (kilometers) (China standard).

2. 1 nautical mile =1.85101kilometer (kilometer) (American standard).

3. 1 nautical mile =1.85455 kilometers (kilometers) (British standard).

4. 1 nautical mile =1.85327 km (km) (French standard).

5. 1 nautical mile =1.85578 km (km) (Russian standard).

6. The shortest sea is at the equator, 1 nautical mile =1843m.

7. The longest sea is at the north and south poles, 1 sea =1862m.

8. The average radius of the earth is 637 1300m, and the calculated 1 nautical mile is: 1 nautical mile = 2 * π * 6371300/360/60 =1853.3m.