A nautical mile, 6076.11549 feet, is one minute of latitude. Some define it as a minute of longitude at the equator, which is as nearly the same as made little difference (about 4 feet) until GPS came in and permitted pinpoint accuracy in navigation. A land mile, of course, is 5,280 feet.
Why did our ancestors choose such ridiculous numbers as 360, 5280 and so on? Because they didn’t use decimals. They needed numbers which could be divided by as many other numbers as possible. Just try working out the factors of 5280!
1 international nautical mile = 1852 metres precisely. This is the definition used in most, if not all, modern circumstances. It’s not an SI unit, but is used universally for shipping and aviation, and so ‘tolerated’ by the SI system. After all, even the SI fanatics can’t change the diameter of the earth.
Though they can have a good try. Originally, a metre was one ten-millionth of the length of a line from the North Pole to the Equator along the meridian of Paris. Neat. Since then, the meter has gone through various definitions, including the length of an iridium rod kept in paris. Now it is defined as the distance light in a vacuum travels in a 299,792,458th of a second.
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