3 ms·
The knot is now defined in terms of an SI unit (1 knot = 1 nautical mile/hour, 1 nautical mile = 1852 meters), and the nautical mile is accepted for use interna
by ubernostrum 13y ago
The knot is now defined in terms of an SI unit (1 knot = 1 nautical mile/hour, 1 nautical mile = 1852 meters), and the nautical mile is accepted for use internationally by BIPM.
Its continued use is due to the fact that the nautical mile is the average length of one minute of arc along a meridian, which allows easy correction, when measuring distances in nautical miles, for the distortions of representing the non-flat Earth on flat charts.
Or, more simply: there are sometimes good reasons for using a unit other than "look how easy it is to move decimal points".
- gaius 13y agoYes it turns out practitioners in the field prefer a convention that makes their jobs easier and not one for the convenience of The Internets. Who'da thunk it? I can imagine someone saying programmers are stupid for insisting that k means 1024 instead of 1000 like, umm, SI units...
- hudibras 13y agoOr to put it another way: a nautical mile is equal to one minute of latitude and 60 nautical miles equals one degree of latitude. I've seen many people become amazed when it's explained to them that a nautical mile is not just an archaic, arbitrary unit of measure, like a hogshead or furlong. Part Two of this explanation is to tell them that the metric system unit of distance, the meter, was also originally based on the earth's size. Ten million meters (or 10,000 km) is the distance from the equator to one of the poles.