4 ms·

The insistence of aviation and naval industries to continue using knots for speeds is infuriating. I can forgive the fact that the article uses U.S. customary

The insistence of aviation and naval industries to continue using knots for speeds is infuriating. I can forgive the fact that the article uses U.S. customary units instead of SI but the article gives distances in miles and altitudes in feet and needing to convert knots into feet per second or miles per hour as you read is awful.

robbles 13y ago
from Wikipedia: > The speeds of vessels relative to the fluids in which they travel (boat speeds and air speeds) are measured in knots. It's a little like the difference between mass and weight - the frame of reference is important for one and not the other.
- deleted 13y ago
  [deleted]
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 ago
  Yes 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 ago
  Or 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.
mikeash 13y ago
The absolute quantities rarely matter. 100 knots in a 777 is completely different from 100 knots in a Cessna 150. The units are not too terribly important, since the reference numbers you're comparing them to are always in the same units.

robbles 13y ago

from Wikipedia: > The speeds of vessels relative to the fluids in which they travel (boat speeds and air speeds) are measured in knots. It's a little like the difference between mass and weight - the frame of reference is important for one and not the other.

deleted 13y ago
[deleted]

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 ago
Yes 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 ago
Or 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.

mikeash 13y ago

The absolute quantities rarely matter. 100 knots in a 777 is completely different from 100 knots in a Cessna 150. The units are not too terribly important, since the reference numbers you're comparing them to are always in the same units.