It's the only mile that metric people approve of :-)
What Is a 'Nautical Mile'? (2011)
21–30 of 51 posts
Re: What Is a 'Nautical Mile'? (2011)
#22Earlier quoted context omitted.
Indeed, IIRC the intention was to define the meter so that the distance between the North Pole and the equator at the meridian through Paris would be exactly 10000 km, making the full circumference along that meridian and the one opposite it 40000 km. EDIT: that information is already in the article, making my comment redundant and unnecessary.
Mine also. ¯\_(ツ)_/¯
Nobody reads tfa so it's cool.
Re: What Is a 'Nautical Mile'? (2011)
#23> A minute of arc on the planet Earth is 1 nautical mile. Only if that minute of arc lies on a great circle route. As an interesting addendum, when measuring distance made good on a nautical chart, you will use a divider to measure the straight line distance, then lay this onto the latitude scale to convert it to nautical miles. If you were to use the longitude scale, you would be off by approximately the cosine of y…
> Only if that minute of arc lies on a great circle route.
That's all arcs. A line of lattitude is not an arc.
Re: What Is a 'Nautical Mile'? (2011)
#24> A minute of arc on the planet Earth is 1 nautical mile. Only if that minute of arc lies on a great circle route. As an interesting addendum, when measuring distance made good on a nautical chart, you will use a divider to measure the straight line distance, then lay this onto the latitude scale to convert it to nautical miles. If you were to use the longitude scale, you would be off by approximately the cosine of y…
> > A minute of arc on the planet Earth is 1 nautical mile.
> Only if that minute of arc lies on a great circle route.
You missed out some context for that quote that already makes it clear that it's talking about a great circle:
> A nautical mile is based on the circumference of the planet Earth. If you were to cut the Earth in half at the equator, you could pick up one of the halves and look at the equator as a circle. ... A minute of arc on the planet Earth is 1 nautical mile.
Re: What Is a 'Nautical Mile'? (2011)
#25Its interesting that the nautical mile is based on a more abstract number that would define when looking at maps and charts, rather then something more immediate and physical like the distance to the horizon when out on the ocean. Most imperial units seem to be based on simple laymen measurements.
I guess this mostly means that Nautical Mile is a unit that traces back to the introduction of the spherical coordinate system in cartography.
Re: What Is a 'Nautical Mile'? (2011)
#26> A kilometer is also defined using the planet Earth as a standard of distance.
Wrong. It used to be that way, but not anymore.
Re: What Is a 'Nautical Mile'? (2011)
#27It's the only mile that metric people approve of :-)
No, the nautical mile is hated by proponents of the metric system. As with all customary units, it favors a specific use-case at the cost of errors and conversions, has limited accuracy and doesn't handle orders of magnitude.
Re: What Is a 'Nautical Mile'? (2011)
#28> A kilometer is also defined using the planet Earth as a standard of distance. Wrong. It used to be that way, but not anymore.
Which is why it says:
... you would have the traditional unit for the kilometer as defined in 1791 by the French Academy of Sciences.
Re: What Is a 'Nautical Mile'? (2011)
#29At what elevation are they measuring these arcs / circumference of the earth? At sea level? Feel like that needs to be explicit if we are trying to be technical. Because you can't "travel around the Earth at the equator" in "21,600 nautical miles, 24,857 miles or 40,003 kilometers" without going underneath a mountain or two.
Re: What Is a 'Nautical Mile'? (2011)
#30At what elevation are they measuring these arcs / circumference of the earth? At sea level? Feel like that needs to be explicit if we are trying to be technical. Because you can't "travel around the Earth at the equator" in "21,600 nautical miles, 24,857 miles or 40,003 kilometers" without going underneath a mountain or two.
i would guess that would be mean-sea-level...