What Is a 'Nautical Mile'? (2011)
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What Is a 'Nautical Mile'? (2011)
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Re: What Is a 'Nautical Mile'? (2011)
#2The metre was originally supposed to be based on a division of the Earth's circumference as well.
Re: What Is a 'Nautical Mile'? (2011)
#3The metre was originally supposed to be based on a division of the Earth's circumference as well.
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.
Re: What Is a 'Nautical Mile'? (2011)
#4The metre was originally supposed to be based on a division of the Earth's circumference as well.
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)_/¯
Re: What Is a 'Nautical Mile'? (2011)
#5> 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 your latitude, because the lines of latitude() (apart from the equator) are not great circles.
() corrected longitude to latitude here - longitude is obviously great circles, latitude apart from the equator are not.
Re: What Is a 'Nautical Mile'? (2011)
#6The metre was originally supposed to be based on a division of the Earth's circumference as well.
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.
Well, the article claims that that is the definition which is false. The definition of a meter is ‘the distance traveled by light in 1/299792458 of a second’ so a kilometer is a thousand times that.
The story in the article is the original, obsolete definition.
Re: What Is a 'Nautical Mile'? (2011)
#7Its 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.
Re: What Is a 'Nautical Mile'? (2011)
#8Its 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.
Distance to the horizon is variable. Sea state, height of deck over water, visibility etc will all affect it. Whereas, with a sextant and a decent maritime chronometer it is very easy (*) to determine longitude and latitude.
Re: What Is a 'Nautical Mile'? (2011)
#9> 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…
I can believe that it's true that lines of longitude are not great circles, but I can't picture why in my head. Isn't a great circle formed by extending the shortest distance between two points on the surface of a sphere?
Re: What Is a 'Nautical Mile'? (2011)
#10> 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…
Also at the equator - the earth is not a perfect sphere.