Groundhog246
Contributor
1 cable = 100 fathomsdiscrepancy:
1 fathom = 6 feet
10 cables =1 nautical mile (actually not quite, but that generally what's stated)
3 nautical miles = 1 league
Are you still imperial?
- Thread starter Arnaud
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1 fathom = 6 feet
10 cables =1 nautical mile (actually not quite, but that generally what's stated)
3 nautical miles = 1 league
Actually, you just restated what I already said.KrisB:
Rick
Guess what?
A "nautical mile" is not an exact measurement!
A specific latitude and longitude isn't an exact position!
And a knot is not an exact speed!
The nautical mile is one minute of latitude, true... but the distance covered in one minute of latitude varies depending on where you are on the surface of this imperfect sphere, or on how high above it you are. And as a knot is one nautical mile per hour, that varies as well.
As for Lat/Long positioning, there are several ways to measure that, and when it gets right down to it, it depends on whose chart you use.
None of these variances are significant to the casual user, but they do exist and are nice little pieces of "back pocket" information.
Rick
A "nautical mile" is not an exact measurement!
A specific latitude and longitude isn't an exact position!
And a knot is not an exact speed!
The nautical mile is one minute of latitude, true... but the distance covered in one minute of latitude varies depending on where you are on the surface of this imperfect sphere, or on how high above it you are. And as a knot is one nautical mile per hour, that varies as well.
As for Lat/Long positioning, there are several ways to measure that, and when it gets right down to it, it depends on whose chart you use.
None of these variances are significant to the casual user, but they do exist and are nice little pieces of "back pocket" information.
Rick
radinator:I convert all my dive depths to fathoms and dive times to fortnights anyway, so the units I start with aren't important.
When I do it that way, my total bottom time looks depressingly small.........
Rick Murchison:Guess what?
A "nautical mile" is not an exact measurement!
A specific latitude and longitude isn't an exact position!
And a knot is not an exact speed!
The nautical mile is one minute of latitude, true... but the distance covered in one minute of latitude varies depending on where you are on the surface of this imperfect sphere, or on how high above it you are. And as a knot is one nautical mile per hour, that varies as well.
As for Lat/Long positioning, there are several ways to measure that, and when it gets right down to it, it depends on whose chart you use.
None of these variances are significant to the casual user, but they do exist and are nice little pieces of "back pocket" information.
Rick
Not anymore. Happily, a nautical mile is now defined as exactly 1852 metres and a knot is one nautical mile per hour.
http://physics.nist.gov/cuu/Units/outside.html
I think distances are now all fundamentally defined in m, which in turn is defined by how far light in a vacuum travels in 1/299792258 of a second.
So the answer to the original question is that we are all metric. It's just that some of us don't realise it yet.
And Canada wants to go back! It was made law in the 70s that we would switch over here in the US. I wish we would have. So much better.
In my life I have had to use Imp, Metric, Chains, Fathoms and I think Im forgetting some assinine measurement system that I had to learn.
I fought the math in diving all the way up to my IDC where I was shown the easy way in metric. I tried to show this to my GF for her Nitrox class and the new PADI books have one or the other, not both any more. ***?
In my life I have had to use Imp, Metric, Chains, Fathoms and I think Im forgetting some assinine measurement system that I had to learn.
I fought the math in diving all the way up to my IDC where I was shown the easy way in metric. I tried to show this to my GF for her Nitrox class and the new PADI books have one or the other, not both any more. ***?
On closer examination I see that this "official" definition of the NM falls in the "Other units outside the SI that are currently accepted for use with the SI, subject to further review"... so... it's almost official, but not quite, and I can legitimately enjoy the vagaries I grew up with for a little while longerMacHeath:
Rick
Rick Murchison:... so... it's almost official, but not quite, and I can legitimately enjoy the vagaries I grew up with for a little while longer
Rick
Do I sense a slippery slope!!!!
Trying to teach an old dog eh?
Indeed... next thing you know they'll be defining a gaggle & deeper'n whale dung.Kim:Do I sense a slippery slope!!!!
"Measure with a micrometer, mark with chalk, cut with an ax."
Rick
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