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Go Back   SailNet Community > Skills and Seamanship > Seamanship & Navigation
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Seamanship & Navigation Forum devoted to seamanship and navigation topics, including paper and electronic charting tools.


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  #11  
Old 01-29-2014
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Re: Magnetic Variance

Quote:
Originally Posted by nolatom View Post
Well since no one's said it, and at the risk of outdated PCness, I'll repeat the jingles I learned back in Power Squadron and around the docks:...


He was already thinking so much I could hear his brain cells popping. I was trying not to answer more than he asked.
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Old 01-29-2014
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Re: Magnetic Variance

Quote:
Originally Posted by nolatom View Post
Well since no one's said it, and at the risk of outdated PCness, I'll repeat the jingles I learned back in Power Squadron and around the docks:

To get from From True to the Compass course to steer, you add Westerly error and subtract Easterly error. So, it's True, + - Variation = Magnetic, which + - Deviation =
Compass (and you add Westerly error and subtract easterly error for both variation and deviation, so in shorthand it's:

"TVMDC--Add W", (meaning True, Variation, Magnetic, Deviation, Compass, and add Westerly errors)

How to remember?? as the old non-PC sailors said,

"True Virgins Make Dull Companions--Add Whiskey"


And to go the opposite way, from Compass to True, it's ("CDMVT, Add E") or the jingle"

"Can Dead Men Vote Twice--At Elections?" (here in Louisiana, of course the answer is yes, ha ha)

There may be a more modern set of jingles, but True Virgins and Dead Men is what I grew up with, and I can remember the jingles when I can't remember the formulas.
That's a good way to remember it I guess! It would probably help me if I had an actual chart in front of me. The ones I have are TVA charts for Kentucky and Barkley lakes. No Roses!
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Old 01-29-2014
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Re: Magnetic Variance

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Originally Posted by DRFerron View Post


He was already thinking so much I could hear his brain cells popping. I was trying not to answer more than he asked.
You heard that, huh? I still have a few hairs left on my head!
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Old 01-29-2014
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Re: Magnetic Variance

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Originally Posted by Dean101 View Post
That's a good way to remember it I guess! It would probably help me if I had an actual chart in front of me. The ones I have are TVA charts for Kentucky and Barkley lakes. No Roses!
You can download free charts from NOAA that contain compass roses:

Nautical Charts & Pubs

The printed charts that I use are full-sized charts divided into 8.5x11 sheets when printed. I end up folding a single-sheet chart anyway so the smaller sizes aren't an issue, although some people don't like them.
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Old 01-29-2014
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Re: Magnetic Variance

Quote:
Originally Posted by Dean101 View Post
That's a good way to remember it I guess! It would probably help me if I had an actual chart in front of me. The ones I have are TVA charts for Kentucky and Barkley lakes. No Roses!
Ah, then you can add Roses to the Whiskey for the True Virgins!! ;-)

okay, to get serious for a nanosecond, you can get the NOAA charts on line, which will get you a look at the Compass Roses:

NOAA's On-Line Chart Viewer

Look at one for, say, Massachusetts Bay, then one for say the Central Gulf of Mexico (such as here in New Orleans) and you'll see that there's considerable variation in the former and almost none in the latter (so down here we seldom use the jingle). It has to do with the location of the iron ore in the northern Canada islands compared to the location of the North Pole, or so I was told. From here, they almost line up, hence almost no variation. But from the Boston area in Mass Bay, those Canada islands are considerably to the left of the North Pole, and your variation (sometimes called Declination) is about 15 degrees West.

Last edited by nolatom; 01-29-2014 at 07:13 PM.
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Re: Magnetic Variance

Quote:
Originally Posted by DRFerron View Post
You can download free charts from NOAA that contain compass roses:

Nautical Charts & Pubs

The printed charts that I use are full-sized charts divided into 8.5x11 sheets when printed. I end up folding a single-sheet chart anyway so the smaller sizes aren't an issue, although some people don't like them.
Quote:
Originally Posted by nolatom View Post
Ah, then you can add Roses to the Whiskey for the True Virgins!! ;-)

okay, to get serious for a nanosecond, you can get the NOAA charts on line, which will get you a look at the Compass Roses:

NOAA's On-Line Chart Viewer
Thanks you guys! I think after supper I will try to print some off and come back to it. I probably need a break.
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Old 01-29-2014
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Re: Magnetic Variance

Not sure if this is to simple and correct. I used hand held GPS compass to correct magnetic one with felt pen. Easier to calculate after that.
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Old 01-29-2014
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Re: Magnetic Variance

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Originally Posted by Osprey 26 View Post
Not sure if this is to simple and correct. I used hand held GPS compass to correct magnetic one with felt pen. Easier to calculate after that.
I may be incorrect, but I think the point of his learning this is to know how to do it without electronics.
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Re: Magnetic Variance

Oh well way back they didn't have books, charts...... where to draw the line.
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Re: Magnetic Variance

For the politically correct navigators out there TVMDC - TV Makes Dull Children.
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