SailNet Community - View Single Post - Magnetic Variance
View Single Post
Old 01-30-2014
nolatom nolatom is offline
Senior Member
Join Date: Jun 2005
Location: New Orleans
Posts: 1,869
Thanks: 6
Thanked 23 Times in 21 Posts
Rep Power: 10
nolatom will become famous soon enough
Re: Magnetic Variance

Good progress you've made! Your math (second line) is correct on all three situations, though I can't match the "Given" wording of numbers 2 and 3 with the TVMDC math part. But the math, in the correct order, is what matters.

Just bear in mind that when you go the other way, from Compass to True, that "East isn't least", it's the other way around--you add East ("at Elections") and subtract West error.

In practice, you usually are going from True to Compass anyway*, seldom do you need to do the reverse. But just sayin'...

*except maybe on a beat, where you tack and find out your compass course first, and then your poor navigator (meaning you??) have to convert to True for your semi-accurate plot of beating to windward. this is probably the most difficult type of compass-only conversion/plotting chartwork you'll have to do. Anything you can plot with only one course line (meaning reaches and runs) is way way simpler and more reliable than "naviguessing" a beat when you have no landmarks and no electronics. Which is why it's worth practicing, ha ha. And it's why we call this "dead reckoning".... ;-)

Last edited by nolatom; 01-30-2014 at 03:15 PM.
Reply With Quote Share with Facebook