SailNet Community - View Single Post - Magnetic Variance
View Single Post
  #23  
Old 01-30-2014
jerryrlitton's Avatar
jerryrlitton jerryrlitton is offline
Senior Member
 
Join Date: Oct 2002
Location: Andaman Sea
Posts: 1,244
Thanks: 1
Thanked 5 Times in 5 Posts
Rep Power: 13
jerryrlitton will become famous soon enough
Send a message via ICQ to jerryrlitton Send a message via MSN to jerryrlitton Send a message via Yahoo to jerryrlitton Send a message via Skype™ to jerryrlitton
Re: Magnetic Variance

Dean, we have this problem (Difference between mag north and true north) because we have a habit of drawing maps with north up however the magnetic north and south poles are the ends of the magnetic field around the earth. The magnetic field is created by magnetic elements in the earth's fluid outer core and this molten rock does not align perfectly with the axis around which the earth spins. Since we do have are maps with north straight up we have an ability to make the compass work with a map. Magnetic variation or declination is the answer. So depending on what point of the earth you are (or going) we have this east/west rule. In aviation we learned "east is least, west is best". So...if you have a true course of 100 degrees and you have a west variation of 4 degrees west... 100 degrees + 4 degrees = 104 degrees is your compass course. Remember that these is a difference between a course and a heading. Now with East variation you would subtract the 4 degrees for a course of 096 degrees. Now you need to add or subtract winds and water currents of your magnetic heading.

Hope this helps,

Jerry
__________________
"Duty, that grim demanding bitch, come to call with all her nagsome sisters, would never give a man a moment of his own."

A Kings Trade
Dewey Lamdin



Money canít buy you happiness.
But it buys you a big enough yacht to
sail you right up to it!
(Johnny Depp)







To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.

Last edited by jerryrlitton; 01-30-2014 at 07:56 PM.
Reply With Quote Share with Facebook