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post #6 of Old 06-17-2010
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Originally Posted by redhead78 View Post
Hello all, I have noticed this year, my pedastal compass, and GPS headings are very close however, the readout on my autohelmis like 40 degrees off. There is nothing metal or magnetic by it, is it an adjustment?? Red
I have to step in here a moment. Your GPS is not showing heading at all. It is showing a direction across the ground. Boats are like aircraft in that respect. Where the nose is pointing is not always thew way we are going. We travel in a moving air mass. Unless we are going directly upwind or downwind our direction we are headed will be different then our ground track. I suppose in a sailboat you can throw in leeway in addition to water currents. In addition to all of that you can throw in magnetic deviation and variation.


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