Originally Posted by jerryrlitton
Ok 1st thing, your GPS is not showing a heading. It is showing a traffic across the ground usually in magnetic but that will depend on how you have yours configured. Of course your track will vary with current, winds and your leeway. Also your compass needs to be calibrated for your installation area (deviation) and it is also subject to magnetic variation. So it is no small wonder there is a difference between the 2.
GPS does not show headings, it shows a course over ground and in any place but a widless pool your heading is always very different from your course...
Some more complete GPS units feature a fluxgate though...And those can show more accurate true and/or magnetic headings...