Roger Long wrote:
"Gary" wrote


are always different, always! You can't swing a compass with a
typical GPS.


Why not? Pick a slack current time and set up a waypoint to distant
landmark. Stop the boat and check the compass. You need to do it on
multiple headings or else have landmark waypoints about every 30
degrees around the horizon. If you're in a good coverage period and
the landmarks are several miles away, it's going to be very accurate.

I didn't think about using the course to steer to a waypoint function.
That would certainly be much better than using the COG function. I am
no sure what the original poster used but your idea seems sound.