I used a magnet to see if there was any iron nearby, and then a hand bearing compass
to see if it's needle moved as I moved it around the area. I'm about 18 inches above a small bilge pump
, but I don't notice any interference--even when it's running.
I drilled the pedestal
and tapped the holes for the mounting screws. When commissioning the system, the deviation was only 2 degrees (I think Raymarine
says 15 degrees is acceptable).
process clued me into the fact that my ship's compass is actually off! So I picked up a magnetic compensation card, and I'm about to go out and turn it, and make a deviation card. The Raymarine
agrees with my hand bearing compass, my dive compass, my iPhone
compass, and range marks in my harbor. The "ships" compass is off by 2-3 degrees through most headings. Grrr....