Using magnetic compass to detect magnetic anomalies

I have been having a lot of issues getting my tugboat to go in a straight line, I kept having problems trying to get the compass calibrated, no matter how many times I calibrated it the heading was incorrect.
So I bought a little £1 magnetic compass to see if it can give some insight to what the issues is.

By moving the magnetic compass around near the GPS/Compass module, I could see that it was deviating almost 40 degrees! and that it was aligning to a go pro mount on the deck of the boat. Turns out the bolt holding the camera mount has become magnetized somehow and was messing with the calibration .

Fortunately the fix is quite simple, just take the bolt out and heat it up with a blowtorch until its red hot then quench it. This removes any magnetism from the metal and once I refitted it and waved the magnetic compass over it again there was no deviation in the magnetic heading.

So if you’re struggling with compass issues, it might be worth getting a cheap compass and checking there are no hidden magnets on your machine causing issues.


You can also try using demagnetizer if the magnetized element is less heat tolerant :slight_smile:


Or use a brass fastener. Not a bad choice for a boat anyway!


I should probably invest in one of those.