I’ve always taken stories of compass reverse polarity with a degree of scepticism as I’ve never personally noticed any problems. But, in preparing for this year’s Challenge, I was thinking of keeping my compass in a hip belt pocket along with my camera so I decided to see what effect it had. My expectation was that any effect would be so small as to be irrelevant. I was astonished – there is a major magnetic effect (about 50 degrees)as you can see in the pictures below. How long it would take to reverse the polarity, I don’t know but for sure it is a possibility.
I also tried other devices – a SPOT tracker which had no effect whatsoever and an iphone, which had a very minor effect. Probably too small to reverse polarity but I wouldn’t risk it. So – be careful and don’t keep your compass in the same pocket as your camera.