The Mountaineering Council of Scotland has issued a warning after the cause of numerous rescue callouts was found to be navigation error due to compass reversed polarity. Without realizing it, your compass can easily be compromised by numerous magnetic fields on your person, not reading true north, but in fact just the opposite.
When hiking or orienteering, you normally wear your compass around your neck or attached to the zipper of your jacket. These are the same areas where you store your keys, cell phone, GPS, and many other items that are electric or contain traces of metal or magnets.
As we know, a compass works off of the earth's magnetic field. However, magnetic fields also exist around many items we commonly carry with us outdoors, such as cell phones, personal locator beacons, GPS, car keys, magnetic belt fasteners, and even underwire bras. Magnetic fields can also be found in obscure places such as grocery store shelves and your car stereo speakers.
Needless to say, there are a number of opportunities for your compass to become reversed polarized, where the proper north and south needle orientation are switched, without your knowledge. The result could range from simply annoying to down right life threatening. Unfortunately, this phenomenon is becoming extremely common, as we carry more items with us on that trail that emit some form of magnetic field.
Your compass needle can become briefly, partially, or totally reversed when in close proximity to one of the above mentioned magnetic fields. If the needle becomes sluggish and slow to settle (it may appear to stick and be out of balance) it has become partially reversed. If the north arrow (usually red) is pointing to south instead of north, your compass has become completely reversed.
In order to prevent reversed polarity, your compass should be kept well away from all potentially hazardous items, especially other electronic gadgets you carry with you on the trail. Always hold your compass away from your body when in use. Alarm bells should instantly ring if the contours and markers on your topo map do not correlate with what you are seeing on the trail or in whiteout situations, what you feel under your feet. Carry a spare compass if possible and most importantly, always check your compass before you head out on any adventure.
Although it is not complicated to reverse the polarization of your compass needle, Silva recommends you send your compass in for maintenance. The company will re-magnetise your compass for you, no matter how old, free of charge.
Has anyone ever experience reversed polarity on their compass?