Walkers risk making serious navigational errors because items they are carrying can stop compasses working properly, says a Scottish mountain safety adviser. Heather Morning, who works for the Mountaineering Council of Scotland, warns that the number of incidents where compasses have been affected by ‘reverse polarity’ caused by metal in devices such as mobile phones, keys, crampons and even underwired bras, has been rising and are also more likely to occur in bad weather.
With most mountain rescue call-outs resulting from navigational mistakes, the MCofS is keen to make hillwalkers more aware of the possibility of reversed polarity and what to do to check that compass bearings and readings are correct. Reversed polarity is caused by small magnetic fields generated by some metal objects, often carried by the walker, and can mean the compass needle gives the wrong reading when in close proximity to the object. The number of times this is happening seems to be increasing and Heather Morning has issued three golden rules to help deal with reversed polarity:
1. Keep your compass in a separate location to other electronic gizmos you carry with you on the hill and ensure when you are using it, that it is held well away from your body.
2. Ensure you read the contours on the map. You should have a very clear idea as to what should happen under your feet as you walk on your compass bearing. If this is not happening, the alarm bells should be ringing and you should re-evaluate.
3. Always carry a spare compass in the event of malfunction, damage or loss.
More information on reversed polarity can be found on the MCofS website.