NSW Nordic Ski Club
GPS doesn't replace your Compass
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Excuse my late contribution but I have been away and among the catching up I'm doing was 'Kick and Glide' for September 2001. The article "GPS - A Users Guide" was very good except for one point that could mislead users: "A compass is not essential in practice but must be carried ...." A compass is essential. There is a common misunderstanding that GPS tells you where North is. It doesn't. It is not a compass and when you're stationary it doesn't have a clue which way you should go to follow a bearing. As one wag says, to tell North just stand the GPS unit upright on the ground or in the snow and use its shadow to estimate N-E-S-W. If you can clearly see where you have come from and where you have to go, then the GPS tells you in relation to those visible things and in relation to your map where you are, where you've been, and where (theoretically) you should go. However, if you need to follow a bearing it can tell you what the bearing is but, from where you're standing, it doesn't know which way you're facing and can't tell you whether you should step forward, sideways or backwards. This is particularly dangerous in conditions of poor visibility. Only a compass knows where the bearings are. To illustrate: Two people standing back to back will get identical information on their GPS units, but without a compass could step off in exactly opposite directions, and wouldn't know until they took their next GPS position. Fancy doing that in a blizzard?! Even then there is a qualifier. Most GPS units are set to True or Grid North and so correspond to your map. Thus you still need to allow for magnetic deviation in setting your course. I hope this helps. I wouldn't like to think of someone setting off with only a GPS and a map, encountering limited or no visibility or whiteout, then knowing with the GPS precisely where they were but not having a clue about which direction to actually move their feet to get to where they want to go.
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