Watches & compass interference?

I've been playing around with the idea of getting a new casual watch for when I'm outdoors and am wondering if there are certain considerations I should be taking into account if I expect to be wearing it while trying to navigate with a compass.

To what degree (if any) will a wrist watch interfere with a compass? Are some watches better than others with regards to playing nice with a compass (materials, movement, etc.)?

I'm not really experienced with navigating with a map & compass yet, but I got a new compass (Suunto MC-2DL) and a book (Wilderness Navigation) for Christmas and plan on taking some courses a bit later this year.

I doubt your watch will interfer with your compass.

I'm right handed, wear a watch on my left wrist, and use the compass in my right hand. I don't even worry about the minor deviations possible with metal framed glasses when sighting.

Remember to compare the map to the ground to what the compass is telling you and keep a decent pacecount. You should be good to go.

Interference of that kind is easy to detect. Move the clock really up close and around the compass until you see the needle move so it points straight at the clock (or away from it). Then increase the distance but not the angle between the clock and the compass. Watch the needle point north again.


Usually, the distance required for your watch to influence your compass is too small for having any practical consequences. But it is good routine to actually CHECK this. In some cases (such as holding the compass in your left hand with a heavy watch) you may actually influence the accuracy. But this is easy to fix (such as moving the compass to your right hand).


I've been to high arctic where the magnetic field lines are close to vertical - which also means that the horizontal magnetic component is very small. Up there it doesn't take much to influence your compass. Standard procedure for having reliable compass readings was to remove any guns and step away from snowmobiles.

Lots of things can mess with your compass. Rocks containing significant amounts of iron, like many volcanics. I have seen needles 45 degrees off from local lava flows.

I always like to check the compass against the North Star just to be sure everything is OK.

The way I've checked for interference, deflection, is to place my compass on a flat surface and orient it so the needle points toward a cardinal direction. Once set up I then move the device or gear I'm checking for influence on the compass nearby and look closely to see if the needle has shifted.

Using this technique a friend found that his belt buckle has highly magnetized and could swing the needle 30 degrees. Which somewhat restored his confidence as a navigator after it was shaken on a trip when nothing showed up where he thought it was supposed to be. A magnetized belt buckle, and differences in how he held the compass, would explain the variable readings.

I read a case where a man's surgical implant, a plate a screws in his arm, would throw off a compass. The good news is that for most people in most places small deflections have little real effect. If you were blind shooting for a tiny un-land-marked water hole across eighty miles of salt flats a small deflection might get you killed. Fortunately most of us are in familiar territory with enough terrain clues to keep us going in the right direction even if the compass goes wonky.

Still, if you have a compass it would be best to have it accurate and to limit interference with its accuracy.

+1 on the above comments.

This past weekend, we were in an area that has literally millions of tons of boulders and rocks that played havoc on the compass (did not need it, but always have it on me). At times, the compass would be off more 30 degrees in many different directions and it is easy to imagine how less experienced people could wander off in the wrong direction and never realize it until they were really lost...

I have worn a Suunto watchband compass right next to my watch on the same band for years. I check the compass every now and then against other compasses. So far, no problems. BTW, my watch is a cheapo Timex expedition.

Come to think of it, my wrist watch incorporates a compass (rarely used). I sure hope the watch plays nicely with the compass....(and it does, to an acceptable degree, when I have checked it out).

The compass you have is a good model, I have used the Silva Ranger 15 CL for years which is very similar.

The compass needle can be effected by metal but it has to be quite close to the compass, I just wear my watch on the other wrist.

I did have a strange thing happen between a watch and a compass. I had a Timex Expedition watch with a built-in compass feature, for quick reference I slid a Brunton #9068 watchband compass on it. After a couple of months the polarity of the small watchband compass reversed 180*, the north arrow now points south even when it is not on the watchband? I think this must have been caused from being in close proximity to the electronic compass in the watch.

Mike

Thank you all for your insights; I appreciate the help.