Discussion: Compass storage and usage questions

Does storing a compass near a battery-powered wristwatch or HRM sensor degrade the speed or accuracy of that compass?

Does wearing a battery-powered wrist watch in the same hand in which you hold your thumb compass affect the accuracy of your compass readings?

In a word: no. You need a lot more voltage than that to mess up a compass.

Though I have seen a really hefty watch made of some kind of steel significantly, though not permanently, affect a compass in a training clinic I offered once.

When I hold my compass right next to my watch, the needle moves. The effect seems to disappear at distance of more than one inch. I normally hold the compass on my thumb 4 inches away, so I would think that this is not an issue, but I was curious what others think.

I remember that I had some compass problems during a race last year, I wonder if it was caused by holding my compass next to the HRM sensor on my chest as I am wont to do when doing very fine orienteering.

wat about a gps watch would that have any effect

There seems to be two questions.
1. Will storing a compass near other metallic/electronic devices have an effect on in the woods performance?

Probably not. The material in the compass that makes it align to the magnetic fields of the earth are in most cases, what are called hard magnetic materials, Iron, nickel, cobalt alloys. It required extremely strong magnetic fields to align the particles and magnetize the material to make them work well (strong response, and fast) in earths weak magnetic fields. So I would not store my compass next to a super magnetic, but putting it in with another compass or a watch, HRM, iPod, will not affect the in the woods performance.

2. Will holding a compass next to objects affect the accuracy of the compass while navigating? Yes. The compass is really just a simple magnetic. Holding it next to any other magnetic materials or electrical devices will have an affect on the in woods performance. To what extent, will depend upon several factors. In basic terms, having a Garmin or a sports watch on your compass hand will probably give less than a deg of variance while running. Bottom line for the best in the woods performance keep electronic devices and metallic objects (Steel, iron, nickel) away from you compass while navigating.

The US Army has a little table of recommended separation distances from certain objects. Unfortunately, it doesn't include GPSs or anything like that.

In World War II, the steel helmet weighed over 4 pounds, and is said to be the cause of some pretty major navigational errors.

Here's what I do. I get the compass out in the open, far from metal stuff, and then I move the object I'm testing close to the compass. If you see the needle deflect, it's affecting the compass. Pick some starting orientation of the object and the compass, and then be sure to try turning the object 90 degrees.

Just sitting here at the computer, I can hold the compass in one hand and move the GPS around it with the other. I'm getting maybe 5 degrees deflection when they're almost touching. Moving them apart far enough to simulate the distance from my wrist to my hand, there is no noticeable effect.

One thing that can really mess up a compass is not holding it level. You can often get the needle to stick as much as 20-30 degrees off by tipping the bezel before the needle has settled. Practice running while keeping your hand completely level and still. Learn to do this without looking at it so the needle has already set by the time you look down.

I will be very careful around field guns from now on. :-)

If I can bend this thread a little, maybe there's some geologists/geophysicists out there who can tell me if the following sounds true or my boss is just trying to wind me up: One site that I'll be visiting thankfully rarely in a new study area allegedly "kills" compasses - that is rather than just becoming unreliable while you're there, the needle loses polarity and has to be remagnitised to be of any use afterwards. This is in the area covered in pumice from the big Taupo eruption about 2000 years ago...

Sounds pretty far fetched. As noted earlier, the materials used for compass magnets do not realign easily. Compasses do lose their polarity over time, but a brief exposure to a natural magnetic field, even a strong one, should have no noticable effect.

Of course, I'm not a geologist or geophysicist...

I liked playing with magnets when I was a kid. Especially electromagnets and cow magnets. I realigned several compass needles. It can be done.

As for Taupo? There is a paper about demagnetization anomalies there. This refers to large areas of rock that have been demagnetized by exposure to hydrothermal steam/water. I suspect your compass is safe.

I've known a compass to realign when it was worn near a holstered Blackberry. The BB cases have magnets which turn the screen of the device off. In this particular case the compass was resting beside the BB case long enough (a few hours) that it realigned the magnet in the compass.

Though for a cautionary piece of anecdotal evidence, I have a compass that spontaneously reversed for no known reason. It rode home from St. Louis* to Boston in the glove compartment of my car, and the next time I looked at it, the red end pointed south.

*I therefore blame ebuckley.

Sure glad that you didn't do a 180 and end up in Seattle.

Yea, we gotta keep those reversed compasses outta here!

*I therefore blame ebuckley.

Even after admitting that he occasionally threw a spitter, Hall of Famer Gaylord Perry acknowldedged that it was the suggestion of cheating that really worked for him: "Let 'em think I cheat, they're the ones getting psyched out by it."

And to follow his lead, I'll admit that Rich Ruid and I managed to jam part of a paper clip into David Frei's compass bezel once which made it read 15-30 degrees off.