Stupid Compass Question

K

Kaylee

Joined
May 12, 2001
Messages
54
So all this time I've been out in the woods, it was usually on relatively short trips and overnights in mostly-known territory. Wasn't it ol' Boone that said something like "I've never been lost.... but I have been powerfully confused at times?"

Well.. that was kinda my style. Not efficient, but still breathing, which I guess is all that matters in the end. *heh*

Anyhow, I finally decided to learn this "land navigation" thing, picked up a Silva (a week before learning US Silvas aren't Silvas, or somesuch) and started playing with the thing. And quickly discovered what I suspect all of you know.

I pass a powerline, it goes wonky. I walk along a railroad, it goes wonky. Sometimes it goes wonky for no reason I can tell... metal deposits in the ground maybe?

Gee.. sounds like a politician. Tells me it's dead-on sure one minute, the next it's pointing in a completely different direction. *heh*


So... I reckon I'm asking, most importantly,
how do you know if your compass isn't telling you the unvarnished truth? I'm presuming some models are better about this than others, but I hear the US Silvas are decent enough.

Is there a double-check method I don't know about? I've discovered cupping it in my hands gets rid of the problem usually, and there's always the sky I guess, but it still makes me nervous.

Ideas/fixes/enlightenment?

-K
 
Kaylee, I feel your pain.

The rule of thumb is to always trust your compass. But I've also learned that trust must be earned. I usually check my compass with another compass or with a GPS before departing on a trip, but there are anomilies that will play havoc with it. I'm from Upstate NY and frequent the Adirondacks in some areas that are ripe with iron ore. If I'm in a suspect area, I'll use the shadow/stick method to check general direction.

Mike

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It's not the pace of life that concerns me, It's the sudden stop at the end.
 
Almost forgot ... Boone said he'd been bewildered a bit ... I was lost. LMAO

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It's not the pace of life that concerns me, It's the sudden stop at the end.
 
I know that if you take a divining rod and walk across your yard you can find the buried pipe for your water lines, sewer lines, etc. And they don't have to be metal pipes either! The explanation that I heard was that whenever you dig a trench in the earth, it disrupts the magnetic field in the ground. Maybe this is what is causing some of the disruptions you are seeing. Yes, power lines can cause it but maybe you are experiencing something else. Tonight, I'm going to go home and walk across my yard holding my compass. I'll let you know if I get the same effect as with a divining rod.
 
Maybe it's something you are carrying on yourself. Double check it by walking and holding the compass out in front of you a good ways...better yet take all your clothes off and walk across the wilderness...just be sure to give me a call because I have a lot of film.

On a serious note, I have never had anything affect a compass except for things that I was carrying with me. Be careful of placing two compasses close together because they will affect each other.

Jeff

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Randall's Adventure & Training
jeff@jungletraining.com
 
Whether it's the "U.S. Silva" (probably made by Suunto) or the old Silva of Sweden (before about 1996) they are both good compasses. A very strong, near-to-surface iron deposit can affect them but it usually won't render them useless. Check the geology in Idaho where you are and see what's under you. Powerline shouldn't be but a momentary problem. I agree with Jeff that it sounds more like something you've got on you, gear, metal fittings, belt buckle. Next time it goes 'South' on you, stop and set it down on something and back away a couple of feet and see what happens. Also grab an extra compass, simple baseplate maybe, and pull it out and see if it's haywire too but like Jeff mentioned, keep the two compasses separated by a couple of feet or they'll monkey with each other. Mike
 
"Cupping it in your hand" won't block a magnetic field in the slightest (unless you're wearing steel gauntlets). This sounds even more like you have just moved the compass away from something that you are carrying that has been magnetized.

Any steel object that you wear, carry, or have in your pack may be magetized. Try spreading all your gear out on a table and run the magnet over the collection. You may find that a hatchet, knife, machete, pack frame, belt buckle etc. has been magnetized. Anything with a speaker in it like a cell phone or radio may have an intentional magnet in it. Anything with direct current running through it like CD player could operate as an electro-magnet. So when you check out things on that table, turn on any electrical gadgets.
 
Kaylee, few simple ideas to consider:
- Shake it up, tilt and let it resettle to see if needle returns to same position. Real bad compasses don't do it.
- Check compass against another one or against sun/clock, sun/shade movement, moon/shade movement, north star method of determining true (non-magnetic) North. Some of these are also useful to determine magnetic declination if it is unknown.
- Place compass on ground and step back to see if it is some metal on you that interferes. If in doubts, move further back and use binocs if necessary
smile.gif

- Orient far object with compass and move 100 m sideway to check if it shows the same. 100 m difference should not change reading if object is very far. By this you can test if closeby object interferes with your readings.

Good luck,

HM
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Thanks for the advice all!

I'll give it a look to see if it's something I'm wearing. I do know I've two compasses -- both Silvas, and unless they get so close they interfere with each other, they both agree, so I don't think it's the compasses themselves.

Jeff C, I don't know what to tell ya, but I saw the needle move 15 degrees or more -- and back -- as I cupped and uncupped my hand around it. No, I wasn't wearing any rings, or otherwise moving my hands. Wierd.

Jeff R, can't say as I've gone woodswalking in the buff lately, but if I do, I'll let ya know.

Thanks again all!

-K
 
Look out for watches and belt buckles as well. That's one reason I laugh at those watchband compasses. I've had watches too close to a compass and through it off.

Belt buckles are notorious for throwing a compass off. At least mine anyhow, yeah their BIG!
wink.gif
But not as big as some cowboys!
biggrin.gif


Just some more ideas to contemplate.



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Plainsman
primitiveguy@hotmail.com
<A HREF="http://www.plainsmanscabin.com" TARGET=_blank>
Plainsman's Cabin</A>
 
Well, I tried my compass as a divining rod last night and it does NOT work the same.

However, I did notice that my belt buckle would cause a 5 or 10 degree variation and walking past my truck made the needle jump about 20 degrees.
 
Here's an interesting experiment:

Take a fine sewing needle and rub it for a few minutes with a refrigerator magnet. This will magnetize it so that it can act as a compass needle. Set the needle on top of a piece of toilet paper and gently float the toilet paper in a ceramic or plastic bowl. The toilet paper will saturate and sink to the bottom, while the surface tension of the water will keep the needle afloat. You can watch the needle orient to magnetic north. Cool!

Try this experiment using a metal bowl and see what happens. Also try it inside your house and out in the open, away from interferences.

This is also a good way to introduce children to the concept of a compass and also for learning about the earth's magnetism. My father taught this to me when I was about eight years old and I'll always remember it.

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Camine con tranquilidad, sirva con humildad, y viva en paz.
 
Kaylee,

First of all, there's no such thing as a stupid question. Different folks are simply at different points along the learning curve. Even Albert Einstein had to learn 1+1=2 before going to the more advanced stuff. He also flunked a math course in high school, if I remember right.

You mentioned power lines. Electricity sets up magnetic fields, and overhead power lines cause very powerful fields. Some believe that these magnetic fields cause health problems in persons who work around high voltage lines.

The following is from FM 21-76, the military manual on map reading and land navigation:

(begin quote)
b. Effects of Metal and Electricity. Metal objects and electrical sources can affect the performance of a compass. However, nonmagnetic metals and alloys do not affect compass readings. The following separation distances are suggested to ensure proper functioning of a compass:

High­tension power lines- 55 meters.
Field gun, truck, or tank- 18 meters.
Telegraph or telephone wires and barbed wire- 10 meters.
Machine gun- 2 meters.
Steel helmet or rifle- 1/2 meter.
(end quote)

21-76 can be found here: http://www.marshall.edu/rotc/fieldmanuals.htm

Be advised that the military does things a little differently- different terminology, mils instead of degrees, etc.- and the material might be confusing at first.

Regarding power lines and such - any linear type landmark such as a road, power line, RR track, river etc is called a baseline. With a baseline you know where you are, at least on one axis. Of course you can miss your baseline if it’s a road and there’s snow on the ground. I’ve heard of this happening.

Here’s a link to info on using a compass:

http://www.uio.no/~kjetikj/compass/

Two books that I like are Staying Found by June Fleming and Be Expert with Map and Compass by Bjorn Kjellstrom. The first book is geared towards backpackers and the second is geared toward the sport of orienteering.

And finally, here’s a breakdown on the confusing mess about a Silva compass isn’t really a Silva, etc, if you’re interested: http://www.equipped.com/devices26.htm

Navigation is one of my real weak areas, simply because I don’t practice and keep the skills fresh.

Good Luck!


 
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