Observations on ferrous interference on compass use

mkhop said:
I like a magnetic compass first learned to navigate and read a map with one , however back up is always wise and a gps with fresh batteries is a blessing , or using the stars or the sun to confirm the compass or even using a topo map and use terrain features to orintate your self.
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The million dollar quote there.:thumbup:

A compass is MUCH less usefull without a map. Natural navigation using map and surrounding landmarks is all part of wilderness navigation.

The ability to move beyond compass magnetic error is part of nav skills.

Most people have a compass and most people have no idea how to navigate with it and a map. Get taught and practice, no different than fire making or shelters etc..

Skam
 
bentblade said:
Unless you plan on hiking nude I would suggest you get a new compass.
I don't know what model compass you have but there are alot of bad ones being produced and sold by what used to be good companies.
As an example The current Silva Ranger is getting terrible reviews on the REI web site. In the past the Ranger was concidered a first class product.
The current Silva Rangers are made in China, the older ones were made in Finland. I heard that the Finnish made rangers are now sold under the Brunton label.
For all I know Silva may not even be a in business anymore It may now just be a name that some corp. bought the rights to. Like Schrade, Smith & wesson and Winchester knives.
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compass is verified and calibrated every year by SUUNTO. Its not the compass, its the ferrous objects near the compass that throw it off. Its a professional (industry rated) grade forestry compass. Fact is its been proven time and time and time again that metal zippers, knives, guns, axes, ice axes, vehicles and ferrous rocks will throw off the reading when using a compass, ANY compass. Fact of life.
 
The current Silva Rangers are made in China, the older ones were made in Finland.
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I don't know about Finland but my Silva Ranger (several years old) is marked Made in Sweden as is my Silva Safari. I also have a much older Silva Ranger (has an aluminum lid/mirror housing instead of plastic). It is marked Made in Sweden Assembled in USA by Silva.

Bill
 
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I was doing a science experiment with my children, showing them how a magnetic compass works and how a magnet could make the needle swing, when I accidentally reversed the polarity of the compass needle. I managed to undo it, but it was fun for a while, lol. I actually learned about metal affecting compass readings when in the boy scouts and later in the Army. Minerals in the earth, as explained above, can also throw a reading.

Does anyone know if it affects electronic compasses like those in GPS units and automobiles?
 
rwiggins said:
Does anyone know if it affects electronic compasses like those in GPS units and automobiles?
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If I'm not mistaken, GPS units point to true north relying on sattelite transmissions for their bearings, and as such would not be affected.
 
rwiggins said:
I was doing a science experiment with my children, showing them how a magnetic compass works and how a magnet could make the needle swing, when I accidentally reversed the polarity of the compass needle. I managed to undo it, but it was fun for a while, lol. I actually learned about metal affecting compass readings when in the boy scouts and later in the Army. Minerals in the earth, as explained above, can also throw a reading.

Does anyone know if it affects electronic compasses like those in GPS units and automobiles?
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How'd you do it? I have a Silva compass that, for a reason unbeknownst to me, reversed its polarity.
 
kycolonel said:
Good information. I have always wondered if a knife, say a neck knife that is magnetized wouldn't royally screw-up a compass that is hanging from a lanyard.
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Yes, it can. After carrying one exactly like that for years and always trying to keep them separate when stowed - it happened. It wasn't an expensive compass but it was always accurate. That's when I learned about carrying a spare...
 
North said:
I don't know about Finland but my Silva Ranger (several years old) is marked Made in Sweden as is my Silva Safari. I also have a much older Silva Ranger (has an aluminum lid/mirror housing instead of plastic). It is marked Made in Sweden Assembled in USA by Silva.

Bill
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Your right for some reason I keep getting sweden and finland confused.
 
Bushman5 said:
compass is verified and calibrated every year by SUUNTO. Its not the compass, its the ferrous objects near the compass that throw it off. Its a professional (industry rated) grade forestry compass. Fact is its been proven time and time and time again that metal zippers, knives, guns, axes, ice axes, vehicles and ferrous rocks will throw off the reading when using a compass, ANY compass. Fact of life.
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That being said, with the amount of variation that you describe how could you ever trust your reading. If your in an area where you cant see identifiable landmarks and your compass reading is off by 5 degrees that would put you way off your mark if you had several miles or more to go.
Nobody carries more metal than the military and their load varies constantly. How did they deal with the problem in pre GPS days?
 
dougo83 said:
What does this mean??
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A back azimuth is 180 degrees opposite of your direction of travel bearing. I think he's just kidding around, as the notion of a dedicated "back azimuth compass" is pretty silly.
 
x39 said:
A back azimuth is 180 degrees opposite of your direction of travel bearing. I think he's just kidding around, as the notion of a dedicated "back azimuth compass" is pretty silly.
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I had never heard of such a thing. We refer to compasses that are 180 out as "broken." I just couldn't figure out why my readings for astronomy were off all the time until I checked this thing to the North Star and my GPS one night. Luckily, it was before I left on a 3-day hike.
 
bentblade said:
That being said, with the amount of variation that you describe how could you ever trust your reading. If your in an area where you cant see identifiable landmarks and your compass reading is off by 5 degrees that would put you way off your mark if you had several miles or more to go.
Nobody carries more metal than the military and their load varies constantly. How did they deal with the problem in pre GPS days?
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i dont trust my readings. I rely on my trailmarks (tree blazes, dated flagging tape) and a topo map + an aeriel photomap. The compasss to me is for quick "general" direction finding
 
We had a compass read perfectly 180 opposite to magnetic north. It was not sold as a back azimuth compass. At the WLC, we teach navigation in three parts, compass use only, map only then we combine both map and compass together. This all takes place over three days and we try to stress the importance of Nav. skills. They are very lacking in many people you would assume are woods worthy. In my opinion, they are essential and one shouldn't venture into the woods unless they have a firm grasp of the basics to get oneself out.

Kev
 
I reversed the polarity of the magnet and kept passing it over the needle in the opposite direction than I did to begin with. It took a few tries, but it finally worked. I decided to use less powerful magnets for any future experiments, lol. I was using a neodymium. I never suspected I could reverse the polarity of the compass needle in the first place since it pivots freely so it came as quite a surprise when it happened. Reversing polarity and direction was just a blind guess that happened to work. Remember though, this was a cheap compass.

Ankar Sheng said:
How'd you do it? I have a Silva compass that, for a reason unbeknownst to me, reversed its polarity.
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I have had several compasses go south on me including the button silva in their brass waterproof match container several electronic compass watches and various button compasses , one marbles with the brass housing but my old Silva Ranger and my Mil spec lensatic compass (you can call in fire support danger close with it) these 2two have never let me down. Once I have removed possiabilty of defect and human error I never question my compass but still give it a little back up.
 
There is something about calibrating the magnetic affects of the vehicle that you are travelling in specifically relating to large ships that can significantly influence the compass reading.

You can assess your own/vehicle/ships affect on a compass by comparing a known bearing off a map to a reading from your compass, this is the same way you can compensate for local declination affects rather than use published general adjustments.

I do this quite often when walking to check a compass before a walk.
 
Bushman5 said:
Fact is its been proven time and time and time again that metal zippers, knives, guns, axes, ice axes, vehicles and ferrous rocks will throw off the reading when using a compass, ANY compass. Fact of life.
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I stumbled upon this thread and it's very interesting :thumbup:.

I didn't want to make a new thread since a lot is already covered here, so here it goes. I thoroughly concur with what you wrote above. That being the case, to get a good reading from the compass, should I strip all my gear beforehand :rolleyes:?
 
Several years ago, as I was on a business trip in a part of the country I'd never been before, I stupidly bought those globe compasses they sell at Walmart/Kmart that you attach to the windshield or dashboard of your car. I checked it against my handheld compass while in the parking lot to make sure the two matched. They were different by a few degrees, but that didn't matter as I only wanted the car compass for a general sense of direction, so that I could veer off onto another road if there was heavy traffic on the main ones.

I couldn't figure out as I was driving why this compass kept showing the same direction. I would be sure I was driving northwards and the thing kept showing southwest. Then on the way home the thing showed southwest. Then I looked online and found that not only is the metal covering of the car affecting the compass, but as soon as you turn the engine on it creates a magnetic field that affects it. So the compass was aligning with the magnetic field of the car, hence showing the same direction no matter which way the car was facing.
 
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