Does your car distort the readings on your handheld compass?

[+slackpacker]

First, as will become readily apparent, I passed high school physics but haven't (knowingly) done much of that stuff recently.

 

Anyway, I was recently looking for an offset cache and, in an effort to be unobtrusive, shot the proscribed reading from inside my car - that is, set my hand held compass to magentic north, picked a reference point at the right heading (in this case, over on the next street) and drove over to that point. I then used my GPS'r to get the distance right for the offset, but I didn't find the cache.

 

After correspendence with the CO I knew I had done something wrong, so revisted the site. I pulled-up, again took a reading from inside the car, and got the same (apparently wrong) heading. I then got out of my car (here's where it gets interesting) and the compass realigned/corrected itself and provided a new heading (where, not surprisingly, I would find the cache.) Anyway, I repeated the experiment a few times (much to the consternation, I am sure, of anyone watching from the nearby office building) and always got the same result - wacky reading in the car, consistent and accurate out of the car.

 

If important, the compass is a $12 Silva handheld cheapo model, the car is a 2004 Subaru wagon (relatively cheapo model.)

 

Anyway, I wondered if anyone else has noticed this? The CO and I think it might be part of a vast but as-yet undetected Subaru conspiracy . . .

[+Kit Fox]

Cars are filled with EMF emissions. A compass is designed to be used in areas free of magnetic influence (other than earth).

[+Renegade Knight]

Quick Physics Answer:

 

Any time a localized magnetic or electromagnetic field is stronger than the earths magnetic field your compass won't point as you are exepecting it too.

 

Sources could included unshielded speakers (normal on a car). Crappy electronics with a lot of generated EMF.

 

I'm fuzzier on what it takes to distort the earths field but that's also a possiblity.

 

A simple way to check this is to just step out of your car and see if it's pointing the right way. Localized fields tend to be small. Walk a few feet or a few dozen feet over and you should be out of the 'zone' and back to normal. You can narrow down your source if interference that way.

[+apetro]

I have no idea what the answer to your question is, but.....i could not resist making an off topic comment!

love the avitar and your location, we are also BIG fans!

Andy: Now, here, here is a map of the United States.

Ernest T.: United States.

Andy: That's right. Now the United States is bounded on the north by Canada, on the south by Mexico, on the east by the Atlantic Ocean and on the west by, uh, would, uh, you happen to know that?

Ernest T.: (thinks) Old Man Kelsey's woods.

Andy: No. All the way to the edge – big body of water.

Ernest T.: Old Man Kelsey's crick.

Andy: Ocean.

Ernest T.: Old Man Kelsey's ocean!

Andy: Pacific Ocean.

Ernest T.: Pacific Ocean.

Andy: Very good, very good.

Ernest T.: Yeah, I sure know my boundaries good, don't I?

Andy: You sure do.

Ernest T.: Just as long as they don't change ‘em ‘fore I take my test

[+trainlove]

Answer, YES.

 

Reason, Earth's magnetic field is very weak, so any ferric and electronic manmade items nearby can, and will, interfeer with it.

 

One should be at least 3 feet away from any iron as any Boy Scout manual states. Magnetic fields do decrease with the inverse cube of distance so a little distance will go a long way (s.i.c) to making your compass give you the actual bearings.

[+Vinny & Sue Team]

First, as will become readily apparent, I passed high school physics but haven't (knowingly) done much of that stuff recently.

 

Anyway, I was recently looking for an offset cache and, in an effort to be unobtrusive, shot the proscribed reading from inside my car - that is, set my hand held compass to magentic north, picked a reference point at the right heading (in this case, over on the next street) and drove over to that point. I then used my GPS'r to get the distance right for the offset, but I didn't find the cache.

 

After correspendence with the CO I knew I had done something wrong, so revisted the site. I pulled-up, again took a reading from inside the car, and got the same (apparently wrong) heading. I then got out of my car (here's where it gets interesting) and the compass realigned/corrected itself and provided a new heading (where, not surprisingly, I would find the cache.) Anyway, I repeated the experiment a few times (much to the consternation, I am sure, of anyone watching from the nearby office building) and always got the same result - wacky reading in the car, consistent and accurate out of the car.

 

If important, the compass is a $12 Silva handheld cheapo model, the car is a 2004 Subaru wagon (relatively cheapo model.)

 

Anyway, I wondered if anyone else has noticed this? The CO and I think it might be part of a vast but as-yet undetected Subaru conspiracy . . .

Yes, operating a compass within or very near a motor vehicle can indeed influence and distort the compass reading, as most vehicles, including particularly their their engines and other parts of the drivetrain, contain significant masses of ferrous metals (various types of iron and steel, other than some types of austenitic stainless steel) and many of these chunks of ferrous metal will often bear residual magnetism, and it is this residual magnetism which can influence the needle or sensor on a compass.

 

It is also worth noting here that statistical studies indicate that a significant co-factor accompanying many reports of sightings of UFOs and close encounters of the third kind with "space aliens" is the presence of strong and very significant magnetic and electromagnetic disturbances in the local area. So, try not to use your compass near any UFOs or space aliens!

[+TheAlabamaRambler]

... other than some types of austenitic stainless steel...

Hah! My new word for the day! http://www.gowelding.com/met/austenitic.html

[+slackpacker]

It is also worth noting here that statistical studies indicate that a significant co-factor accompanying many reports of sightings of UFOs and close encounters of the third kind with "space aliens" is the presence of strong and very significant magnetic and electromagnetic disturbances in the local area. So, try not to use your compass near any UFOs or space aliens!

 

Interesting . . . the cache is located in the Atlanta suburbs, near Roswell(!), GA - coincidence? Maybe not . . .

[+slackpacker]

Thanks to all for your responses. It is refreshing to know that I spent 10 minutes, amazed, this morning in an empty parking lot proving to myself what is apparently common scientific knowledge. That said, at least I now know I don't have to go buy another compass (although I still think this might be part of Subaru's plot to take over the world . . )

[+slackpacker]

I have no idea what the answer to your question is, but.....i could not resist making an off topic comment!

love the avitar and your location, we are also BIG fans!

 

Thanks! Ernest T. was only in 5 episodes - I think - any more than that and he would've taken over the show. His episodes are the best of a very good show.

 

My apologies - back on topic.

Edited July 2, 2008 by slackpacker

[+TheAlabamaRambler]

I love to watch folks do this! Mostly newbies but I have seen the very experienced do it as well...

 

I do radio communications for Search and Rescue teams. You will see, almost every time, someone lay a map out on the hood of a car, plop a compass on top of it and set to plotting!

 

Of course their compass is totally off, so soon you will see them trot off in entirely the wrong direction!

[+The red-haired witch]

I love to watch folks do this! Mostly newbies but I have seen the very experienced do it as well...

 

I do radio communications for Search and Rescue teams. You will see, almost every time, someone lay a map out on the hood of a car, plop a compass on top of it and set to plotting!

 

Of course their compass is totally off, so soon you will see them trot off in entirely the wrong direction!

 

Actually, when plotting things on the map, the compass is only used as a ruler or roamer, the position of the needle is unimportant. So the car shouldn't have any effect on the bearings they decide on. Off course, if they then proceed to take their first bearing sighting while standing in the same spot, they'll start in the wrong direction for sure

 

So the search manager can use the car to plan, but the searchers should stay away from the car.

[+stagunner]

First, as will become readily apparent, I passed high school physics but haven't (knowingly) done much of that stuff recently.

 

Anyway, I was recently looking for an offset cache and, in an effort to be unobtrusive, shot the proscribed reading from inside my car - that is, set my hand held compass to magentic north, picked a reference point at the right heading (in this case, over on the next street) and drove over to that point. I then used my GPS'r to get the distance right for the offset, but I didn't find the cache.

 

 

If important, the compass is a $12 Silva handheld cheapo model, the car is a 2004 Subaru wagon (relatively cheapo model.)

 

 

Of course all Iron or steel objects will attract the magnet that is on the NORTH needle of any compass

even cheap imitation rolex watches, metal zippers, keys etc.

Just be careful when shooting your bearing,..

[+The Jester]

One course for women backpackers found that even the underwire in a bra can affect the needle.

[+WRITE SHOP ROBERT]

There are a lot of magnets in your car(every speaker) and a lot of electrical current/charge as well.

 

Especially odd I thought was when I hold mine near the gear shifter in my Big Truck(18 wheeler) and move the compass in a circle around it, the needle always directly at the shifter. I would expect some interference, but that's a lot.

[+TheAlabamaRambler]

One course for women backpackers found that even the underwire in a bra can affect the needle.

Yeah, but does it affect your compass?

[+Runaround]

I was plotting an orienteering course and noticed the ballpoint pen I was carrying would move the compass needle if I got it too close. It doesn't have to be a big piece of metal like a car to affect to compass.

[+DonB]

First, as will become readily apparent, I passed high school physics but haven't (knowingly) done much of that stuff recently.

 

Anyway, I was recently looking for an offset cache and, in an effort to be unobtrusive, shot the proscribed reading from inside my car - that is, set my hand held compass to magentic north, picked a reference point at the right heading (in this case, over on the next street) and drove over to that point. I then used my GPS'r to get the distance right for the offset, but I didn't find the cache.

 

After correspendence with the CO I knew I had done something wrong, so revisted the site. I pulled-up, again took a reading from inside the car, and got the same (apparently wrong) heading. I then got out of my car (here's where it gets interesting) and the compass realigned/corrected itself and provided a new heading (where, not surprisingly, I would find the cache.) Anyway, I repeated the experiment a few times (much to the consternation, I am sure, of anyone watching from the nearby office building) and always got the same result - wacky reading in the car, consistent and accurate out of the car.

 

If important, the compass is a $12 Silva handheld cheapo model, the car is a 2004 Subaru wagon (relatively cheapo model.)

 

Anyway, I wondered if anyone else has noticed this? The CO and I think it might be part of a vast but as-yet undetected Subaru conspiracy . . .

I don't know if cheap has anything to do with it or not. Some vehicles will distort the readings on the electronic compass in my GPS and some will not.

[+DonB]

First, as will become readily apparent, I passed high school physics but haven't (knowingly) done much of that stuff recently.

 

Anyway, I was recently looking for an offset cache and, in an effort to be unobtrusive, shot the proscribed reading from inside my car - that is, set my hand held compass to magentic north, picked a reference point at the right heading (in this case, over on the next street) and drove over to that point. I then used my GPS'r to get the distance right for the offset, but I didn't find the cache.

 

After correspendence with the CO I knew I had done something wrong, so revisted the site. I pulled-up, again took a reading from inside the car, and got the same (apparently wrong) heading. I then got out of my car (here's where it gets interesting) and the compass realigned/corrected itself and provided a new heading (where, not surprisingly, I would find the cache.) Anyway, I repeated the experiment a few times (much to the consternation, I am sure, of anyone watching from the nearby office building) and always got the same result - wacky reading in the car, consistent and accurate out of the car.

 

If important, the compass is a $12 Silva handheld cheapo model, the car is a 2004 Subaru wagon (relatively cheapo model.)

 

Anyway, I wondered if anyone else has noticed this? The CO and I think it might be part of a vast but as-yet undetected Subaru conspiracy . . .

I don't know if cheap has anything to do with it or not. Some vehicles will distort the readings on the electronic compass in my GPS and some will not.

[+edscott]

I love to watch folks do this! Mostly newbies but I have seen the very experienced do it as well...

 

I do radio communications for Search and Rescue teams. You will see, almost every time, someone lay a map out on the hood of a car, plop a compass on top of it and set to plotting!

 

Of course their compass is totally off, so soon you will see them trot off in entirely the wrong direction!

 

Reminds me of people plotting a course at a picnic table... with their map and compass right over a nail head. Same result.

[+va griz]

I had a cheapo pin on compass sitting on the little shelf below the steering wheel. Just happened to be looking at it when I opened the door, and it would track the door as it opened and closed. I thought I had discovered some new magnetic property until I realized there was a speaker, with its magnet, in the door.

[+trainlove]

I just discovered that even though most carabiners are made of aluminum (the non climbing ones), there is a steel spring inside that will distort your compass if it's on your clip.

True climbing ones are mostly aluminum but there are some stainless steel (non-magnetic). And those mostly do not have a spring, either a fast secure lock or screw/twist lock.