Compass Interference?

[Guest Olar]

Today I was at a potential cache site and needed a compass bearing. I took a hand-held reading and then decided to get an absolute exact number. I set it down on top of a stone pillar which was part of an observation deck railing system and got a bearing 10 degrees different than the original. I double and triple checked and tried on another pillar and still got differing results. The deck is all stone and wood. No metal. Can the discrepancy be caused by metal deposits in the stone?? What else could cause it?

 

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Happy Caching, Olar

 

"if you come to a fork in the trail, then take it!"

[Guest brokenwing]

quote:

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Originally posted by Olar:

Today I was at a potential cache site and needed a compass bearing. I took a hand-held reading and then decided to get an absolute exact number. I set it down on top of a stone pillar which was part of an observation deck railing system and got a bearing 10 degrees different than the original. I double and triple checked and tried on another pillar and still got differing results. The deck is all stone and wood. No metal. Can the discrepancy be caused by metal deposits in the stone?? What else could cause it?

 

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I suppose it's possible. Were the readings on the second post consistent with the readings on the first post?

[Guest brokenwing]

Are you sure there were'nt iron re-enforcing rods in the stones? I'd think the stones would have to have a significant amount of iron ore on one side or the other to skew the compass that far off.

[Guest Olar]

quote:

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Originally posted by brokenwing:

Are you sure there were'nt iron re-enforcing rods in the stones? I'd think the stones would have to have a significant amount of iron ore on one side or the other to skew the compass that far off.

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Readings at each post were consistent. I'll bet there is metal re-rods in the middle.

Thanks Brokenwing.

[Guest Olar]

quote:

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Originally posted by brokenwing:

Are you sure there were'nt iron re-enforcing rods in the stones? I'd think the stones would have to have a significant amount of iron ore on one side or the other to skew the compass that far off.

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Readings at each post were consistent. I'll bet there is metal re-rods in the middle.

Thanks Brokenwing.

[Guest Baston]

Hi Olar

There is a scout camp between Acton and Guelph were we can not teach the scouts compass work. There is so much iron ore in the area so you cannot get a good bearing. But the chances are that there is rebar in the pillers.

 

Baston

[Guest rediguana]

I have noticed two types of interference with magnetic compasses so far.

 

1. Less common, when I was in a national park in Australia the compass started giving some very funny directions. The compass was still in the correct zone, I believe it was a large localised iron ore deposit. (Either that or there were aliens flying overhead )

 

2. More common, don't the compass get too close to electronic devices as the electromagnetic emissions can play a little havoc. Try it by holding the compass next to a phone/GPSR whilst its on and see what happens

 

Cheers Gav

 

[This message has been edited by rediguana (edited 04 September 2001).]

[Guest rediguana]

I have noticed two types of interference with magnetic compasses so far.

 

1. Less common, when I was in a national park in Australia the compass started giving some very funny directions. The compass was still in the correct zone, I believe it was a large localised iron ore deposit. (Either that or there were aliens flying overhead )

 

2. More common, don't the compass get too close to electronic devices as the electromagnetic emissions can play a little havoc. Try it by holding the compass next to a phone/GPSR whilst its on and see what happens

 

Cheers Gav

 

[This message has been edited by rediguana (edited 04 September 2001).]