Swinging the vehicle to check the compass is a basic navigator duty. For
aircraft there's a compass rose on the tarmac, for boats/ships there are
hand bearing compasses and pelorus (pelori??), but see
http://www.boatsafe.com/nauticalknowhow/bearing.htm Check with all
equipment on board and energized and the engine running (if applicable). A
deviation card should be mounted on the compass, or close by. Speaker
magnets are just one of many sources of deviation.

Then again, there are really cheap hiking-type GPS units that will tell you
your track (but not your heading).

Roger

http://home.insightbb.com/~derbyrm

"Jim Conlin" wrote in message
. ..
I missed that day in fre\shman physics, so i remain not informed but
concerned.

A long time ago, i almost had a very nasty grounding because some speakers
which had been brought on board deranged the compass.


"Maynard G. Krebbs" wrote in message
...
On Fri, 17 Mar 2006 14:44:53 GMT, chuck wrote:

Marine-type speakers are generally shielded (as are speakers intended
for use near CRTs) so this should not be a problem. The speaker
description/packaging should indicate whether it is magnetically
shielded.

I'd be interested in hearing of any cases where a magnetically shielded
speaker has interfered with magnetic compass readings.

Chuck


Something I always wondered about is, "How do you magnetically shield
something."
Doesn't Magnetism pretty much go through things. How could you shield
a speaker's magnet so it wouldn't affect a compass?
Mark E. Williams