My children told me that in one area around Mount Fuji, the magnetic
compass goes completely haywire; this is something they learned in
junior high school science class.
I assume underground metallic magma plays havoc with the magnetic field
lines. If I recall their explanation, the compass needle actually
fluctuates wildly in some areas around Fuji Yama.
I am sell aware of magnetic deviation from navigation studies, but I
had never heard of local fluctuations of the kind my children told me
about. Live and learn.
On Wednesday, Jul 6, 2005, at 00:59 Asia/Tokyo, Wayne Fugitt wrote:
I have followed this thread with interest.
Unless I missed it, no one yet has described how a compass actually
works.
Likely most of the technical people know this, but some may not,
unless they have been intimately involved with the compass.
> PLEASE! Do not allow yourself to become confused over this issue!!!
Wishful thinking......
>
> The "North SEEKING Pole" of a compass will point to the North Pole of
> the Earth, and also to the North pole of a magnet.
While this appears to be correct and logical, it is not true !
The compass, in most areas of the earth does not point to the North
Pole of the earth.
Instead, the compass needle aligns itself with the magnetic field of
the earth.
This is why we have the terms, Grid North, Magnetic North, True
North, and Magnetic Declination.
The error of the compass can be 5, 10 15 or more degrees due to the
way it works, paralleling the magnetic lines of the earth. Typically,
one will refer to a map, chart, or other reliable source to find out
the exact
angle of adjustment.
As one moves east or west on the earth, the compass must be adjusted
for this error. If one was planning to use his compass for several
miles of navigation, this better be done right. Not doing so, could
get you lost and cost you your life.
When I was hunting in Colorado, seems the magnetic error was 14
degrees. Most good compasses have an external adjustment and it is
very easy to adjust. Don't economize on your compass.
Do your homework. Making a mistake in the wilderness can be fatal, in
more ways than one.
I agree, this is mostly academic to the masses. The few that need to
know it, usually do.
Wayne
