| Jack Erbes 2007-05-29, 10:33 am |
| sarah bennett wrote:
> On Mon, 28 May 2007 19:16:14 -0400, Pieter wrote:
>
> Hi there Pieter,
>
> Does a (magnetic) compass work inside a (steel) automobile?
>
> sarah
If you are in the driver's seat and hold a handheld compass in your
right hand, sort of in the open space to your right, you may see a
fairly accurate display on the compass. But if you start moving the
compass nearer to the metal sides of the car or the metal, electrics,
and electronics in the dash area, the readings will change as the flux
fields around the compass are affected.
A compass in a car, boat, plane, ship, etc., is normally installed with
regard to the possible affects of nearby metal and electric fields.
Then it is calibrated to that location.
If you have a compass, stand outside your car (a few yards away) and
spot North. Then get in the car, with engine running and normal
electrics and electronics on, and see what the difference is. If you
can find a place to hold the compass where you can get the same North
reading, you have just calibrated your compass to the environment in the
car.
Do the same thing on the four cardinal headings and if the headings stay
consistently accurate, your compass will work in the car.
If your car happened to be parked over a large mass of metal (iron ore
in the ground for example) this might change as you move on.
One thing I like about using the GPS heading you get with a walking
speed movement or faster, is that it is calculated from the geometry of
your location and the satellites and is consistent and accurate.
Jack
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