That's correct, but the earth's magnetic field is often the dominating. If a classical compass can point out the earth's magnetic field, why shouldn't it be possible with an electronic sensor? Quick fluctuations could be filtered out.
/Erik John Smith skrev: > On 25 March 2010 10:20, Erik Lundin <[email protected]> wrote: >> I have thought of a solution were you have a GPS device together with an >> electronic compass sensor. In the tunnel, the position is calculated by >> knowing the last position, the speed (either from the speedometer in a >> car or keeping the same speed as before the tunnel) and the compass >> direction. Since the error in this case increases exponentially with >> time (right?), it would help to drive through the tunnel in both directions. > > Magnetometer sensors are sensitive to all sorts of magnetic fields, > not just the magnet field of the earth and so aren't very accurate, to > prove this point someone made a metal detector for android phones a > while back and it really does detect metal, or at least the magnetic > field around metal. _______________________________________________ talk mailing list [email protected] http://lists.openstreetmap.org/listinfo/talk
