[OSM-talk] Motion sensors for navigation

[John Smith]

On 25 March 2010 10:20, Erik Lundin <erik at lists.lun.nu> 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.