Am 23.01.2008 um 14:37 schrieb Sébastien Lorquet:
I'm not sure a magnetic sensor is useful when you have a GPS,
because a GPS can give you a heading as soon as the measured
velocity is not zero!
It is exactly useful for this reason: if you are not travelling by
car but as a pedestrian, the GPS direction calculation is quite
imprecise. And if you simply rotate the device to rotate the map, you
have velocity zero.
However I think it's possible to calibrate a magnetic sensor so
that it forgets its close magnetic environment and is only
sensitive to the intented magnetic signals. The magnetic
environment is stored as a "fingerprint" and is then substracted to
the raw measurements to get a correct value.
Look how the "Garmin eTrex summit" https://buy.garmin.com/shop/
shop.do?pID=143 is doing:
1. it has an additional magnetic sensor
2. you have to calibrate it once you replace the batteries (metallic/
magnetic!)
3. calibration is done by rotating the device once by 360 degrees in
approx. 2-3 seconds
Am 23.01.2008 um 14:25 schrieb Schmidt András:
I was thinking about two possible applications:
1. The map of a GPS map viewer application turns when you turn the
machine so it is always aligned with the environment (this
feature
is included on some GPS tools.)
2. A software rendered compass (I have already seen one on a
phone as
I mentioned in a previous mail)
4. the waypoint tracking map is rotated accoring to the orientation
of your device
5. a compass can be shown graphically
So, these ideas are indeed reasonable and already implemented in a
commercial GPS device but not in mobile phones.
Nikolaus Schaller
_______________________________________________
OpenMoko community mailing list
[email protected]
http://lists.openmoko.org/mailman/listinfo/community
