2009/1/27, Helge Hafting <[email protected]>: > Gunnar Aastrand Grimnes wrote: >> This page does: http://wiki.openmoko.org/wiki/Accelerometer_Fundamentals >> >> Noise is around 3cm/s^2, i.e: >> >> " >> It can fill in _short_ - 3-5s gaps in GPS coverage, if the orientation >> of the phone is known. > > Not enough for a 4km tunnel then, which is 3 min when going 80km/h. > 5s is enough for a 111m tunnel, but 5s signal loss is usually not a > problem anyway. > > Of course, the car speedometer readout can take care of speed and > braking/acceleration, the accelerometer would only be needed to notice > turning. Could be interesting to see where it thinks I am after 3 min, > if 5s is all I can expect. I guess those 3-5s is the interval where > precision matces the gps. But it will be useful for longer than that, as > long as estimate is more accurate than "stopped at the tunnel entrance." > > The error increase with time, but so do the real distance from the entrance. > > Helge Hafting
Yes, I too think it would be useful for a longer period. In a time of 3-5 seconds one could propably get away with simply projecting the route at signal loss with constant speed. And I think navit snaps to streets anyway, so it wouldn't matter if its off by a bit. _______________________________________________ Openmoko community mailing list [email protected] http://lists.openmoko.org/mailman/listinfo/community
