Dbus api for gta2 accelerometers

Al Johnson openmoko at mazikeen.demon.co.uk
Wed Sep 16 23:47:15 CEST 2009


On Wednesday 16 September 2009, Ed Kapitein wrote:
> Rask Ingemann Lambertsen wrote:
> > On Sat, Sep 12, 2009 at 07:50:26PM +0200, Ivo van den Maagdenberg wrote:
> >> The use case is as follows: take the openmoko and make it a cycleway
> >> shock measuring platform, utilizing the accelerometers. So, direct reads
> >> from the are going to be needed. The gps unit is of course of interest
> >> to make the measurements location-based.
> >
> >    I've had an idea along the same lines: Use accelerometer data to log
> > the position of points during a train ride. Only, I'd need GPS readings
> > that are accurately timestamped, i.e. not rounded to whole seconds.
>
> Since a train has a large mass and a reasonable speed, why not use the
> whole second readings of speed and heading and use
> interpolation/extrapolation to determine the actual time and location?
> It should be rather accurate i guess.

We would want to interpolate anyway, but the error bound is set by the 
rounding error introduced by using integer seconds. Even at relatively low 
vehicle speeds this may be greater than the error in the reported GPS 
position. 100km/h is just under 30m/s.

Ideally I would like to see ogpsd extended to provide more accurate timestamps 
and more control over the gps.



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