Dbus api for gta2 accelerometers

Al Johnson openmoko at mazikeen.demon.co.uk
Mon Sep 14 14:36:35 CEST 2009


On Sunday 13 September 2009, 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.

I think you can get the more accurate timestamp if you talk to the  GPS direct 
in UBX format as omgps can. I don't remember whether the NMEA output uses 
integer or fractional seconds on this unit. Gypsy uses integer seconds since 
epoch as its timestamp, and I think this is where the rounding occurs. fso-
gpsd reads from gypsy so inherits the rounding.

Out of interest why you want to know the position of the points, and how do 
you intend to distinguish them from a lateral track defect? As a former 
railway test engineer I'm interested.



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