Accelerometer brainstorming

Flemming Richter Mikkelsen quatrox at
Wed Apr 2 17:52:56 CEST 2008

On 4/1/08, Al Johnson <openmoko at> wrote:
> On Tuesday 01 April 2008, Flemming Richter Mikkelsen wrote:
> > On 4/1/08, Alexey Feldgendler <alexey at> wrote:
> > > In Norway, where I live, some tunnels are very long and even sometimes
> > > contain internal enter and exit lanes, so there can be more than one way
> > > to go. My Garmin navigator tries to estimate where I am basing on the
> > > speed I had when entering the tunnel, so sometimes it notifies me of an
> > > internal exit I have to take too late.
> >
> > Correct! We even have round abouts inside tunnels. If you take the wrong
> > exit,
> > you would have to drive for a long time to be able to turn and get back (on
> > the
> > highway). So the phone needs a system that is better than the one from
> > Garmin.
> >
> > -=Flemming=-
> So you need a car cradle with a CAN interface - IIRC there have been USB-CAN
> adaptors listed here before. This would give you access to the vehicle speed,
> and perhaps other useful things - steering angle perhaps? Accelerometer input
> for finding corners may be useful even if it's not accurate enough for
> inertial navigation. The interesting part comes in combining the available
> data to give the location estimate.

What do we need the CAN interface for?
We already know the speed before we enter the tunnel, and if the neo
is in a car holder in a stable position, calibrated with some
software, it knows from the accelerometers if we are driving strait
ahead or making a turn and also if we are accelerating. With a little
bit of mathematics, this can turn out to be very precise.

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