Accelerometer brainstorming

Crane, Matthew mcrane03 at
Wed Apr 2 18:10:03 CEST 2008

I think that generally mems devices have proven to work badly for this
sort of thing.  Because of random drift and other errors.  It would need
to assume that the car is on a path, the road, and attempt to infer
where on the path it is.  It wouldn't likely work with just the acell
data, and it would take some finely tuned software and then some to get
even an aproximation.

Of course, it might be ok for the typical case of periodic short term
obscured gps signal.  Any distance or turns and it's liekly to diverge
pretty fast. 


-----Original Message-----
From: community-bounces at
[mailto:community-bounces at] On Behalf Of Flemming
Richter Mikkelsen
Sent: Wednesday, April 02, 2008 11:53 AM
To: List for Openmoko community discussion
Subject: Re: Accelerometer brainstorming

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
> > > 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
> > > 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
> > 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
> > Garmin.
> >
> > -=Flemming=-
> So you need a car cradle with a CAN interface - IIRC there have been
> adaptors listed here before. This would give you access to the vehicle
> 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
> 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.

Please don't send me Word or PowerPoint attachments. See

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