Accelerometer brainstorming

[Al Johnson]

On Tuesday 01 April 2008, Flemming Richter Mikkelsen wrote:
> On 4/1/08, Alexey Feldgendler <alexey at feldgendler.ru> 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.