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. Matt -----Original Message----- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] 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 <[EMAIL PROTECTED]> wrote: > On Tuesday 01 April 2008, Flemming Richter Mikkelsen wrote: > > On 4/1/08, Alexey Feldgendler <[EMAIL PROTECTED]> 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. -- Please don't send me Word or PowerPoint attachments. See http://www.gnu.org/philosophy/no-word-attachments.html Join the FSF as an Associate Member at: <URL:http://www.fsf.org/register_form?referrer=5774> _______________________________________________ Openmoko community mailing list community@lists.openmoko.org http://lists.openmoko.org/mailman/listinfo/community _______________________________________________ Openmoko community mailing list community@lists.openmoko.org http://lists.openmoko.org/mailman/listinfo/community