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#58867 - 14/01/2002 17:46 Autocalibration of positions, OBD-II usage for nav
smu
old hand

Registered: 30/07/2000
Posts: 879
Loc: Germany (Ruhrgebiet)
Hi.

I was wondering if OBD-II data would be usefull for Kim's navigation software, especially for auto-calibration of map/GPS positions, estiating time till next turn, etc.
I know many commercial navigation systems use a compass in addition to the GPS (though not a very precise one) as well as the information from many onboard sensors, like acceleration (available for airbag and/or breaking control), mileage and speed. Some even check how much you turn your front wheels (i.e if you are driving straight or not). I just don't know if they just get that info from OBD-II on a different way.
Anyway, I am certain that at least speed and mileage would be available through OBD-II, and I think that those would be useful for a navigation software. And if I am right with that, it might be a good idea to find a way to receive both GPS and OBD-II data through the same serial port, even though that would require an additional device to multiplex the serial port. Well, discussion of this might be better kept in the OBD-II thread at the programming forum, where I originally posted this question.

cu,
sven
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#58868 - 14/01/2002 18:04 Re: Autocalibration of positions, OBD-II usage for nav [Re: smu]
mcomb
pooh-bah

Registered: 31/08/1999
Posts: 1649
Loc: San Carlos, CA
estiating time till next turn

FWIW Kim's software already does this. Some of the screens tell you how many meters until your next turn and some of the voice prompts will tell you an estimated time of arrival.

Anyway, I am certain that at least speed and mileage would be available through OBD-II, and I think that those would be useful for a navigation software.

You can get speed directly from the GPS and it seems to be quite accurate (my GPS shows speed that is accurate enough that I can not tell if there is a difference between it and my speedo).

Anyway, it may be useful as a double check, but I wonder how much it would really help.

-Mike
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EmpMenuX - ext3 filesystem - Empeg iTunes integration

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#58869 - 15/01/2002 00:06 Re: Autocalibration of positions, OBD-II usage for [Re: mcomb]
ellweber
member

Registered: 14/01/2002
Posts: 156
Loc: Saratoga, CA, USA
Vehicle speed and compass direction are useful for dead reckoning when GPS data is unavailable such as in a tunnel or covered garage. GPS velocity is typically acurate to better than 0.1 m/s (~0.25 mph) but only when the satellite signals are present.

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#58870 - 15/01/2002 06:48 Re: Autocalibration of positions, OBD-II usage for nav [Re: smu]
rtundo
addict

Registered: 27/02/2001
Posts: 569
Loc: Albany, NY
On a side-note. Does anyone know how to access GPS data from a vehicle with onstar. Would this also be available through OBD-II?

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#58871 - 15/01/2002 06:57 Re: Autocalibration of positions, OBD-II usage for [Re: ellweber]
smu
old hand

Registered: 30/07/2000
Posts: 879
Loc: Germany (Ruhrgebiet)
Hi.

Thats what I thought of, plus: My Garmin only recalculates the speed about every 4 seconds (sometimes even slower). And you can be sure that we have quite a few locations around here (well, not necessarily in Dortmund, but in Duesseldorf or Cologne), where GPS reception is almost impossible and you still need to know how far away your next turn is. Also, if the car is standing, or moving at walking speed, I noticed that the GPS reported heading is often _far_ away from truth.
Also, when you leave the originating place, how should the GPS/nav system know whether you are already heading in the right direction, or should turn 180?

Compass is really usefull I would guess (but that isn't available through ODB-II either), and mileage/speed is useful in tunnels and also sometimes when driving between tall buildings (especially if they are made of concrete with a lot of iron in it).

That isn't meant to stop Kim from releasing his software, but I would like to mention these additional information sources for his software, and would like to discuss their optional integration with the system.

I would love to see a little box that can be stuck in the serial line, which adds an interface to ODB-II (for speed/mileage) and possibly a small, not necessarily highly accurate, compass. Mind you, I don't know anything about electronic readable compasses at all except for the fact that they exist.

cu,
sven
_________________________
proud owner of MkII 40GB & MkIIa 60GB both lit by God and HiJacked by Lord

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#58872 - 15/01/2002 13:02 Re: Autocalibration of positions, OBD-II usage for [Re: smu]
Derek
addict

Registered: 16/08/1999
Posts: 453
Loc: NRW, Germany
Some of the Garmin etrex models include an electronic compass and the compass readings are available as NMEA sentences over the serial interface.
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(list 6284, Mk1 S/N 00299 4GB blue [sold]. Mk2 S/N 080000094 20GB blue)

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