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BMW 3-Series (E90 E92) Forum > E90 / E92 / E93 3-series Technical Forums > AUDIO/VIDEO + BLUETOOTH + Electronics/Alarm/Software > Nav system works without line-of-sight?



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      04-10-2006, 09:12 AM   #1
Mitch1138
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Nav system works without line-of-sight?

I noticed the other day that my GPS Navigation system seems to track location even if it doesn't have a line-of-sight to the sky. Both in a long tunnel and in a parking garage, it seemed to track my location. Does anyone know if the system has inertial tracking or some other trickery when it can't see the sky?
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      04-10-2006, 10:47 AM   #2
SteveMD
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It likely has something called 'Dead Reckoning' that a lot of the higher end standalone units have. It probably is hooked to the speedometer so that during brief 'outages' the unit will keep on truckin'.
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      04-10-2006, 12:15 PM   #3
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Had the same thing happen in the Big Dig in Boston. Blew my f'ing mind!!!!!!!! I assumed I was going to lose navigation so I remembered the underground exit I had to get off at.. Wasn't necessary!!
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      04-10-2006, 12:43 PM   #4
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From my E46 days, I seem to recall that the Nav systems take info from the wheel sensors to augment the satellite data. From this they can get information about vehicle movement including accurate info about turns.

I'll see if I can find this info again.
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      04-10-2006, 01:23 PM   #5
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Just dug out some more info. Strictly, this info refers to an earlier system, but I think we can be fairly sure that the E90 does this as well.

It appears that the GPS data is augmented by both the wheel speed sensors and an inbuilt compass. This adds to the accuracy of the position fix when you turn as well as filling in losses in GPS signal.
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      04-10-2006, 02:09 PM   #6
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Quote:
Originally Posted by London320d
Just dug out some more info. Strictly, this info refers to an earlier system, but I think we can be fairly sure that the E90 does this as well.

It appears that the GPS data is augmented by both the wheel speed sensors and an inbuilt compass. This adds to the accuracy of the position fix when you turn as well as filling in losses in GPS signal.
It is refered to in the manual and says it uses the anti-lock brake sensors. Still think my E46 was better and more accurate though.
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