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Discussion Starter #1
Now, it's not so much that I'm concerned. I know which to rely on; this was more out of curiosity. I opted for the Uconnect 8.4N in my charger, and by clicking on the "current speed" in the lower right hand it pops up a menu that includes engine time, top recorded speed, average speed, average moving speed, time moving and time stopped. These are all awesome things to know, I'm just a stat junky, so it's a delight having all of that available.

What caught my eye this evening is a discrepancy between the mileage count on the nav, and the odometer. It's off by 8 miles (the nav has 8 miles more than the odo, over nearly 3500mi. I suppose it's not that bad), but I was curious if this was just due to the minor inaccuracies inherent to GPS, or an actual problem I should be concerned about.


and going off that, (since, until now I figured that mileage was just pulled from the odo) is the "current speed" indicated by the nav calculated based on GPS or pulled from the speedo? I figured it was all pretty well integrated, but I guess maybe it's all just one way, and the nav can put stuff up on the EVIC, but can't get anything from it.
 

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GPS can be inaccurate, although it's less so since the military stopped dithering the signal.

Speedometer is based on an average tire size, and some mfg also throw in a minor safety factor. As the tread wears down, the tire diameter changes.

To answer your question, nothing to worry about.
 

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Also, GPS doesn't take into account terrain variation as accurately as the rolling measurement taken by the ODO. Every up and down on the road adds mileage and every lane change and corner apex reduces mileage as compared to the GPS which doesn't accurately fix your position in the lane to that level of precision. GPS can't tell which lane you are in, just that you are on the road.
 

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Discussion Starter #4
Also, GPS doesn't take into account terrain variation as accurately as the rolling measurement taken by the ODO. Every up and down on the road adds mileage and every lane change and corner apex reduces mileage as compared to the GPS which doesn't accurately fix your position in the lane to that level of precision. GPS can't tell which lane you are in, just that you are on the road.
I'd assume that this would account for the ODO reading more than the GPS, not the other way around. That was really what piqued my interest. I could see the GPS not having some tunnels included in that mileage, and little stuff like lane changes and u-turns, etc. cutting some distance from the GPS-mileage.

And I would certainly hope it wasn't an issue of tread wear decreasing the wheel diameter, the car doesn't even have 3500mi on it.
 
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