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Sat Nav Problems

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I have six month Avensis and noticed that the Sat NAv is becoming incresingly in accruate at determing exact location. Somteimes it appears to be 100 yards ahead of where the car is exactly, and then at the next direction it will appear to be 150 yards behine of car's exact location. I know it is not a mapping problem as I have used system from when I purchased car. I have not changed tyres so the problem is not that. ny users had simalr problem and how did you resolve it?

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I haven't noticed symptoms like yours - my satnav appears to keep its positional accuracy. I think you should try the tyre change option on the menus anyway. This will force the satnav system to recallibrate itself by comparing estimated position to actual decoded position. I don't understand the exact reason why or how this works, if anyone can explain I'd be glad to hear it.


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I've had the same problem with my satnav since new. It's only a theory, but, as you are aware the satnav system "guesses" your position from the three data sources available: the GPS locator, the speed distance computer linked to the wheels (hence the need to re-calibrate when changing tyres) and the CD map. Unfortunately it often makes a bad guess! When you leave a motor way exit for instance, have you ever noticed how it thinks your still on the motorway for quite some time before suddenly snapping to your actual location? I know for sure the speed distance calculator is inaccurate on mine as the satnav's total distance traveled is around 20% more than the trip meter. This I think is due to the unique wheels found on G6R's and not on other Corollas (for which I suspect the system is set up for?). Inaccuracies in the data will obviously cause inaccuracies in the "guessed location". Why the manufactures don't use the speed distance calculating ability of the GPS system I don't know? It is also possible that the map data is slightly inaccurate in places causing still more confusion for the computer, then factor in low GPS coverage at times. As to a solution, are your wheels & tyres a standard fitment? Does the satnav distance calculator tally with the trip meter?

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