Ok, got a problem which has been annoying me for months and I'm hoping someone here has come across the same problem and found a resolution.

I've got a Pioneer F10BT with the GPS installed under the dash of my A3. I'm finding that the vehicle location displayed on the nav is generally a constant 30 metres from where I acually am. whenever I turn into a street the arrow turns prior to the actual street and then once it realises it jumps onto the correct street but again lags 30 metres or so. Even when I manually correct it eventuall lags off again.

Does anyone one think the dash is somehow causing the problem? I generally receive full satellite reception and I'm advised that the GPS antenna is mounted well away from the unit as per specs.

I've got an old TomTom which I used as a comparison and it tracks superbly.

I know the quick answer would be to have it moved from under the dash to see how it affects it but I not technically minded and I don't want to move it if it will have the same result.