[laxman1100]

It seems as though I'm always 2-3 car lengths behind on the nav unit. It's kind of annoying when I'm trying to determine where I am while I'm driving and looking for streets.

It seems as though the speed signal is too slow or the positioning is updating slowly. Is there a way to "trick" the nav into thinking I'm going faster than I am to assume where I am, not where I was?

 

[philip_g]

set our tire size correctly.

 

[laxman1100]

Can I set them to a different size, so the nav unit will think I'm moving more/faster than I am? If so, I assume I should set them to a smaller size, right?

 

[PetrolDave]

It will auto-learn what it thinks is the correct tire size, so your trick won't work for very long.

BTW the accuracy of GPS is in the order of 10 metres, i.e. about 2-3 car lengths - so what you are seeing is IMHO as good as it gets with any GPS based system.

 

[laxman1100]

Got a Temp fix...

So, I was thinking about it and it makes sense to set it to a larger size, so the Nav is thinking it's moving faster than it really is. So, here are my results:

I have 225/45/17 Goodyear GSD3 F1's.

Reco is 1930.

1980: too fast, overshot overpasses at 70, almost dead on at 30-40
1975 (auto adjust): drove around for about 10 min, Nav adjusted by itself, but still overshot streets at 60-70.
1965: a little behind on streets at 30-40mph, and a little ahead at 70.

I'm going to leave it here for awhile and tweak as necessary.