went to Myrtle Beach over weekend, did lots of turning and twisting,

which i suppose could goof up the internal synchro.

but not GPS?

we drove home, and the arrow for our location was off the actual road for about 3 miles, until we made a hard right turn.

was kind of a wooded area, with some overhanging trees.

then, got up in morning, the GPS had the truck parked about a block away from our house, and wanted to route me all over the neighborhood.

it got straight after that, and hasn't missed a beat since.

i have the GPS antenna inside the front dash, the stock Navi system has a little shelf at the base of the windshield, beside the center speaker, and it lays there.

do i need to move the GPS to the roof to be more accurate?

Is your VSS hooked up?

no, my understanding is the unit can locate it self via GPS,

and the VSS and Internal syncro would be used to correlate the GPS location,

and dead reckon the position/accleration/location in case the GPS signal was blocked

now maybe the signal could have been blocked in the overhanging trees, but we were out in the open for ~10 miles and headed south, so the windshield mount should have provided a good look angle to the GPS Satellites.

don't think this was speed related (wasn't ahead or behind, just off to the side), in the woods, instead of on the road.

and in the morning, it was just sitting there all night. and i live 100 feet from the last turn into my house, and it knew where it was when i parked it (arrow was on the road)

Guys:

Be sure you don't have the GPS antenna under any metal, such as a speaker grille, and that you don't mount it under a window with too many metal defroster lines in it.

In my 2008 Audi A4, the installer hid the antenna underneath the front center speaker grille (which is plastic) and it works fine. Had to give up that speaker, though...I have 9 more!

no, my understanding is the unit can locate it self via GPS,

 

and the VSS and Internal syncro would be used to correlate the GPS location,

 

and dead reckon the position/accleration/location in case the GPS signal was blocked

 

now maybe the signal could have been blocked in the overhanging trees, but we were out in the open for ~10 miles and headed south, so the windshield mount should have provided a good look angle to the GPS Satellites.

 

don't think this was speed related (wasn't ahead or behind, just off to the side), in the woods, instead of on the road.

 

and in the morning, it was just sitting there all night. and i live 100 feet from the last turn into my house, and it knew where it was when i parked it (arrow was on the road)

I had that problem, hooked up the VSS and it worked just fine! The VSS wire is used so when your GPS isn't getting a good GPS signal it'll still know where you really are.