Lateral accuracy

Hello Packman. Yes, this is 'normal', and it's due to the amount of detail used to build the maps. The maps used in car/commercial GPS receivers have limited geodata to make their size manageable: In theory, you could make a map as precise as to include the lanes in the road, crosswalks, etc. but this would make them not only huge, but much more harder to maintain, and would demand more computing power to process your location -all this information would overwhelm the CPU of normal units.

Highways have a little bit more detail than general streets, but you might have noticed also, that your receiver doesn't show you if you are closer to the right side or the left side of the road. It may not even be able to tell if you are driving on the wrong lane on a two-way street (unless divided)! What the software does then, is that it "snaps" the cursor to the closest road, by using averaging and heuristic algorithms - or, to put it on layman's terms, makes an educated guess of your current position in the map. This is why, if you go in a tunnel and loose a signal, you would still see the cursor move down the road (it guesses your position, based on the speed you were traveling).

Again, there's nothing wrong with your receiver, its a little trade-off for making the maps, and receivers overall, inexpensive and user-friendly. If you display your latitude and longitude alone, it will be as accurate as it can be.

On a side note, aviation and receivers geared towards hiking, outdoors, etc, don't work this way, and their maps are built differently - They don't need to snap to a road grid.

Hope this made sense!
Krieger

If however, this always happens on the same spot, the map data may need tweaking to make it work better. You may try getting a newer version of the map, update the receiver's software, or submitting feedback for it. I'm not very familiar with Garmins, but I suppose you could submit the feedback on Navteq's website, to be used in future maps.

Hope this helps!
Krieger

The map data must be pretty detailed because if I am not on a route the device shows exactly where I am at. But on a route it stays on the road it thinks I am on even if I pull off. The other day I went through some construction on a divided hwy. Traffic was shifted onto the oncoming lanes several hundred feet from the original lane. The display show two very distinct lanes of traffic with a large gap in between but my cursor stayed on the original road. When I stopped the route the cursor jumped over to the other lane.

In that case it was no big deal because it still got me where I was going. But missing an onramp because of a stalled vehicle and having Jill think we were happily on the road was the pits. It wouldn't reroute because it thought we going the right way.
Oh well, I guess it is one of those things we all have to live with.

Thanks for your response!