TL Nav System / GPS question

I've have an '07 TL-S.

When I input an address into the nav system, the accuracy is pretty
good...within 15-20 yds.

When I touch the little circle on the screen, sometimes it's WAY off, by
maybe several hundred yards. I presume that when you do that, you're
getting the location via GPS as opposed to the data base on the DVD.

Is that a normal deviation range? Can the dealer tighten it up some?

Thanks.

Tom S.
Houston, TX