Quote Originally Posted by Matt_ View Post
GPS doesn't account for altitude changes. If you live in a flat area it's not bad.
Depends on what brand and model you're using. I use a hand held for land navigation that does take hills and stuff into consideration as it tracks you mileage. I don't know to much about the ones mounted in cars though. I have to wedge it in the window sometimes I have to hold it in the window I hardly if ever use the nav unit installed in my jeep.