The last time I used a very, very expensive GPS system it was telling me I was several hundred miles out to sea, apparently floating along in my jeep, when I was actually driving along I-5. And several times the very new, supposedly up-to-date system was urging me to do things like merge into concrete dividers, or turn into the side of a huge building.

I'll settle for maps, guesswork, and asking locals.


ETA:


My sister has one built into her BMW, and from what I have seen and heard the built-in ones tend to be more reliable than the portables, but even then should not be totally trusted.