The GPS antenna works fine without a data connection, but gmaps requires one. If you have a mapping/navigation app that can preload it should work fine. I have never tried though.
To clarify, gmaps does use cell tower triangulation, wifi signals, AND the GPS antenna. It uses the other two methods to approximate your location while it waits for a GPS lock.
If you preload areas you are traveling to cash them in gmaps before losing signal you can continue navigating for some time. That works for smaller "dead zones".