Wy not? I have a wifi only iPad. Do I need Internet connection to be able to use gps? Well if that's the case, good thing I never sold my garmin nuvi gps
The WiFi-only iPad does not have GPS functionality. GPS is part of the electronics included in the 3G versions of the iPad. WiFi iPads have some navigational capability by using a database of known WiFi basestation locations. But once this type of iPad cannot receive a WiFi signal it has virtually no navigational capability.
It is possible to connect an external GPS unit to these WiFi iPads and several models are available for purchase but, if you already have a sat nav system, this probably doesn't make a lot of sense.