can the ipad mini be used as a sat nav?

A Wifi + 3G iPad mini has an onboard GPS chip so in theory it could be used as a satnav.

A Wifi only iPad does not have a GPS chip so it would depend on something else to get its position.

Yes, that is also possible. The iPad would get its location form the Phone's position. Which it gets from its GPS chip.

Glad I could help.