You are talking about a vehicle that would have to carry dozens if not hundreds of terabytes of data. The boot would literally have to be filled with hard drives. If you are in the US you should be able to tell it to drive from one coast to the other, or if you are in Europe the car should be able to drive from Warsaw, Poland, to Aberdeen, Scotland. And what do you mean only local data needs to be updated? Why? Updating a "dumb" TomTom map takes hundreds of megabytes a month just for one country, and we are talking about much more complex data, not just a 2D map.