When you don't have a cell signal your Map Viewer doesn't work.
I saw this early December when the wifes daughter was getting married. I offered to set the GPS in the car to the destination but I was overruled because one of the passengers had their Apple Phone and had the destination programed into it. They took off and promptly drove into a Cell Phone Black Spot and with no signal no directions or any idea of where it was that they where.
As the driver didn't know where it was that they where going other than it was the Historical Village and no one in the car knew exactly where it was that they where going things got more than a little stressed.
The In car GPS worked though no one in it knew how to set it to get them where they wanted to go.
I should also point out that all GPS units specifically tell the people who bother to read the Destruction Books that they are a Guide Only and you should look at the roads before following the given directions. If you blindly follow the directions you are likely to end up being charged with Neglect Driving and I should say Quite Rightly as the Car GPS's are not Military Spec Devices and are only accurate to a couple of hundred meters not millimeters.
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