Could you not pre-plan your route "Ok Maps" to download them and use headphones instead of having the map out?
Annoyingly despite letting you cache maps offline Google still needs a connection to use the 'Nav' feature, don't think it can calculate routes offline. Punters. Caching the maps is still a good idea, in the event of getting lost where there's no signal, you'd just have to do it the old fashioned way and map read!
Most navs or nav apps designed for cars won't follow a pre-determined route, and if you let them calculate a route they will prioritise motorways and A-roads, not ideal.
