the android app can be used offline. Initially it takes a while to download a;; the maps, but once on the tablet, you can use it offline.
It really helped in Byfield NP having the tablet with the detailed maps providing a GPS fix on a map. Made navigation significantly easier ...
Its unreal hey.
We've been doing a few of the treks in the Dirty Weekends in The South East. Rather than have soembody read all the differnt turn, here, go left, go straight etc we plot new tracks into the app before we leave home and follow the route. Saves any bickering with the "navigator" and keeps everyting in harmony while driving LOL
Only problem we have encountered is the app crashed a couple times on the weekend for some reason. But reloads in a flash so wasn't a biggie.