As I am beginning my quest towards a capable off road rig, I need a way to have maps of the trails. JD, Roadie and KaRo have laptops to use for this. I wanted to use my iPad. I have a WiFi only iPad so no internal GPS. I solved this by getting a external blue tooth GPS Receiver by Dual Electronics. I tried on one app by Trimble navigation but was PITA to get maps on the iPad. I found another app that you could down load the maps right from the iPad. Sweet. Topo Maps
All the green areas are maps that I have DL and I have 3.8 Gig so far.
The maps are just 2D but I am cool with that. Here is a example the Quadrangle maps.