Both Google Maps and WAZE work just fine OFFLINE. You just need to download your trip before you go. Even if you did not, it's highly unlikely that you have no idea where you are going when you leave so just wait until you pass in and out or cellular service and your mapping program will work perfectly.
Neither service will keep you from driving under a low bridge or across a low weight limit bridge so if you like to wander the back roads more than anything then you should buy a truckers paper map to plan your trip around these kinds of obstructions.