Hi, first post. For a cheap and easy yet incredibly powerful setup, You all need to check out osmand+ for android. It is mapping and navigation app built around openstreetmaps. You download the maps for the States you need and it works flawlessly without cellular data signal. You can download hill shade files and topographic layers as well. You can even download Wikipedia entries for POIs for and given state. I have been using openstreetmaps for years and I find it is leaps and bounds better that googl, especially for including hiking and biking trails. Osmand+ is a serious cartography tool, there is a learning curve to get the most out of it, but it is well worth the effort IMO. Also, I recommend installing it via the Fdroid store rather than gapps, that was it costs nothing ! Though if you find it useful it is worthwhile to donate to the project. It is an open source / libre licensed code base and needs the support of its user community .
If there are any gnu/Linux users here who like to tinker, there is also a project called foxtrotgps, that I have used extensively on trips. I run it on a touchscreen thinkpad which I rig up to the center console. It requires an external GPS dongle (unless you laptop has a module built in, like some Panasonic toughbook models). Foxtrot GPS also uses openstreetmap tile data that is downloaded to your device , it is a bit simplistic when compared to osmand+, but quite functional for GPS tracing and passive navigating (no directions). If anyone is interested in foxtrotgps, I can provide more details, there are some quirks I have learned to work around by changing minor settings in the source code before compiling. I would be happy to help out.
Edit: RVCuisineScene, check out openCPN for nautical chartplotting it is free software and works flawlessly, I use it on a laptop while, cruising . It can even interface with AIS receivers and other NEMA devices. A+