I am looking for an app to use while offroading, ideally it would allow me to download a topo map and then use GPS to show where I am, where I have been, allow me to mark obstacles etc... Any suggestions on what others have used?
Gaia is super popular with the overland community.
I like using Avenza Maps since you can download USFS Motor Vehicle Use Maps with GPS locations programmed into it. That way you can pull up the map and even when you don't have cell service find your location. You can add waypoints on it as well.