Ive been seeing this app get unjustly downvoted because certain users are plainly ignorant of what this is for. OTM will not hold your hand. This is not an app for an amateur city person on a weekend stroll, someone who needs 24/7 mobile data. I know its hard for some people to believe, but your phone is not God, and doesnt work everywhere.
For the skilled adventurer in remote locations, however, this are as good as it gets. There are a wide variety of maps, and more if you upgrade to Gaia GPS. They download easily, but yes, can be HUGE, so use dsl/cable. Once youve downloaded the areas at the resolution youve selected, OTM comes VERY much in handy.
The map maker could improve things by making the interface clearer, and making the maps on device a bit easier to negotiate.
Also, this app used to have Mapquest roadmaps; when Mapquest recently eliminated their 3rd party service, this was quietly eliminated. Current roadmap options dont cut it. I feel for the devs in this issue. But some heads up for when map servers are cut would be nice, as would a roadmap which has some decent terrain relief and clarity.
Look, kids, for the price, this cant be beat. No subscription nonsense, no clutter, no bloated fees for map packs like other apps... just lots and lots and LOTS of topo maps for jaunts to just about anywhere. Thats the deal.