Just to reiterate a couple of reasons why I'm a Mapy.cz fanboy...
- I like that you can move almost seemlessly between big screen computer and smartphone app - so I actually use it a lot more at home exploring routes than on the camino.
- Take a camino like the Madrid, where you might be in the middle of nowhere, walking dusty tracks between wind turbines, where the sky meets the flat empty horizon in all directions.. there's a vague fork in the road and no marker, you choose the one that looks most in line with the path you've arrived on, and walk on. After about 10-15 minutes of not seeing any other markers you get that gnawing feeling that this might not be the right path at all - do you go on or return and scout the other route? Or just pull out phone and check Mapy..
- GPS only seems to fire up when you open the app and shuts down after you close the phone, so negligible battery drain (at least on my Android Fairphone). You only need/use GPS, not data, if you have already downloaded the maps. I have downloaded several in Spain, France and here in the UK and have yet to be asked to pay for any.
- Mapy.cz in Outdoor layer doesn't just show you camino routes - but lots of other recognised paths, including the French GRs which dick bird mentions above. This gives you excellent additional information, particularly if you see a jumble of signs at a 5-way junction, or want to take a more scenic route/option (like the E9 coastal path on the Norte, or the GR109 on the Primitivo)