When out on my dirtbike around forests , hills .. where it is pretty easy to get lost , I use Oruxmaps .
A free app , well made , made for mountainbiking , with tons of stuff like offline maps download with different layers and formats , position , points of interests , multitracking , emergency sms , .. it's the best app I've ever seen , looks like a pro one .
It's very powerful , you can also upload different maps of the same place a create a multilayer hybrid map , share tracks ... it's damn crazy , I'm not capable to use it at 100% ( I believe I use the 1% of its potential ) but I love it , incredible that a person developed such an app and shared to others for free .