You can use OruxMaps for your outdoor activities. It is an online and offline map viewer. With this app you can use different map formats, such as GeoPDF from USGS store, GeoTIFF maps, .ozf2, .img garmin (vector, full support is not provided), .mbtiles and others. You can register in the OruxMaps servers, but it's not mandatory, the app will work without this step. If you sign up for an account, the app will ask you for various personal information, including an email account, date of birth, gender, weight and height. These data will be stored on an OruxMaps server and will not be shared with any other user, person or company; I'm just at your disposal. If you delete your account, that data is deleted from the server.
Supported Android Devices : [4.1–4.3.1] Jelly Bean - [4.4–4.4.4] KitKat - [5.0–5.0.2] Lollipop - [6.0 - 6.0.1] Marshmallow - [7.0 – 7.1.1] Nougat - [8.0-8.1] Oreo -  Pie