OpenMapTiles

Maps under your control! Get the source code and detailed OpenStreetMap vector tiles saved in MBTiles format - usable offline, with your GPS location. The OpenMapTiles team (https://openmaptiles.org/) made this app as a starter for your app development!
Try offline map functionality by downloading a street map for the whole planet, country or city of your choice. The map data can also be embedded and distributed together with your app!
The complete source code of this mobile application is available for re-branding and customization - just add your business logic and extra mapping functionality with open-source Mapbox SDK.
By using OpenMapTiles.org project, you can design and style the maps according to your needs, host the map tiles on your servers (even on a standard Apache web hosting), create optimised map extracts for offline use and unlimited redistribution. You can simply make your own independent maps for any place on a planet!
Compatible raster tiles can be generated with MapTiler software (http://www.maptiler.com/).
For more advanced editing functionality, drawing of the features, attaching photos and collecting field data we have developed GeoEditor mobile app (https://www.maptiler.com/mobile/). It is available including source code too!
We offer support, consulting and contracted development of mobile applications, including geodata processing and creating of vector and raster map tiles in custom coordinate systems. For more information see https://openmaptiles.com/ and https://www.klokatnech.com/