OpenStreetMap

From AndNavWiki

OpenStreetMap (OSM) is a collaborative project to create a free editable map of the world. Please see its page on Wikipedia. At the time of this writing, OSM may often have much better coverage than, for example, Google Maps. Compare Galaţi, Romania on Google Maps vs. OpenStreetMap.

AndNav2 uses OSM to generate turn-by-turn directions, and it can also contribute GPS tracks back to OSM, improving its coverage.