@openstreetmap is a map service which lets you use a very high-standard map based on open source software.
The web service is available to create maps for use on a website, and you can create maps using OSM data for walking trips with fieldpapers.org.
You can even host your own OSM server - see more on https://switch2osm.org.
The OSM data are crowdsourced, so it is very possible to contribute with data on areas you know - you can even complete missing data using the app #StreetComplete.
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