Geohashing

(w:en:geohashing is not to be confused with w:en:geohash, for example JOSM/Plugins/GeoHash)

From the https://geohashing.site/ homepage:

Geohashing is an adventure, comprising journeys to random places within a given area. Every day, effectively random locations are generated by an algorithm that achieves randomness using stock market data.

Geohashing can easily be combined with mapping.

More information and tools:

• Coordinate calculator: http://geohashing.info (see also https://geohashing.info/wiki)
• Small Hash Inquiry Tool: http://tjum.anthill.de/geohash.html
• Geohashing Poster Tool: https://geohashing.site/geohashing/user:Crox/Poster
• OpenStreetMap Achievement for Geohashers: https://geohashing.site/geohashing/OpenStreetMap_achievement#Background (encourages editing and tracklog uploading)

See also geocaching, another geogame.

https://geohashing.org is dead, long live https://geohashing.site