Open Location Code: An Open Source Standard for Addresses
Some alternatives that I am aware of:https://wikimili.com/en/Natural_Area_Code ,
https://what3words.com/ ,
https://geokey.io/ ,
http://geohash.org/ ,
https://www.mapcode.com/ .Some of which are proprietary.Edit: plus.codes was this same proposal. Removed from the list.