The big problem with what3words (leaving aside the disconjunction of individual areas) is that the data is their IP and you’re not allowed to reuse it for your own purposes (http://developer.what3words.com/api/licence/)
Rough location: Country , City , Street.
Exact location: Latitude , Longitude.
https://news.ycombinator.com/item?id=12260958
http://xaddress.org (Note: not https)