As well as geographic coordinates using latitude/longitude and the OS grid system, UPRN UK also shows the encoded location using some popular open source encoding systems. The ones we currently use are:
Mapcode. This is an open source location encoding system maintained by the Mapcode Foundation. The aim of Mapcode is to create a short, memorable location code for any set of coordinates.
Open Location Code (Pluscode). This was developed by Google as a means of encoding location into a form that is easier to use than geographic coordinates. Google Maps, both on the web and in smartphone apps, supports Pluscodes as an addressing system.
Maidenhead Locator System (QTH Locator). This is a geographic coordinate system used by amateur radio operators.