- C-Squares is an international coding system for geographical areas - subdividing into smaller and smaller squares. A similar z-order algorithm. The OpenPostcode could be easily converted to it's equivalent c-square.
- Geohashes are a base32 format for encoding global coordinates in URLs and databases - public domain since 2008. It is, as base32, very precise. It uses alternate binary bits to repeatedly divide up or down either longitude or latitude. It does however include some vowels and one would only have to convert these coordinates, 52.5225 -7.1681, in Ireland to see how it is never suitable as a postcode. Using a bitwise division between longitude and latitude, while efficient for a base32 code produces rather odd neighbouring codes on the ground.
- Another noteable is the free public domain international 10:10 code proposed from an idea in 2006 which covers the globe to 10m accuracy with just 10 characters.
- Also see http://en.wikipedia.org/wiki/Geocoding.