Geocode

A geocode or geographic identifier (sometimes shortened as geo ID) is a code or unique identifier that represents a geographic entity (location or object), as distinguished from other entities in the same geocode system. In general, a geocode is a human-readable and short identifier. The ISO 19112 standard also admits long labels as geocodes. Geocodes are mainly used (in general as an atomic data type) for labelling, data integrity, geotagging and spatial indexing.

Typical geocodes (in bold) and entities represented by it:

• Country code and subdivision code. Polygon of the administrative boundaries of a country or a subdivision.
  The main examples are ISO codes: ISO 3166-1 alpha-2 code (e.g. AF for Afghanistan or BR for Brazil), and its subdivision conventions, such as AF subdivision codes (e.g. AF-GHO for Ghor province) or BR subdivision codes (e.g. BR-AM for Amazonas state).
• DGG cell ID. Identifier of a cell of a discrete global grid: a Geohash code (e.g. ~0.023km cell 6vd23gq at Brazil's centroid) or a Plus Code (e.g. ~0.0002km cell 58Q8XXXX+XX within the same area).
• Postal code. Polygon of a postal area: a CEP code (e.g. 70040 represents a Brazilian's central area for postal distribution).

In theoretical computer science a geocode system is a hash function, and, an important class of utilitarian geocode systems is described as a locality-preserving hashing function.