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Concept
Code géographique
Résumé
A geocode is a code that represents a geographic entity (location or object). It is a unique identifier of the entity, to distinguish it from others in a finite set of geographic entities. In general the geocode is a human-readable and short identifier.
Typical geocodes 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 subdivision codes (e.g. AF-GHO for Ghor province) or 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. ~0.023 km2 cell 6vjyngd at the Brazilian's center) or an OLC code (e.g. ~0.004 km2 cell 58PJ642P+4 at the same point).
Postal code. Polygon of a postal area: a CEP code (e.g. 70040 represents a Brazilian's central area for postal distribution).
The ISO 19112:2019 standard (section 3.1.2) adopted the term "geographic identifier" instead geocode, to encompass long labels: spatial reference in the form of a label or code that identifies a location. For example, for ISO, the country name “People's Republic of China” is a label.
Geocodes are mainly used (in general as an atomic data type) for labelling, data integrity, geotagging and spatial indexing.
In theoretical computer science a geocode system is a locality-preserving hashing function.
There are some common aspects of many geocodes (or geocode systems) that can be used as classification criteria:
Ownership: proprietary or free, differing by its licences.
Formation: the geocode can be originated from a name (ex. abbreviation of official name the country) or from mathematical function (encoding algorithm to compress latitude-longitude). See geocode system types below (of names and of grids).
Hierarchy: geocode's syntax hierarchy corresponding to the spatial hierarchy of its represented entities. A geocode system can hierarchical (name or grid) or non-hierarchical.
Source officielle
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