C-squares

C-squares (acronym for the concise spatial query and representation system) is a system of geocodes (actually a type of global grid) that provides a basis for simple spatial indexing of geographic features or data. It was devised by Tony Rees of CSIRO Marine and Atmospheric Research (then "CSIRO Marine Research") in 2001-2, and described in the literature in 2003. The notation system of c-squares incorporates a compact encoding of latitude and longitude coordinates into a machine- and human-readable c-squares code, which can then be used either for spatial search or display via a suitable mapping application. The c-squares codes also provide an application- and vendor-independent, interoperable notation system for any gridded data whose units of organization correspond with steps of the c-squares hierarchy (e.g. 5-, 1-, 0.5 degree cells, etc.).

Rationale

According to the initial system description, c-squares was devised as an improved (more precise) method for expressing dataset geographic extents in searchable metadata catalogues, in place of (or in addition to) conventional bounding rectangle representations. The method is also useful as a generic, interoperable notation for gridded data (see above), for example a variety of datasets that describe environmental characteristics of global half-degree cells (see AquaMaps site). C-squares can also simply be used for mapping (example: CSIRO Marine and Atmospheric Research's "CAAB" application), although the most value is obtained when the system is used for spatial search as well (e.g. OBIS database, CMAR's "MarLIN" metadatabase, etc.).