A reference system contains the metadata required to interpret spatial location information unambiguously. The description of an object's attributes can be done
- explicitly, by providing all defining parameters, or
- by identifier, a reference to a recognised source that contains a full description of the object.
IdentifiedObjectinterface contains attributes common to several objects used in spatial referencing by coordinates. For example, a datum primary names might be “North American Datum of 1983”. This may have alternative names or aliases, for example the abbreviation “NAD83”.
Another attribute is identifiers.
This is a unique code used to reference an object in a given place. For example, an external geodetic register might
give the NAD83 datum a unique code of “6269”. Identifiers have a data type of
In addition to the use of an identifier as a reference to a definition in a remote register, it may also be included
in an object definition to allow remote users to refer to the object.
Most interfaced objects are immutable. This means that implementations promise not to change an object's internal state once they have handed out an interface pointer. Since most interfaced objects are specified to be immutable, there do not need to be any constraints on operation sequencing. This means that these interfaces can be used in parallel computing environments (e.g. Internet servers).
Well-Known Text format
Many entities in this specification can be printed in a well-known text format. This allows objects to be stored in databases (persistence), and transmitted between interoperating computer programs. Well-Known Texts (WKT) may come in two formats:
- The current standard, WKT 2, is defined by ISO 19162.
- The legacy format, WKT 1, is shown using Extended Backus Naur Form (EBNF) here.
Interface Summary Interface Description AuthorityFactoryBase interface for all authority factories. IdentifiedObjectIdentification and remarks information for a reference system or CRS-related object. ObjectFactoryBase interface for all factories of identified objects. ReferenceIdentifierIdentifier used for reference systems. ReferenceSystemDescription of a spatial and temporal reference system used by a dataset.
Class Summary Class Description ReferenceSystemTypeDefines type of reference system used.