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.
IdentifiedObject interface contains
attributes common to several objects used in spatial referencing by coordinates. For example, a
datum name might be "North American Datum
of 1983". This may have alternative names or aliases, for example the abbreviation "NAD83".
Object primary names have a
Identifier whilst aliases have a data type
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
Identifier. 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. The definition for WKT is shown using Extended Backus Naur Form (EBNF).
- GeoAPI 1.0
Interface Summary Interface Description AuthorityFactoryBase interface for all authority factories. FactoryBase interface for all factories. IdentifiedObjectSupplementary identification and remarks information for a CRS 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. SpatialReferenceSystemUsingGeographicIdentifierSpatial reference system using geographic identifier, a reference to a feature with a known spatial location.
Exception Summary Exception Description FactoryExceptionThrown when a factory can't create an instance of the requested object. NoSuchAuthorityCodeExceptionThrown when an authority factory can't find the requested authority code. NoSuchIdentifierException