{@linkplain org.opengis.referencing.AuthorityFactory Authority factories} for the EPSG database.

EPSG codes are numerical identifiers. For example "4326" is the EPSG identifier for the "WGS 84" geographic CRS. However, the default implementation accepts names as well as numeric identifiers. For example "NTF (Paris) / France I" and {@code "27581"} both fetchs the same object. Note that names may be ambiguous since the same name may be used for more than one object. This is the case of "WGS 84" for example. If such an ambiguity is found, an exception will be thrown.

An EPSG authority factory is created using the following code:

> `{@linkplain org.opengis.referencing.crs.CRSAuthorityFactory} factory = {@linkplain org.geotools.referencing.ReferencingFactoryFinder}.getCRSAuthorityFactory("EPSG", null);`

This package provides the general framework for accessing an EPSG database, but the actual connection to a database requires the existence of an EPSG plugin in the classpath. Otherwise, a {@link org.geotools.factory.FactoryNotFoundException} will be thrown. Available plugins are:

Required software | Data source | Plugin / JAR file | Additional notes
--- | --- | --- | ---
MS-Access ODBC driver | {@link org.geotools.referencing.factory.epsg.FactoryOnAccess} | {@code epsg-access} | See installation instructions
HSQL embedded database | {@link org.geotools.referencing.factory.epsg.FactoryOnHSQL} | {@code epsg-hsql} | Note for module mainteners
PostgreSQL database | {@link org.geotools.referencing.factory.epsg.FactoryOnPostgreSQL} | {@code epsg-postgresql} | Note for module mainteners