EPSG Geodetic Parameter Dataset (also EPSG registry) is a public registry of spatial reference systems, Earth ellipsoids, coordinate transformations and related units of measurement. Each entity is assigned an EPSG code between 1024-32767,:39 along with a standard machine-readable well-known text (WKT) representation. The dataset is actively maintained by the IOGP Geomatics Committee.
Most geographic information systems (GIS) and GIS libraries use EPSG codes as Spatial Reference System Identifiers (SRIDs) and EPSG definition data for identifying projections and performing transformations between these systems, while some also support SRIDs issued by other organizations (such as Esri).
In 2005, the EPSG organisation was merged into International Association of Oil & Gas Producers (IOGP), and became the Geomatics Committee. However, the name of the EPSG registry was kept to avoid confusion. Since then, the acronym "EPSG" became increasingly synonymous with the dataset or registry itself.