EPSG

EPSG stands for the "European Petrolum Standads Group". However, this group was brought into the International Association of Oil & Gas Producers (OGP) and renamed the "EPSG Geodetic Parameter Registry".

Note: The EPSG Database on the HSU Data Hub is currently under maintenance

EPSG is really a database of spatial references and coordinate system transformations. One way to quickly view the contents of this database is through the HSU Data Hub. You will see that the database defines numbers, or EPSGCodes, for everything that is involved in defining a spatial reference. This includes units, coordinate system axis, ellipsoids, datums, geographic coordinate systems, and projtected coordinate systems. EPSG is the most widely used standard for spatil reference system and is even now used by Esri in ArcGIS 10.1. You will see they have added EPSGCodes as an "authority" to many of the spatial references defined in "prj" files.

We are introducting you to EPSG codes here because we will use them for managing spatial references in QGIS.