European Petroleum Survey Group
European Petroleum Survey Group or EPSG (1986 – 2005) was a scientific organization with ties to the European petroleum industry consisting of specialists working in applied geodesy, surveying, and cartography related to oil exploration. EPSG compiled and disseminated the EPSG Geodetic Parameter Set, a widely used database of Earth ellipsoids, geodetic datums, geographic and projected coordinate systems, units of measurement, etc. The role of EPSG was taken over in 2005 by the newly formed OGP Surveying and Positioning Committee.
EPSG was created in 1985 by Jean-Patrick GIRBIG and chaired by him during 4 years, at that time with Elf. The initial obective was to improve and share locational data all around the World. In 1994, Jean-Patrick GIRBIG managed to create the APSG which is the sister of EPSG for the Americas.
The Geodetic Parameter Set continues to be known as EPSG Geodetic Parameter Data Set and is accessible through a web interface and published by OGP in Microsoft Access database format. The database structure claims to be compliant with ISO 19111 Geographic information - Spatial referencing by coordinates. The downloadable database gets updated approximately three to four times a year, with intermediate versions. Changes could arise
- identify coordinates such that those coordinates which describe position unambiguously. This is through a coordinate reference system (CRS) definition.
- define transformations and conversions that allow coordinates to be changed from one CRS to another CRS. Transformations and conversions are collectively called "coordinate operations".
The European Petroleum Survey Group tables define numeric identifiers (the EPSG code) for many common projections and associate projection or coordinate metadata (such as measurement units or central meridian) for each identifier.
The EPSG codes can be used to identify the Coordinate Reference System (CRS) for coordinates used in dataset encoded in GML (Geography Markup Language). They can also be used to request the desired map projection for a Web Map Service (WMS) getMap request.
EPSG:4326 is a common coordinate reference system that refers to WGS84 as (latitude, longitude) pair coordinates in degrees with Greenwich as the central meridian. Any degree representation (e.g., decimal or DMSH: degrees minutes seconds hemisphere) may be used. Which degree representation is used must be declared for the user by the supplier of data.