International Association of Oil & Gas Producers

The European Petroleum Survey Group Geodesy (EPSG ) is a working group of the European oil and gas exploration company. It was founded in 1986 and has its headquarters in London. In 2005, she was replaced by the Surveying and Positioning Committee of the International Association of Oil & Gas Producers ( OGP ). The EPSG has become known by the construction of their system of globally unique identity numbers geodetic records as coordinate reference systems, reference ellipsoids or projections (EPSG codes), which will continue under the same name of the successor organization OGP.

EPSG codes

The EPSG code is a unique system in the world 4 - to 5 -digit code numbers ( SRID ) for coordinate reference systems and other geodetic data sets. The information on EPSG codes are present in a database that is available on the website of the former EPSG for download.

Besides coordinate reference systems other geospatial data, such as conversions between different reference systems, geodetic data, validity areas and even units with code numbers are provided. The keys are unique only within the respective category.

The individual objects refer to each other hierarchically. For example, is the projected coordinate reference system EPSG: 31466 ( Gauss - Kruger zone 2 ) from the geodetic datum EPSG: 6314 (Deutsches main triangle mesh ) and the map projection EPSG: 16262 together. The date is again based on the Bessel ellipsoid ( EPSG: 7004 ). The projection is defined by specifying the algorithm ' EPSG: 9807 determines ( Transverse Mercator projection) and corresponding parameter as false easting and central meridian.

Examples of different codes

In Germany

The commonly used in Germany Gauss - Kruger zones 2-5 of the German main triangle mesh have the EPSG codes 31466-31469.

In the new federal states working with the Gauss -Krüger coordinate system and the Krasovsky ellipsoid in part. The EPSG codes are here EPSG: 2398 for Gauss - Krüger ( 4 strips Krassowski 3 degrees) and EPSG: 2399 for Gauss - Krüger ( 5 strips Krassowski 3 degrees).

The UTM zones of the European Terrestrial Reference System ETRS89 32N and 33N have the EPSG codes 25832 and 25833rd

WGS 84 ( EPSG: 4326 )

Probably the most commonly used EPSG code is 4326 for the World Geodetic System 1984 ( WGS 84 short ), a global two-dimensional geodetic reference system, based on which also the Global Positioning System (GPS ) works.

WGS 84 / Pseudo- Mercator ( EPSG: 3857 )

Through Google Maps found a simple and efficient method of projection distribution, which is subject to some uncertainty ( the ellipsoid is ignored and the Mercator projection to the raw WGS -84 coordinates used ). There were some time no established name or code number. To specify the Tile Map Service OSGeo led the key OSGEO: 41001 a. Furthermore, the designation of EPSG was OpenLayers project: 900913 disseminated.

Finally, the EPSG saw the need for an official code number. The first specification EPSG: 3785 turned out to be incorrect ( as Ausgangsellipsoid is a ball accepted) and was therefore by the now official key EPSG: 3857 superseded.

Application

Many applications have implemented the EPSG code, thus simplifying the use of geodetic data. The format of PROJ.4 WKT format and are also known.

The two following statements are equivalent, they describe the Swiss coordinates, EPSG: 2056 in PROJ.4 format:

init = epsg: 2056 no_defs proj = somerc lat_0 = 46.95240555555556 lon_0 = 7.439583333333333 K_0 = 1 x_0 = 2600000 y_0 = 1200000 ellps = bessel towgs84 = 674.374,15.056,405.346,0,0,0,0 units = m no_defs Here is an example for EPSG: 2007 " St. Vincent 1945" in WKT format:

PROJCS [" St. Vincent 45 / British West Indies Grid ," GEOGCS [" St. Vincent 1945", DATUM [" St_Vincent_1945 " SPHEROID [" Clarke 1880 ( RGS) ", 6378249.145,293.465, AUTHORITY [" EPSG ", " 7012 "]], TOWGS84 [ 195.671,332.517,274.607,0,0,0,0 ], AUTHORITY [" EPSG ", " 6607 "]], Primers [" Greenwich ", 0, AUTHORITY [" EPSG ", " 8901 "]], UNIT [ "degree ", 0.01745329251994328, AUTHORITY [" EPSG ", " 9122 "]], AUTHORITY [" EPSG ", " 4607 "]], UNIT [" ​​meter", 1, AUTHORITY [" EPSG ", " 9001 "]], PROJECTION [" Transverse_Mercator " ], PARAMETER [ " latitude_of_origin ", 0 ], PARAMETER [ " central_meridian ", -62 ], PARAMETER [ " scale_factor ", 0.9995 ], PARAMETER [ " false_easting ", 400000 ], PARAMETER [ " false_northing ", 0 ], AUTHORITY [" EPSG ", "2007" ], AXIS [" Easting ", EAST ], AXIS [" Northing ", NORTH ] ] References