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There are two main CRS definition authorities that are relevant for the AI domain: International Association of Oil and & Gas Producers (OGPIOGP), formerly known as the European Petroleum Survey Group (EPSG) and the OGC. The two sets of CRS definitions have many common points. For example, the
OGC:CRS84 is a variant of EPSG:4326 (differing only in its coordinate order: longitude/latitude). The EPSG CRS database is available at http://www.epsg.org. Recommendations for the use of CRS references in GML data sets are provided in the OGC recommendation paper 07-092r3
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