Geographic MetaData (GMD) extensible markup language is a component of the XML Schema Implementation of Geographic Information Metadata documented in ISO/TS 19139:2007. GMD includes all the definitions of http://www.isotc211.org/2005/gmd namespace. The root document of this namespace is the file gmd.xsd. This referenceSystem.xsd schema implements the UML conceptual schema defined in A.2.7 of ISO 19115:2003 and ISO 19115:2003/Cor. 1:2006. It contains the implementation of the following classes: RS_Identifier, MD_ReferenceSystem, MD_Identifier and RS_Reference System. Description of the spatial and temporal reference systems used in the dataset