8.18.3.2 IfcCoordinateReferenceSystem

ABSTRACT This definition may not be instantiated

8.18.3.2.1 Semantic definition

The IfcCoordinateReferenceSystem is a definition of a coordinate reference system by means of qualified identifiers only. The interpretation of the identifier is expected to be well-known to the receiving software.

The unambiguous identifier by which the coordinate reference system is know, is stored in the Name attribute. Well defined identifiers include the geodetic and often also the vertical datum. In these cases the GeodeticDatum and the VerticalDatum can be omitted.

8.18.3.2.2 Entity inheritance

8.18.3.2.3 Attributes

#	Attribute	Type	Description
IfcCoordinateReferenceSystem (5)
1	Name	IfcLabel	Name by which the coordinate reference system is identified. NOTE 1 The name shall be taken from the list recognized by the European Petroleum Survey Group EPSG. It should then be qualified by the EPSG name space, for example as 'EPSG:5555'. NOTE 2 The name shall be 'WKT' if an EPSG code does not exist for the CRS.
2	Description	OPTIONAL IfcText	Informal description of this coordinate reference system NOTE In case Name equals 'WKT' the Description is well-known text that corresponds to ISO 19162 definition specifying the necessary parameters for the coordinate reference system. Example for ellipsoid: ELLIPSOID[,,,]
3	GeodeticDatum	OPTIONAL IfcIdentifier	Name by which this datum is identified. The geodetic datum is associated with the coordinate reference system and indicates the shape and size of the rotation ellipsoid and this ellipsoid's connection and orientation to the actual globe/earth. It needs to be provided, if the Name identifier does not unambiguously define the geodetic datum as well. EXAMPLE geodetic datums include: * ED50 * EUREF89 * WSG84
4	VerticalDatum	OPTIONAL IfcIdentifier	Name by which the vertical datum is identified. The vertical datum is associated with the height axis of the coordinate reference system and indicates the reference plane and fundamental point defining the origin of a height system. It needs to be provided, if the Name identifier does not unambiguously define the vertical datum as well and if the coordinate reference system is a 3D reference system. EXAMPLE vertical datums include: * DHHN92: the German 'Haupth枚hennetz' * EVRS2007; the European Vertical Reference System
	HasCoordinateOperation	SET [0:1] OF IfcCoordinateOperation FOR SourceCRS	Indicates conversion between coordinate systems. In particular it refers to an IfcCoordinateOperation between this coordinate reference system, and another Geographic coordinate reference system.

Table 8.18.3.2.A

8.18.3.2.4 Formal representation

ENTITY IfcCoordinateReferenceSystem
 ABSTRACT SUPERTYPE OF (ONEOF
	(IfcProjectedCRS));
	Name : IfcLabel;
	Description : OPTIONAL IfcText;
	GeodeticDatum : OPTIONAL IfcIdentifier;
	VerticalDatum : OPTIONAL IfcIdentifier;
 INVERSE
	HasCoordinateOperation : SET [0:1] OF IfcCoordinateOperation FOR SourceCRS;
END_ENTITY;