IFC (IFC4X3_ADD2) under development IfcGeographicCRS Semantic definition

A IfcGeographicCRS is a coordinate reference system (CRS) that uses a three-dimensional ellipsoid surface to reference locations on the Earth. Any location on Earth can be described by a point with longitude and latitude coordinates and the height above or below the ellipsoid surface. Entity inheritance Attributes

# Attribute Type Description
IfcCoordinateReferenceSystem (5)
1 Name OPTIONAL IfcLabel

Name by which the coordinate reference system is identified.

2 Description OPTIONAL IfcText

Informal description of this coordinate reference system.

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.

HasCoordinateOperation SET [0:1] OF IfcCoordinateOperation FOR SourceCRS

Indicates conversion between coordinate reference systems. In particular it refers to an IfcCoordinateOperation between this coordinate reference system, and another coordinate reference system.

WellKnownText SET [0:1] OF IfcWellKnownText FOR CoordinateReferenceSystem

Well Known Text (WKT) definition for this coordinate reference system inversely associated as a IfcWellKnownText entity.

Click to show 5 hidden inherited attributes Click to hide 5 inherited attributes
IfcGeographicCRS (3)
4 PrimeMeridian OPTIONAL IfcIdentifier

The identification of the meridian defining zero longitude in the used geographic CRS.

5 AngleUnit OPTIONAL IfcNamedUnit

Unit of latitude and longitude coordinate axes composing the geographic coordinate system.

6 HeightUnit OPTIONAL IfcNamedUnit

Unit of the height coordinate axis of the geographic coordinate system.

Table Formal propositions

Name Description

The type of AngleUnit in the operation shall be IfcUnitEnum.PLANEANGLEUNIT.


The type of HeightUnit in the operation shall be IfcUnitEnum.LENGTHUNIT.

NOT(EXISTS(SELF.HeightUnit)) OR (SELF.HeightUnit.UnitType=IfcUnitEnum.LENGTHUNIT)
Table Examples Formal representation

ENTITY IfcGeographicCRS
 SUBTYPE OF (IfcCoordinateReferenceSystem);
	PrimeMeridian : OPTIONAL IfcIdentifier;
	AngleUnit : OPTIONAL IfcNamedUnit;
	HeightUnit : OPTIONAL IfcNamedUnit;
	AngleUnitIsPlaneAngle : NOT(EXISTS(SELF.AngleUnit)) OR (SELF.AngleUnit.UnitType=IfcUnitEnum.PLANEANGLEUNIT);
	HeightUnitIsLength : NOT(EXISTS(SELF.HeightUnit)) OR (SELF.HeightUnit.UnitType=IfcUnitEnum.LENGTHUNIT);
END_ENTITY; References

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