IFC 4.3.1.0 (IFC4X3_ADD1) development

8.18.3.3 IfcGeographicCRS

8.18.3.3.1 Semantic definition

A IfcGeographicCRS is a non-Cartesian CRS that uses a three-dimensional ellipsoid surface to reference locations on the Earth as a latitude, longitude pair and the elevation above or below the ellipsoid.

8.18.3.3.2 Entity inheritance

8.18.3.3.3 Attributes

# Attribute Type Description
IfcCoordinateReferenceSystem (4)
1 Name OPTIONAL IfcLabel

Name by which the coordinate reference system is identified.

2 Description OPTIONAL IfcText

Informal description of this coordinate reference system

Example for ellipsoid: ELLIPSOID[,,,]

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.

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 4 hidden inherited attributes Click to hide 4 inherited attributes
IfcGeographicCRS (3)
3 GeodeticDatum OPTIONAL IfcIdentifier

Name by which this datum is identified.

4 PrimeMeridian OPTIONAL IfcIdentifier

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

5 Unit OPTIONAL IfcNamedUnit

Unit of the coordinate tuple composing the coordinate system.

Table 8.18.3.3.A

8.18.3.3.4 Formal propositions

Name Description
IsPlaneAngleUnit

The map unit shall be given, if present, as a plane angle unit.

NOT(EXISTS(Unit)) OR (Unit.UnitType=IfcUnitEnum.PLANEANGLEUNIT)
Table 8.18.3.3.B

8.18.3.3.5 Formal representation

ENTITY IfcGeographicCRS
 SUBTYPE OF (IfcCoordinateReferenceSystem);
	GeodeticDatum : OPTIONAL IfcIdentifier;
	PrimeMeridian : OPTIONAL IfcIdentifier;
	Unit : OPTIONAL IfcNamedUnit;
 WHERE
	IsPlaneAngleUnit : NOT(EXISTS(Unit)) OR (Unit.UnitType=IfcUnitEnum.PLANEANGLEUNIT);
END_ENTITY;

8.18.3.3.6 References

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8.18.3.3.7 Changelog

8.18.3.3.7.1 IFC4.3_DEV_9f90c1f0

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