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 the vertical CRS, each with its own datum. In these cases the GeodeticDatum can be omitted.
8.18.3.2.2 Entity inheritance
8.18.3.2.3 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. |
|
8.18.3.2.4 Formal propositions
| Name | Description |
|---|---|
| NameOrWKT |
Ensures that the coordinate reference system is properly specified by either a reference to an EPSG code in Name or a well known text in WellKnownText. |
|
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8.18.3.2.5 Formal representation
ENTITY IfcCoordinateReferenceSystem
ABSTRACT SUPERTYPE OF (ONEOF
(IfcGeographicCRS
,IfcProjectedCRS));
Name : OPTIONAL IfcLabel;
Description : OPTIONAL IfcText;
GeodeticDatum : OPTIONAL IfcIdentifier;
INVERSE
HasCoordinateOperation : SET [0:1] OF IfcCoordinateOperation FOR SourceCRS;
WellKnownText : SET [0:1] OF IfcWellKnownText FOR CoordinateReferenceSystem;
WHERE
NameOrWKT : (HIINDEX(WellKnownText) = 1) OR EXISTS(Name);
END_ENTITY;