Definition from IFC: The IfcLocalPlacement defines the relative placement of a product in relation to the placement of another product or the absolute placement of a product within the geometric representation context of the project.

It defines that the IfcProduct which is placed by this IfcLocalPlacement (through the inherited PlacesProduct) is placed within the local coordinate system of the IfcProduct, which is referenced by the PlacementRelTo. Rules to prevent cyclic relative placements have to be introduced on the application level.

The following conventions shall apply if relative placement is used (more detailed placement information is given at the level of subtypes of IfcProduct):

If the PlacementRelTo relationship is not given, then it defaults to an absolute placement within the world coordinate system established by the referenced geometric representation context within the project.

HISTORY: New entity in IFC Release 1.0
ISSUE: See issue logs for changes made in IFC Release 1.5 and see issue and change log for changes made IFC Release 2.x.

EXPRESS specification:

ENTITY IfcLocalPlacement
SUBTYPE OF ( IfcObjectPlacement);
PlacementRelTo  :  OPTIONAL IfcObjectPlacement;
RelativePlacement  :  IfcAxis2Placement;

Attribute definitions:

PlacementRelTo  :  Reference to Object that provides the relative placement by its local coordinate system. If it is omitted, then the local placement is given to the WCS, established by the geometric representation context.
RelativePlacement  :  Geometric placement that defines the transformation from the related coordinate system into the relating. The placement can be either 2D or 3D, depending on the dimension count of the coordinate system.

References (2):

Name Type Referred through Express-G
IfcObjectPlacement Entity
Attribute 'ReferencedByPlacements'
Diagram 1

Inheritance graph

ENTITY IfcLocalPlacement;
ENTITY IfcObjectPlacement;
ReferencedByPlacements  :  SET OF IfcLocalPlacement FOR PlacementRelTo;
ENTITY IfcLocalPlacement;
PlacementRelTo  :  OPTIONAL IfcObjectPlacement;
RelativePlacement  :  IfcAxis2Placement;