#### IfcAxis2Placement2D

Natural language names

##### Semantic definitions at the entity

Entity definition

Definition from ISO/CD 10303-42:1992: The location and orientation in two dimensional space of two mutually perpendicular axes. An axis2_placement_2d is defined in terms of a point, (inherited from the placement supertype), and an axis. It can be used to locate and originate an object in two dimensional space and to define a placement coordinate system. The class includes a point which forms the origin of the placement coordinate system. A direction vector is required to complete the definition of the placement coordinate system. The reference direction defines the placement X axis direction, the placement Y axis is derived from this.

If the RefDirection attribute is not given, the placement defaults to P[1] (x-axis) as [1.,0.] and P[2] (y-axis) as [0.,1.].

> NOTE: Corresponding STEP name: axis2_placement_2d, please refer to ISO/IS 10303-42:1994, p. 28 for the final definition of the formal standard.

> HISTORY: New entity in IFC Release 1.5.

Illustration

| Definition of the IfcAxis2Placement2D within the two-dimensional coordinate system.

Attribute definitions

# | Attribute | Type | Cardinality | Description | A
--- | --- | --- | --- | --- | ---
2 | RefDirection | - |  | This attribute is out of scope for this model view definition and shall not be set. |
| P :=IfcBuild2Axes(RefDirection) | IfcDirection | L[2:2] | P[1]: The normalized direction of the placement X Axis. This is (1.0,0.0,0.0) if RefDirection is omitted. P[2]: The normalized direction of the placement Y Axis. This is a derived attribute and is orthogonal to P[1]. | X

##### Inherited definitions from supertypes

Entity inheritance
Attribute inheritance

# | Attribute | Type | Cardinality | Description | A
--- | --- | --- | --- | --- | ---
IfcRepresentationItem
IfcGeometricRepresentationItem
IfcPlacement
1 | Location | IfcCartesianPoint | [1:1] | The geometric position of a reference point, such as the center of a circle, of the item to be located. | X
| Dim :=Location.Dim | IfcDimensionCount | [1:1] | The space dimensionality of this class, derived from the dimensionality of the location. | X
IfcAxis2Placement2D
2 | RefDirection | - |  | This attribute is out of scope for this model view definition and shall not be set. |
| P :=IfcBuild2Axes(RefDirection) | IfcDirection | L[2:2] | P[1]: The normalized direction of the placement X Axis. This is (1.0,0.0,0.0) if RefDirection is omitted. P[2]: The normalized direction of the placement Y Axis. This is a derived attribute and is orthogonal to P[1]. | X

##### Formal representations

XSD Specification
`<xs:element name="IfcAxis2Placement2D" type="ifc:IfcAxis2Placement2D" substitutionGroup="ifc:IfcPlacement" nillable="true"/>
<xs:complexType name="IfcAxis2Placement2D">
<xs:complexContent>
<xs:extension base="ifc:IfcPlacement"/>
</xs:complexContent>
</xs:complexType>
`
EXPRESS Specification
`ENTITY IfcAxis2Placement2D
SUBTYPE OF (IfcPlacement);
RefDirection : OPTIONAL IfcStrippedOptional;
DERIVE
P : LIST [2:2] OF IfcDirection := IfcBuild2Axes(RefDirection);
WHERE
WR1 : (NOT (EXISTS (RefDirection))) OR (RefDirection.Dim = 2);
WR2 : SELF\IfcPlacement.Location.Dim = 2;
END_ENTITY;

EXPRESS-G diagram

`

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