IfcAlignment2DHorizontal

Natural language names
Alignment Curve 2D Horizontal
Change log
ItemSPFXMLChangeDescription
IFC4x1 Final 4.1.0.0
    IfcAlignment2DHorizontalADDED
IFC4x1 Final 4.1.0.0
    IfcAlignment2DHorizontalADDED
Semantic definitions at the entity
Entity definition

An IfcAlignment2DHorizontal is a linear reference projected onto the horizontal x/y plane. Points along a horizontal alignment have two coordinate values, x and y in the local Cartesian engineering system.

The horizontal alignment is defined by segments that are connected end-to-start. The transition at the segment connection is not enforced to be tangential, if the “tangential continuity” flag is set to false, otherwise a tangential continuity shall be preserved. Based on the context of the project, they are geo-referenced and convertible into Northing and Easting values.

NOTE  Georeferencing is provided by IfcMapConversion through the IfcGeometricRepresentationContext defined at IfcProject.

Attribute definitions
#AttributeTypeCardinalityDescription G
1StartDistAlongIfcLengthMeasure? The value of the distance along at the start of the horizontal alignment. If omited (standard) it is set to zero. X
2SegmentsIfcAlignment2DHorizontalSegmentL[1:?] An ordered list of unique horizontal alignment segments, each (but the last) are joint end to start X
ToAlignmentCurveIfcAlignmentCurve
@Horizontal
S[1:?]X
Inherited definitions from supertypes
Entity inheritance IfcGeometricRepresentationItem IfcRepresentationItem
Attribute inheritance
#AttributeTypeCardinalityDescriptionG
IfcRepresentationItem
LayerAssignmentIfcPresentationLayerAssignment
@AssignedItems
S[0:1]Assignment of the representation item to a single or multiple layer(s). The LayerAssignments can override a LayerAssignments of the IfcRepresentation it is used within the list of Items.
IFC2x3 CHANGE  The inverse attribute LayerAssignments has been added.
IFC4 CHANGE  The inverse attribute LayerAssignment has been restricted to max 1. Upward compatibility for file based exchange is guaranteed.
X
StyledByItemIfcStyledItem
@Item
S[0:1]Reference to the IfcStyledItem that provides presentation information to the representation, e.g. a curve style, including colour and thickness to a geometric curve.
IFC2x3 CHANGE  The inverse attribute StyledByItem has been added.
X
IfcGeometricRepresentationItem
IfcAlignment2DHorizontal
1StartDistAlongIfcLengthMeasure? The value of the distance along at the start of the horizontal alignment. If omited (standard) it is set to zero. X
2SegmentsIfcAlignment2DHorizontalSegmentL[1:?] An ordered list of unique horizontal alignment segments, each (but the last) are joint end to start X
ToAlignmentCurveIfcAlignmentCurve
@Horizontal
S[1:?]X
Formal representations
XML Specification
 <xs:element name="IfcAlignment2DHorizontal" type="ifc:IfcAlignment2DHorizontal" substitutionGroup="ifc:IfcGeometricRepresentationItem" nillable="true"/>
 <xs:complexType name="IfcAlignment2DHorizontal">
  <xs:complexContent>
   <xs:extension base="ifc:IfcGeometricRepresentationItem">
    <xs:sequence>
     <xs:element name="Segments">
      <xs:complexType>
       <xs:sequence>
        <xs:element ref="ifc:IfcAlignment2DHorizontalSegment" maxOccurs="unbounded"/>
       </xs:sequence>
       <xs:attribute ref="ifc:itemType" fixed="ifc:IfcAlignment2DHorizontalSegment"/>
       <xs:attribute ref="ifc:cType" fixed="list"/>
       <xs:attribute ref="ifc:arraySize" use="optional"/>
      </xs:complexType>
     </xs:element>
    </xs:sequence>
    <xs:attribute name="StartDistAlong" type="ifc:IfcLengthMeasure" use="optional"/>
   </xs:extension>
  </xs:complexContent>
 </xs:complexType>
EXPRESS Specification
ENTITY IfcAlignment2DHorizontal
 SUBTYPE OF (IfcGeometricRepresentationItem);
  StartDistAlong : OPTIONAL IfcLengthMeasure;
  Segments : LIST [1:?] OF IfcAlignment2DHorizontalSegment;
 INVERSE
  ToAlignmentCurve : SET [1:?] OF IfcAlignmentCurve FOR Horizontal;
END_ENTITY;

Link to EXPRESS-G diagram EXPRESS-G diagram

References  References: IfcAlignment2DHorizontalSegment IfcAlignmentCurve

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