IfcAlignment2DHorizontalSegment

Item	SPF	XML	Change	Description
IFC4 ADD1 to IFC4x1
IfcAlignment2DHorizontalSegment			ADDED

Semantic definitions at the entity

Entity definition

Individual segment along the IfcAlignment2DHorizontal, being defined in the x/y coordinate space. Each single horizontal alignment segment has an associated curve geometry. The following segment curve types are defined by the CurveGeometry:

for line segment - IfcLineSegment2D
circular arc segment - IfcCircularArcSegment2D
clothoidal arc segment - IfcClothoidalArcSegment2D

For each horizontal segment, the following non-redundant information is provided:

the start point (in x/y coordinates)
the start direction (in radians or degree, with local x (east) being 0, and increasing counter-clock wise)
the segment length
the curve parameter needed for circular and clothoidal arc segments

The following information can be calculated (and is therefore not exchanged explicitly to avoid redundancy and inconsistencies)

the end point (from start point, direction, segment length and curve parameter)
the start distance along (from the end distance along of the previous segment, or the start distance along of the horizontal alignment (if it is the first segment)
the end distance along (from the start distance and the segment length)
the end direction (from the curve parameter, the start direction and the segment length)
the point of intersection (from the start direction and the end direction)

The following checks can be done to validate the correct exchange:

continuity – does the calculated end point of the previous segment matches with the provided start point of this segment
tangential continuity – does the calculated end direction of the previous segment matches with the provided start direction of this segment

Attribute definitions

#	Attribute	Type	Cardinality	Description	B
4	CurveGeometry	IfcCurveSegment2D	[1:1]	Geometric representation of the horizontal alignment within the 2D X/Y coordinate space.	X
	ToHorizontal	IfcAlignment2DHorizontal @Segments	S[1:1]	Link to the IfcAlignment2DHorizontal to which this horizontal segment belongs.

Inherited definitions from supertypes

Entity inheritance

Attribute inheritance

#	Attribute	Type	Cardinality	Description	B
IfcAlignment2DSegment
1	TangentialContinuity	IfcBoolean	[0:1]	Connectivity between the continuous segments is not enforced per se to be tangential. Setting "TangentialContinuity" to True means that the current segment shall continue with tangential continuity to the previous one.	X
2	StartTag	IfcLabel	[0:1]	Tag to annotate the start point of the alignment segment.	X
3	EndTag	IfcLabel	[0:1]	Tag to annotate the end point of the alignment segment.	X
IfcAlignment2DHorizontalSegment
4	CurveGeometry	IfcCurveSegment2D	[1:1]	Geometric representation of the horizontal alignment within the 2D X/Y coordinate space.	X
	ToHorizontal	IfcAlignment2DHorizontal @Segments	S[1:1]	Link to the IfcAlignment2DHorizontal to which this horizontal segment belongs.

Formal representations

XSD Specification

 <xs:element name="IfcAlignment2DHorizontalSegment" type="ifc:IfcAlignment2DHorizontalSegment" substitutionGroup="ifc:IfcAlignment2DSegment" nillable="true"/>

 <xs:complexType name="IfcAlignment2DHorizontalSegment">

  <xs:complexContent>

   <xs:extension base="ifc:IfcAlignment2DSegment">

    <xs:sequence>

     <xs:element name="CurveGeometry" type="ifc:IfcCurveSegment2D" nillable="true"/>

    </xs:sequence>

   </xs:extension>

  </xs:complexContent>

 </xs:complexType>

EXPRESS Specification


ENTITY IfcAlignment2DHorizontalSegment

 SUBTYPE OF (IfcAlignment2DSegment);

  CurveGeometry : IfcCurveSegment2D;

 INVERSE

  ToHorizontal : SET [1:1] OF IfcAlignment2DHorizontal FOR Segments;

END_ENTITY;

 EXPRESS-G diagram