IfcAlignment2DVerticalSegment

Natural language names
Alignment 2D Vertical Segment
Change log
ItemSPFXMLChangeDescription
IFC4x1 Release Candidate 1
    IfcAlignment2DVerticalSegmentADDED
Semantic definitions at the entity
Entity definition

Individual segment along the IfcAlignment2DVertical, being defined in the distance-along/z coordinate space.

The vertical alignment is defined by segments that connects end-to-start. The vertical alignment curve geometry is defined in a plane with x = distance along horizontal, the y = height (or elevation). 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.

The following vertical segment types are defined:

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

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

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

NOTE  Specific subtypes of the IfcAlignment2DVerticalSegment add specific geometric curve parameters. Connectivity between vertical segments is not necessarily tangential, but this can be enforced as a requirement through the attribute TangentialContinuity.

Figure 317 — Alignment vertical segment

Attribute definitions
#AttributeTypeCardinalityDescription G
4StartDistAlongIfcLengthMeasure Distance along the horizontal alignment, measured along the IfcAlignment2DHorizontal given in the length unit of the global IfcUnitAssignment.X
5HorizontalLengthIfcPositiveLengthMeasure Length measured as distance along the horizontal alignment of the segment.X
6StartHeightIfcLengthMeasure Elevation in Z of the start point relative to the IfcAlignment coordinate system.
NOTE  It is strongly advised to not offset the IfcAlignment coordinate system from the project engineering coordinate system.
X
7StartGradientIfcRatioMeasure Gradient of the tangent of the vertical segment at the start point. It is provided as a ratio measure. The ratio is percentage/100 (0.1 is equal to 10%). It has a theoretical range of -∞ < n < ∞ using a ratio measure. The equivalent range measured in degree is -90° < n < 90°.
NOTE  For practical application of start gradient, the range of the ratio measure should be within the limits of -1 ≤ n ≤ 1 (equivalent in degree -45° ≤ n ≤ 45°). However larger limits might apply for particular usages.

Positive gradient means an increasing height at the start (or uphill), a negative gradient means decreasing height at the start (or downhill).

X
ToVerticalIfcAlignment2DVertical
@Segments
S[1:1]X
Inherited definitions from supertypes
Entity inheritance IfcAlignment2DVerSegCircularArc IfcAlignment2DVerSegLine IfcAlignment2DVerSegParabolicArc IfcAlignment2DSegment 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
IfcAlignment2DSegment
1TangentialContinuityIfcBoolean? 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
2StartTagIfcLabel? Tag to annotate the start point of the alignment segment.X
3EndTagIfcLabel? Tag to annotate the end point of the alignment segment.X
IfcAlignment2DVerticalSegment
4StartDistAlongIfcLengthMeasure Distance along the horizontal alignment, measured along the IfcAlignment2DHorizontal given in the length unit of the global IfcUnitAssignment.X
5HorizontalLengthIfcPositiveLengthMeasure Length measured as distance along the horizontal alignment of the segment.X
6StartHeightIfcLengthMeasure Elevation in Z of the start point relative to the IfcAlignment coordinate system.
NOTE  It is strongly advised to not offset the IfcAlignment coordinate system from the project engineering coordinate system.
X
7StartGradientIfcRatioMeasure Gradient of the tangent of the vertical segment at the start point. It is provided as a ratio measure. The ratio is percentage/100 (0.1 is equal to 10%). It has a theoretical range of -∞ < n < ∞ using a ratio measure. The equivalent range measured in degree is -90° < n < 90°.
NOTE  For practical application of start gradient, the range of the ratio measure should be within the limits of -1 ≤ n ≤ 1 (equivalent in degree -45° ≤ n ≤ 45°). However larger limits might apply for particular usages.

Positive gradient means an increasing height at the start (or uphill), a negative gradient means decreasing height at the start (or downhill).

X
ToVerticalIfcAlignment2DVertical
@Segments
S[1:1]X
Formal representations
XML Specification
 <xs:element name="IfcAlignment2DVerticalSegment" type="ifc:IfcAlignment2DVerticalSegment" abstract="true" substitutionGroup="ifc:IfcAlignment2DSegment" nillable="true"/>
 <xs:complexType name="IfcAlignment2DVerticalSegment" abstract="true">
  <xs:complexContent>
   <xs:extension base="ifc:IfcAlignment2DSegment">
    <xs:attribute name="StartDistAlong" type="ifc:IfcLengthMeasure" use="optional"/>
    <xs:attribute name="HorizontalLength" type="ifc:IfcPositiveLengthMeasure" use="optional"/>
    <xs:attribute name="StartHeight" type="ifc:IfcLengthMeasure" use="optional"/>
    <xs:attribute name="StartGradient" type="ifc:IfcRatioMeasure" use="optional"/>
   </xs:extension>
  </xs:complexContent>
 </xs:complexType>
EXPRESS Specification
ENTITY IfcAlignment2DVerticalSegment
 ABSTRACT SUPERTYPE OF(ONEOF(IfcAlignment2DVerSegCircularArc, IfcAlignment2DVerSegLine, IfcAlignment2DVerSegParabolicArc))
 SUBTYPE OF (IfcAlignment2DSegment);
  StartDistAlong : IfcLengthMeasure;
  HorizontalLength : IfcPositiveLengthMeasure;
  StartHeight : IfcLengthMeasure;
  StartGradient : IfcRatioMeasure;
 INVERSE
  ToVertical : SET [1:1] OF IfcAlignment2DVertical FOR Segments;
END_ENTITY;

Link to EXPRESS-G diagram EXPRESS-G diagram

References  References: IfcAlignment2DVertical

Link to this page  Link to this page