Individual segment along the IfcAlignmentVertical, 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, The IfcSegment Transition enumeration specifies the type of transition explicitly.
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 IfcAlignmentVerticalSegment 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.
|1||StartTag||OPTIONAL IfcLabel||Tag to annotate the start point of the alignment segment.|
|2||EndTag||OPTIONAL IfcLabel||Tag to annotate the end point of the alignment segment.|
|3||StartDistAlong||IfcLengthMeasure||Distance along the horizontal alignment as measured along the corresponding IfcAlignmentHorizontal.|
> NOTE 1 The distance along is measured from the start point of IfcAlignmentHorizontal, any optionally provided offset expressed by IfcAlignmentHorizontal.StartDistanceAlong is not taken into account.
> NOTE 2 The unit of measurement is the global length unit, as set by IfcContext.UnitInContext
|4||HorizontalLength||IfcPositiveLengthMeasure||Length measured as distance along the horizontal alignment of the segment.|
|5||StartHeight||IfcLengthMeasure||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.
|6||StartGradient||IfcRatioMeasure||Start gradient of the segment.|
|7||EndGradient||IfcRatioMeasure||End gradient of the segment. In the case of a PredefinedType='.CONSTANTGRADIENT.' the value is the same as StartGradient.|
|8||RadiusOfCurvature||OPTIONAL IfcPositiveLengthMeasure||Radius of parabola or arc. Positive values imply a CCW direction whereas negative CW.|
> NOTE1 For PredefinedType is ARC. The radius of the basis circle for the arc.
> NOTE2 For PredefinedType is PARABOLICARC. Parabola constant (determining the “steepness” of the parabola). The parabola constant is provided by the “minimum parabola radius”, the true radius of a parabola at its vertical axis (the zero-gradient point of the parabola). The minimum radius is twice the focal length of the parabola (the distance between the focal point and the vertex).
> NOTE3 For PredefinedType that is not either ARC or PARABOLICARC the value should be empty.
|9||PredefinedType||IfcAlignmentVerticalSegmentTypeEnum||Predefined type of the vertical alignmnent segment.|
ENTITY IfcAlignmentVerticalSegment SUBTYPE OF (IfcAlignmentParameterSegment); StartDistAlong : IfcLengthMeasure; HorizontalLength : IfcPositiveLengthMeasure; StartHeight : IfcLengthMeasure; StartGradient : IfcRatioMeasure; EndGradient : IfcRatioMeasure; RadiusOfCurvature : OPTIONAL IfcPositiveLengthMeasure; PredefinedType : IfcAlignmentVerticalSegmentTypeEnum; END_ENTITY;