buildingSMART Forums

How to define the geometry of a rail

Dear IfcRail project team,

we are a software vendor interested in implementing the candidate standard published recently. We have stumbled upon a question, where we cannot find the relevant Information: How can we define the geometry of a rail (not as a BRep, but as an extrusion, preferably along the alignment)?

Our progress so far:

  • A rail is a kind of product and building element from Data Requirement Report, Section 2.1.31.
    We assume it is going to inherit from IfcProduct in the final schema extension and thus have a geometric representation.
  • You write in Context Approach Report, Section 4, Priority 1: “Provide a geometric model of all lineside and trackside elements of a railway system.”
  • You then mention in Requirement Analysis Report, Section 8: “… railway cant must be defined as another parameterized item for defining railway alignment. With such information, the IFC model should be able to parametrically create track geometry or other 3D elements by sweeping a profile along track axis or computing other 3D shapes like loading gauge.” and “At this stage of the project, except cant alignment, there are no requirements identified to define additional parametric representations.”

Therefore, we deduct that you did not define any new geometry representations, but we should reuse the existing ones within the IFC model.

Which ones, though? Can you please point us to the relevant section(s) of the relevant document(s)? Can you please provide us with a hint how to address the geometry of a rail?

Hi @matthias.frei - I am not familiar with the rail project team’s work, but if they have not specified a particular geometry representation item type, then I can perhaps recommend an IfcSurfaceCurveSweptAreaSolid.

There is a thread discussing its use here.

Hope it helps :slight_smile: