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Topography with IfcGeographicElement?


Does someone how to export an IFC with the topography from some BIM software? I would need it using an IfcGeographicElement. I tried to model it with Revit, but it includes all the 3D representation of the terrain in the IfcSite. I need this entity because I’m only interested on the terrain and the site includes cars, trees …



I’m not sure completely the answer to your question, but in Revit, there is documentation for how to override various IFC properties. You can set those for your cars and trees to be exported as other things, or not to export at all.

I hear ArchiCAD has better IFC support, so you might want to try that though. FreeCAD (open-source BIM) also has support for all IfcProduct types if you want to be very selective about how you export.


Thank you Moult, I knew that documentation, but it says that they have a mapping table where you can translate classes from Revit to IFC entities, but it doesn’t work :-(. In the same way, I tried to export sanitary terminals with the specific predefined type such us BIDET, BATH, SHOWER, however all those ones have their predefined types as NOTDEFINED.

I’ll try it with ArchiCAD.


I have also had poor support with IFC classifications in Revit. I have tested it somewhat myself and found that it does work on custom families / in-place families. Good luck with system families - I don’t think it works.

You might want to try out FreeCAD (get the latest 0.18 version, and if the property sets are out of date, I can point you to a file in the bleeding edge repo which has the latest data), which currently supports the ability to assign any geometric representation to any IFC Product type, and also supports all property sets. I am working on improving this support to include the attributes of each IFC product and updating the values to IFC4Add2, which should be implemented soon.


Ok! I didn’t know freeCAD but that you say sounds very well. I’m going to install it tomorrow at work! I’ll tell you if it resolves my issue…
Good night :slight_smile:


I just tried exporting a IfcGeographicElement in FreeCAD and it errors out. Perhaps it is a localised bug, so let me know if it works for you. If not, let me know what error you get and we’ll fix it :slight_smile:


I’m assuming, of course, that you are referring to IFC4 and NOT IFC2x3.

This is currently being worked on by the vendors supporting IFC4 RV1.2, for certification. Until those certifications are finished, you may find results a bit… inconsistent.


as @jwouellette says - the IfcGeographicElement is a new class in IFC4. In IFC2x3 coordination view the topography was directly included as a shape representation of IfcSite. In IFC4 it had been separated out, the IfcSite is now a container and top of the spatial structure. The terrain, IfcGeographicElement/TERRAIN is now an independent entity and associated with the site.

Maybe it is worth testing the BIM Authoring tool’s early IFC4 support.


Of course you are right…if the IFC comes in 2X3 I work with the site representation but very often contains other element representations and the result is not as good as I would like it.


I apologize but I didn’t have enough time at work to test freeCAD well. I installed it and tried to import and IFC with the topography from sketchup. It was imported good apparently. After that I exported to IFC without changing anything but this new IFC lost the geometry…
I’ll keep on working on it next week, thanks…


It is indeed possible with Revit R2019, if you use the current IFC-exporter on Github:
If you add the parameter IfcExportAs to the Topography, with value IfcGeographicElement, and export it as IFC4 Reference View.


Interesting, things must be starting to improve. For the record, tested under Revit 2018, using the IFC exporter, it does not work. When exporting to IFC2X3, Topography becomes IfcSite. When exporting to IFC4, the Topography is simply not exported, regardless of the value in the IfcExportAs parameter, at least in my file.


Indeed, there is a lot of improvement. And indeed the development on Github is only for R2019.
To fully benefit the latest improvements you can build your own solution, or you could try the latest pre-build beta:
For IFC4 RV 1.1 all Classes of IfcElement and IfcSpatialElement are now supported.
Sample with all the RV valid classes (viewable with BIMVision or FZKviewer):

IfcClass_R2019_IFC4RV1.1_ValidOnly.ifc (2.7 MB)


I apologise for the delay with my answer but I was on a trip. I’m going to check that! Thanks