How to expose source length unit from IFC file?

Hi @jacobbuckley,

If it is not already exposed, you can use the AttributeExposer to expose the lengthunit attribute on the source IFC features.

Hi Dave,

Thanks for your response. I have found that Lengthunit is not accurately describing units used when creating the IFC file. For instance on several recent files the actual unit is millimeter (as confirmed on visual preview), while lengthunit is displayed as metre. Could this be a default attribute?

Thanks

Hi @jacobbuckley,

Would you mind sending a copy of the IFC to so we can create a problem report for our development team about the lengthunit?

You may find the FME Hub transformer https://hub.safe.com/publishers/bleuminkgeo/transformers/coordinatesystemmapunitextractor useful, to get the length unit from the coordinate system.

Hi Dave @daveatsafe​ ,

I'm facing the almost same question as Jacob. Need to identify the units of input IFC firstly, and decide which conversion process to go. Also, the attribute of LengthUnit seems not complete for the input IFC.

I've tried the transformer: CoordinateSystemMapUnitExtractor for two IFC files, the results varied. It works fine for the IFC generated from Revit, an attribute called _units was created containing the correct units information (mm); however, for the IFC generated from Civil 3D, it seems the transformer didn't work.

I uploaded two of the IFC data here for your review: https://we.tl/t-BGoInZAlfv. Thanks in advance!