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IFC attributes with derived units are not displayed (m/s, m3/h, ...) while non-derived units (m, Pa, ...) are

Question asked by Stephan Günther on May 9, 2019

We experience the following behaviour with all our imported ifc files:

Attributes with derived units such as m3/h are not shown in Trimble Connect.
This is true for the web and desktop version.


On inspection of the original ifc file (find it attached below) we find the attributes to be present.

For example:

   #640=IFCPROPERTYSINGLEVALUE('Calc-Velocity (m/s)',$,IFCREAL(0.111304308930937734256617),#635);

but the attribute is not shown in the attributes of the PSet section in Trimble Connect.


For testing purposes we changed this line to

   #640=IFCPROPERTYSINGLEVALUE('Calc-Velocity (m/s)',$,IFCREAL(0.111304308930937734256617),$);

making the attribute unit-less.

This made trimble connect display the attribute (without the correct unit of course).


Non-derived units like "m", "Pa", "m2" and so on are not affected.

Other BIM viewers show the attributes correctly.

The ifc is also constructed correctly as far as we can determine:

   IFC-Object > PropertySet > PropertySingleValue > DerivedUnit > DerivedUnitElement [x2] > SIUnit [x2]
with the correct corresponding #number given for each reference.


Please tell us if something is wrong with our file, still.

When can a bugfix be expected (warning about malformed ifc or correctly displaying derived-unit-attributes)?

P.S.: We exported the ifc files with NOVA 14 (also made by trimble).



Stephan Günther

Günther ingenieure GmbH