Very confused by units in appended files

[david.byrnes]

I've been trying in Navisworks Manage 2012 to get a point cloud delivered to us as a 2012 NWC into a site NWF. It does not appear in the correct place so I checked the units - they are metres, same as the default units set in Navisworks Options, and in fact, the design units for the site.

However, bringing that file in is not the issue or the immediate question. The site NWF in question contains 17 NWCs exported from Revit Structure 2012, 2 DWGs directly appended from Civil 3D 2012, and one IAM directly appended from Inventor 2012. I checked the units on some of the other appended files and notice that the Units and Transform dialogue box says that the Revit NWCs are all in feet, the Inventor IAM is in centimetres, and the C3D DWGs are in metres.

And yet they are all in the correct size and location relative to each other, and when I use Measure in Navisworks to ID a point, it returns the correct coordinate location in metres.

The Revit RVTs and the Inventor assembly (sources of the NWCs) are all designed in millimetres. So what units is Navisworks actually reporting in the Units and Transform dialogue?

[john.lipp]

Hi david.byrnes

Even though in Revit, a project may be set to metric units rather than imperial, the file units used when converting the file in Navisworks are feet. If you try setting File Units to millimeters or meters for a Revit File, you'll find the model is scaled incorrectly.

Revit is different from AutoCAD in this way.  In AutoCAD you could set the units to Inches or meters, and Navisworks will use that unit to convert them as the file units to scale the model correctly. 

More information can be found here:
http://docs.autodesk.com/NAVMAN/10.0/ENU/Autodesk%20Navisworks%20Manage%202013%20Online%20Help/files...


Best regards,

 

John Lipp
Support Specialist
Product Support
Autodesk, Inc.

[david.byrnes]

John, thanks for your response.

So is the model correct even though Navisworks is reporting the wrong units? If I were to create a new NWF from the same Revit files, and set Units and Transform to millimetres (their actual design units in Revit) as I brought each in, would the Revit data come in incorrectly scaled? Why does it recognize the DWG units correctly (the C3D drawings are in metres) and not the Revit ones?

It's also very odd that it says the Inventor assembly units are centimetres - we never, never use centimetres as they are not SI Metric.

[john.lipp]

If you change the file units to millimeters it will incorrectly scale the revit file.

Navisworks or the Revit API libraries used to convert the file were just written in such a way that the units it reads are feet, I don't know why, but it shouldn't have any negative effects.  File Units and Transform isn't really used for reporting what units the file was created in, rather as a means to make adjustment if files aren't converting correctly due to an incorrect origin or units being read.

I've opened a couple IPT files from inventor, and I'm seeing the same thing regarding centimeters as file units, so it appears to be similar to Revit.  Apparently Navisworks uses CM for Inventor file units and feet for Revit regardless of what your project units are in the actual applications, and this scales the model correctly in Navisworks. 

To check if the files are correct, I would take a point to point measure using measure tools on a wall for instance which you know the height of to see if the measurement is correct.

 - John