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Friday, October 18, 2024

Units - International Feet and US Survey Feet

 Bizarro world remains for the software company. When you add features should you expect everyone to change their behavior? What do you do with legacy drawings? Should the software company actually make sure their own features work with the new feature? 

If you are Autodesk that is a resounding NO! Ignore the new feature and wonder why users are complaining. 

In this case the software providers have provided support for "Feet" (which was the only option for decades) and then added an option for "US Survey Feet". Unfortunately, if you export to IFC Civil 3D doesn't read the drawing units. The feature defaults to "International Feet" instead of "US Survey Feet". 


You can see that in line 13 of the output files (note yours might be different). That the conversion factor from feet to meters is set to "Internation Feet" instead of using the appropriate factor. 

To fix this you can modify the text files with the desired value of conversion. In this case the desired value should be 39.37 inches per meter or 0.3048006096012192


 

Then when you import the file into another drawing, as long as it reads the factor, it should import in at the desired location instead of being scaled incorrectly. 



I haven't tested Civil 3D 2025, but Map 3D also has issues recognizing "US Survey Feet" for most of the commands in Civil 3D 2024 and prior drawings. These were reported to Autodesk, but like most bugs I don't think they cared to fix them. As bugs to be fixed are bugs to be ignored.

The help file indicates it supports US Survey Feet, but I'm not seeing that in practice on the export. 



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