This is an option of the DXF/DWG Translation Setup dialog box
See DXF/DWG Translation Setup.
Value of 1 DXF/DWG Drawing Unit in ArchiCAD: As you export or import something in DXF or DWG, you must set the size and distance conversion factor to ensure that ArchiCAD interprets the data correctly.
•Prefer Drawing Unit definition in DXF/DWG file. This checkbox means that ArchiCAD will use the Drawing Unit definition as set in the original imported DXF-DWG file.
•If no such original definition is available, or if you want to redefine it, use the pop-up list to choose either a standard drawing unit (1 meter, 1 millimeter, 1 inch, 1 foot); or a custom unit (any number of millimeters or inches).
When opening a DXF/DWG file, you must define a scale at which you would like to see the correct ratios of elements drawn in AutoCAD. This particularly applies to arrowheads, symbol line types and symbol fills.
Set Scale Factor for converting texts and arrowheads: Choose one of the three options:
•Set scale factor separately with each conversion: In this case, a dialog box appears after clicking the Open button, letting you set the desired scale factor.
You may click the arrow before the text ‘Show Example’ to display an explanation of the effect of the scale factor:
This scale factor has an effect on Texts and Arrowheads of the imported AutoCAD drawing. Click OK to accept the scale factor.
•Use constant factor for all conversions: Set a scale factor for ArchiCAD to use for these conversions. In this case the Scale Factor Dialog will not come up.
•Always use the scale set in the currently active ArchiCAD window: The scale of the ArchiCAD Floor Plan will be used for conversion. This is the same method which worked in ArchiCAD versions up to 8.1.
Note: If you used the Set scale factor separately with each conversion option, the Scale Factor Dialog will also come up in case an AutoCAD drawing is dragged and dropped onto the ArchiCAD Window background (drag-and-drop Open), and in case an AutoCAD drawing is merged into the ArchiCAD Floor Plan, a Section/Elevation/IE Window or a Detail/Worksheet (drag-and-drop merge).