How are units defined in imported DWG files in Tekla Structures?
Tekla Structures reference model import must apply a dimension (m, ft, etc.) to the numeric values of the imported model. However, the DWG file does not exactly specify the dimension of the modeling units. DWG has a parameter called "INSUNITS" (please see the Autocad documentation page for more details), which specifies a drawing-units value for automatic scaling of blocks, images, or xrefs when inserted or attached to a drawing.
When the 'INSUNITS' parameter is found, the reference model import takes that into account and applies the necessary scaling to convert the imported DWG model into the Tekla Structures model units.
However, if the 'INSUNITS' is left in an unspecified state (=numeric value is zero), the import falls back to another DWG parameter called 'MEASUREMENT' to determine whether the source file is in metric or imperial units. When 'MEASUREMENT' is set to metric, the DWG model units are presumed to be millimeters. If it is set to 'imperial', the DWG model units are presumed to be inches. The 'MEASUREMENT' parameter is less well known than the 'INSUNITS' parameter, and may therefore cause confusion.
For example, if the user imports the DWG to a Tekla Structures model using metric units when the INSUNITS is set to 0 and the MEASUREMENT is set to imperial (numeric value 0), the reference model import presumes that the imported model is in inches and applies the necessary scaling.
To scale an imperial reference model manually to metric units, enter the scale 1: 0.03937 when adding the reference model.
Note that you need to set the scale for a DWG (or a DXF) file already in AutoCAD. When you define the measurement unit for a DWG (or a DXF) file and save the file in AutoCAD, the unit is recognized in Tekla Structures , and the reference model is scaled correctly.