converting DGN (ft) to DWG (sf)

I am needing to convert an existing dgn file in FT unit to a DWG with a unit of SF (Survey Foot). I have already modified the units.def file so when I attach a file I can choose the proper unit, but I don't have the same option when saving as dwg.

  • Chris,

    Are you trying to have the working units in the DWG file read as survey feet in MicroStation or AutoCAD?

    I ask this because DWG format does not really have a linear unit concept and it really is a unitless system. There is no reliable way to determine what units are used in a DWG file. You can open a DWG file in MicroStation and set the working units in the DWG options or going to the Design File Settings>Working Units. This does not apply in AutoCAD as the environment is a unitless system.

    See the following blog that discusses DWG units.

    communities.bentley.com/.../dwg-units

    AutoCAD does not have survey feet, but there should not be actual difference in coordinates or sizes.  The only difference is readout.



  • Even in Civil 3D, the file format is unitless. Within the Application Objects it stores the unit conversion information. Somehow, I have our system at work set up that it allows me to select US Survey feet when opening, saving or referencing a DWG. It will remind me thay DWG does not support special units, but in practice, a file saves as feet with Civil 3D configured to use Survey Feet aligns correctly and all coordinates are reported correctly.

    Charles (Chuck) Rheault
    CADD Manager

    MDOT State Highway Administration

    • MicroStation user since IGDS, InRoads user since TDP.
    • AutoCAD, Land Desktop and Civil 3D, off and on since 1996
  • what would happen  if you changed a dgn  to survey feet  first and then saved as dwg... then ref attach the DWG   to the SF dgn 

    do all the  objects  line  up  can you also ref in on top the orginal FT  are there any differences?

    If your FT dgn doesnt  match your DWG and more importantly the DGN (SF) model,  but your DGN (SF) matches your DWG then I think its converted correctly...even though acad is unitless it still uses Cartesian  coords from 0,0.

    Lorys

    Started msnt work 1990 - Retired  Nov 2022 ( oh boy am I old )

    But was long time user V8iss10 (8.11.09.919) dabbler CE  update 16 (10.16.00.80) 

    MicroStation user since 1990 Melbourne Australia.
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