Round-Robin translations DGN->DWG->DGN and maintaining survey feet units

Anyone have any tips for AutoCAD users that need to work in Survey Feet?

Our sub uses (only) AutoCAD (surprise!), and they don't know a survey foot from a rabbit's foot. On some early tests they were able to work in AutoCAD with some DGN files I translated to DWG for them, but now that's all falling apart rapidly as they butcher the files AutoCAD. I assume one of their users got a death-and-doom warning about units when they opened the file, and let AutoCAD "fix" it for them...

 

I searched in Google (from an AutoCAD POV), but all I can find is "nope, ain't happening, it's the international feet way or the highway!" or "Civil 3D sort of maybe does it, but AutoCAD can't--so sue us." Not very helpful...

 

In summary:

-Project is in DGN format, client requirement

-The project has coordinates over 1 million, thus the error

-The sub is working in DWG files and AutoCAD doesn't support Survey Feet (True? False?)

-The client and everyone else on the team is using MicroStation and working in Survey Feet

-The sub and the other disciplines need each other's files to do their work, so I already have a heinous translation schedule and juggling Survey Feet vs. International Feet is a big pain

 

Is there a way to trick AutoCAD into using Survey Feet by redefining its units, sort of assigning custom units? Or do I have to downscale (once our DGNs are in DWG format) and upscale (once their DWGs are in DGN format)?

 

Thanks!

Parents
  • As David has correctly pointed out that there is no units in ACAD - it really is a unitless system. When you save your Survey Feet file to DWG using Master Units, ACAD can have a unitless readout of your coordinates which can be interpreted as decimal feet. What ACAD cannot do is to interpret the coordinate readout in Survey Foot-Survey Inch format. It only has an international feet-inches format which is hard coded to show Feet as multiples of 12.0 and Inches from the remainder of a coordinate. But if decimal foot (or decimal inch) readout is acceptable, perhaps your subs can still work in ACAD.



  • Civil 3D does have a place where you can set the foot as US Survey or International. In fact, their imperial seed (DWT) file is delivered with its feet set to international, but if you use the default survey units, they are set to US Survey. This will create survey points and figures that display in the DWG using International Feet coordinates (shifted) while listing them in COGO as US Survey Feet coordinates (true). These settings are internal to Civil 3D and are not exposed to OTB AutoCAD nor to MicroStation via RealDWG. They are stored in non-graphical Civil 3D objects and only graphical Civil 3D objects are exposed if Civil 3D Object Enablers are installed.

    So, what is happening is that the software know there is a conversion factor, but still stores the file as "unitless". So if you know the file is drawn using Survey Feet Coordinates in the "unitless" system - in the Options dialog box of MicroStation when selecting a DWG Reference File to attach or a DWG file to open, is a place to specify units upon opening a file - you can even set Architectural or Engineering units to US Inches and Decimal or unspecified to US Feet.

    This is separate from the dialog box that opens once a DWG file is selected (which also has a "Do not show this box anymore" option, so you might never see this second box.)

    Anyway, this should help. This is not too different from V7, when we knew our FT in the Working units were Survey Feet, and if we needed to reference in a metric file, we knew we needed to use the correct scale ratio for US Survey Feet to Meters.


    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
  • I wonder if C3D users are mandated to use C3D object enabler in ACAD where C3D as a product is not available? I ask because if C3D stores unit definition in the dictionary, instead of using existing system variables, its coordinates can be wrong without running the object enabler because ACAD would not be able to know the true units. A way around that is to mandate the use of C3D OE.



Reply Children
No Data