Handling UCS Objects from Imported CAD Files (DWG, DXF)

We have noticed over the past year a massive increase in the occurrence of UCS objects in AutoCAD Civil 3D created CAD Files (DWG, DXF). I was training some users last week on their data and it was so painful because the UCS objects needed to basically be replaced. Normally the UCS (User Defined Coordinate System) is used on Arc objects because AutoCAD does not support Arc Geometry that has varying elevation along it’s length in any other way than this UCS technique that basically draws the Arc on a Tilted Plane. When we import those UCS objects into TBC they have a UCS property to replicate the objects native properties. However UCS objects cannot be joined to normal global coordinate system objects, and there are numerous restrictions on what ou can do with the objects, to the point that I like many of you was pulling my hair out!.

I discussed with Trimble Development, and they added a UCS Fix Function into the Convert To Linestring TML command. This allows you to auto convert all polylines and shortly all Text and all CAD Lines to Global Coordinate System objects. This is a huge help and time saver for Data Prep applications.

Note: that if you start out with an Arc in 2D of 5m radius, and then add elevations to it that places it into a UCS in AutoCAD, Autocad will often adjust the Radius so that it still fits the source linework - resulting in a radius of e.g. 5.01m. When you remove the UCS from the objects, TBC’s unique Linestring elements can fully support variable elevations and vertical curves and arcs on a global coordinate element arc, and you likely should let TBC recompute the correct radius as it removes the UCS data. I would look at the Arc Radius of UCS objects to see if they have close to but not perfect radii, and if so let TBC recompute the radius as it removes the UCS data from the objects.

I did say that UCS is typically applied to Arcs however in the data set we were working with last week, it was found on all sorts of lines including bits of contours as well as straight line elements. The new tool works great on this type of data - here is a short video of the new tools.