It is possible, quite likely in fact, that a Revit model and CAD data will be constructed independently of each other. Although they can both be drawn using the correct coordinates, they may not be drawn in exactly the same spatial location.
If you have developed a Revit model using Shared Coordinates how can you link a CAD model and ensure the two align?
Using Positioning of “Auto – Origin to Origin” cannot be guaranteed to work, as Revit does not like distances far from the origin.
You may get the following error dialogue:
Note: The file name in the error dialogue will match the name of the linked file.
If you click OK the following warning will appear:
“Center to Center” is no good as the CAD data will not align. In the image below, the grid is clearly offset from the green building footprint.
To get the CAD data and the building footprint aligned, use the following procedure:
- Switch to a plan view, typically “Site”.
- Set the Properties Palette > Graphics > Orientation to Project North.
- Link the DWG using:
Positioning = Auto – By Shared Coordinates.
Orient to View = Ticked
The grid will appear exactly as shown in the image above – offset.
A warning will be displayed:
Strangely enough, that’s exactly what you want.
- Click Close. The grid will be realigned perfectly with the building footprint.
Note: When saving the Revit model, you will be warned that the position of the CAD file has been changed. This is normal and is used to align Revit models using differing coordinate systems. However, you must pick “Disable shared positioning” to avoid Revit trying to write the Shared Coordinates back to the DWG file. If that happens, you will end up with all kinds of issues.
Follow this procedure for all relevant CAD files and they will always come through in the correct location.