Limits in accurancy in bring in an Autocad Model to coordinates

[Anonymous]

I posted this one a week ago: http://forums.autodesk.com/t5/Autodesk-Revit-Architecture/DWG-files-coming-into-Revit-in-wrong-place... 

I'm wondering, is there a limit to Revit's ability to be accurate when it comes to bring in an Autocad model, where the Autocad World UCS position is a long way from the geometry?

I've just retried this, adding an object in the Autocad origin point, with a line to where my model (so I can find it).

I'm a little puzzled by the behaviour though.

• Linking with Auto Origin to Origin, Orientation True North, places the Autocad Origin on the Revit Project Base Point, nowhere near the Revit Survey point. It is however the correct orientation. Is this supposed to happen?
• Linking with Auto Shared Coordinates, places the Autocad Origin close to (but not on) the Revit survey point. It is also the correct orientation.
• Changing the Revit Orientation to Project North, places the DWG origin again on the Revit Project Base Point, but with the wrong orientation.
• Linking with Auto shared coordinates, places it again near the Revit Origin, but again with the wrong orientation.

I can understand rounding errors, but which of these formats am I supposed to use to bring in DWG's consistently?

Am I asking too much, when the Autocad Origin is so far from the Revit Survey point that this should happen, should I simply give up, get it in approximately right, and move it where I need it?

[Anonymous]

I should add, UK practice is to work with Autocad base files having their origin to be equal to the UK Ordnance Survey National Grid, this inevitably results in the Origin being a very long way from the actual area where we are drawing things up, as is the case with the DWG I attached.

If Revit can't handle this, we need to know about it and work around it....

[Anonymous]

OK, now I'm confused.

I have two DWG files in the attached ZIP file, they both have the drawing geometry working to the same World UCS Origin. Xref one into the other and they sit right where they should on top of each other.

When I bring them into Revit however, with positioning using Auto - By Shared Coordinates, the Grid drawing to come in right needs to come in with the View Orientation set to Project North; if I do this with the LVL-0 drawing however it comes in out of place, and with a skew rotation.

To come in with the right orientation for LVL-0, I have to set the view orientation to be by True North, it then comes in the right way around but still well out of position. 

Can someone out there explain why there should be such a major difference?

Is it possible I have published the project shared coordinates back to the DWG and these are now working correctly for the Grid file, but not anything else? Or vice versa?  Or is something else going on?

I've tried with the original file that LVL-0 was based on (the .dwg file, not the zipped one), and it comes in right where it should, using the same orientation as the grid drawing.

I'm trying to write the workflow for my company and this kind of unexplained and confusing inconsistency is the kind of thing that turns people right off using it.

Can I have an answer from one of the Megaminds at Autodesk please.

[Anonymous · Accepted solution]

Right, from an additional hour of mucking around, it seems the problem was in the DWG.

There was a small bit of drawing geometry somewhere off in space, it was enough that the linked file was coming in and then changing itself from being set by Shared Coordinates, to being centre to centre.

Either that or it was an xref.

Grrrrrr, altogether I've spent hours figuring this out!