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**mark b** · March 8, 2011, 11:41 AM

Just curious, have you dimensioned the Revit drawing and the dwg ? Is there any difference between the two. Also have you measured across the walls in the dwg and checked the wall thickness ?

**G Jowett** · March 8, 2011, 12:39 PM

Was the linked CAD file exploded before linking it into your Revit project?

Refer to my post below

http://revitst.blogspot.com/2010/12/...cad-files.html

Revit seems to struggle aligning and snapping to linked CAD files that are un-exploded x-refs or blocks.

**jaypro** · March 9, 2011, 02:44 AM

Hi guys,

thank u for the quick reply...
Yup the dimension of both the revit and cad are the same..I already adjusted the decimal places just to check the similarities.
I also have the exploded cad linked to revit.
Maybe need to purge and audit the cad file.
I'll post if I already have the solutions. thanks again.

jaypro

**mdradvies** · March 12, 2011, 08:17 AM

This is why you shouldn't do this. Revit doesn't have the same accuracy as autocad in this matter. Are the walls a tiny bit rotated in your dwg? (not being exactly horizontal or vertical that is) This will create numerous faults. There is a post about that here somewhere, but I can't seem to find it just right now.

**Karalon10** · March 13, 2011, 10:19 PM

My thinking is that you have it set to display thick lines. This can often show two seperate lines (as they are different thickness) even though they sit on top of each other. Type "TL" in your view, and see if they still dont quite match up in thin line mode.

**jaypro** · March 14, 2011, 12:05 AM

thanks for your replies guys..

I found the 'cuplrit, and it has nothing to do with the views, or TL..the linked autocad has a frozen layer which is away from 0,0..so i have to layer 'thawed' it and delete...and everything looks fine.

regards
jayprp

**hypnox1** · March 15, 2011, 09:25 PM

I've noticed a number of problems with linking CAD files much like this. Especially with large extents files like Civil files. I've found that this can be mitigated to a degree by setting your project units out to the maximum available accuracies. For instance, setting decimal places out to the nearest 10th by setting it to a custom option. Also setting accuracy of dimensions to the nearest 256th of an inch. This seems to bring in the CAD dwgs' nearly as accurate as they were in AutoCAD and helps mitigate these visual issues. As was noted above, Revit simply does not have the accuracy level AutoCAD did when it came to reinforcing exact lengths of items.

Where AutoCAD used some crazy double checking routine to assure dimensional accuracy, Revit does not. On the other hand trying to have the pure accuracy of AutoCAD in Revit at this time may not be possible on extremely large buildings as the amount of data Revit handles in comparison to AutoCAD is phenomenal to say the least. Hence why you run into issues like lines under a certain length simply cannot be created by Revit. I can't seem to find the technicals but someone at Autodesk did an actual comparison of these 2 and why there seems to be less accuracy with Revit.

**mdradvies** · March 15, 2011, 11:31 PM

Originally posted by hypnox1 View Post

I've noticed a number of problems with linking CAD files much like this. Especially with large extents files like Civil files. I've found that this can be mitigated to a degree by setting your project units out to the maximum available accuracies. For instance, setting decimal places out to the nearest 10th by setting it to a custom option. Also setting accuracy of dimensions to the nearest 256th of an inch. This seems to bring in the CAD dwgs' nearly as accurate as they were in AutoCAD and helps mitigate these visual issues. As was noted above, Revit simply does not have the accuracy level AutoCAD did when it came to reinforcing exact lengths of items.

Where AutoCAD used some crazy double checking routine to assure dimensional accuracy, Revit does not. On the other hand trying to have the pure accuracy of AutoCAD in Revit at this time may not be possible on extremely large buildings as the amount of data Revit handles in comparison to AutoCAD is phenomenal to say the least. Hence why you run into issues like lines under a certain length simply cannot be created by Revit. I can't seem to find the technicals but someone at Autodesk did an actual comparison of these 2 and why there seems to be less accuracy with Revit.

Well, maybe it's because I never really used Autocad on a professional base (I graduated using Revit and stayed with it ever since), but I have never understood the obsession with Revit's accuracy. I get a lot of remarks about this when training former cad-drafters. It should be more accurate, that was better with Autocad, etc.
Let's face it: anyone who has spent any time on a construction site knows that a accuracy margin of 0.0000001mm is completely nuts. I really do hope there will never be any Lab-hours lost on increasing Revit's accuracy. I do wish some guy thought of a way that Revit would ignore the 0.6mm diversion in Autocad and keep the lines aligned to each other when in a situation like the OP.

**Ben-May** · March 16, 2011, 10:29 AM

Originally posted by mdradvies View Post

Snipanyone who has spent any time on a construction site knows that a accuracy margin of 0.0000001mm is completely nuts..

Especially when you are talking about a linking a Civil drawing which is issued at 1:250(Metric) at its largest scale, you would be lucky to dimension to the nearest 100mm!

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