Dealing with dwg surveys - jagged lines

[hwo_osa]

Hi everyone,

We frequently receive site plans from our surveyors as dwg files.

We usually link these into our model, move them according to our project base point and use "acquire coordinates" to ensure we're all working in the same coordinate system.

As we all know, Revit can't handle geometry that is further than 10 miles / 16 kilometers from the internal origin and that linking in files with geometry outside of these limits can have unwanted side effects.

However, I am currently having issues with jagged lines in dwg's (to be more precise: links inside of blocks in dwg's) even if all the geometry is whithin these limits.

I triple checked my dwg file and I am 100% positive that all my actual geometry - lines, blocks, hatches etc. - is whithin a 600 by 800 m bounding box. However, the dwg itself is drawn on real-world coordinates, I.E. hundreds of kilometers from the internal origin of the dwg (as surveyor files usually are).

I can't simply move all geometry to 0,0 because that would mean losing the geolocation info. And even if I did, this would not work because all of the blocks would still have their geometry relative to the old origin.

Has anyone ever encountered this issue? What's the best way to deal with it?

[SteveKStafford]

Revit can handle elements far from the origin but it does not like elements that are both far from the origin AND near the origin, specifically when the extent of everything in the model is greater than the threshold, that's when the graphics gets jittery or hidden line no longer works.

I have encountered files that appear to have modest extents but very far from the origin that still exhibit the extent issue. In those files I have found a block entity that needed to be exploded to eliminate a nested element that is at the origin (creating a larger extent that the file itself recognized). I have also found curved polyline and 3D polyline elements that Revit did not like. More recently we have observed that Parcel elements (Civil 3D) seem to cause the issue sometimes. Nested Xrefs that are attached can/will cause the issue because their origin will "track" back to the origin of the host file and Revit seems to notice this. Also remember that there can be layers that are turned off or frozen and they can contain elements too far away. I've also seen recently that Revit will not link a DWG by shared coordinates if there is a locked layer.

What I have done before is start slicing up the DWG into discreet parts until I get a file without the issue. For example delete everything to the east side and see if the issue goes away. If is does then I reset the DWG and narrow down the area I delete until the problem goes away. In one file a single curved polyline was the culprit. I replaced it with a new curved line and it was fine after that. I wish it was simpler but it isn't. If the file was generated by Civil 3D make sure they are using the Export to CAD option to generate the file for you, that tends to work more consistently in Revit.

[hwo_osa]

@SteveKStafford Thank you for clarifying.

This is more or less in line with what I expected to be the answer - "it kinda sorta works with a couple tedious workarounds". 😉

Excuse my sarcasm, but it is pretty mindblowing to me that there is no "official" solution for this standard everyday workflow; especially when considering that dwg is a format developed by Autodesk. 

[SteveKStafford]

Yes, I agree. I realize that even though Autodesk owns both products they are still fundamentally different collections of code developed at completely different times by different people, and originally they were in distinct competition with each other. Translating between any two software applications is still a translation. I can say I speak Spanish but utter one sentence and a Spanish speaker will know I'm not a native speaker.