Property lines changed in dwg imports!

[MRV]

I just imported a survey dwg file into my project, and two of the four property lines in the import were changed, from a bearing of N89 57 56W to N90W !!! These were not native Revit lines, but the property lines in the dwg file! This is a huge issue for us, for now we can't rely on the surveyor's dwg files to import into Revit!


Unfortunately this is a limitation with Revit - if the program encounters a line that is almost horizontal, it will make it exactly horizontal. Unfortunately there is no way to modify the precision of imported lines. Development is aware of this issue and they are looking at ways to improve this functionality in future releases. The only workaround, at this point, is to break the line up into smaller segments. Revit will still adjust the lines, but the changes will be less noticeable.

I've always believed that I could trust the import dwg files to be correct, but now I found out that Revit is changing the entity coordinates, and you have no way to know what is changed!!!

[tomnewsom]

O_O !!!!

This is unforgiveable behaviour! Fix it now now now please, autodesk.

[chodosh]

...Unfortunately this is a limitation with Revit - if the program encounters a line that is almost horizontal, it will make it exactly horizontal...

This goes hand in hand with warnings that your "line is slightly off-axis and may cause inaccuracies." Same behvior trend. I have heard of the same issue with arcs created by a trigonometric formula in a family parameter on a very large job...

-LC

[Liz437]

Absolutely unforgiveable!! We have a very large slightly curved building, and generate over 2000 (yes, that’s OVER 2000!!) warnings in each model of ‘line is slightly off axis’ which we can’t get rid of & simply bloat our model. Everyone does not build or design at 90*. This is, for us, a serious problem and deserves some correction. There is no reason that a line ‘slightly off’ vertical or horizontal should generate a problem.

[chodosh]

Over 2000 just for "line is slightly off axis???" How many lines are being corrected, then, if there are that many warnings? Do you see similar things to what MRV originally posted that the lines were auto-correcting to due horizontal?

[Liz437]

Yep, we have an average of around 2000 warnings per project file just of ‘line slightly off axis.’ With 13 project files linking into one another to create the one model you can see where our performance suffers. Nothing we can do about "slightly off axis" other than delete, which, obviously, is not an option, as that would delete essentially our entire project.

The 'break into smaller segments' makes zero sense in our case, as lines would continue to be 'slightly off axis.' We have seen some auto-correct, but really have a very hard time keeping track of those occurrences.

[Liz437]

This is STILL a hot-button issue with us; serious problem.....anyone?

[Steve_Stafford]

This doesn't resolve or change how Revit deals with the imported lines in the cad file. If you enter the property boundary data into the Table of Distances and Bearing you'll find that Revit is willing to display this information accurately.

Are the 2k lines that are generating the errors Revit lines? I find that if you put details that have such errors in a detail component family first and place that in the project that the errors do not follow the family into the project. I don't know if this is practical for your situation or not. In my case we had many many cad details that were getting imported and exploded into a project (bad idea). This generated many such warning as you can imagine. We removed this work and did the "same" thing in a detail component family and placed this family instead, no errors in the project.

[sbrown]

I'm running into this type of error on a remodel. The as-built revit model is just that as-built, so walls aren't truely square and its a bit of a pain. I'm hoping the performance isn't affected by the warnings. The property line issue is huge though. Have you filed a support request and if so what did they say. Thats definately NOT something they can leave unfixed for long.

[MRV]

They basically told me that's the way it is, take it or leave it. I was pretty upset about the whole thing at the time, and haven't calmed down a whole lot since then. I was drawing whole subdivisions by sketching over the dwg file, and never noticed the property lines were being changed. That's the really bad part, Revit was changing the lines without any notification at all. My trust factor in Revit drawings is down a few notches now, I don't assume anything is correct now without verifying!

[patricks]

Well I have noticed that plenty of surveys, site plans, legal descriptions, etc. aren't terribly accurate, either. Many times I create a property line by table of distances and bearings based on what is on my CAD file, or on a legal description, and the shape does not actually close according to Revit. I've seen it several inches off between the start and end points.

So you kind of need to take some of those surveys with a grain of salt, also.

[chodosh]

Are the 2k lines that are generating the errors Revit lines?

Not entirely, sorry. The warnings and issues on the project in question were not due to Revit lines alone and that while your solution is elegant for details, the issue with Revit rounding is far more serious for this instance. The most critical problems we were seeing on that project were specifically related to a trigonometric formula that was generating an arc. The trig worked. When dimensioned, however it did not. So, essentially, the issue was not with Revit lines, but Revit objects that were not truly the dimension they should be. This was a radius function. The radius after Revit generated the arc was rounding up or down, my best guess was because the angle that was generating the arc was self-correcting to a rounded set of decimal degrees, and therefore knocking the length value off in the trig... resulting in a radius that was off, too.

Then, regarding the 2000 warnings issue... If the building is radial, what would you suggest?

Like Liz said, still a serious issue, one that any suggestions would assuredly be welcome, not just for the team working around the radius rounding, but for everyone else working with similar radial geometries or slight angle differentiations like seen in a site survey...

Best,
LC

[mrice.47661]

Can anyone provide any guidance with this issue or any workarounds? It seems to still persist as of Revit 2010.

I have a moderate sized survey file from our civil engineer in .DWG format. I need to use that file to both set up a site model and then link my building to it. But my question is ... how can I possibly do this if I can't ensure that the linework is maintained in Revit. The property lines ARE accurate and need to be consistent between the documents. In addition, I need to generate a topo based on the surveyed information, and I have a lack of confidence that the topo lines are consistent with the survey information, they seem to "wobble" from the positions they have in AutoCAD. I know I can import the topo data directly via a .csv file or the like, but without some confidence in the property line and bench mark locations I don't have confidence I can align the information accurately if I bring it in via a different avenue.

I'm try to follow along with Steve Stafford's site coordinate setup demo, but am getting hung up on this initial step.

Thanks in advance for any ideas/advice.

[Steve_Stafford]

As I mentioned in an earlier post use the property boundary tool that uses the table option to enter values. The property boundary will be as accurate as the data provided in the cad file. It is just the lines that are part of the cad file that are getting this "subtle" alteration during import. The toposurface tool has never been intended for highly accurate civil engineering, more a "ball-park" tool to assess the cut/fill conditions of a given design.

[mrice.47661]

Thanks for the reply Steve.

I can understand the concept of inputing the property line in that manner ... but what I get hung up on is how we're supposed to locate the building with respect to the property line/site benchmark if we can't count on any of this information being imported correctly? I assume the export CAD geometry is accurate - so in theory a one-directional pipeline for reliable geometry exists one we've entered the property line in a tabular format ... but I can envision hang-ups with not being able to bring back and confirm the information.

In particular I'm running through your AU presentation on shared coordinates, and I noticed that even my project benchmark is unreliable in terms of location on its import (the civil engineer used a few different pieces of linework to locate this, and while in AutoCAD all of the geometry is coincident, in Revit the various markers are all slightly off.) So there is really no way of graphically locating this point. I suppose I could just do it numerically from the coordinates as an option.

But that doesn't seem to be the workflow you're suggesting in the AU presentation. Is there something I'm missing?

[Steve_Stafford]

I always try to settle on a coordinate in the civil file to use as a benchmark. I'm pretty sure I mentioned that in the recording during the virtual class, if not I should have. Revit doesn't recognize AutoCAD points so I recommend a line or set of lines. If they aren't drawn at really small angles relative to the world coordinate system they won't get "adjusted" by Revit during import. The "only" lines that get altered are those that are really close to vertical or horizontal. Otherwise the CAD import is, or should be, reliable enough for what we are using it for.

Pick a reliable spot in the civil file, a benchmark or building corner that isn't going to be affected by construction, and create a couple lines that spring from it. Then find out what the coordinate value is at the intersection, record that and use it in the Specify Coordinates at point tool. Should get you there...