importing DWG surveys & acquiring coordinates

[andrewharle]

Hi,

Although Revit 2011 seems a bit better at importing DWGs there still seem to be (undocumented) bugs.

We are trying tgo establish office standards so I have been running some tests which I thought I would share for information and comment....
.... and possibly for Autodesk to take note and fix!

The site survey DWG is set out 211km north and 272km east of 0,0 in AutoCAD (that’s over 130 miles)

Test 1 – bringing in survey to Revit in new file

• Survey brought in centre to centre
• Revit cannot acquire coordinates (a known issue)
• So coordinates specified at given point
• Revit will import other site DWGs in correct place
• Revit will reload survey in correct place

Test 2 – rotating true north after survey loaded - View set to True North

• Revit will reload survey wrongly rotated in True North view – it loads DWG as if true north pointed straight up screen
• Revit will not load other site DWGs in correct place
- Warning Dialog ‘Imported object located a large distance from origin …’

Test 3 – rotating true north after survey loaded - View changed to Project North

• Revit will now reload survey in correct place
• Revit will load other site DWGs in wrong rotation

Test 4 – rotating project north - view set to Project North

• Revit will reload survey in correct place
• Revit will import other site DWGs in correct place

Test 5 – rotating project north - view changed to True North

• Revit will reload survey in wrong rotation – rotated as Project North view
• Revit will not load other site DWGs in correct place
- Warning Dialog ‘Imported object located a large distance from origin …’

Test 6 –rotating project north - view set to True North in a copied view

• Revit will reload survey in correct place
• Revit will load other DWGs in wrong place & wrong rotation

Conclusions

• Do not rotate True North if survey is a large distance from origin
• Revit remembers the view in which the DWG was loaded, and this view must remain set to Project North to update Links correctly
• Load all DWG links into views set to Project North - set up a specific view for this

Hope this helps

[andrewharle]

why not just refer to those AutoCAD lines AWAY from your Revit project and build it CLEAN in Revit?

Simply because we aim to work in a collaborative manner with other non-Revit consultants.

We share topographic surveys with them and cleaned-up base site plans. We need to link their DWGs into Revit accurately without them jumping around & rotating. We often work with structural engineers, highway engineers, hydrologists, civil engineers, MEP engineers, landscape architects etc. all working to the coordinate system of the base survey.

In short we want Revit to do what it says in the manual not something different!

... but thanks for your comment

[cdatechguy]

Why should someone spend the time to recreate a topographic survey if they don't have to? I would prefer to just link in the DWG than try to get Revit to show the same thing....unfortunately Revit's surface tool isn't as friendly as Civil3D...But at least I can import the TIN and create somewhat of a surface from the DWG...

I tend to keep my site surveys always in the True North view, since that is where the dwg is oriented.

I wonder if what your trying to accomplish has something to do with the Survey Point...I know its there, but I haven't had time to figure out what it does...and the Project Base Point never seems to work well either...at least me and my structural counterpart haven't figured it out.

[cdatechguy]

Are you sure about that?

Try bringing in a surface with retaining walls...Revit doesn't know what do do about those points and just meshes them together...

And then they change the topo a few times....Do you really want to re-create your surface each time?

For a flat site this is probably no big deal.....but when you have a 12 meter difference...I would rather use the dwg....

[andrewharle]

I wonder if what your trying to accomplish has something to do with the Survey Point...
The Survey Point does move if you rotate Project North, but the coordiantes change accordingly.

[aargumaniz]

Andrew,
I'm doing the exact same thing that you are and I thought I was doing something wrong. My survey is a dgn file and in some of my sites the survey would rotate on me. I kept on reloading the file and fixing the position later to find out that the file was rotated.

What I have been doing now is creating two separate files, one that has the site information and then another that has the building information. In the site file I import the dgn to my site view set at true north. I then create another file for the building and rotate the site to the proper project north. This way I know that my site file will always show the dgn file at True North.

I wish there was an easier way to do this, or at least documentation on how to properly collaborate between disciplines and software. The project I am working on is using Microsation, Revit and Navisworks for clash detection. We need everything to line up exactly, so far everything does. But it took hours of trial and error and research to figure things out.

Aracely

[sbrown]

Great post and breakdown, I just ran into this today.