Revit IFC Export Coordinates

[jonasoverby]

Hello,

I really need some help on this one!

I have modeled a project using an old coordinate system. The project has then decided to change to a newer coordinate system that lies 500 mm above the old system in the z-direction.

To have my DWG exports appear in the new system, I solved it by using Specify Coordinates at Point in an elevation view, and just typed in 10500 instead of 10000 when selecting one Level. When I export to DWG i used Shared Coordinates, and the DWG:s land in the new system. All fine.

Now, when I export to IFC I can't seem to make it export correctly. I read the article at:

http://revitclinic.typepad.com/my_weblog/2010/09/ifc-export-with-shared-or-project-coordinates-using...

I created a new Site and made it Current. Then I tried to move the the Survey Point and The Base Point. Not at the same time though. For example I moved the Survey Point when clipped, exported to IFC, chose undo of the move, unclipped the Survey Point, moved it, chose undo and so forth. One test at a time. I managed to move the IFC in the x och y directions, but not in the z direction. I used IFC Export UI for Autodesk Revit 2014 v2.8.0 when exporting to IFC.

I would really appreciate some help on this!

Below are the results of my trials:

Moving Survey Point only in the  z direction (Clipped) ---> No difference

Moving Survey Point only in the  z direction (Unclipped) ---> No difference

Moving Project Base Point only in the  z direction (Clipped) ---> No difference

Moving Project Base Point only in the  z direction (Unclipped) ---> No difference

Moving Survey Point only in plan (x and y directions) (Clipped) ---> IFC model is moved in plan

Moving Survey Point only in plan (x and y directions) (Unclipped) ---> No difference

Moving Project Base Point only in plan (x and y directions) (Clipped) ---> IFC model is moved in plan

Moving Project Base Point only in plan (x and y directions) (Unclipped) ---> No difference

Moving Survey Point only in the  x, y and z direction (Clipped) ---> IFC model is moved only in plan

Moving Survey Point only in the  x, y and z direction (Unclipped) ---> No difference

Moving Project Base Point only in the  x, y and z direction (Clipped) ---> IFC model is moved only in plan

Moving Project Base Point only in the  x, y and z direction (Clipped) ---> No difference

[Mekholm]

Hello,

I'm having a similar issue.

I have two different revit files with content linked in a third empty revit file.

When I export the content files seperately they align perfectly horizontally, but not vertically. And nothing I do seems to change this.

So I was wondering if you solved this issue somehow?

Regards,

Martin

[jonasoverby]

Hi,

I solved this issue with a 3rd party plugin called Naviate IFC. It has support for exporting IFC:s with the shared coordinate system as basis for the z values. It's an option called "Include IFCSITE elevation in the site local placement origin".

I believe this option is also availabe through the IFC Exporter for Revit for Autodesk, available at:

http://sourceforge.net/projects/ifcexporter/

Good luck!

/Jonas

[Mekholm]

Hello,

Thanks for your answer!

Unfortunately it didn't solve my problem.
I tried exporting with "include IFCSITE..." using both IFC exporter for revit and Naviate IFC but it didn't change anything.

When I export to .dwg I get the option to use either Project Internal or Shared coordinates. That works like a charm.
But when I export to ifc I don't get an option like that, so I have no idea where the export takes the position from. It seems completely random.

Regards,
Martin

[jonasoverby]

When you are doing the export, if you move the survey point in the z direction before the export, does that do it? As far as I know, Revit uses the Survey point for the current Site when exporting to IFC.

[Mekholm]

Moving the survey point in z-direction doesn't change anything.
Regardless of the "Include IFCSITE..." being ticked or not.

For clarification:
I use navisworks to open up the model, then append an adjacent model to check if they align. Which they don't do yet.

[jonasoverby]

Then I'm out of ideas, sorry. Good luck!

[Mekholm]

Shoot!
Well thanks a lot for your help anyway! 🙂

If I ever find a solution I'll post it here.
I'm also in contact with our cad-support in search of a solution...

Thanks again!

//Martin

[chenfei.chen]

"You can open IFC files in a Text editor (I just use notepad). 

In the file there will be a line like (use the find tool in your editor to location the IFCSITE heading, it will be in a different location in your file most likely):

#610=IFCSITE('3EuQW2ppjFFu7PKxGoCwn0',#42,'Default',$,'',#609,$,$,.ELEMENT.,(42,21,30,344238),(-71,-3,-35,-194702),-0.,$,$);

We look at the 6th argument,  #609, which points to another line like this:

#609=IFCLOCALPLACEMENT($,#608);

We look at the 2nd argument, #608, which in turn points to a line like this:

#608=IFCAXIS2PLACEMENT3D(#3,$,$);

In this simple case, the #3 line is

#3=IFCCARTESIANPOINT((0.,0.,0.));

Which means ‘use the internal Revit origin’.  In a case using shared coordinates, that #3 will be some other number.  To fix it, change this other number in #3.

What do you think?  Is this useful?  Love to hear your comments about this. from http://revitclinic.typepad.com/my_weblog/2010/09/ifc-export-with-shared-or-project-coordinates-using..."

Change the Z number in #3 to elevation height of Origin point related to Survey point.

It do work!