Did you know that in Revit 2011 IFC files can be exported with Shared Coordinates?
This is a new feature in 2011. In previous releases, only the project coordinates would be exported to IFC.
This feature works by exporting to IFC whatever coordinates are set as the current location for the project. If the current location uses Shared Coordinates, those coordinates will be exported, if it is using a different coordinate system, Revit exports based on that system.
To export using a different coordinate system, you can create a new location, make it the current location and adjust the coordinates of the file by using specify coordinates at a point, or moving the survey/project base point. As long as you export with the coordinates you want in the location that is current, Revit will export the model based on those coordinates.
When you are ready to keep working with the original coordinate system (done with your export) go back to the location dialog (Manage tab on the Ribbon) and make the original location current.
You will notice that when you switch locations the survey and project base point remember their locations from that location position and move to the position defined in the current location.
If you want, we can take this one step further if you want to play around with the actual IFC file (could cause some damage to the IFC file).
Take for example, if you have a IFC file that was exported to the incorrect coordinate system (forgot to switch locations) and you don't want to re-export the file with a different location, you can modify the IFC file yourself to adjust where it is located.
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):
We look at the 6th argument, #609, which points to another line like this:
We look at the 2nd argument, #608, which in turn points to a line like this:
In this simple case, the #3 line is
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.