Export to IFC 4.3 - Set IFC Base Point

[kubastan89]

Hi,

I`d like to gain an insight into export to IFC 4.3 using IFC 4.3 Extension.

I`ve started with setting IFC Base Point and already have a problem ...

I can`t understand the concept of this Base Point. While working with infrastructure projects we always work with real coordinates not local ones how it is e.g. in Revit.

Anyway I chose a point in my drawing (attached) that is located in lower right corner of my surface

realcoord.jpg

and exported IFC using the addin.

After checking the coordinates in 3D, model is not located according to real coordinates.

3d coord.jpg

I thought that maybe if I set IFC Base Point in 0,0,0 coordinates model will export in good coordinates but after setting it up I get an error:

error.jpg

and IFC is not exporting.

I edited previous exported IFC and looks like addin does some coordinates conversion based on selected base point.

map conv.jpg

cart point.jpg

We can find only this in product help:

https://help.autodesk.com/view/CIV3D/2022/ENU/?guid=GUID-C617C68E-A28E-481A-917A-A1D30E758D50

We didn`t have to set any base points while exporting to IFC 2x3 and models are exporting properly.

How to set this point properly and export model in real coordinates in order to be able to federate this model with other ifc models exported with real coordinates ?

Regards

[nigel_peters]

Hi,

A lot of work was done for IFC 4.3, by buildingSMART and the community, to extended support for coordinate systems and map reference points.  The large coordinates used in Infra models exported to IFC 2x and 4 caused model and data  distortion in down stream applications, IFC 2x3 allowed the "base/Datum point" to be defined at the files root, but in IFC 4.3 IFCMapConversions are available to define a local base point. By setting a base point there is lower distortion in the geometry and the file sizes are greatly reduced (I have seen 500mb files half in size). 

There are two ways to handle base points the "old" IFC 2 solution of setting a base point at project root level or by using the newer best practice IFCMapConversions convention along with a true coordinate system definition. At the moment there are a lot of down stream tools (like your viewer) that does not yet support IFCMapConversions. 

You have 3 possible workarounds:

       1) Update your tools to versions that support IFCMapConversions 

       2) Use the IFCEnfra Set base point command and pick 0,0,0 and ignore the warning about it being a long way from the exported geometry. This will increase filesize and in some downstream tools geometry might get distorted.

       3) Use the IFCInfraSavveConfig command and edit the file changing the option ProjectBasePointOnRootPlacement to true. THis will force the exporter not to place the base point at the root of the IFC file.

[kubastan89]

Hi @nigel_peters 

Thank you for your answer.

1) It looks BIMivison doesn`t support MapConversion yet.

2) When I set Base Point to 0,0,0 and get that error model is not exporting, just .json file is created.

Do you have any idea why IFC is still not exporting ?

3) Editing the file changing the option ProjectBasePointOnRootPlacement to true helped and IFC viewers that doesn`t support MapConversion can read proper coordinates now.

[nigel_peters]

Hi,

I will look into why setting the base point to 0,0,0 is failing. As you discovered, reverting to Root Placement of the base point is often needed for some downstream tools.

[VitorChaves]

Hello @kubastan89 

I don't know if you fixed this issue. I was having the same problem, and @nigel_peters  advices helped

I realized that in the IFCInfraSavveConfig you can configure "Base Point Error Kilometers" as shown below

VitorChaves_0-1738694392538.png

So, I changed this configuration to a number that would not conflit with my global coordinate systems

VitorChaves_1-1738694735501.png

Now my IFC has global coordinates and it works fine =D

[nigel_peters]

Just be aware if you use a base point at the origin (0,0,0) then you will have very large coordinates in the file this often causes down stream tools to distort / round the geometry which was a very common issue when using files IFC 2x3 with Infrastructure projects. 

Best practice for IFC 4.3 is to use a MapConversion to define a local datum and export the geometry transformed to that datum, if your tools to not support this mode, then a second method is to use a common IFC2x3 workflow of placing the datum on the project root (this can be done with the ProjectBasePointOnRootPlacement setting).

[michael]

Hi Nigel, we have had this issue in Revit (I Assume that's what you refer to) using the old IFC export, the simple workaround is to include a cube at a known location and level (Shared coordinate point).

Following import you move all entities so they are closer to zero then position the model using the cube, that clears up model degredation issues.
I agree not Ideal and so this with Revit is a game changer our end.

Saying that, I have Revit 22.1.1.516 which I understand should be compatible with this method but testing it said it could not import the file.

Can you confirm if it does work with Revit and what Versions?

I also cannot seem to find how to downgrade the export to a previous release, I suppose that you should use the older export tool for that or am I missing a trick?

Mike

[VitorChaves]

Would you have any material about using MapConversion along with Civil 3D? I am searching for material to better understand this workflo, but I did not find.

I have already experienced this problem of distortion in downstream tools, althought most of those which I have already tried works fine with large coordinates

I see no advantage of usign local coordinates with Infraestructure projects. In sanitation projects for exemple, you have several kilometers of networks, and using a local coordinate for each one is really inconvenient

[michael]

Nigel, I am now also confused, in 2022 we used to export IFC's (using IFCExport function) into Navisworks and Revit and they brought in Property Set data.

I note now using 2024 V13.6.342 this does not seem to be the case, is this a Bug or has this function been removed can you or someone else please confirm?

Mike