Export to ifc file using Survey Point as the project base.

[Anonymous]

When I tried to import ifc file using the "survey point" as project base in the embedded export window, results appear to be wired.

The coordinate value of "internal coordinate" are set to the Ifcproject's Cartesianpoint in the produced ifc file, rather than the coordinate of the actual "survey point".

I used the sample project on Reivit architecture to test this. And I do not know why this will happen.

[barthbradley]

Is the Survey Point MARKER actually sitting on top of the Survey Point ORIGIN?

[Anonymous]

I suppose the answer is yes. I used the revit sample project to test the
case (the first figure). You can see in the following figure, if I use the
survey point as the project base to export ifc file, the cartesianpoint of
ifcproject is not that of the survey point. I checked it to be the internal
coordinates (the point in the second picture) .

[image: image.png]
[image: image.png]

[Anonymous]

Please see the attachments.

[georg.grebenyuk]

Yifan,

I suggest that you need read more about code of IFC's commands - such here. I agree that functional in Revit in IFC-exporting parameters in choosing "start point" don't correct. I don't understand real benefit to select Survey point, but difference between scenarios "Shared coordinates" and "Base point" more interested. 

Main parameters in IFC that answered of geometry there are IFCSITE and IFCGEOMETRICREPRESENTATIONCONTEXT. Revit building all geometry in IFC file only from "Revit zero point" - you don't see it in project with base commands but can start easy Dynamo script to show it (look in attachment). Often Revit zero point is placed in same place that Base point. When you select scenario "from Survey point" or "from Base point" in IFC there are codes that defines directions to that points with comands IFCDIRECTION [vector from Revit zero to IFCCARTESIANPOINT]. Command IFCCARTESIANPOINT is define fact coordinates needing point

Let's watch on string below from one IFC file (scenario from Survey point):

#101= IFCGEOMETRICREPRESENTATIONCONTEXT($,'Model',3,0.01,#98,#99);

#98= IFCAXIS2PLACEMENT3D(#94,#19,#96);

#99= IFCDIRECTION((-0.14788817519201,0.989004088787492));

#94= IFCCARTESIANPOINT((513016591.,5405264922.,337690.))

#99 = its parameter of TrueNorth - angle in definition of Points [when select scenario "shared coordinates" it don't writes correct value]

#98 = Establishment of the engineering coordinate system

As conclusion - try 4 iteration of export one project in 4 scenarios and compare IFC files - only comparing helps you inderstand logic of code and manual of IFC commands

[Anonymous]

Yes. Egor. Thanks for your reply. I understand your concern.

The reason to use survey point as the base point to import IFC file is to verify the results of the four import scenarios provided in Revit (internal coordinate, project base point, survey point, shared coordinate) should be consistent. Theoretically, I can choose random point as the project point if I like and get the accurate and consistent position of building elements through transformation between different coordinate systems. 

But the results of using survey point as project base to import IFC files are different from the other three scenarios.

That is the point I found quite strange.

Yifan

Yifan

[georg.grebenyuk]

Yifan,

Don't agree with IFC from revit [try work with initial Revit data and it's possibilities]- more comfortable way in your Case (with changing coordinate systems) use a Civil 3D or AutoCAD and link your Revit file with DWG-file in whicn already is yourself coordinates system. Also Civil 3D can transform data from another coordinates to your needing data - and it function you also can use in your Cases with changing data of Revit's file, linking with DWG-drawing. 

Changing any of parameter of geospatial reference in Revit will crash all project if it contain a lot of data - and you must be careful in future with it operations - more reliable way to use linking data such as outside resourses to Revit's coordination file that change coordinaes of revit's base point [or survey point] to needing. 

I can't provide links to knowledge resources because I'm not know them in English for Revit. Sorry.

[dayandlight]

Hi!

Could you solve the problem?

I have exactly the same issue - trying everthing to get the origin point in ifc set by the survey point and not the base point or internal origin.

[Mohamed-Nassar]

https://www.cadlinecommunity.co.uk/hc/en-us/articles/360000942158-Using-IFC-files-with-a-Shared-Coor...

https://knowledge.autodesk.com/support/revit-products/troubleshooting/caas/sfdcarticles/sfdcarticles...

this will help you , thanks

[dayandlight]

Thank you for that fast answer, but I already know all the Revit Basics and about the option "Survey Point" in the ifc export settings.

That´s the way I did it so often and it worked. But funnily enough this is not working any more. 

The only thing I did in this project, was to use a dwg file with the grid and the origin point and used this as a base for the model. (User Coordinate System called "REVIT60-DefaultLocation) So I retrieved the coordinate from that dwg file. Then i linked other rvt files in my project, aligned it to the geographical north (survey point) and afterwards I rotated my base point to the grid in the linked file. The internatl origin turned also with the base point - i don´t know why.

So all the points are at the same place, it´s just about the rotation - true north and project north. 

And the fact is, that in Revit 2020.2.3 there´s no clip at the base point, just the survey point has one. So i can´t really control this point.

But fortunatelly I found a way that worked for now. I tried to use the "shared coordinates" instead of "survey point" and the ifc is aligned to geographical north 🙂 Did not really understand but I can go ahead with the modelling now.