Use models from Revit for model coordination

Use models from Revit for model coordination

Revit contains three kinds of origins which are important for model coordination.
  1. Project Base Point, which represents the origin of the project coordinate system around which the model should be setup. It is mostly used for measuring distances and positioning of the project within Revit, and the project should be modelled close to this point.
  2. Survey Point, which represents a known topographical point in the physical world. It forms the basis of a shared coordinates system.
  3. The Internal Origin, or startup location, is the starting point for the internal coordinate system.
The Revit Survey Point creates a data driven approach that allows for the translation of coordinates between Revit and other BIM tools like BIMcollab. It provides a real-world context for the Revit model. 

When getting started with a new BIM project using Revit, take these recommendations into account:

General recommendations

  1. Agree in advance with the various parties of a project on the position and orientation of the origin for model coordination.
  2. Test the model alignment of the different models in the project early on, as it is easier to make adjustments to the coordination at an early stage. As a best practice, we recommend placing a coordination object, like a 1 m3 cube, at an agreed point, and making sure the cubes for all models align.

Coordination recommendations

  1. When using the model for issue management, we recommend keeping the Project Base Point and Internal Origin at the same location, and only moving the Survey Point to provide a real world context to the model.
  2. Make use of Shared Coordinates. They relate to the position of the project in the real world. When your team uses multiple Revit models, use the Shared Coordinate tools to establish the relative positions of the different files. For more information on how to share coordinates between multiple projects, please visit the Autodesk Helpcenter.
  3. Make sure the True North of all Revit models in the project is the same. The Project North of the different models can be different. Rotate it using the method described in the Autodesk Helpcenter. Do not change the rotation of the Project Base Point directly in the settings of the Project Base Point, as this will change the position of that point relative to the Survey Point.
  4. Always move the Survey Point while it is clipped . If the Survey Point is moved while unclipped , only the icon representation of the Survey Point is moved, not the coordinate system itself.
  5. It is advisable to correctly position the Survey Point and share coordinates immediately when starting a new project, especially if the model will be used for issue management.
    If issues are created, and the position and/or orientation of the Survey Point is changed later, all camera positions of the issue viewpoints in the 3D model will no longer be correct.
For a more in-depth explanation of the Origins in Revit, please visit the Autodesk Helpcenter.

Exporting an IFC model from Revit

When exporting the Revit model to IFC, it is best to make use of 'Shared Coordinates' as a Coordinate base. This way, the Survey Point will be used as the IFC Global Origin in the exported IFC file. The Internal Origin is matched to the IFC Site Location, or local placement of the model.



Additionally, make sure to always include the IFC Site Elevation in the exported file, since the elevation is also used to correctly place the viewpoint camera of issues.



When coordinating the Revit model which is exported in this way, with other IFC models for example from Archicad, the origins will correspond as follows:

IFC
Revit
Archicad
IFC Global Origin
Survey Point
Survey Point
IFC Site Location
Internal Origin
Project Origin

Note that the Project Base point in Revit can be moved independently to the Internal Origin. We strongly recommend that the Project Base Point in Revit is not moved independently to the Internal Origin when coordinating with BIMcollab between multiple BIM tools.

Importing an IFC model into Revit

When importing or linking an IFC model into Revit, the IFC Site Location of the imported file will be matched to the Internal Origin. The Survey Point and Project Base Point already present in the Revit file will remain active.
Learn more about linking IFC files to a Revit model in the Autodesk helpcenter.

Creating and zooming to issues with the BCF Manager in Revit

When an issue is created in Revit, the Survey Point present in the file will ALWAYS be used as the reference point for the camera location of the issue viewpoint. 
Because of this, it is important to make sure the location of the IFC Global Origin of the IFC files that are being used for project coordination, and the location of the Survey Point present in Revit match.
If they do not match, the camera might be placed differently when zooming to an issue in other software, like BIMcollab ZOOM.

Example

An IFC file is exported from Revit. The IFC Global Origin is in a different location than the IFC Site Location.
The file is opened in BIMcollab ZOOM, and a viewpoint is created. The viewpoint camera is positioned in relation to the IFC Global Origin.

  

If the Survey Point in Revit remains at the same location in regards to the IFC Global Origin, the viewpoint can be recreated correctly in Revit.

  

If the Survey Point is moved in the Revit file, the Camera viewpoint will move along with it when recreating the issue viewpoint in Revit.

  

The same counts the other way around. If an issue is created in the BCF manager from Revit, the viewpoint can only be recreated on the correct location in other software if the IFC Global Origin is in the same location as the Survey Point at the moment of issue creation.

Creating issues in a file with linked models

In Revit, components located in linked models cannot be individually manipulated by the BCF manager. This is a limitation of Revit itself. Therefore only components in the main model can be found when performing a zoom-to.
Because of this, always make sure to include components from the main model in the list of components that are linked to the issue. Learn more about how to choose which components are linked to an issue in the article Create fast, light-weight and effective viewpoints.

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