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How to set up coordinates in Revit & Archicad

Project coordinates are used to position the project correctly amongst different applications; exporting a file from Revit or Archicad to .IFC preserves location data. After conversion of .IFC files to Unity, if project location was set up, this information will be preserved.

But! Sometimes coordinates set up correctly in BIM might cause the converted model to import into Unity out of view – far away from Unity project origin.

Setting up the project location in Revit
A few things have to be set up in order to represent project location:

Project Base Point
The project base point defines the origin (0,0,0) of the project coordinate system. It also can be used to position the building on the site and for locating the design elements of a building during construction. Spot coordinates and spot elevations that reference the project coordinate system are displayed relative to this point.

 

Project Survey Point
The survey point represents a known point in the physical world, such as a geodetic survey marker. The survey point is used to correctly orient the building geometry in another coordinate system, such as the coordinate system used in a civil engineering application.

It is advisable that Project Survey Point has some project-sensible values and Project Base Point is assigned to match the Survey Point. More info on moving the Project Base Point and Survey Point.

To make these points visible:

  1. Click View tab > Graphics panel >  (Visibility/Graphics).
  2. On the Model Categories tab of the Visibility/Graphics dialog, scroll down to Site, and expand it.
  3. To display the project base point, select Project Base Point.
  4. To display the survey point, select Survey Point.
  5. You can also click  (Reveal Hidden Elements) on the View Control bar to turn on the visibility of the project base point and survey point in a view.

Survey Point and Project Base Point placed at the same location:

Project base point being placed away from Survey Point:

Site has coordinates and location settings preserved after IFC export. Global X and Global Y display coordinates for first point of site’s topographic surface.

Setting up the project location in ArchiCAD

In ArchiCAD, the project location is represented by:

Project Origin
A constant location which remains fixed for the life of your Project. The Project Origin of the coordinate system, marked with an X, is close to the lower left corner of the Floor Plan window, when using the default view of the default template.The Coordinates Palette shows the coordinates as (0, 0).
In Floor Plan and other 2D views, the origin is always marked by a bold X.

User Origin
By default, the User Origin is located at the Project Origin. However, the User Origin can be moved to any location, allowing you to “reset the zero point” to any location.

There are three ways to reposition the User Origin:
•At any element node: clickAlt + Shift (Mac: Opt + Shift).
•At any location in a model window: Click the Move User Originbutton from the Standardtoolbar (or the Coordinates palette), then click at any point in the window. The origin is instantly relocated there.

Project Origin is immovable in ArchiCAD however it is possible to move entire project to match the Project Origin.

Project origin imported to Unity

All IFC properties present in the project get preserved in Unity as well. Project location might be stored in site topography description:

RefLatitude  : World Latitude at reference point (most likely defined in legal description). Defined as integer values for degrees, minutes, seconds, etc
RefLongitude  : World Longitude at reference point (most likely defined in legal description). Defined as integer values for degrees, minutes, seconds, etc
RefElevation  : Datum elevation relative to sea level.
LandTitleNumber  : The land title number (designation of the site within a regional system).
SiteAddress  : Address given to the site for postal purposes in text format.

If original BIM project used user-defined location offset, it might be preserved in Unity as the default import location; this might cause project to not be visible in default view after import.

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