Geographic Reference

Coordinate base allows the selection between Shared Coordinates, Internal Origin, Project Base Point and Survey Point.

Every Revit project has initially three origins, which are usually hidden by default, but can be shown by going to Visibility Settings of your View > Site:

- Internal Origin cannot be moved and also represents the center of the 20 mile region in which Revit tolerates Geometry. Any kind of Geometry created beyond this region will cause error messages and are to be avoided.

- Project Base Point defines the project coordinates and is usually placed at a grid intersection or a building corner on the ground level. Typically, all point coordinates and heights in the project will be referenced to this point. This point can be moved (manually or by typing in coordinates) to a desired position, but won’t move the project (unless the Project North, which is also visible in the Project Base Point, is changed). Prior to Revit 2020 the Project Base Point also had a clipped state, however, this has been removed. The Project Base Point from Revit 2020 on is always unclipped.

- Survey Point marks a relevant point in the real world and can be clipped on unclipped. Moving a clipped survey point will actually change the shared coordinate system of the model, while the unclipped survey point can be moved (either manually or by typing in coordinates) without any effect on the shared system, similar to the Project Base Point.

In the default templates all points should be located at the same spot and should be adjusted according to the project agreement.

Shared site is an additional concept used to set up the relation between linked models. One Revit project can contain multiple shared sites and this option will refer to the currently selected one:

More best practices are documented in this blog article and video: https://bim-me-up.com/en/revit-ifc-und-koordinatensysteme/ ▶️ Geo-referencing in Revit and IFC - The Basics