I've been doing a lot of research in the past few days regarding the Project Base Point and Survey Point so that I can ensure that I am using the coordinate systems properly. I've read a lot of posts by Steve Stafford regarding these systems, as he seems to be quite knowledgeable on the subject, but there are still a few things I think I may be misunderstanding.

Correct me if I am wrong here, but this is how I understand the coordinate systems to function:

- The "Internal Origin" point of a Revit project is the same exact origin point of the Project Base Point coordinate system. I see the terms used separately, but I don't understand why, unless this is an incorrect statement.
- The "Internal Origin" point never moves. If, the Project Base Point origin and the internal origin are the same, when the Project Base Point is moved while clipped, the origin point does not move, rather the project moves around it.
- The x,y,z values referenced on the Project Base Point have no relation to the Project Base Point coordinate system, rather it is referring to the origin of the Survey Point coordinate system. By extension, it is possible to have a Project Base Point that reads 0,0,0 by moving a clipped Survey Point to a Project Base Point that had been unclipped and relocated, possibly miles away from the origin of the Project Base Point coordinate system.
- The x,y,z values referenced on the Survey Point also reflect the location of the Survey Point coordinate system origin. If a Survey Point is moved while clipped, the value remains 0,0,0 because the origin has moved with the symbol. If a Survey Point is moved while unclipped, the value will change relative to the origin of the coordinate system as the symbol is no longer located at the point of the origin.

If the internal origin point of the project, and the origin of the Project Base Point coordinate system are the same, and the internal origin point never moves, is there ever any reason to move the Project Base Point while it is clipped? Or, rather, is it just a different way of moving the Survey Point?

I feel like I'm missing something here, and any corrections would be appreciated.