I've been around and around with this topic for years, trying to dial in a best practice for Project Base Point and Survey Point vs Internal Origin for linked files. I always have one Site file and at least one Building file, and now potentially a Survey file, that are all linked. My question is where is the best place to locate the Project Base Point and Survey Point in each file.
In the Site file, the Survey Point is located at the Internal Origin, 0,0,0, which is where I place the site at one corner of the property boundary. In the Building file, the Project Base Point is located at one corner of the building, at the ground floor elevation, and at the Internal Origin. When I link the Building and Site files, the Survey Point is the same, the Project Base Point is the same, but the Internal Origin is different.
Once the Site and Topo are set, they do not move, and the Survey Point does not move. When the Building file is linked in, it can be moved around, up and down, and the Project Base Point moves along with it accordingly. If, in the Building file, Project Base Point is at Internal Origin, then it will always be different between the Building and Site files. I always come back to the conclusion that is just the way it is, and not sweat it too much.
One aspect of Internal Origin I do not understand is, in the Site file - or Survey file - when I rotate Project North, the Intern Origin rotates with it. In a True North view, Internal Origin is rotated to align with project north - not "up" in the view. In a Project North view, Internal Origin is "up" and True North is rotated accordingly. I'd assumed that since Internal Origin can't be moved, it would always be aligned to True North.
One issue my method presents is when linking files, selecting by Internal Origin does not work, because the Internal Origin is the files is different. Shared Coordinates is the only method, and this only works when the coordinates are properly coordinated. And I often have issues with this.
So, one question is should I have the Internal Origin located at the Survey Point for all project files? Or should I continue to keep the Survey Point in the Site file - and Survey file - at the Internal Origin, and in the Building File continue to keep the Project Base Point at the Internal Origin? I see pros and cons to both methods.
I do not like or agree with how Revit's coordinate system has been designed and implemented, but I have to adapt my method accordingly.
