Resyncing Coordinates Between host and Linked Models

[tmohrMN6T3]

So I took a day off and the architectural model changed for one of our projects.  It's a different model than the one we originally had linked.  

When I set up our project, I linked using PBP to PBP, and all the coordinates (PBP, SP, IO) for BOTH models were 0,0,0.  Meaning every coordinate for both models were in the exact same spot at 0,0,0.

When I opened the model today, I see that the coordinates for our model don't match the coordinates for the linked model, although both coordinates for the two models are still at 0,0,0 (See attached).

When I inquired with one of the drafters, they said they reloaded the new model through ACC, but they noticed the linked model was in a different spot than our model, so THEY MOVED OUR MODEL OVER.  

HOW do I fix this, or CAN I fix this so that the coordinates of both models are lined up again?  I already tried Acquire coordinates, but of course all that does is move the Survey Point and doesn't align the PBP between the two models.  Do I have to move our model back to realign the PBP?    Or do I just ignore the discrepancy, or will that just create problems down the line?  We're already showing 7/8" for our ground level and it should be 0.

Any insight greatly appreciated.  Thanks!

[RDAOU · Accepted solution]

Happens when someone moves the model the follow that by moving the survey point clipped

as it is not far off and you are neither using survey coordinates nor shared coordinates, simply align the link to your model and move on.

otherwise check who did that and investigate the reason;

• if the reason is valid, align your model (including the survey point - ie: reset your model’s 0,0,0) 
• if the reason is not valid, ask the custodian of the link to reset theirs to that of your model - ie:
  1. relocate (moves model including internal origin and project base point
  2. then move survey point clipped back (reset the survey 0,0,0)

Using aquire does the opposite of the above…it moves the survey point clipped to match that of the link you are squiring from and leaves the internal origin and base point where they are. That won’t fix the issue for you especially when it comes to cad and IFC exports. To fix this you have to go down the manual route described above.

[tmohrMN6T3 · Accepted solution]

Thanks for your quick response.

No valid reason.  They saw that the linked model was in a different spot and decided that our model needed to move, not that the linked model was linked incorrectly.

All my drafters have only been using Revit for about 6 mos - 1 yr and are at the point where they know just enough and have gotten confident enough to be dangerous 🤣

Unfortunately, there was no BEP for them to reference, and I had taken the day off.

I relinked the arch model using PBP, and the coordinates line up correctly.   

So at this point, since we are just starting the structural model and we have time, I am going to move our model back to where it belongs, and in the next staff meeting we will be discussing model linking and coordinate systems, and why it matters!

Tracy

[SteveKStafford]

I'll add...

In the future consider using Auto - Origin to Origin when starting a linked file relationship with other models. This is no different strategy than all of us agreeing to use the same World Coordinate System origin in AutoCAD. One firm should take the lead in establishing where the model is located relative to Revit's internal origin. Revit wants us to build the model close to the origin to ensure graphical accuracy, it makes the math easier for the application.

Using Project Base Point to Project Base Point (PBP) exists as an option for when firms don't establish the origin to origin logic from the outset and begin modeling without having any other links to reference. This means we all start our models in different locations. To resolve that lack of coordination we can all move our PBP to a specific location so we can then link using that option instead of internal origin, since that's not going to provide model alignment.

Shared Coordinates is meant to let us create the correct site relationship separate from the model orientation in Revit.

Start projects with Project North in mind, make it easy to draw, and you can define what the real world coordinates are, as well as the True North orientation, later.

[tmohrMN6T3]

Since we are following the architect's lead, we need to know how they are going to link our model, is that not correct?

My understand of Internal origin is that you can't specify it, and that it can change.  No? 

[SteveKStafford]

Assuming the architect has modeled their building properly, near Revit's Internal Origin you can/should link their file using Auto - Internal Origin to Internal Origin (IO-IO). Then create your model within and around their building model. The only reason alignment would fail later is if they decide to redesign and that some or many parts of the building move into different locations or at different angles. The file alignment would be intact but the building form and design changed. We all should agree that Project North is the orientation of the building so we don't find they've created the building at 33 degrees. However, if we don't begin our work until we have a their model to link using IO-IO we'll always have the context of their design to work within/around.

Internal Origin is fixed, cannot be changed. The PBP can be moved to create a "local coordinate system" that can be used by spot Coordinate annotation to identify useful coordinates relative to the building itself. The SP and shared coordinate system is an additional system to provide an accurate relationship to site.

The only compelling reason, (my opinion) to use PBP to PBP is that you (we) have begun work without the context of their building and now their link is not aligning with us.

This is the kind of discussion a project should have at a project kickoff meeting when everyone joins the project. Many firms place their first grid intersection at the internal origin as a habit. That doesn't mean the building HAS to be founded AT the origin. All Revit cares about is that it is not too far away from the origin (more than 20 miles away).

[tmohrMN6T3]

Totally makes sense.  If there was a project kickoff meeting 🤔

[SteveKStafford]

If I were the architecture lead on a project.

• The building's prime grid intersection (Grid A and 1) would land at the internal origin. Hopefully the design would allow that to remain true but it doesn't always...since *architecture* happens. 🙂
• The building will be oriented so it is as easy to draw as possible, angled portions giving way to the biggest orthogonal portion oriented so it fits on sheets.
• If multiple buildings, then a single model for each distinct building each oriented to a Project North for easy model building and documentation.
• Use a survey to define the shared coordinate system so exported data for civil and landscape design will be easier to align, assuming it's not done within Revit too.
• Tell each discipline to link my model using Internal Origin to Internal Origin and to use Copy/Monitor to create their own copies and "watch" my grids and levels for changes.
• Tell each discipline when shared coordinates are defined and that they can use Acquire Coordinates (selecting my model), in case any exports are also required of them (AutoCAD, Civil3D, Navisworks etc).
• Link each discipline model to my model using Auto - IO-IO also.
• When multiple buildings are involved then linking By Shared Coordinates is useful for building to building relationships. Building A can be linked to Building B (and vice versa) so we can demonstrate how they relate to each other in our documentation.
• Usually create a Site model for documentation required of the overall site and link those buildings by shared coordinates so they all land on site correctly. Alternatively use one building model to show all the overall site relationships, linking the other required building models using By Shared Coordinates.