When you combine multiple models and files in a single project, use shared coordinates to establish the positions of the files in relation to each other.
A Revit project has internal coordinates for all the elements that compose the model in a project. Those coordinates are known to this project only. This is sufficient if you have a standalone model whose position is not relevant to other models or to a site. However, if you want the position of the model to be known to other linked models, you need to share coordinates.
Use the Shared Coordinate tools to establish the relative positions of the different files and ensure that those relationships are maintained. To establish a common coordinate position and then share that position between files, use the Acquire Coordinates tool or the Publish Coordinates tool.
Recommended Uses for Shared Positioning
If the significant coordinates for a project are in a linked model or file, such as a building model with a linked site, acquire the coordinates from the linked model.
If the significant coordinates for a project are in the host model, such as a site with linked building models, publish coordinates from the host to the linked models.