During coordination, the first thing we need to check is the correct alignment of the models with each other. More than once, I saw situations where designers checked models that had completely different coordinate systems or were moved a few meters from one another.

Wrong model placement may cause one of two situations :

• Situation A: Lack of collisions, because the models don’t overlap each other (picture below)

• Situation B: Models overlap each other incorrectly thus many nonexistent collisions appear in the check (picture below)

  

  Example of incorrectly placed models. You see that the Mechanical model is clashing with the Architectural one.

We want to avoid such situations, and make sure that disciplinary models use the same coordinates and coordinate system (situation C).

• Situation C - 3 disciplinary models combined properly.

There are many ways to do this, and it all depends on the modeling software you use.

For example: Using Tekla Structures, Revit, or Archicad you have to follow different techniques to place models in relation to the coordinate system. A detailed description of the process itself based on one tool (e.g: Revit) would be too extensive for this guide.

As a user of Autodesk Revit, I have learned that to understand how the coordinates work and how to set up models correctly in this program, you need to know a few things:

• Differences between two coordinate systems in the Revit: Internal Coordinates and Shared Coordinates;
• 3 origin points: Internal Origin Point, Project Base Point, and Survey Point, and how they work together,
• Difference between True North and Project North,
• Understand Elevation property,
• Understand what Shared Sites and locations,
• Understand how you Acquire and Puliblish coordinates,