BIM vs. Digital Twin

The thing with BIM is that BIM models are VERY complicated. That’s just the nature of BIM. People talk about digital twins all the time, and BIM (as an extension of CAD) is probably one of the first representations of a digital twin. BIM though by its nature isn’t an “as-built.” It is just a picture of what the real world object should be, where-as a digital twin is a digital copy of an existing asset. Now the best way to start a digital twin is to import a BIM model, but there are some areas you need to be aware of before doing so.

  1. A BIM model might not be an as-built. As I said above, BIM is what something should be, not what it ends up being. During construction, changes are always made to the building, and in doing so, the BIM model ceases to be a digital twin. Just importing a BIM model without field verification can result in your digital twin not genuinely being a digital twin.

  2. What detail do you need in hour digital twin? A BIM model might have millions of entities making up even a simple asset, such as a window frame that is unique and requires high accuracy. This is very important in the construction phase where even a millimeter off can cause problems, but for a digital twin, that detail is not needed. This is where BIM and digital twins diverge; the BIM model is the engineering representation of something vs. a digital twin is just the digital replica. There is no reason why you couldn’t import in such an elaborate window frame of course, but throughout a whole building or even a city, these extra details get lost in the LOD. The key here is knowing what your LOD is and how you want to view it. There is much going on in the 3D space where you can use LOD to display the elaborate window frame above, yet still be performant where needed.
  3. Aftermarket features are generally part of a digital twin. BIM models are idealized in that they only show what was spec’d out. Digital twins need to show all those modifications that were made after the building was turned over to the owner. Doors removed, walls put up, windows boarded over. These things all need to be reflected in your digital twin. Just importing a BIM model that doesn’t address these changes means that when you go to link up your digital twin to IoT or other services, there is no one-to-one relationship. Preparation work of that BIM model before ingestion into a digital twin helps immeasurably.

It is easy to want to jump into creating digital twins of your buildings but it is critical to make sure that before you do so you’ve review your files to ensure that they are as-built and a twin of the real world asset.