LoD, Detail, Development or Despair
The other day a contractor asked me if they needed to model carpet tiles as individual tile objects. I answered back with the question “will it be of any use to anyone to see those tiles in the model?”
And this brings me to the subject of LOD. Level of Detail, Level of Definition, Level of Development or as I learned at RTC Asia 2015, Level of Despair. I think I like the latter the best, although the original intention was very well meaning.
LOD sets out to specify and articulate the content and suitable purposes of building information models at various stages of a project. The AIA’s E202 exhibit is now synonymous with how we define LOD through a series of numbers from 100-500 and in more recent times BIMForum’s regularly updated LOD Specification are a good go to guide.
However, as our BIM maturity develops, I meet more and more people who find that LOD is more a burden than a blessing. All too often contract requirements are too vague and consultants and contractors are being asked to develop models to LOD 350-400 and in some cases 500. Catch all clauses mean that effectively entire models must meet a higher LOD than is necessary for practical use. We need to understand why and what data is actually needed. The topic of over modelling has existed since the start of BIM and a paper definition of LOD doesn’t necessarily resolve that.
So perhaps instead of asking what LOD a model should be. We need to ask:
- Who’s using the information?
- What information do they need?
- What are they going to do with it?
Ultimately if at any given time those three things are being evaluated; then the LOD of your BIM is irrelevant. The LOD will be whatever it needs to be for any given element for any needed purpose. The way we model and what we model should be about what is practical, necessary, and useful. BIM should be about information and collaboration. Lets be reasonable people and perhaps focus on the quality and usefulness of data before the minutiae and quantity.