The LOD Battle

Those three little letters have been a battle cry for many projects. What do they mean? To some it is Level of Detail, everything that goes into the model. To others it’s Level of Development, items that go into the model and at what phase of the project.

So who is winning this battle the designers, contractors, or the owner? The sad truth is no one.

There is so much confusion surrounding these three little letters that there are several groups working to define exactly what it means. For the most part these groups are operating in a vacuum and not communicating with each other. You will find several references for LOD and they all start off with, “LOD is generally defined as follows:” In fact the AIA has a document called the E202 which addresses this that was created in 2008. The problem is the LOD definitions do not really correspond to models or the lifecycle use of the model. In fact so much confusion has been caused by these factors that the AIA is in the process of revising their document.

So if the AIA has a good start with the E202 where does it go wrong and where does it go right?

First it doesn’t address standardization. What if the document defined what state the model would be in at each phase of the project? It does give us a structured table of elements that one can standardize that is pretty thorough. It also implements the K.I.S.S. format that I am found of if you just look at the table and forego the lawyer speak. What if the definitions addressed not only the 3D aspect of the model but the 2D as well? After all in a true BIM it will have both 3D and 2D model elements.

Drawings are derived from the model right? Unfortunately we still see a disclaimer resembling this one:

“The model may be used for Reference Only and the construction documents take precedence. The model is a representation of the project and no dimensions shall be derived from the model.”

Don’t the drawings come from the model?

This is where LOD becomes important. Let’s take interior partitions for example. I can model eight foot high walls and call it good if I interpret LOD 200 which says, “Model elements are modeled as generalized systems or assemblies approximate quantities, size, shape, location, and orientation. Non-geometric information may also be attached to model elements.” to be my deliverable, even though all walls should be a LOD 300 especially when it comes to the construction document phase.

Are you starting to see the confusion?

There is hope; a government agency that shall remain nameless until their work is published has answered the call and done just that. They have established a standard that several other government agencies are looking to adopt. It takes over where the AIA’s E202 left off. It created a standard not a blank table. The battle isn’t over just yet but I see a white flag on the horizon.

1 Comment

  1. Some very good points made here. It certainly would be nice to have a "table" style document for reference. I'm curious as to what government agency would have taken this on…

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