BIM models contain information. Information can be both graphical and non-graphical. Level of detail (LOD) is the term that we use for the amount of detail within a model. Defining the amount of information required within a model and when the LOD is required are fundamental requirements of the BIM process.
For this to happen, clear and consistently defined terms are required. Within PAS 1192-2 alone all the following terms relate to the detail within a model:
Level of Model Detail, Levels of Detail, Level of Detail, Graphical Detail, Level of Definition, Levels of Model Definition, Levels of Model Information, Level of Information Detail.
These are the terms provided within one set of guidance, when you also consider the other UK standards and standards from other countries this is an area open to confusion. BIM deliverables will not be consistent if the interpretation of the terms is left to chance.
At BIMsense we attempt to use the following consistent terms and acronyms:
LOD = Level of Detail
LOI = Level of Information
LOMD = Level of Model Definition
LEVEL OF DETAIL
LOD = The amount of detail contained within the visual or graphical parts of a model
The graphical content of a model is what you see, the shapes that make up the visual model. The visual representation of a door would provide graphical content. The level of detail (LOD) is used to define the required graphical content of a model at a certain stage of a project. As a project progresses the graphical detail will increase. The components within a model will be provided with more detail. For an internal door, the model may start with a door being represented by a cuboid, then as the project develops additional detail will be added such as vision panels and hardware.
The level of detail required is referenced by LOD and a number, such as LOD 2.
The NBS BIM toolkit contains many examples, such as the LOD for a doorset.
LEVEL OF INFORMATION
LOD = The amount of detail contained within the non-visual parts of a model – The Data
Model information provides non-graphical content, for example the fire and acoustic rating of a door would be non-graphical content. The level of information (LOI) defines the non-graphical content of a model at a project’s defined stages. As a project progresses the non-graphical detail will increase. For a door, at the start of a project the graphical cuboid representing the door will contain limited non-graphical data such as the classification of a door. As the project design develops performance data such as fire resistance will be provided and then later in the project the manufacturers data.
The level of detail required is referenced by LOI and a number, such as LOI 2.
The NBS BIM toolkit contains many examples, such as the LOI for a doorset.
LEVEL OF MODEL DEFINITION
LOMD = The amount of detail contained within both the graphical and non-graphical parts of a model
Level of model definition describes the combination of LOD and LOI. It is used to define the detail required in a model at various project stages, both graphical and non-graphical.
LOMD = LOD + LOI