Levels of development (LOD)
Why it has to be agreed
Section titled “Why it has to be agreed”Because “a detailed model” means something different to everyone.
To an architect a wall may be a layered element; to the manufacturer that same wall is several hundred sections, each cut to length.
Without an agreement two faults threaten:
- over-modelling: wasted work, a slow, unmanageable model,
- under-modelling: a model unfit for the purpose it is wanted for.
What the level of development describes
Section titled “What the level of development describes”The geometry
Section titled “The geometry”How accurate the shape and size of the element are: indicative, approximate or manufacture-accurate.
The data content
Section titled “The data content”What information belongs to the element: material, type, performance, manufacturer’s data.
The reliability
Section titled “The reliability”What the model may be used for: orientation, quantities, manufacture.
The typical stages
Section titled “The typical stages”Concept
Section titled “Concept”Masses, large elements, indicative geometry. Quantities only in order of magnitude.
Permit
Section titled “Permit”The real geometry of the building, uses, main structures.
Detailed design
Section titled “Detailed design”Build-ups, connections, the exact position of services elements. Quantities can be derived from it.
Manufacture
Section titled “Manufacture”Piece-level accuracy: every member, with its real dimensions and operations. This is the level a machine program is made from.
Where LGS differs from the norm
Section titled “Where LGS differs from the norm”On most projects a manufacture-accurate model is only produced for certain elements. In LGS the whole frame is produced at that level — because manufacture works directly from it.
That means the level of detail in the structural model differs from the other disciplines’. So two model levels are kept: a coordination model and a manufacturing model. The system and the BIM environment.
What has to be recorded
Section titled “What has to be recorded”At the start of the project, in writing: which group of elements is produced at which level at which stage, and who is responsible for it.
The point
Section titled “The point”A good model is not the most detailed one but the one at the level its task requires. That can and should be agreed in advance.