What is Level of Definition?
When creating an information model as part of the BIM process, you would not expect to have all your data collated right from day one. The aim is to deliver the right information, in the right format, to the right people at the right time.
A building information model contains both graphical and non-graphical information, accurately linked, clearly defined and well structured. As stages progress and proposals develop, the graphical and non-graphical data builds in a shared digital space, known as a Common Data Environment (CDE). The different amounts of data are termed Levels of Definition.
The amount of non-graphical information developed for a given stage is termed “Level of Information” or LOI and the amount of graphical information developed is termed “Level of Detail” or LOD. Both form part of the overall umbrella term: “Level of Definition”.
“You wouldn’t expect to have all your data collated from day one.” Scott Berry
Level of Definition and the Digital Plan of Work
Here in the UK, Level of Definition is aligned to the Digital Plan of Work (DPoW), created by the UK BIM Task Group. This provides the UK construction industry with an eight-stage design, construction and operation plan that encompasses the information requirements throughout the whole life of an asset.
Furthermore, the NBS BIM Toolkit gives high-level guidance as to what “Level of Information” and what “Level of Detail” should be produced at each of the stages by the various members of the project team.
According to Scott Berry, “It’s important that the expected minimum levels of definition for each work stage are made clear from the outset.”
To maximise efficiencies, the project team must clearly understand how much information is required for each different stage of a project. Indeed, too little information and risks may not be effectively managed, and too much information and waste can be added into the process.
Requirements for the Levels of Definition
The British Standard guidance document PAS 1192-2 details the typical requirements for each Level of Definition over a project’s lifecycle. This is available as a free download from the British Standards Institution here.
It is therefore important that the expected minimum levels of definition for each work stage are made clear from the outset of a project before you start in the BIM Execution Plan (BEP) and Master Information Delivery Plan (MIDP), as indicated within the Information Delivery Cycle diagram in PAS 1192-2.
The DPoW is effectively the lean part of the BIM process – ensuring that the right data is available. At project delivery stage, those decisions might include budget sign-offs, design approvals, planning submissions or the issuing of completion certificates.
“Scott says, The whole purpose of BIM is delivering the right information, in the right format, to the right people at the right time.”