Are you currently working on a BIM project? Perhaps your client or boss has asked you to produce a BIM model to ‘LOD 300’ or in line with a specific Level of Information? If you’re wondering about all the jargon and what it really means, then read on to find the answers or ask BIM consultant to help you.
BIM LOD and other acronyms
The world of BIM is full of acronyms which sometimes can be difficult to understand or remember. LOD, LOI, LOMD, LOIN… what do they all mean? Before we even attempt to explain the difference between them and what they mean, we need to know what they stand for:
- LOD: Level of Detail
- LOI: Level of Information
- LOMD: Level of Model Definition (also referred to as Level of Development within American texts)
- LOIN: Level of Information Need
You may be thinking: ‘That’s a lot of acronyms! Do I really need to remember them all?’ Well, if you are working in a BIM environment, probably you should.
So, what’s the Level of Model Definition?
To answer the question, we need to understand where these principles come from. Firstly, LOD, LOI and LOMD came to life through PAS1192, the provisional standard that defined BIM in the UK. The following formula links the three of them:
LOMD = LOD + LOI
So, the Level of Model Definition is the sum of the Level of Detail plus the Level of Information. Since PAS1192 was launched, BIM professionals have been using these terms to define how much information is contained in a BIM Model. In that sense, the LOMD defines the overall level of information and detail contained in the Project Information Model (PIM), commonly known as the BIM model.
As we explained in a previous post, the BIM model contains geometric information, non-geometric information and documentation. The Level of Detail (LOD) refers to the geometric information, whilst the Level of Information refers to the non-geometric information and documentation. To put it in other words, the LOD refers to how much detail needs to be modelled into the 2D or 3D models. On the other hand, the LOI refers to the amount of information that needs to be added to the metadata, or asset tags.
Levels of Model Definition according to PAS1192
PAS1192-2:2013 establishes 7 Levels of Model Definition:
- LOMD 1 Brief: typically includes only documentation like the project brief and scope.
- LOMD 2 Concept: associated with a very high-level design or feasibility study. Approximate volumes or shapes will represent the assets. Some asset information may be attached to the geometric information.
- LOMD 3 Definition: equivalent to a preliminary design. Elements are modelled showing approximate volumes, quantities, sizes, etc. Also, some asset information may be attached to the models.
- LOMD 4 Design: meaning a detailed design ready for construction. Elements are modelled to a level of detail sufficient for construction. They should include building specifications and information about access, maintenance, operation, etc.
- LOMD 5 Build and commission: detailed design including contractor’s and sub-contractor’s specific design elements. At this stage, manufacturers’ specific assets will replace generic asset models.
- LOMD 6 Handover and closeout: the model will include as-built data. This model will include an accurate representation of the built asset. It should also include relevant information such as Health and Safety, maintenance and operation.
- LOMD 7 Operation: the model will also include operation and maintenance information. At this stage, performance is verified against the project brief and the model is updated as necessary.
And what about the Level of Development?
Instead of going by the LOMD, the UK’s architectural industry has widely adopted the Levels of Development (also LOD) defined by the American Institute of Architects. This organisation has the following classification:
- LOD 100 Concept design – equivalent to LOMD 2.
- LOD 200 Schematic design – equivalent to LOMD 3.
- LOD 300 Detailed design – equivalent to LOMD 4.
- LOD 400 Fabrication and assembly – equivalent to LOMD 5.
- LOD 500 As-built – equivalent to LOMD 6.
Recently they have also included a LOD 350, referred to as ‘Construction Documentation.’ This model includes how building elements interface with other various elements with graphics and written definitions.
What then is the Level of Information Need?
Recently, BS EN ISO 19650 superseded PAS1192. In an attempt to minimise the confusion created by so many acronyms, this new standard has removed many of the interlinked buzzwords. It has in fact removed the LOMD, LOD and the LOI, replacing them with the Level of Information Need. This aligns with the goal of ISO 19650 to have ‘one world, one standard’ for all BIM-related aspects. There are rumours that the European Committee for Standardisation will create more guidance on the Levels of Information Need. Until that time comes, BIM professionals should still refer to the Level of Model Detail or Level of Development mentioned above.
Next time your client asks you to deliver a BIM model to LOD300, hopefully you’ll have a better understanding of what this means (perhaps more so than your client!). And if you still have questions on the topic, get in touch with us. At GlobalCAD we specialise in the delivery of CAD and BIM services and are confident we can help bring more value to your projects!
