Building Information Modelling (BIM) implementation is consequently challenging, challenges include unstructured data and processes that often lead to time and cost overruns. Having clarity on up to what level of geometry has to be modeled and how much information should include plays an important role in any project which directly affects the time and cost. At this point, LOD comes into the picture, gives clarity, clears many doubts, and sets standard expectations.
Level of Detail or Level of Development (LOD) is a theoretical concept to support model development. The idea is that you attach a LOD status attribute to objects in conjunction with standardized reusable checklists. Thus you can, with increased certainty, guarantee a certain quality of information at a given point.
LOD differs between geometry and properties. A model can be well developed through geometry without having much information concerning the properties of the model. In such a case, the model has a low level of properties and a high level of geometry
If Drawing is the engineer's language then the LOD is the BIM model development language.
The construction industry, projects, and the amount of stakeholders involved make owners and consultants push their strategies and plan of action to get the desired, expected outcome. First, the project team needs to agree on what information at what detail and quality level need to be provided at what stage of the project. There is a need for agreement, coordination, and collaboration and it is appreciated to deliver the project efficiently within the planned time and budget.
Each construction project is unique! Construction projects are like prototypes, even if similar projects have been completed in the past, each time a team breaks ground they are creating something new.
LOD gives clarity through a well-defined agreement and model development. Suppose, The owner asked for the digital model of his facility, Then a few questions arose from the consultant! How accurately is he expecting that model? What is the exact scope? Is he expecting just a layout? Base build? Core and shell ? Alone or with including each and every ASMEPF element with accurate dimensions, geometry, orientations, and information it contains?
Building Information Models (BIM) are widely adopted in design processes as the center of information flow. Furthermore, it is a good tool for visualization, helping increase the understanding between trades and speeding up the decision process. The structure of a BIM is built up of several main components denoted as building elements. Essential questions to be answered before starting design management of BIM projects are; which building elements, from which trades, should be developed at what time and at what level?
The different versions around the world are dividing the levels in different ways. BIMForum uses these definitions (here summarized):
LOD100: Approximately information, often generic representation. Seldom geometry.
LOD200: Approximately geometry as a system or element with size, form, and location.
LOD300: Element represented as a specific system or object with size, form, location, and amount.
LOD350: As 300, including interface with other building elements. Example: Assembly plate between columns and foundation
LOD400: The element is modeled sufficiently to exact production as bases for fabrication. LOD500: The element gives an exact picture of the real element. As built.
Design management can be seen as managing people and information. In construction projects, there are many different trades to manage (architects, structural engineers, electrical engineers, road planners, etc.). In a project with BIM workflow, the trades provide all information about building elements in the BIM.
Before specifying the LOD requirement of the project we need to identify the use cases of BIM. Though the BIM technology can enable hundreds of use cases, the project team needs to decide on the use cases identified for the project.
Some use cases are Existing conditions modeling, Site utilization planning, Site analysis, Architectural programming, Visualization and Simulation, Cost analysis/estimation/quantity take off, Design authoring and briefing, Design to maintain analysis, Energy analysis, facility management and documentation, Security and Property management, 3D control and planning, etc.
Each use case may require a specific level of detail or development model and model elements. Not all elements modeling is required in 3D to develop a detailed quantity. A specialized software environment can enable formula-based extrapolation. This will avoid modeling time-consuming to less useful elements into 3D models.
LOD acknowledges the part of the project scope and creates the standardized definition, checklist, and how much amount of detail (information) and development (geometry accuracy) has to be developed.
Not all elements modeling is required in 3D to develop a detailed quantity. Owner organization should clearly specify the use cases project in the bidding stage to understand the expectations.
3D models can be extremely detailed in terms of how they look visually. But the development should be in the interest time & cost restricted to the use case. This exercise should not be to test the organization's capability or software rendering capabilities.
We at Desapex aim to use fewer terminologies and bring more relevance to use cases identified for the project to make BIM work in the interest of the project. We coordinate with project owners and stakeholders right from the planning stage and also help them to create and specify the project requirements.
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