Exploring LOD in Architecture & Engineering
Terminology in any industry is a sign of growth. In the construction industry, new terms crop up with regularity and older terms adapt or are modified to encompass new realities. One such term used extensively in the AEC industry is LOD or Level of Detail or Level of Development. Within a world managed by Building Information Modelling (BIM) and BIM services, LOD is a universal term used to describe and explain how precise a model is and what it lacks in terms of architectural BIM modelling.
The term LOD references the input of the model. For example, LOD, or Level of Detail, can identify specific shapes and measurable locations of steel pipes in a model.
Speaking of Level of Development, this refers to the depth of thinking applied to a model, or how reliable a model is. For example, the Level of Development can specify whether the pipes in a model have been engineered and it can mention how permanent their placement is.
When a component is developed to increased levels, then more detail is provided also.
Architects and consulting engineers have moved from AutoCAD to Revit. But several MEP contractors still work in AutoCAD. With Level of Development (LOD) standards, an MEP contractor knows what to expect from the owner, architect and consulting engineers, regardless of the software being used.
So, what is the most efficient method of progressing a model from the architect and consulting engineer’s LOD 200 to construction LOD 400?
- First, the Revit platform can be shared to leverage the LOD 200 design data and add the LOD 400 data as needed to prefabricate and install components with BIM tools.
- Today, architects and consulting engineers may still provide standard walls with single line penetrations. Construction stakeholders can schedule and estimate what is required as the model progresses from a design level LOD 200 to LOD 300, LOD 350 and LOD 400.
An interpretation of the AIA defined Level of Development is as follows:
- LOD 100 – involves a conceptual model, with data derived from other model elements
- LOD 200 – includes a schematic layout with approximate sizes, shapes and locations
- LOD 300 – has a model with design-specified sizes, shapes, spacing and locations of equipment
- LOD 350 – includes a model with actual sizes, shapes, spacing, locations and equipment connections
- LOD 400 – supplementary components are added to the model, which is required for fabrication and installation
Contractors are more likely to bid projects from an LOD 300 drawing or model.
Virtual Design and Construction (VDC) can be achieved at LOD 350, but the potential for profitability occurs at LOD 400. This is because LOD 400 allows for the planning and virtually practices how to fabricate and later install each component.
With LOD 400, confidence in prefabrication is gained, completion of milestones can be tracked with the scope and changes to the scope can be identified and documented. It is vital to have the right skillset, software and access to the right data to achieve LOD 400.
Contractors may sometimes use generic, highly detailed models that lack other relevant data. Using models from manufacturers or model-sharing websites needs a lot of work to add the development data needed for a streamlined workflow. These challenges can be eased with the right partners to support the development of models using Revit 3D BIM modelling.
Viewing 3D city models on mobile devices (smart phones and tablets) enables informed planning, augmented reality projects, real estate sales and 3D navigation. In today’s world, 3D datasets are used for research and in real life applications. Applications include determining illegal residential buildings using heat sensing equipment and using 3D mapping to help town planners with noise mapping. It is important to be able to access 3D data and integrate it with 2D data, while displaying the data on a mobile.
Increasingly, detailed, realistic 3D features, such as full roof structures rather than small blocks or individual buildings resulting from computer-aided design (CAD) models or terrestrial LiDaR (Light Detection and Ranging) or other scanning, are made available.
Both flat roofs and detailed 3D structures result in vast amounts of complex 3D data, which may not be easy to visualise. To better understand performance implications, it is useful to generate 3D city models with different levels of detail (LOD) – ranging from LOD 0 – 4:
- LOD 0 – is a digital terrain model. The footprint or roof outline of every building is represented by a horizontal polygon with a well-defined constant height.
- LOD 1 – is a block model without any roof structures. The outer shell of every building is represented by one prismatic extrusion solid. Ground, floor and roof surfaces are horizontal, while lateral boundary surfaces are vertical.
- LOD 2 – is a city model having detailed roof structures and may have roof textures. The simplified outer shell of every building is represented by horizontal and vertical outer surfaces and simple roof shapes. All surfaces (e.g. ground surfaces, wall surfaces, roof surfaces, outer ceiling surfaces, outer floor surfaces, virtual closure surfaces) and other building elements (e.g. balconies, dormers and chimneys) are also represented.
- LOD 3 – The detailed outer shell of every building is represented by detailed outer surfaces and detailed roof shapes. All surfaces are represented with greater detail.
- LOD 4 – is a model that includes the interiors of structures. The detailed outer shell and interior of every building are represented by detailed outer and inner surfaces and detailed roof shapes. All surfaces (e.g. ground surfaces, inner and outer wall surfaces, inner and outer roof surfaces, outer ceiling surfaces, outer floor surfaces, virtual closure surfaces) and all building elements (e.g. balconies, dormers, chimneys, interior and furniture) are represented in greater detail.
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This detailed and complex data can be generated from digital ortho-photos, computer-aided design (CAD) models, LiDaR point clouds or terrestrial laser scanning. For more depth in detailed modelling, it is BIM modelling based on CAD or Revit BIM 3D modelling tools that are required. It is pertinent for design support providers to clearly understand and provide high-quality 3D models through architectural BIM modelling and recognised BIM virtual construction methodologies.
XS CAD has valuable experience providing Revit 3D BIM modelling services, architectural BIM modelling and other BIM services for general contractors and consultants. Our range of services for consultants and manufacturers across the world include BIM modelling, creating models and drawings by using Revit BIM, AutoCAD and BIM Collaborate Pro for cloud collaboration.