There is often confusion in the construction and engineering industry regarding level of detail and level of development. The acronym LOD can be used to describe both level of detail and level of development. AEC professionals tend to use these terms interchangeably; however, there are important differences.
Level of detail and level of development are both used in the AEC industry to describe the amount of information and detail included in a 3D building information model (BIM). The main difference is that level of detail refers to the graphical representation of an object, while level of development refers both to the graphical representation and to the information properties of that object.
There is a defined set of LOD specifications for both level of detail and level of development that help AEC professionals document, articulate, and specify BIM models effectively. By using these LOD specifications to scope projects, architects, engineers, and other construction professionals can clearly communicate the precision requirements of the BIM model for faster project execution.
Level of Detail vs. Level of Development
While the two terms are related, they have different meanings when it comes to the 3D modeling of laser scan data. Level of detail is more focused on the visual detail, while level of development is more focused on the completeness and accuracy of the information included in the model.
What is Level of Detail for BIM?
The level of detail refers to the amount of graphical and non-graphical information associated with each element of the building information model. This can be thought of as the graphical depiction and associated text properties of each element in the model. LOD defines the amount of detail and accuracy of the elements within the model. It's typically categorized into five different levels, with higher levels indicating more detail and accuracy.
BIM Level of Detail (LOD) – LOD 100, 200, 300, 400, 500
LOD 100
LOD 100 modeling represents the envelope of objects with simple volumes. Models are designed in a symbolic and generic way. Elements are not fully detailed and may come from other models of the same type. An LOD 100 model can be useful for a simple pre-design study, to conceptualize an idea, or to conduct a basic feasibility study that only requires a rough representation of the volumes of the building or site.
LOD 200
Models are graphically created in a simplified way and are recognizable as an object. The objects remain generic – the position, orientation, shape, and size of the geometric objects are approximate. Specifications such as material characteristics are not integrated in an LOD 200 model.
LOD 300
Models offers more precise geometry of objects and includes accurate quantities, shapes, positions, and orientations.
LOD 400
Models are realistically plotted, with quantities, shapes, positions, and orientations being accurate. Walls, slabs, and ceilings are modeled in such a way that the various layers that compose them are detailed. The purpose of this level of detail is to provide detailed and accurate geometric references. LOD 400 models become a reference point for design and construction planning.
LOD 500
The level of detail LOD 500 is equal to that of the LOD 400, but with all modeled elements verified in the field. This delivers an as-built model of the building, site or asset.
What is Level of Development for BIM?
Level of development refers to the depth of thinking applied to the modeled element within the building information model. Another way to say this is that Level of Development is the completeness of information included in the 3D model, such as the detail about the structural elements, MEP systems, or materials. Each defined “level” outlines requirements to specified visual detail and attached information for an individual modeled element. It also refers to how reliable the depiction and associated properties of the modeled object are.
Level of development specifications guide AEC professionals to develop reliable and understandable building information models (BIM). There are typically five levels of development that are used: the LOD 100, 200, 300, 400, and 500 definitions are produced by the AIA (American Institute of Architects), and the LOD 350 was developed by the BIMForum working group.
BIM Level of Development (LOD) – LOD 100, 200, 300, 350, 400, 500
LOD 100 – CONCEPTUAL
The model element is graphically represented by generic shapes or symbols with approximate geometry, size, shape, location, and orientation. This level is to gain an understanding of the design and the spatial environment.
LOD 200 – APPROXIMATE GEOMETRY
In this level, model elements are graphically represented within the model as a generic system, object, or assembly with approximate specifications, quantities, size, shape, location, and orientation. Any information derived from LOD 200 elements must be considered approximate. LOD 200 models are often used for schematic design purposes.
LOD 300 – PRECISE GEOMETRY
The model includes accurate geometry with specific quantities, sizes, shapes, locations, and orientations of the elements with detailing, fabrication, assembly, and installation information. It's often used for generating construction documents, for design planning and for coordination among disciplines.
LOD 350 – PRECISE GEOMETRY WITH CONNECTIONS
The model element is graphically represented within the model as a specific system, object, or assembly in terms of quantity, size, shape, location, orientation, and interfaces with other building systems. LOD 350 is intended to define requirements for model elements that are sufficiently developed to support construction-level coordination. If a CAD design team has craft knowledge available, they can develop elements to LOD 350 or higher.
LOD 400 – FABRICATION-READY GEOMETRY
At this level, the model element is graphically represented as a specific system, object, or assembly in terms of size, shape, location, quantity, and orientation, detailing, fabrication, assembly, and installation information. At this level, the elements already have the information of a LOD 300, plus the parameters and precise geometry of a specific product, its model, manufacturer, cost, etc. This would be a fabrication level model.
LOD 500 – AS-BUILT MODEL
This is the highest level of detail, and the level is known as an as-built. The modeled element is a field verified representation in terms of size, shape, location, quantity, and orientation. This model is a close replica of the existing building. This LOD generally contains 100% of the necessary information for decision making. LOD 500 models are typically used for facility management and maintenance purposes.
How Does LOD Relate to 3D Laser Scanning?
Efficient communication and collaboration are important during a design or construction project. LOD specifications were designed to standardize models and eliminate questions in the level of detail or level of development included in a building information model. It is important to understand that LOD’s were not originally designed with laser scanning in mind, and therefore not all of the language pertains or relates directly with the technology.
3D laser scanning captures accurate data of a structure or site in the form of a point cloud. This point cloud data is used to generate BIM models through extraction software, tracing methods, and interpretation. This can be done at many different levels of detail and levels of development. It is important to specify the LOD when developing the project proposal. If you are unsure what to spec, one of our GPRS team members can walk you through the detail included in each LOD specification.
CAD designers will model building elements to the LOD specification that is defined in the project proposal. The higher the LOD, the more detail required for the modeled element of interest. LOD specifications can vary throughout the model, often based on element categories, or other grouping methodology. This helps optimize modeling efforts to those elements important to the specific project. LOD specifications also inform the project engineers and designers how much they can rely on details in the building information model. This information allows them to communicate with other team members about the usability and limitations of the model.
For more information on BIM modeling, level of detail, level of development, or as-built models contact GPRS 3D Laser Scanning today at 419-843-7226 or Laser@gprsinc.com. We are happy to answer any questions you have or talk you through the differences between level of detail and level of development.
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Frequently Asked Questions
What is BIM?
Building information modeling (BIM) is an intelligent software modeling process that engineers, contractors, and architects can use to collaborate on a building’s design, construction, and operation. BIM encompasses not only geometry and spatial relationships, but it also documents building features, such as specific information about the type of materials used, the quantity used, and how those characteristics impact the building as a whole. BIM can be thought of as a database of information ranging from project materials and cost to the 3D model after construction. This information can be used to actively manage a project every step of the way.
What is level of development in construction?
LOD in building information modeling (BIM) stands for level of development, representing the degree of detail and accuracy in the modeling of building elements. It ranges from LOD 100 (conceptual) to LOD 500 (as-built). At LOD 100, basic representations are conceptual, progressing to LOD 500 where elements are precisely as-built. This level of development classification is crucial for communicating with the project team and ensuring the correct level of accuracy for construction documentation.
What is 3D laser scanning?
3D laser scanners use LiDAR (light detection and ranging) technology to map millions of data points of a project site. The primary way a laser scanner works is to send light pulses at high speeds which reflect off objects and return back to the scanner’s sensor. For each pulse, the distance between the scanner and object is measured by determining the elapsed time between the sent and received pulses. Each data point is converted to a pixel with a known x, y, and z coordinate.
Millions of data points from multiple positions and viewpoints are captured and processed into a point cloud, creating an accurate 3D as-built data set of the site. This all happens very quickly, with some scanners, like the Leica RTC360, capturing and calculating 2 million data points per second with 2-4 mm accuracy. The result is a complete and accurate set of real-time data which can be mined for information or processed into customized 2D CAD drawings and 3D BIM models at any level of detail.