Level Of Development(LOD)
An information model combines graphical data, such as geometry and shape, and non-graphical information such as performance requirements and other associated documents. The BIM Execution Plan (BEP) includes detailed information on the LOD required for each given project milestone or specific BIM use, defining who is responsible for producing the information.
Some organisations provide a template for this, based on Uniformat (North America) or Uniclass (UK), which are standards for classifying building specifications, cost estimating and cost analysis. The AIA suggest that the LOD framework recognises that different elements of the project will develop at different rates and '…allows the Project Participants to efficiently communicate to one another the extent to which a Model Element has been developed … It also allows the Project Participants to communicate the extent to which a Model element may be used and relied on…'
Level of Development (LOD) in BIM are an AEC industry standard that specifies how the geometry of the 3D building model can reach different levels of refinement. These development models are purposefully built for various stages of design, 3D visualization level, construction-quantities level, planning & scheduling, estimations, control over on-site production with fabrication. The LOD specification helps designers define the inherent characteristics of the elements in a model at different stages of development. Using the Level of Detail (LOD) AEC industry specifications as a guide, one can create a 3D model of your projects based on the specific requirements. Using LOD, designers and engineers can communicate with other professionals who will be using the model further about the usability and limitations of a model. LOD specifications were designed to standardize the use of the LOD framework and use it as an efficient and collaborative communication tool.
Level of Development is often misunderstood as the Level of Details, but both are different from each other. Level of Details signifies the proportion of details enclosed within the element of the model. Whereas Level of Development is the degree to which the specification and geometry of the elements and the information attached to it have been thought through, or it can be referred to as the degree to which the team members involved may depend on the information while using the model. It may be said that Level of Detail serves as an input to the element, whereas Level of Development is the output.
We have delivered LOD for different levels. We offer five LOD options ranging from 100 to 500. We adopt internationally accepted standard for LOD.
Level of Development (LOD) specification allows professionals in the industry to articulate how an element’s geometry and associated information has evolved throughout the entire process. The LOD specification helps designers define the inherent characteristics of the elements in a model at different stages of development.
Using LOD, designers and engineers can communicate with other professionals who will be using the model further about the usability and limitations of a model. LOD specifications were designed to standardize the use of the LOD framework and use it as an efficient and collaborative communication tool.
According to the American Institute of Architects (AIA), LOD outlines the design requirements at each stage.
- At LOD 100, which is the pre-design stage, the model consists of 2D symbols and the masses to signify an element’s existence.
- At LOD 200, the elements are partially defined by outlining its approximate quantity, size, shape, and location.
- By LOD 300, the elements are defined with exact dimensions and their relative positions bolstering precision.
- LOD 350 describes the information about an element precisely and outlines an element’s relation and connection with other components.
- The LOD 400 level outlines the basic information about the construction of various elements.
- By LOD 500, the model begins representing the real-life functions of elements in a real building. Here are all the levels of development with their definitions in detail.
A. LOD 100 - Conceptual
The building 3D model is developed to represent the information on basic level. It is the pre-designing stage of LOD. The LOD 100 element is a conceptual model where the parameters such as height, area, volume, orientation, and location are defined. Information related to the Model element, i.e. cost per square foot, tonnage of HVAC etc., can be derived from the model elements. The information in this stage is considered as an approximation.
BIMForum Interpretation: LOD 100 elements are not geometric representations. Examples are information attached to other model elements or symbols showing the existence of a component but not its shape, size, or precise location.
B. LOD 200 - Approximate Geometry
It is the schematic designing stage of LOD. General model where elements are modeled with approximate quantities, size, shape, location and orientation. We can also attach non- geometric information to the model elements. The information at this stage is also considered as an approximation.
BIMForum Interpretation: At this LOD elements are generic placeholders. They may be recognizable as the components they represent, or they may be volumes for space reservation.
C. LOD 300 - Precise Geometry
The Model Element is graphically represented within the Model as a specific system, object or assembly in terms of quantity, size, shape, location, and orientation.
It is the building design development stage of LOD. The graphical representations of LOD 300 may be the same as that of the graphical representation of LOD 200, but what makes it different from LOD 200 is that the geometry and features at this stage are considered accurate. The information at this stage can be used in the construction stag.
BIMForum INterprestation: The quantity, size, shape, location, and orientation of the element as designed can be measured directly from the model without referring to non-modeled information such as notes or dimension call-outs.
D. LOD 350 - Precise Geometry with Connections
LOD 350 The Model Element is graphically represented within the Model as a specific system, object, or assembly in terms of quantity, size, shape, location, orientation.
It is the construction documentation stage. The information obtained in LOD 350 is the same as that obtained in LOD 300, but in this stage, the interfaces with other building components like connections and support are also included. It indicates the way the component can be installed and the way it interacts with the systems of other buildings.
BIMForum Interpresentation: Parts necessary for coordination of the element with nearby or attached elements are modeled. These parts will include such items as supports and connections. The quantity, size, shape, location, and orientation of the element as designed can be measured directly from the model without referring to non-modeled information such as notes or dimension call-outs.
E. LOD 400 - Fabrication-ready Geometry
LOD 400 The Model Element is graphically represented within the Model as a specific system, object or assembly in terms of size, shape, location, quantity.
It is the construction stage of LOD. Model elements are modeled as specific assemblies, with complete fabrication, assembly, and detailing information in addition to precise quantity, size, shape, location and orientation.Non- geometric information to the model elements can also be attached. These details are of great use for the suppliers for manufacturing the components that are represented.
BIMForum Interpresentation: An LOD 400 element is modeled at sufficient detail and accuracy for fabrication of the represented component. The quantity, size, shape, location, and orientation of the element as designed can be measured directly from the model without referring to non-modeled information such as notes or dimension call-outs.
F. LOD 500 - Operational/As-built Models
LOD 500 The Model Element is a field verified representation in terms of size, shape, location, quantity, and orientation. Non-graphic information may also be attached to the Model Elements.
It is the as-built stage of LOD. These are the fields that are verified in terms of shape, size, quantity, orientation, and location, which are considered to be accurate representations of the building elements post-construction. These elements can be used as references for operation and maintenance by the facility managers.
The level of development is a vital element in the overall BIM process as Level of Development (LOD) Specification is a reference that enables practitioners in the AEC Industry to specify and articulate with a high level of clarity, the content and reliability of Building Information Models (BIMs) at various stages in the design and construction process.
The LOD Framework addresses various issues faced by AEC professionals by providing an industry-developed standard to describe the state of development of various systems within a BIM. This standard enables consistency in communication and execution by facilitating the detailed definition of BIM milestones and deliverables.
The LOD specification can be beneficial in the design process in the following ways:
- With standardized specifications and detailed information about all the elements, designers can deliver guidelines and data for people working downstream to ensure that there are no lapses in execution and maintenance.
- LOD makes defining a standard easier for contractors to take care of BIM execution. Simultaneously, design managers can explain the necessities at various levels of the design process to the teams with ease.
- LOD helps in making accurate BIM models. Concurrently, all the teams including the owners can specify accurately the level of detail they need from a BIM model and get clearance about the scope of the final BIM.