Level of Development LOD

[edit] Introduction

Level of Development (LOD) enables practitioners in the architecture, engineering and construction (AEC) sector to clearly describe Building Information Models (BIMs) throughout the design and construction process.

[edit] The Origin of LOD

The LOD framework was formally established by the American Institute of Architects (AIA) in 2008. Further development has been undertaken by the Associated General Contractors of America (AGC).

However, LOD existed prior to the AIA’s formalised introduction. An early variation of the concept was present in construction analysis software that linked digital models to project costs. Introduced by Vico Software (now part of Trimble), a Model Progression Specification (MPS) was created in order to coordinate consistent BIM model data and associated information.

[edit] LOD or LOd?

In this early instance, LOD was defined as Level of Detail. However, the acronym LOD (in all upper case letters) has since become associated with Level of Development (in the USA - see level of detail for more information about the UK) while LOd is an indication of the original term, Level of Detail.

In the AIA's G202-2013 Building Information Modelling Protocol Form, LOD refers to the Level of Development required for model element content. LOD is the degree to which the components’ specification, geometry, and attached information have been thought through – or the degree to which project team members can depend on the information when using the model.

On the other hand, LOd is associated with the proportion of detail enclosed within the model element. In other words, a visually detailed element might in fact be generic, and despite its appearance, it might be at a low level of design development.

In the article, “The LOD on the LOD”, Jim Reis, Managing Director of SysQue and Building Data at Trimble notes that LOD (meaning Level of Development) is the most commonly used reference. He adds that as the element or model becomes more developed (LOD), more detail (LOd) subsequently becomes available.

Reis explains that LOD is the depth of thinking applied to the model; thus, it is associated with the reliability of the model. Example: Whether the pipes in a model have been engineered and the permanence of their placement. By contrast, Reis says LOd is associated with the way a model looks. The level of detail refers to the input of the model. Example: Specific shapes and measurable location of steel pipes in a model.

[edit] Six stages of LOD

Ranging from LOD 100 to LOD 500, the LOD framework defines the extent of design detailing in the BIM model for each component.

The six LOD stages are:

• LOD 100 (conceptual design) - At this pre-design stage, elements are a generic representation, giving the viewer a basic idea of existence but no idea about size, exact shape or orientation. The model consists of 2D symbols and masses to signify the existence of an element.
• LOD 200 (schematic design) - A representation of a partially defined idea of elements’ size, location in the facility etc. but with much rough approximation. .
• LOD 300 (modelled as design-specified) - This shows the specific geometric size and exact dimensions of the element and orientation, location, and quantity used across the facility.
• LOD 350 (modelled as actual size) - A revision of LOD 300 depicting precise information about how the component will be connected to nearby elements. This is usually the minimum requirement of construction firms.
• LOD 400 (supplementary components added) - Sufficient information to fabricate the component with individual holes, weld sizes and so on.
• LOD 500 (final design) - The fully developed and functional model, showing the operational geometry of the component and the stage of installation of the component with verified information such as manufacturer details, dates, parts, and model number etc.

The BIM forum has contributed to interpreting the six levels of this framework for building product manufacturers and fabricators in particular - including plumbing, electrical, foundation, roofing, etc. The purpose of this is to foster better collaboration during the design and construction process.

[edit] Related articles on Designing Buildings Wiki

• American Institute of Architects AIA.
• BIM guidelines around the world.
• BIM resources.
• Design drawings.
• Glossary of BIM Terms.
• Level of detail for BIM.
• LOD: Linguistics Needs of the Construction Industry.

[edit] External resources

• Jim Reis, "The LOD on the LOD”