Globally, the building and construction industry is continuously struggling to find clarity around the usefulness and correct application of Level of Development (LOD).
Scott Beazley, digital technologies manager at Mitchell Brandtman, explains that “LOD is a measure of confidence and reliability of information at the various stages of the project. When LOD was initially introduced it filled a void and allowed project teams (particularly those downstream) to understand the content and reliability of the model data they could expect to receive.
“It has been exposed to broader interpretation in relation to its application and what it is expected to deliver since its acceptance as a standard of reliability and integration within BIM and 3D models.”
The LOD Specification document, published by the BIM Forum, which is derived from the AIA G202-2013 Building Information Modeling Protocol Form document, helps to add clarity to the LOD concepts by objects and their attributes. It has had a large uptake by many (including Mitchell Brandtman) as a default industry standard and used as a basis for contracts. However, this may be pushing the LOD specification a bit too far. The LOD specification is designed as a reference guide to assist industry to specify the reliability of the information at each stage of the project.
Beazley suggests that the “misinterpretation of the role and use of LOD perhaps masks the bigger issue associated with building model data exchanges.”
“For example, models are often now ill-defined as LOD 200 or LOD 300, rather than containing objects of a particular LOD level,” he said. “Industry needs to agree on how to exchange data effectively and consistently throughout the project phases on a discipline to discipline basis - both geometric and non-geometric.”
Information delivery manuals and data exchanges
Globally, the building industry needs a robust and reliable means of exchanging digital information that is easily readable and easy to check and validate at each stage of development.
Since 1994, buildingSMART, formerly the International Alliance for Interoperability (IAI), has aimed to improve engagement, knowledge sharing and education amongst members and to take the lead in defining user needs and determining OpenBIM solutions for all through internationally recognised standards, tools and training.
The Industry Foundation Classes (IFC) concept was developed by buildingSMART to better enable project teams to share information across the various software applications used for design, construction, procurement and ongoing operation of a building. Currently, it is considered the standard in rich data exchange. buildingSMART certifies applications that comply with IFC, which provides a platform of industry-wide acceptance and use in relation to how data is entered, used and extracted within the model.
They also developed the ISO 29481-1:2010 Building information modelling - Information delivery manual - Part 1: Methodology and format standard to capture and specify processes and information flow during the life cycle of a building. The standard provides a methodology for the accurate exchange of data between parties, known as the Information Delivery Manual (IDM). This helps create the technical specifications of the project known as the Model View Definition (MVD). The beauty of MVD is that it allows easy access for consultants and contractors to the information relevant to their part of the project.
Data exchanges are the future
"buildingSMART has a working group developing IDMs," said Beazley. "This roadmap covers the full range of project phases and aims to identify discipline to discipline exchanges. These data exchanges are then more fully defined in MVDs that detail the objects and their properties (or attributes) that should be present. By defining these requirements, it is then possible to automate the exchange and checking of the embodied data. This helps build confidence and reliability.”
Examples are found on the buildingSMART IFC Solutions Factory website. These exchanges are also put in the context of Process Maps that have Exchange Requirements.
This is what I believe we need in the building and construction industry - this level of detail in defining building data exchanges on a discipline to discipline basis at different phases of the project.
The Concept Design BIM 2010 MVD, developed by GSA and CSI from USA, Statsbygg from Norway, and Senate from Finland, is a good place to look for further development of data exchanges. It covers Spatial Program Validation, Circulation/Security Analysis, Energy Performance Analysis and Quantity Takeoff, which enable four types of analyses early in the process to optimise the design and helps to see the application of MVDs.
The Information Delivery Manual for Structural Steel by AISC and Georgia Tech is a more focused IDM which addresses the exchanges required by the structural steel industry with Exchange Models created by the architect, structural engineer or steel detailing engineer. Exchanges by project stages and the people who will create or receive them is shown in the following table.
Where do we go from here?
The IDM Roadmap shows the work that is still to be done to define and refine the full range of exchanges for industry, and buildingSMART welcomes assistance to make this happen.
The need to better define, produce and deliver building and construction data is an urgent issue. LOD has helped to identify the issue but we still need to simplify the structure of data exchanges for project stakeholders and more precisely for software.
Perhaps the IDM and MVD work can help here.