Level of Development (LOD): Looking at BIM Data across the Building Lifecycle.
Contributing Author: Lot Kaduma
Whenever we think about BIM, we often start with a portrait in our mind of three-dimensional (3D) models. These models serve as digital representations of the data related to the lifecycle of a built structure such as a house, road, or bridge. In our blog post titled BIM as a database: Why the “I” in the buzzword matters, we categorized BIM data into ‘graphical’ and ‘non-graphical’ data related to the 3D model.
But have you ever wondered how the quality of data in these models impacts the processes in the lifecycle of a building? In this article, we would like to explore the concept of ‘Level of Development’ — why it is critical for the quality of data in BIM models and how it serves as an important connection between BIM and the building lifecycle.
What is Level of Development?
Level of Development popularly referred to by the acronym LOD, is simply a means of specifying and measuring the quality of a BIM model in terms of its completeness. This serves as a basis for determining to what extent the data in a model can be relied upon and for what purpose it can be used. As such, it is usually measured according to two (2) main components:
1. Graphical/Visual representation of the model, also known as ‘Level of Geometry’ (LOG) or ‘Level of Graphical Detail’ (LOd). This focuses on the appearance of the objects in a model. It gives us an idea of what they look like, along with their position and orientation within the model space. For instance, a door would be shaped like an upstanding rectangular box with a frame, panel, and handle. Its location could be within an internal wall of a classroom at the 3rd floor level, and oriented with one side facing the adjacent lobby.
2. Non-graphical/Embedded information of the model, also known as ‘Level of Information’ or LOI. This focuses on the properties of the objects in a model. It provides all the data that is related to the object in an alphanumerical format. For instance, the object Name could be D76, and the object type could be a Single Panel Swing Door. The dimensions can be Height = 2.1 meters, Width = 0.9 meters, and Thickness = 0.15 meters. Quantity can be 2 pieces, while materials include steel (frame and handle) and timber and glass (panel). User Requirements could be ‘kids aged 3 to 10’, and so on. An important aspect of LOI is its ‘presentation in a tabular and alpha-numerical format’. This allows the data to be processed in a ‘structured manner’ using spreadsheets and databases.
A good way to understand this concept is using the formula: LOD = LOG + LOI. In essence, a BIM model’s Level of Development would be determined by the completeness of its graphical representation in relation to the properties embedded in it.
Please note the following:
· In some contexts, the Level of Graphical Detail (LOd) is used in place of Level of Geometry (LOG). However, in order not to confuse it with Level of Development, the acronym is replaced with a small letter ‘d’.
· Also, you might find Level of Definition used in place of Level of Development in some contexts. They both mean the same thing and only serve as UK and US variants, respectively.
The Stages of LOD
Level of Development (LOD) is categorized according to stages ranging from 100 to 500, where the numbers represent a lower to a high level of completeness of the BIM model as it relates to each phase of the Building Lifecycle.
The LOD stages are:
Caution: Beware of Information Overload — Focus on the Information Need.
Ideally, each LOD tends to coincide with the various phases of the building lifecycle as illustrated earlier. For instance, it is required to model at LOD 400 at the Execution Phase. In principle, the BIM model becomes more developed as more detail and information are added to it over time. As the stages progress, it would be expected that the LOD increases. However, in practice, this tends to yield a problem of ‘Information Overload’ — where BIM models are created with too much detail and information without consideration for the specific type of information needed by each stakeholder. Not all components require the same LOD. For instance, in a project where it is specified to model at least LOD 400 for the Execution Phase, the Building owner might only need a model of a classroom door at LOG 300 and some specific data in LOI 400 for operation and maintenance purposes, while a subcontractor would require the same model at LOG and LOI 400 for the purpose of fabrication and production. In the same project, the owner would need the plumbing systems modelled at least LOG and LOI 400 for future operation and maintenance purposes. This is why a new concept called ‘Level of Information Need’ or LOIN was initiated by the ISO 19650 standard to serve as a complementary approach to LOD. It recognizes that each project information deliverable needs to be determined based on its purpose(s). Without such consideration, the drawbacks that could occur are inconsistencies in model requirements, heavy model files that are difficult to load, too much required human effort for model creation, and some model data ending up unused because they weren’t needed by the stakeholder in the first place.
Why is LOD important in the BIM and the Building Lifecycle Process?
As it is the common practice nowadays, we decided to ask the popular AI Chatbot — ChatGPT and it provided some interesting feedback as seen in the image below:
In summary, it mentions that “LOD provides a consistent framework for modelling and data management that helps stakeholders to make informed decisions, improves collaboration and coordination, and enhances quality and efficiency across the building life cycle”. This is interesting feedback, right? Nonetheless, we are going to shed some light on this and provide better context about the importance of LOD to the BIM and Building Lifecycle process. Here are some of our thoughts on the matter:
Cost Savings
Unknown changes or variations in design tend to have a negative impact during the execution of a building project, especially in the area of costs. As such, the earlier the changes are communicated and integrated amongst stakeholders, the lower the costs incurred in the project. This is why a model at a minimum LOD 300/350 is recommended before construction execution starts. Because all objects are modeled with precise geometry, contractors can bid and schedule their work without the risk of omissions or errors that normally occur when work begins..
Structured Data
A key ingredient to a successful data-driven construction project is access to structured data. A major challenge currently faced in the construction industry is the ability to organize and structure the enormous amount of data being generated in the construction industry. As mentioned earlier, the risks of information overload persist, and data is littered all over the digital ecosystem. A solution to ensure that stakeholders utilize the needed amount of information would be access to structured data. A combination of Platforms and Application Programming Interfaces (APIs) can be used to automate the capture and connection of all types of data related to the BIM model. Also, Artificial Intelligence could help users structure, organize and utilize graphical and non-graphical data according to their information needs much easier and faster.
Learning Opportunities
Construction projects are ever-evolving due to their unique and complex nature. This provides learning opportunities for stakeholders to be able to compare the various aspects and occurrences in each stage of previous and current projects. Questions regarding what was built and how it should have been built can easily be analyzed with models of a high degree of geometrical detail and relevant data. This allows knowledge to be transferred from a previous construction site to the planning of future projects.
Sustainability
It is expected that carbon emissions for all buildings and infrastructure across the world should be at net zero by 2050. To deliver the buildings of the future, we will need to be able to track and assess the environmental impacts of every single component — from cradle to grave, and across its entire lifecycle would be the right approach. This is why access to a BIM model with sufficient environmental and energy-related data is important for achieving the sustainability targets of the construction industry.
Digital Fabrication and Robotics
As construction seeks to embrace the use of robotics and 3D printing to speed up the delivery process, access to BIM data with a high degree of accuracy at the pre-execution phase would translate to better performance on the construction site. A lot of components can be fabricated offsite with the aid of robots in a factory before work begins on site, which can be assembled as units in a short period. Also, production in controlled systems removes the risks of complications resulting from external variables that are present on the construction site such as weather and logistics issues. In this case, a model with objects at LOD 400 would be necessary for the production plant. Considering the drawbacks of human efforts in relation to developing models at higher LODs, soon modelers will be able to automatically generate LOGs and LOIs at the click of a button with the aid of Artificial Intelligence tools.
Conclusion
In essence, the concept of Level of Development (LOD) is important for understanding the link between BIM data and the building lifecycle. It provides guidelines for specifying and measuring the quality of BIM data in each stage of the building project. Access to accurate and complete BIM data enables better decision-making and collaboration between stakeholders and thus enhances efficiencies across the board. Considering the enormous challenges currently faced by stakeholders in meeting their information needs, it would be important to simplify the way we create, organize, and utilize BIM data. Our solution would be to remove strenuous and repetitive BIM-related tasks through automation; connect all kinds of data through Platforms and APIs; and utilize Artificial Intelligence to streamline BIM data according to the needs of each project and stakeholder through all stages of the building lifecycle.
References
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