Understanding LOD specification in Building Information Modeling
Find out about LOD specification and understand the characteristics of the five LOD definitions and what each one means for your BIM project.
When it comes to BIM, there are many terms worth familiarising yourself with. One of these is LOD – Level of Development. Despite being a relatively common term within the industry, there is still a fair bit of confusion about what LOD is.
In this course, we are going to clear that up. We’ll give you a general introduction to LOD, before taking a closer look at the fundamental definitions of LOD as well as the various rendition types.
First of all, let’s go through the concept of LOD. Briefly put, LOD specification is a reference that allows practitioners to clearly specify the content and reliability of BIM during the design and construction processes. But it’s the meaning behind LOD that continues to cause a degree of confusion. So, let’s try to clear it up.
Interpreting LOD correctly has proven to be a challenge in the industry. In some cases, it is interpreted as Level of Detail, which is incorrect. As the name suggests, Level of Detail essentially signals how much visual detail is included in the object, while Level of Development highlights the extent to which an object’s geometry and attached information has been thought through.
There are five definitions of LOD that all define and illustrate the characteristics of model elements. In each definition, the level of articulation differs, allowing practitioners to define what their systems can be used for, while also giving a better understanding of the functions and reliability of the product.
Let’s take a closer look at these definitions using a Grundfos MAGNA3 as our starting point.
First, we have LOD 100. It’s the most basic of all the definitions and it’s often used in the early stages of a project. The object is graphically represented with a symbol or basic shape, and the information is sparse. For a MAGNA3, the information would read ‘Pump 0,5 kW’. Therefore, any information from LOD 100 elements should be considered a first step towards the final solution.
Secondly, we have LOD 200. Here, the information describing the object becomes more specific, while still not corresponding to the final solution. A MAGNA3 at LOD 200 would read ‘Circulator pump 0,5kW’. Even though the object is more detailed, we still remain in the early stages of a project.
At LOD 300, the object is represented as a specific system. Essentially, this means that features such as size, shape, orientation and much more can be measured directly from the model. At LOD 300, we are able to specify that we are dealing with a MAGNA3 rather than just a circulator pump. LOD 300 is close to representing the finished product.
Next up is LOD 350. Together with LOD 300, this is an accurate representation of the final product – especially with regard to a circulator pump such as the Grundfos MAGNA3. Here, a specific product number is added along with electrical and mechanical data.
LOD 400 is very similar to LOD 350. Where it differs, however, is in terms of the information added to the object. An LOD 400 element can have its quantity, size, shape, location and orientation measured directly from the model. A MAGNA3 at LOD 400 is similar to a MAGNA3 at LOD 350, but adds all the delivered data rather than just electrical and mechanical data. This data is often added by other stakeholders in the project, such as the contractor.
Finally, there’s LOD 500. An LOD 500 object, also referred to as an as-built model, is a fully verified model containing all the information needed throughout the specific projects lifetime; such as exact location, warranty, associated parts and service information.
Take a look at these three renditions. Although they all have a vastly different level of visual detail, they contain the same amount of data. The only difference is on a visual scale, which can be rendered according to the customer’s needs.
There are three types of rendition levels in AUTODESK REVIT: Coarse, medium and fine. The different renditions allow you to work on your model as you wish. For instance, if you prefer working on your model in a blocky environment, you can use the coarse rendition, while if you prefer a greater level of visual detail you can use the fine rendition.
While all the data is available in each LOD definition, the data you ask for varies depending on whether you’re a system designer, a contractor, an operator or holding any other position. That way, it is important that you are able to specify who needs what information throughout the project lifecycle.
That covers the most important aspects of LOD specifications. Let’s round up the main points.
First of all, the LOD specification lets you specify the content and reliability of BIM during the design and construction processes.
Secondly, it’s important to remember that LOD is not just about visual representation – it is really about information.
And finally, the various renditions allow you to work in the environment of your choice. Just because you change your rendition level doesn’t require that you change your LOD.