Understanding LOD and LOIN in BIM: Definitions and Applications

You often hear about LOD in BIM and want to delve deeper into this topic? What are LOD 300, 400, 500? So, what’s the difference between LOD 1 and LOD 100? And by the way, what on earth is a LOIN?

In practice, LOD describes the level of detail of the information associated with the 3D model of a project and is used to establish or define its degree of development. To manage LOD and the set of informative and geometric data they consist of, it is essential to use a BIM management system. So, stay seated and continue to read this article to find out more!

What are LODs in BIM

The term LOD is an acronym that has two different meanings, depending on whether you consider its English or American definition.

For the English, LOD indicates the “Level of Definition” of the BIM architectural model and is a concept introduced by PAS 1192.

For the Americans, on the other hand, it is the “Level of Development” of an element of the BIM model. In this case, the term “level of development” was preferred to the term “level of detail” in recognition of the fact that a graphically detailed element does not always correspond to a high level of actual project development.

In any case, LOD is structured on a scale where each level is assigned a standard nomenclature (which varies depending on the reference regulations) that defines the quantity and quality of the data entered in an architectural model.

In simple terms, LOD defines the content of a BIM project at different stages of its development and grows as the project progresses and enriches with details, evolving from a simple initial concept to a construction-ready model.

LOD consists of 2 elements:

• geometry or visual representation of a project – LOG (Level of Geometry);
• data attached to objects in the BIM model – LOI (Level of Information).

The attached data create intelligent objects and distinguish simple modeling of shapes and extrusions from BIM modeling.

Let’s see what LODs are defined by the American, Italian, and UK experiences.

From LOD 100 to 500: the American experience

The AIA (American Institute of Architects) has published an LOD framework for the AIA G202-2013 Building Information Modeling Protocol to suggest a standard framework representing the different development levels of each project element and to facilitate communication and data exchange among the various stakeholders involved.

The established development levels are:

• LOD 100 (symbolic representation) – is the elementary model of the project and is graphically represented with a symbol or another generic and schematic representation;
• LOD 200 (generic system) – the model element is graphically represented within the model as a generic object with approximate quantities, dimensions, shape, position, and orientation. Non-graphical information can also be linked to geometric elements;
• LOD 300 (specific system) – the model element is graphically represented within the model as a specific system, where the object has specific quantities, dimensions, shapes, positions, and orientations. More in-depth non-graphical information is linked to geometric elements compared to the previous level;
• LOD 400 (fabrication) – the model element is graphically represented within the model as a specific system, where the object has specific dimensions, shape, position, quantity, and orientation with additional details for its realization, assembly, or installation. More in-depth non-graphical information is linked to geometric elements compared to the previous level;
• LOD 500 (verified representation – as built) – the model element is a verified representation on-site in terms of dimensions, shape, position, quantity, and orientation. Definitive non-graphical information is linked to geometric elements.

LOD BIM UK

In the United Kingdom, the Construction Industry Council (CIC) first published a BIM protocol in 2013 in response to the government’s strategy and set the deadline for compliance with BIM level 2 for projects funded with public funds by 2016.

The CIC BIM protocol defines the responsibilities, limits, and outcomes of the project team members in key process stages corresponding to a specific “level of detail.”

The stages are essentially analogous to the American definitions, although numbered differently.

The UK definitions contained in PAS 1192 are as follows:

• LOD 1 (brief) – block model with performance requirements and site constraints;
• LOD 2 (concept) – conceptual or volumetric model including basic areas and volumes, orientation, and cost;
• LOD 3 (developed design) – generalized systems with approximate quantities, dimensions, shape, position, and orientation;
• LOD 4 (production) – technical design model with accurately modeled and coordinated elements that can be used to estimate costs and verify regulatory compliance;
• LOD 5 (installation) – model suitable for construction and assembly, with accurate requirements and specific components;
• LOD 6 (as constructed) – model with details describing how the asset was built and can be used in the management and maintenance phase;
• LOD 7 (in use) – asset information model to be used for maintenance operations and continuous monitoring.

LOD in USA, UK and in Italy

The evolution of LOD: LOIN

Usually, to avoid possible information deficiencies, professionals tend to exaggerate the amount of information to be communicated. In this way, they make the mistake of producing and sharing an excess of information that is often unnecessary.

To overcome this inconvenience, ISO 19650-1 introduces the concept of Level of Information Need or LOIN, effectively surpassing the LOD concept.

It is also important to rely on a tool that allows you to manage a certain complexity of operations like the so-called BIM management system, which I recommend trying to understand its enormous potential.

But now let’s go back to LOIN.

What is meant by LOIN?

The name itself denotes a change in perspective: the focus is no longer on the object’s characteristics but on the need for information that the object must contain to meet the professional’s requirement at that specific moment of the design.

The concept of LOIN starts from the awareness that the degree of detail of a model is not an absolute parameter but must be evaluated based on different conditions.

The concept of granularity in LOINs

The level of information need describes the granularity of exchanged information in terms of geometric, alphanumeric, and documentation information.

Let’s take an example.
If we were to prepare the project’s graphic documents to be delivered to the window manufacturer to place an order, it would be necessary to have a high level of detail on all the necessary information for this purpose (type of fixtures, presence of thresholds, type of mullions, void size, direction and type of door opening, etc.), while it would be completely unnecessary to delve into, with the same level of detail, for example, information related to the heating system, false ceilings, etc. This difference in the level of information detail within the same model is precisely called granularity.

In practice, the levels of information need indicate how many and what information must be included in each object based on:

• purpose (why?);
• deadlines (when?);
• actors involved (who?);
• organization in one or more breakdown structures (what?).

LOIN never specifies purposes, deadlines, actors, or breakdown structure because the same Level of Information Need can serve multiple purposes, actors, etc.: its placement within an overall framework will specify its uses.

The level of information need is given by the combination of 3 types of information:

• geometric, expressed using shape, size, dimension, and position;
• alphanumeric, expressed using characters, numbers, symbols, etc.;
• documentation, i.e., the set of documents related to a specified subject.