What is LOD and what is its function for BIM?

August 4, 2022
UncategorizedNo Comments

THE data are a fundamental part of BIM design, but it is not always necessary to insert all types of information into a model. Let's see what is the LOD, the Level of Development, and what is its use in the world of BIM.

What is LOD?

The LOD, in English Level of Definition and Level of Development for Americans, in Italian translates as level of definition or detail.

To resume the definition included in the UNI 11337-4 regulation, the LOD is the level of detail and stability of the data and information of the digital objects that make up the models.

It consists of a ladder divided into levels which define the quality and quantity of data entered into a BIM model and is made up of:

  • LOG, Level of Geometry, or the geometry of the project;
  • YOU, Level of Information, or the data inserted into BIM objects.

Why is it needed in BIM?

It is often thought that in the BIM model it is necessary to insert as much information as possible and render all objects at the highest level of detail.

This it's not always true, in fact it depends on theuse that must be made of the model, and in most cases can lead to numerous disadvantages:

  • Not all information, especially in the initial phase of the project, is always easy to find and this may compromise data quality;
  • An excessive level of detail makes the heavy model both at software and hardware level;
  • Becomes difficult to find the necessary information inside the model;
  • There is a higher risk of errors, having a lot of data can become misleading for the project;

This is precisely why the LOD in BIM methodology it has become necessary, for define the level of detail needed in the model at a specific design stage without having to enter excessive data.

Furthermore, LOD is also used in BIM at a contractual level, For regulate the level of detail of the informationof the model and the graphic rendering and information of the BIM objects.

LOD in BIM in Italy and in the world

In every country The LOD is structured differently depending on the regulations, but the scales are generally aligned with each other, as in the case of the American and Italian scales.

In the USA a is used ascending numerical scale, which goes from LOD 100, with basic geometric information, at LOD 500, which indicates an As Build model.   

In Italy instead a is used letter system, which goes from LODGE A, equivalent of LOD 100, up to LOD F, equivalent of LOD 500, and LOD G, which indicates that the object has been updated since As Build.

The LOIN, the next step after the LOD

We have seen how LOD in BIM has become necessary for avoid inserting too much information into the template.

To further address this problem, ISO 19650-1 introduces the LONG, The Level of Information Need, which goes beyond the concept of LOD.

The Level of information need consider the amount of information necessary in a model variable depending on the design phase. For this reason it is no longer based on the qualities of the object, but on what information it must contain for a specific design phase.

It is composed of documentation And geometric and alphanumeric information, combined together based on:

  • Purpose of the model;
  • Team members involved in the design;
  • Activities to be carried out in the project;
  • Deadlines.