It is not LOD, It is LO"daic"



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March 18, 2015

Unfortunately, Levels of Development have frequently been defined largely by reference to level of detail (e.g., the BIM Forum LOD Specification). However, this can be a deceptive measure as a very detailed object can be placed into the model, but it may be the wrong object or the wrong size.

Level of Development as a concept is the sum of different aspects (daic) that define the information and geometry of each element, including:

Level of detail (LOd): 

Defines the level of geometric precision relative to the real object. For example, a highly detailed model of a chair may be considered to have a high level of detail.

Level of accuracy (LOa):

An object may be highly detailed, but it may be the wrong size, finalizing a choice of construction or product as part of the design and, therefore, model development. A highly detailed air conditioning unit could be placed in the model at an early stage; it could represent the approximate likely footprint of the final air conditioning unit, but the same capacity unit could perhaps differ in size by 100mm or more. It is only once a final product selection is made that the accuracy of the object is determined. The issue of tolerances needs to be considered as part of this concept. A plasterboard wall will never be built to the same level of tolerance as a factory assembled piece of laboratory equipment. If this is the case, this should be taken into account in the model. There is little point coordinating something to the nearest millimeter if construction techniques mean it can’t be built this way.

Level of information (LOi):

Also referred to as level of data. In order to achieve true BIM and allow for use in 4D and Facilities Management, LOD needs to define what information is to be supplied with each element. This information could also relate to costing information at the beginning of the design, or engineering information for further analysis.

Level of coordination (LOc):

Is not defined as part of the element LOD but refers to the level of coordination with other model elements. A highly detailed door could be placed in an “architectural wall”; the door could contain the correct information for a specific LOD, but it might not be coordinated with the structural opening in the “structural wall”.

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