Level of development (LOD)

A model always looks more finished than it is; LOD exists to say, element by element, how finished it actually is. The commonly used scale runs from conceptual placeholders through approximate and then accurately modelled geometry, on to fabrication-level detail and finally field-verified as-built representation, with each step defining what a consumer may legitimately do with the element — coordinate against it, quantify from it, fabricate from it. Project BIM plans assign target LODs per element type per stage, turning "model the design" into a specified deliverable.

The terminology itself forks, in fine glossary tradition: development versus detail — an element can be geometrically detailed yet unreliable — and various frameworks split geometry from information or restate the whole idea as the level of information need. The words differ; the underlying question is constant: what, exactly, can I trust here?

The failure is relying past the label — quantities taken off placeholder geometry, clearances checked against approximate shapes — usually because the label was in the BIM plan and the reliance happened in a hurry.