Level of development and information need

Without agreement, some teams model every bolt while others leave placeholders, and nobody can rely on the model. Specifying the required detail per element and stage makes the model fit for its purpose.

The widely used Level of Development scale (from the BIMForum LOD Specification) describes how far an element has been developed and how reliable it is:

• LOD 100 — conceptual; a symbol or mass indicating something exists.

• LOD 200 — generic element with approximate size and location.

• LOD 300 — specific element with accurate size, shape, location and orientation.

• LOD 350 — adds interfaces with other elements (connections, supports).

• LOD 400 — fabrication detail.

• LOD 500 — field-verified (as-built), though often treated separately.

The key idea: LOD is about how much others can rely on the element, not how pretty it is.

Many frameworks split geometry (LOG, or geometric detail) from information (LOI — the data attached). A pump may be a simple box (low geometry) with complete manufacturer, capacity and maintenance data (high information). Specify both.

ISO 19650 and ISO 7817-1 replace fixed LOD tables with the idea of Level of Information Need: for each purpose, milestone and object, define the geometry, alphanumeric data and documentation actually needed. It's the same principle — only produce what's needed — made explicit per requirement.