In short
- Scan to BIM = capture the building as a point cloud, then model it in BIM software against the points.
- Specify both LOD (how developed the elements are) and LOA (how accurate the geometry is).
- Pair them so the model never claims more than the scan: LOD 300 with LOA30, LOD 400 with LOA40.
- It pays most where prefabricated parts must fit first time: busbar, pipework, CDUs, facade brackets.
What scan to BIM is
A laser scanner measures millions of points per second, each with a position and often a colour. Many scans registered together form a point cloud of the space. Modellers then trace walls, floors, steel, ducts, pipes, cable trays and equipment in BIM software, using the cloud as the reference. The result is an as-built model, usually far more reliable than old drawings.
Six steps
- Brief: purpose, extent, LOA and LOD, deliverables, coordinate system.
- Control: a survey control network, usually with a total station, so scans tie to the project grid.
- Capture: terrestrial scanner, SLAM mobile scanner or drone, depending on accuracy and area.
- Registration: scans joined into one cloud, checked against control; residuals reported.
- Modelling: elements built to the agreed LOD from the cloud.
- QA: model-to-cloud deviation checks prove the represented accuracy.
LOD and LOA, together
| LOD | Meaning | Pair with |
|---|---|---|
| 100 Concept | Massing and zones | Any LOA |
| 200 Approximate | Generic elements, approximate size | LOA10–20 |
| 300 Precise | Specific elements, measured size and position | LOA30 |
| 350 Coordinated | Interfaces and connections for clash checks | LOA30–40 |
| 400 Fabrication | Enough detail to fabricate and install | LOA40 |
LOD definitions follow the BIMForum LOD Specification 2025; the LOA pairings are a recommendation, not part of either specification. Accuracy levels are explained in the LOA guide.
What to put in a scan to BIM brief
- Purpose: retrofit design, prefabrication, facility management, digital twin.
- Extent: rooms, floors, voids above ceilings and below raised floors, roofs, facades.
- Accuracy: measured LOA for the survey and represented LOA for the model, separately.
- Model content: LOD per discipline and the element list (what is and is not modelled).
- Deliverables: registered cloud format, model format and version, registration report, deviation report.
- Access: operating constraints, security, working hours and escorts in live areas.
Where it pays
| Sector | Use | Why it matters |
|---|---|---|
| Data center | As-built before retrofit | Liquid cooling, CDUs and pipework drawn against what is really there |
| Data center | Busbar and tray routes | Clash checks before prefabricated lengths are ordered |
| Data center | Capacity planning | Rack positions, clearances and floor voids for the digital twin |
| Facade | Bracket and anchor survey | Structure deviation known before fabrication |
| Facade | Panel-by-panel geometry | Unitised panels made to measured openings |
| Facade | Flatness and plumb | Evidence for tolerance claims and handover |
Questions about scan to BIM
How long does scan to BIM take?
Capture is often a day or two for a data hall; registration and modelling take longer, typically several times the field time, depending on LOD and the number of elements.
Which software is used?
Registration in the scanner maker's or a third-party registration tool; modelling in the project's BIM platform, often with point-cloud plug-ins for pipes, steel and ducts.
Can everything be modelled from a scan?
Only what the scanner can see. Hidden services in walls, under floors or above ceilings need access, extra scans or other records.
Is the model as accurate as the scan?
Not automatically. Modelling adds its own error; that is why represented accuracy is specified and checked separately.
Sources
- USIBD Level of Accuracy specification v3.0 (v3.1 current).
- BIMForum LOD Specification 2025.
- LOD–LOA pairings are a recommendation from this site.