Scan to BIM: A Practical Guide to Laser Scanning for As-Built Models
Laser scanning gives you a millimeter-accurate picture of existing conditions. Converting that point cloud into a usable BIM model is where most projects get it wrong. Here's the right way to do scan to BIM.
Scan to BIM is the process of using laser scanning technology to capture existing conditions and converting that data into an accurate BIM model. It is essential for renovation, retrofit, and historic preservation projects and increasingly common on new construction for QA/QC and as-built documentation.
How Laser Scanning Works
A terrestrial laser scanner (like a Leica RTC360 or Faro Focus) emits millions of laser pulses per second. Each pulse bounces off a surface and returns to the scanner, recording the precise x, y, z coordinates of that point. After scanning a space from multiple positions, you have a point cloud a dense three-dimensional map of every visible surface.
Modern scanners like the Leica RTC360 capture full 360° scans in approximately 2 minutes with 1 mm positional accuracy at 10 m range. The resulting point clouds can be hundreds of gigabytes for a large building.
The point cloud is not the deliverable the model is. Laser scanning is only the first step. What you do with the data how you model it, to what LOD, and with what QA/QC process determines whether the scan to BIM was worth doing.
The Scan to BIM Process: Step by Step
- 1Scan Planning Determine scanner positions to achieve full coverage with minimal shadowing. For a typical floor plate, 4–8 positions. Complex areas (mechanical rooms, congested corridors) need more.
- 2Registration Individual scan positions are combined into a unified coordinate system using ReCap Pro. Reference targets placed between scans ensure accurate alignment.
- 3Model Creation The registered point cloud is loaded into Revit as a background reference. Modelers trace walls, structure, MEP systems, and other elements against the point cloud.
- 4QA/QC The finished model is compared against the point cloud. Deviation analysis identifies where the model diverges from reality. Acceptable tolerances: ±3/8" structural, ±1/2" MEP.
Choosing the Right LOD
This is the question most scan to BIM projects get wrong. More detail is not always better it is more expensive and produces data nobody uses.
- LOD 200 Walls, floors, ceilings, structural members. Sufficient for early design planning and area calculations.
- LOD 300 Detailed structural, architectural, and major MEP elements. Required for renovation design and coordination.
- LOD 400 Fabrication-level detail. Required when existing conditions interface directly with new prefabricated components.
Define the required LOD for each building system before scanning begins. It determines how many scan positions you need, how long modeling takes, and how much you spend. A LOD matrix in the project BEP prevents scope creep and ensures the model is fit for purpose.
Common Scan to BIM Mistakes
Scanning without a modeling scope. Define what gets modeled before the scan crew arrives. If you scan everything but only model walls and ceilings, you paid for data you will never use. If you scan sparsely and then need MEP at LOD 350, you are scanning again.
Under-scanning complex areas. Mechanical rooms, pipe chases, and congested corridors need dense scanning coverage from multiple positions. Shadowed areas where the scanner could not see become gaps in the model that force assumptions, not measurements.
Scan to BIM on Active Healthcare Projects
EZ-VDC has executed scan to BIM on multiple hospital projects, including two active healthcare facilities where accurate as-built documentation was critical for coordinating new MEP systems with existing structure without disrupting operations.
On these projects, the scan to BIM process enabled the coordination team to model existing conditions to LOD 350, identify clearance conflicts before new MEP was designed, and provide the field team with a reliable reference model that replaced guesswork with measured data.
Stanford MS · Published Autodesk Marketplace Developer
Stanford-trained civil engineer with over a decade leading VDC on projects from $30M to $1.5B across healthcare, pharma, hospitality, and infrastructure.
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