Quality Assurance & Accuracy Verification Processes

Unlike design-stage BIM modelling, Scan-to-BIM requires geometry to reflect measured, real-world conditions.
If errors slip through:

• Design coordination becomes unreliable
• Fabrication drawings may not fit
• Structural assumptions become incorrect
• Contractors face delays and rework
• Costs increase
• Health & safety risks can arise

Our ISO-aligned QA framework and BIM Modelling Standards ensure that every delivered model is dependable and traceable.

Before modelling begins, we conduct verification on the raw and registered point cloud:

Registration Error Checks

• Reviewing RMS values
• Checking for misalignments between scans
• Ensuring acceptable overlap
• Confirming target-based accuracy where applicable
• Identifying dropped or misaligned scan stations

Coverage Review

We confirm that:

• All required areas have been scanned
• All rooms and corridors are represented
• External façades are complete
• Roof access is documented (if included)
• No major blind spots remain

Noise & Cleanliness Assessment

• Removing stray points
• Removing reflective artefacts
• Reducing excessive noise
• Identifying moving objects (people, vehicles, machinery)

This ensures the modelling team starts with a clean, accurate, trusted dataset.

Before any modelling occurs:

Template Consistency

We verify:

• Correct project template
• View templates
• Units, tolerances, and Revit settings
• Correct shared coordinate approach

Workset Structure (if required)

• Point cloud workset in place
• Architecture / Structure / MEP worksets correctly named
• Links and reference files assigned properly

LOD Review

We check the agreed LOD (2/3/4) is documented and achievable based on:

• Point cloud density
• Visibility of elements
• Client requirements

By validating these foundations early, we remove ambiguity and prevent rework later.

Our modellers and senior reviewers check work continuously throughout production.

Element Placement Verification

• Walls modelled to centreline or finish (as agreed)
• Openings aligned with measured extents
• Floors/slabs correctly aligned to point cloud elevations
• Roof slopes, ridges and parapets accurately represented

Family Use & Naming

• Revit-native families preferred
• No duplicated or unapproved families
• Correct category usage
• Correct family naming conventions applied

Consistency Checks

• Levels and grids consistently used
• Views managed with correct templates
• Model performance monitored (file size, warnings, speed)

This “live QA” ensures errors do not accumulate.

Once modelling is complete, a structured validation process begins.

Point Cloud Overlay Checks

This is the most important part of Scan-to-BIM QA.

A senior modeller or QA specialist reviews:

• Every elevation
• Major architectural elements
• Structural elements
• Openings (windows, doors, rooflights)
• Roof geometry
• Stairs and balustrades
• MEP features (if included)

The model is compared directly against the point cloud using:

• Section cuts
• Slices
• Elevation overlays
• 3D visual comparisons

Any deviation outside tolerance is flagged and corrected.

Accuracy Tolerances

Typical acceptance criteria:

• LOD3: Elements within 15–30 mm of point cloud
• LOD4: Elements within 0–15 mm

Items that cannot be confirmed (obscured areas) are tagged.

We verify compliance against:

BS 1192

• File naming
• Layer conventions
• Revision control
• Shared coordinate structure

PAS 1192-2

• Information requirements
• Clear purpose and suitability of the model
• CDE compatibility

AEC (UK) BIM Protocol

• Naming conventions
• View templates
• Family standards
• Object category compliance

This ensures our deliverables integrate easily with multidisciplinary teams.

A BIM model must be accurate and healthy.
We check:

Model Health

• No excessive warnings
• No broken constraints
• No orphaned elements
• No corrupt families
• Appropriate use of detail levels

Workset Hygiene

• All elements on correct worksets
• No misplaced or hidden geometry
• Linked files correctly positioned

View Management

• Only essential views retained
• View templates applied
• No redundant or duplicate views left behind

Good model hygiene improves performance and usability.

We check that the model’s geometry matches the agreed LOD, including:

LOD2

• Correct massing
• Basic geometry only
• Minimal detail

LOD3

• Full architectural detail
• Accurate openings
• Correct modelling of floors, ceilings and roofs
• Structural elements included if required

LOD4

• High detail for heritage and complex areas
• Detailed mouldings
• Accurate plant and mechanical fixtures
• Fabrication-level features (where included)

Any elements that exceed or fall short of the LOD are flagged.

Before issuing to the client, the model undergoes:

• Senior modeller review
• Team leader review (if complex or large-scale)
• Checklist verification
• Suitability stamp (S1/S2/S3 etc., where applicable)

Only once the model passes all checks is it formally approved for issue.

Clients receive:

QA-approved BIM model

• Clean, structured and verified deliverables
• Accurate to the agreed tolerance
• Delivered in RVT, IFC or DWG formats

Validated point cloud dataset

• RCS/RCP primary formats
• Optional E57, LAS, PTX

Supporting QA Documentation

• Notes on obscured areas
• Assumptions log
• Limitations
• Model disclaimers and LOD notes

TruView / 360° imagery for visual verification

This makes downstream design and coordination significantly more reliable.

Our QA methodology ensures:

• Accuracy you can measure and verify
• Better design coordination
• Reduced project risk
• Increased confidence in existing conditions
• Structured and transparent documentation
• Smooth integration with contractor and consultant workflows

Few BIM companies describe or share their QA process — doing so strengthens your authority and differentiates you from competitors.

Return to the full Scan-To-BIM Specification

Tel: 07731 747329
Tel: 07928 653296
Email: info@towersurveys3d.co.uk