Scan-to-BIM Workflow

How We Transform Laser Scan Data into Accurate As-Existing BIM Models

A successful BIM model begins with a robust, traceable and repeatable workflow. At Tower Surveys 3D Modelling, our Scan-to-BIM process has been developed through years of experience across buildings, industrial environments, heritage structures, churches, colleges and production plants.

This page explains each stage of our workflow — from initial project briefing through to final delivery — giving clients complete transparency across the entire process.

Why Our Workflow Matters

The accuracy and reliability of a BIM model are dictated by the quality of the survey, the consistency of the scanning methodology, the precision of point cloud processing and the skill of the modelling team.

Our workflow ensures:

Consistent, repeatable outputs
Accurate and complete point cloud coverage
Documented modelling assumptions
Verified geometry before issue
Smooth integration with design and coordination tools
Reduced risk, cost and rework for your project

Whether you require an early-stage LOD2 model or a highly detailed LOD4 deliverable, this workflow provides the foundation for exceptional results.

1. Project Briefing & Requirements Capture

Every project begins with a detailed discussion to understand:

The purpose of the model (design, refurbishment, planning, coordination, asset management)
Required Levels of Detail (LOD2, LOD3 or LOD4)
Required Levels of Information
Areas and disciplines to be surveyed
File formats and software requirements
Coordinate system preferences
Access constraints and site conditions

We gather all available existing information (drawings, previous surveys, BIM models, specifications) to ensure a clear and well-defined scope.

This allows us to provide an accurate quotation and prevents over-modelling, scope creep or misaligned expectations.

2. Site Survey & Laser Scanning

Once the scope is agreed, our surveyors attend site to capture the physical environment using high-accuracy terrestrial laser scanners.

Scanning includes:

External elevations
Internal rooms and circulation spaces
Roof structures (where accessible)
MEP plant areas (if required)
Production spaces
Heritage features
Surrounding context (if required)

Line-of-sight approach

Our scan plan ensures maximum coverage by positioning scanners at strategic vantage points throughout the building or site.

High-density scanning

We typically target:

6 mm at 10 m for buildings
3 mm at 5–10 m for fine architectural detail
Higher density scanning for ornate or heritage work

The goal is to create a complete, measurable representation of the environment.

3. Underground Services (Utility Survey Integration & 3D Modelling)

Where projects require an understanding of buried or concealed utilities, Tower Surveys 3D Modelling can integrate underground services data into the Scan-to-BIM workflow through our close collaboration with Tower Surveys Utilities.

Tower Surveys Utilities undertake specialist utility detection and mapping using a combination of electromagnetic locating, ground penetrating radar (GPR), and complementary survey techniques to accurately identify and record underground services. Once captured, this data is structured and delivered in a format suitable for BIM integration.

How Underground Services Are Incorporated into BIM

Where underground services are required as part of the project scope, our process typically follows these stages:

1. Utility Survey Capture (Tower Surveys Utilities)
  1. Detection and mapping of underground services using industry-recognised survey methods.
  2. Classification of service types (e.g. electricity, gas, water, telecommunications, drainage).
  3. Positioning of services in relation to above-ground features and survey control.
2. Data Preparation & Coordination
  1. Conversion of utility survey outputs into structured 3D data.
  2. Alignment to the agreed project coordinate system (OS grid, local grid, or client datum).
  3. Verification of spatial relationships between above-ground scan data and underground utilities.
3. 3D Modelling of Underground Services (Tower Surveys 3D Modelling)
  1. Creation of 3D Revit elements representing underground services where required by the project brief.
  2. Modelling of services in a clear, coordinated manner that supports design, clash detection and risk management.
  3. Differentiation between detected services, inferred routes, and areas of uncertainty.

Typical Deliverables

Where included in scope, underground services information can be provided as:

3D Revit elements representing key buried services
Coordinated overlays with above-ground Scan-to-BIM models
Export formats such as IFC or DWG for multi-disciplinary use
Clearly documented assumptions, limitations and areas of uncertainty
Layered utility data aligned with the point cloud and BIM environment

Accuracy, Limitations & Risk

As with all underground surveys, there are inherent limitations due to access, ground conditions and service depth. Our approach ensures:

All detected services are clearly documented and traceable to the original utility survey.
Areas where services could not be confidently identified are explicitly noted.
Distinction between confirmed, probable and inferred services is maintained within the model.

This transparent approach supports safer design decision-making and reduces risk during construction or excavation.

When Underground Services Are Recommended

Including underground services within the BIM model is particularly beneficial for:

Refurbishment and redevelopment projects
Site logistics and temporary works planning
Infrastructure and civils coordination
Excavation, groundworks or new foundations
Clash detection between proposed works and existing utilities

Where underground services are required, we can coordinate directly with Tower Surveys Utilities to define an appropriate survey methodology and BIM integration strategy at project outset.

4. Registration & Point Cloud Processing

Once scanning is complete, all raw scan data is registered into a unified, accurate point cloud dataset.

Our process includes:

Target-based registration: Using reflective or spherical targets to align individual scans.

Cloud-to-cloud registration: Aligning overlapping scans where 30%+ shared geometry is available.

Hybrid registration: Combining the above methods to maximise accuracy.

Cleaning & optimisation

Removing stray points and noise
Refining accuracy
Verifying registration error tolerances
Applying RGB colour (if required)
Aligning to OS grid or client-specific coordinate systems

A well-registered point cloud forms the absolute foundation of the BIM model’s accuracy.

5. Model Setup in Autodesk Revit

Before modelling begins, our BIM team prepares the Revit environment:

Importing the registered point cloud
Establishing project templates
Setting shared coordinates
Preparing levels and grids
Defining modelling standards and naming conventions
Reviewing LOD requirements for each discipline

This ensures consistency across all models and disciplines (Architecture, Structure, MEP, External Works).

For large or complex sites, the model may be split into separate Revit files for usability.

6. As-Existing BIM Modelling

Our experienced team builds the BIM model directly from the point cloud, following strict internal standards aligned with BS 1192, PAS 1192-2 and AEC (UK) protocols.

What We Model (Depending on LOD):

Architectural

Walls, floors, roofs
Openings (windows, doors, rooflights)
Stairs, ramps, balustrades
Ceilings, soffits, internal partitions
External façade detail (LOD4)

Structural

Columns, beams, slabs
Roof structure
Bracing
Foundations (if visible)

MEP (where required)

Ducts, pipes and trays above 100mm (LOD3+)
Plant equipment
Fixtures (toilets, basins, radiators)
Major mechanical or industrial equipment

For heritage, industrial or technical environments, we apply specialised modelling methodologies to ensure both clarity and accuracy.

Full list available here

Modelling Tolerances

Typical tolerances achieved are:

LOD3: ±30 mm
LOD4: ±15 mm

All tolerances are agreed before modelling begins.

7. Quality Assurance & Model Verification

Before issue, each model undergoes a structured QA process:

Visual comparison against the point cloud
Clash and alignment checks
LOD compliance review
Family integrity checks
Naming convention compliance
Workset and template consistency
Accuracy verification

This multi-stage process ensures the delivered model meets the agreed specification, BIM modelling standards and industry best practice.

8. Delivery of BIM Outputs

Once QA is complete, we provide:

Primary Deliverables

Revit model (.RVT)
Registered point clouds (RCS/RCP)
TruView / 360° imagery

Optional Deliverables

2D drawings (plans, sections, elevations)
IFC exports
DWG exports
Schedules
Meta-data enriched components
High-resolution orthophotos
Topographical data (if surveyed)

All files can be delivered via SharePoint, email (where feasible) or secure download.

Why Our Workflow Outperforms Others

Clients choose Tower Surveys 3D Modelling because our workflow ensures:

High repeatability
Fully auditable processes
Accurate, scalable models
Fast delivery
Professional standards
Transparent documentation
Reliable integration with design tools

This workflow reduces project risk and provides a dependable foundation for design, planning, refurbishment or asset management.

Return to the full Scan-to-BIM Survey Specification

Need a Quote or Have a Project to Discuss?

We provide rapid quotations and can advise on scope, deliverables, LOD levels and expected workflows.
Contact us today to discuss your Scan-to-BIM requirements.