A Comparison of Scan to BIM Workflows: Photogrammetry or LIDAR?

Singapore has seen a rise in demand for Scan to BIM workflows among project owners. One reason is that Alteration & Addition (A&A) works above 5000sqm now require BIM submissions to the authorities.

Recreating existing assets in BIM can be prohibitively expensive. Fortunately, scanning has become a more cost-effective and time-efficient way to do so. Scan to BIM is now a preferred approach for capturing existing structures, systems, and conditions in a digital format.

Which Method Should I Choose: LiDAR or Photogrammetry?

Feature	LiDAR	Photogrammetry
Technology	Laser pulses to measure distances	Photos to reconstruct 3D models
Accuracy	High – ideal for detailed geometry	Moderate – image-dependent
Data Output	Point clouds (.e57, .laz, .ptx)	Meshes (.obj, .stl, .3mx) + textures
Environmental Conditions	Works in low light and cluttered environments	Requires good lighting
Cost	Higher – uses specialized scanners	Lower – uses standard cameras/drones
Processing Time	Faster collection, slower cleanup	Slower collection, faster mesh output
Use Cases	Infrastructure, topography, clash detection	Site context, architectural surveys, heritage scans
Vegetation Penetration	Can capture through foliage	Limited penetration

LiDAR generally produces higher accuracy point clouds. It’s better for modeling mechanical systems or verifying structural works. On the other hand, photogrammetry offers a lower-cost, fast turnaround option for creating presentation-ready mesh models or capturing large outdoor sites.

Why Do Engineering Firms Scan Their Existing Assets?

Common use cases for Scan to BIM include:

Capturing existing site conditions
Reconstructing missing design documentation
Verifying as-built models against design intent
Visualizing buildings in a digital twin platform

In most engineering workflows, LiDAR is preferred due to its precision. However, photogrammetry offers speed and affordability, especially when the goal is to visualize rather than measure.

An Overview of the Scan to BIM Workflow

Step 1: Define the Use Case

The business need drives the data capture method.

Precision & coordination? Go with LiDAR
Speed & presentation? Choose photogrammetry

Step 2: Data Capture

For facilities management or asset positioning, a control survey should be conducted. This geo-references the point cloud and ensures it aligns with GIS coordinates.

Sharing design drawings in advance helps surveyors plan:

Drone flight paths
Scan segmentation
Control point locations

This improves accuracy and prevents files from becoming too large to manage.

Step 3: Data Processing

The captured data is:

Registered to a coordinate system
Cleaned to remove noise
Modeled in BIM, especially for elements that cannot be scanned (e.g. concealed MEP)

Step 4: Review and Insights

The point cloud is overlaid on the design BIM for:

Clash detection
Deviation analysis
As-built validation

The final BIM deliverable is typically LOD 300, but clients can request 5D/6D/7D attributes for advanced workflows.

Visualizing Assets with Mesh Models

Mesh models may not offer perfect edge definition, but they’re effective for:

Stakeholder presentations
Contextual site reviews
Web-based visualizations

They can be integrated with BIM and opened using free viewers.

Permitting Considerations for Drone Scans

Some sites in Singapore, like Jurong Island, have restricted airspace. Before flying drones:

Check for weekday flight caps (e.g. 60m ceiling)
Maintain 15m minimum clearance from tallest structures
Seek special permits or clearances

Weekend flights may offer greater flexibility, but always confirm regulations with local authorities before planning a drone survey.

🧠 Conclusion

Scan to BIM is becoming a standard delivery method in the AEC industry due to its efficiency, accuracy, and cost savings.

Use LiDAR for engineering precision
Use photogrammetry for quick visual captures

Each method has its strengths. Choosing the right one depends on your project’s scope, regulatory requirements, and intended use of the model.

Frequently Asked Questions

Question	Answer
Which is cheaper, drone or terrestrial scanning	Drones are a more cost-effective option when the area to be scanned is large
How can I view the final point cloud?	Bentley Viewer is a free software you can use to view point clouds.
How long does it take to generate the final point-cloud	1–3 working days
Can we get structural dimensions from the Point Cloud	Yes
What is the difference between a point cloud and a mesh model	A mesh model is a 3D representation of an object made up of interconnected polygons, while a point cloud is a collection of individual points that represent the surface of an object or environment.
When should I use a mesh model over a point cloud?	For Scan-to-BIM, simulations, inspections, and surveying use-cases, a mesh model is preferred. Visually, the 3D textures generated by a mesh model are more appealing and load faster in software due to smaller file sizes. For precision tasks, terrestrial LiDAR is recommended.