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Liverpool Central Station roof inspection - Keith Wakeley - H&W Surveying and Consulting Ltd

Good Monday everyone!

Let’s start the week with a roof inspection of a site in central Liverpool, in Northern England:

You can measure and inspect the roof on Pix4D Cloud:

To visualize the model in VR you can go to Sketchfab:

Keith Wakeley, Director of H&W Surveying and Consulting Ltd. answered our questions about this project:

What was the goal of the project?

Our client - Malcolm Hughes Land Surveyors - are engaged on a long-term project providing terrestrial scan data for detailed 3D modeling of the site as part of ongoing redevelopment works.  Due to there being no safe access to the roof areas they called on H&W Surveying and Consulting Ltd to provide accurate 3D point cloud data of the roof to support existing scan data. we were able to quickly and safely capture the data required, providing both point cloud outputs together with high-resolution aerial images of the site to aid with the production of the 3D CAD drawings.

This project was flown on a double grid, with a 65-degree camera angle at 80/80 overlap at circa 15m above the roof level giving an average GSD of 6.2mm. 12 GCP’s were used over the site derived from existing Survey Control stations and reference features taken from the previous completed topographical survey. Flown in three flights due to the shape of the site and surrounding building constraints.

How do you use photogrammetry in your business?

At H&W Surveying and Consulting Ltd, we provide a range of photogrammetry services to our clients from detailed point cloud capture of roof structures to support terrestrial scanning projects, detailed building facade inspection and mapping providing high resolution to scale orthomosaics, large area mapping using our fixed wing assets through to stockpile volumetric surveys.

What is the role of drone mapping in your workflow?

Using drones allows us to quickly and safely capture the data we require to support our client’s requirements. We fly both rotary and fixed-wing aircraft, allowing us to undertake a range of projects from small confined site inspection with our smaller aircraft through to large area mapping with our fixed wing resources.

We use Pix4Dcapture for the majority of our rotary mission planning and capture and we use eMotion 3 for mission planning our fixed wing projects.

Why did you choose Pix4D?

Pix4Dmapper provides us with a powerful, reliable software platform that delivers the flexibility and the results we require. Accuracy is key to the work we undertake, the detail of the quality report allowing accuracy to be verified together with the flexibility of the workflow allows us to generate the quality of results we require. We are Pix4D Certified users.

Technical details:

  • Device used: DJI Phantom 4 Pro

  • Flight-planning app: Pix4Dcapture

  • Image capture strategy: Double grid, 65° camera angle, 80/80 overlap, ≅15m above the roof level.

  • Number of images: 613

  • Photogrammetry software: Pix4Dmapper

  • Platform used: Desktop

  • Specs: Intel Xeon CPU E5-2623 v4 @ 2.60Ghz, 30GB RAM, NVIDIA Quadro P5000 GPU

  • GCPs: The project had 12 GCPs, no further MTPs were required on this occasion.

Enjoy your virtual visit, feel free to ask questions, share comments and your own projects.

Pix4D team

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