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Is handheld lidar accuracy enough for construction survey?

Posted by Sean Higgins on 8/23/19, 2:41 PM

Earlier this year, UK-based general contractor nmcn tested a PX-80 against a tripod-based lidar scanner. The main objective: Determining whether the handheld lidar scanner was accurate enough for site documentation.

You might expect them to answer this question by scanning a site once with the tripod-based lidar scanner, and once with the PX-80 handheld lidar, and then comparing the two point clouds.

However, nmcn's head of digital transformation Gary Ross argues that comparing raw data couldn't tell them whether the handheld laser scanner was accurate enough for their needs in real-world use cases. That's because nmcn doesn't use the raw point cloud as a final deliverable for any of its projects—the company uses it as a transitional step while generating a final deliverable like a 3D CAD model.

Ross argues that if you're going to test whether a scanner is accurate enough, you have to do it by quantifying the accuracy of the final deliverable you generate from the scan, and not the scan itself.

That's why nmcn scanned the site once with a PX-80, and once with a tripod-based lidar scanner, and then converted each set of raw data to a 3D CAD model for a comparison. This enabled them to determine how the handheld SLAM-based scanner stacked up against the static scanner in their real-world workflow.

The results? When comparing the final deliverables, nmcn found that there was negligible difference between the 3D models generated by the two 3D laser scanners. The actual difference in accuracy was only +/- 0.06% across the 57 meter site. That means nmcn gained the time and cost savings of handheld lidar scanning, but without any tradeoff in the quality of the company's work.

nmcn determined that the handheld lidar scanner produced point clouds that are accurate enough for these tasks:

  • Greenfield topology
  • Refurb as-is records
  • As-built records
  • Progress monitoring
  • Billing evidence
  • Dilapidation monitoring
  • Logistics/ traffic management
  • Incident records
  • Site diary

Click through to our resource portal to read the full case study, which includes hard numbers, images, and a cost-savings analysis that compares the expense of using PX-80 in-house vs contracting out to a team of service providers.

Once you're done with that, check out some of our other quantitative comparisons, technology beginner's guides, and step-by-step case studies for PX-80 applications ranging from 2D floor-plan generation to forest inventory.

 

The cover of nmcn's PX-80 case study

 

Topics: construction, Accuracy, Case Study