LiDAR, photogrammetry and models

Digital Twin and 3D Modelling

A digital twin, as NDTScan uses the term, is a measurable 3D model of a structure with the survey findings placed on it, so an engineer can see where the reinforcement is, where the cover is low, where the steel is thin and where the cracks are, in the geometry of the real building rather than on a flat drawing. It is a way of recording and using survey data, not a product on its own.

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  • Level 4 UKCSS Operator
  • Interpreted and reported for engineers
  • Oxford based, UK and Europe
Faro laser scanner being set up by an NDTScan operative

How the model is captured

  • Walk-through LiDAR. The Faro Orbis with SLAM records a building, a plant or a tunnel as a point cloud while the operator walks it, without targets or set-ups.
  • Aerial photogrammetry and LiDAR. The DJI Matrice 400 records roofs, facades, estates and earthworks from the air. See drone-based aerial surveying.
  • Interior capture. Matterport for navigable interiors where a visual record matters more than millimetres.
  • Underwater. Sonar and ROV imagery placed on the model for the parts of a structure below the waterline.
Faro laser scanner being set up on site
A laser scanner being set up. The point cloud becomes the drawing the scan findings are placed on.

What it is for

  • Placing findings in context. Reinforcement, tendons, voids, low cover, thin steel and cracks drawn onto the geometry of the structure, so the next engineer, the contractor or the insurer sees the same picture.
  • Measuring change. A repeat capture on the same route shows deflection, settlement, loss of section and crack growth between visits.
  • Planning work. Clash checks for new services and plant against the reinforcement and ducts the scan found; quantities and access for a repair.
  • Records. A navigable, measurable record of an estate for asset management, in formats that open in CAD, BIM and GIS software.

Accuracy, stated

A SLAM point cloud and a photogrammetric model each carry a tolerance, which depends on the capture, the control used and the surface; it is given in the report for every model NDTScan delivers. Where millimetres matter, a control survey with a total station is the right instrument and NDTScan says so. A model also records surfaces only: what is inside the concrete comes from the scan, not the scanner.

What the engineer receives

The point cloud or mesh in the agreed format, the survey findings placed on it and referenced to the element numbering used in the report, orthographic elevations and plans cut from the model where drawings are wanted, and the capture method, control and tolerance recorded. The interpreted report follows within an agreed number of working days. The equipment is described on the equipment page and under digital twin and 3D modelling equipment; NDTScan attends from Oxford anywhere in the UK, usually within one to two working days and same day where the diary allows.

Can the scan data be shown on the model?

Yes. That is the point of capturing the model: reinforcement, cover, thickness and defects are placed on the geometry so they can be found again on site.

How reliable is it?

To a stated tolerance, given in the report for each model. Where millimetres matter, a control survey is specified instead.

Questions we are asked

Is a digital twin the same as a BIM model?

No. BIM is a designed model of what a building should be; a twin from a survey is a measured record of what it is, which can be brought into BIM software and compared with the design.

Tell us about the structure.

A postcode, the element in question and what you need to do to it is enough to start. Every survey is quoted on the structure, the access and the reporting required.

Book a survey01865 704407