Technology

New generation 3D scanner accelerates scan-to-BIM

4 December 2014 | By Stephen Cousins

A cutting-edge mobile laser scanner has been used to scan a redevelopment project in central London in just 40 minutes, compared to five days using a traditional static system, according to surveying company Severn Partnership.

The trial project, to scan a block of buildings in Lambeth earmarked for redevelopment, was set up to compare the accuracy and productivity of the new Pegasus:Two mobile mapping system, manufactured by Leica Geosystems, with data previously recorded using a static laser scanner.

The Pegasus:Two is a vehicle-mounted scanner, similar to the one used to create images in Google Street View, capable of scanning one million points per second with a 120 metre range and up to 5mm accuracy, enabling the rapid collection of accurate data.

Severn Partnerships is currently the only firm in the UK and one of just two firms in the world to own the innovative device.

Rollo Rigby, associate director at Severn Partnership, told BIM+: “The system was incredibly fast, which was a benefit because the owner wanted to keep the works inconspicuous, and the level of accuracy was also comparable, managing to achieve 20mmaccuracy compared to 10mm using a static scanner.”

Rigby explained that scanning technology means that although the data precision of 1mm at 20m is achievable, accuracy is related to the trajectory of the instrument. "Think of it as though we can measure the height of the building to 1mm, but we only know where the building is in space to 20mm."

Pegasus:Two can achieve this level of accuracy by using an integrated rapid collector Z&F Profiler Scanner, seven cameras, a twin GPS system, and an inertial navigation system.

Severn Partnership claims the product will revolutionise the mobile mapping process, allowing the capture of calibrated imagery and point cloud data simultaneously, making for higher accuracy and faster data collection.

Data is gathered in a similar way to Google Street View. The device is attached to the roof of a car, or other vehicle, seven cameras capture a full 360-degree dome image every two metres, while a LIDAR scanner records cross section data every 2mm that can be built up into a 3D  image.

“This is the most portable unit of its kind,” says Rigby. “Where most systems are linked permanently to one vehicle, this can be attached to any car with a roof rack. It is easily man handled by two people on or off a vehicle. The other main benefit is safety – with surveyors  spending less time on site, and inside a vehicle, not by the carriageway.”

The same system was used in another trial by the firm to mobile map the highways around Shrewsbury town centre, and it is about to be deployed on its first live project, to scan stretches of road in Bettenfeld, Germany, to create 3D models for driver training simulators.

In addition, Severn is thought to be close to winning a job using Pegasus:Two to scan 30-40 miles of railway line in Bradford, using the data to create a Level 2 BIM model for use by the rail operator.

Rigby said: “With just a couple of hours working window at night to map the railway, the new system is instantly worthwhile and should speed up the process dramatically.”

Mark Combes, managing director at Severn Partnership, said: “Pegasus:Two is probably the most accurate mobile mapping unit on the market and does not need survey ground control installed ahead of it. We will be transferring it between mobile vehicles, cars, vans, rail roaders,  trolleys, and other vehicles to scan data across all number of terrains.”

This is the most portable unit of its kind. Where most systems are linked permanently to one vehicle, this can be attached to any car with a roof rack. It is easily man handled by two people on or off a vehicle. – Rollo Rigby, Severn Partnership