Laser scan of Forth Rail Bridge
Marking three centuries of Scottish engineering triumphs, Renishaw was invited by the Centre for Digital Documentation and Visualisation (CDDV), a collaboration between Historic Scotland and The Glasgow School of Art's Digital Design Studio, to carry out the first mobile laser scanning of the Firth of Forth Rail Bridge and the Forth Road Bridge.
Having already completed surveying for Historic Scotland, Renishaw was tasked with conducting a survey of a section of each bridge that would be used for modelling a vast range of deliverables and create a digital archive for future generations.
Armed with two decades of experience in 3D laser scanning, Renishaw was able to capture the bridge in fine detail and overcome several factors such as tidal patterns, heavy traffic on the riverway and poor Global Navigation Satellite System coverage essential for laser scanning and positioning.
The Renishaw team installed a Trimble MX2 single-head laser scanner on the front of a coastguard rescue boat and used the on-board GNSS-aided inertial navigation system to guide the position and orientation of the scanner. The single head unit provides a better lateral range for marine applications than dual head scanners and was used for further scanning alongside the bridges and underneath.
Lead operator, Jonathan Robinson explained: “The Firth of Forth Rail Bridge is over 2.5 km long and 156 m high. We planned to survey both from the river to capture engineering details from the bottom of the bridge, and from surrounding roads to acquire data on the top of the structures and along the riverbanks. Our experience in many challenging environments, and above all our expertise in pre-planning, are as essential as the system itself in enabling us to complete projects to time, even when there are many variable factors, which are impossible to predict.”
Laser scanners such as the Trimble MX2 and the Renishaw Dynascan range, capture data by firing a laser beam at a solid surface. The laser beam is reflected by the solid surface and bounces back to the scanner forming a data ‘point' which creates a ‘point cloud’. The collection of points can then be used by digital experts for 3D models, maps, flythroughs and operational resources.
The project took just two people, one day to complete and Renishaw’s post-processing team completed work in just three hours. CDDV had their results within 36 hours of the coastguard vessel setting sail.
“After considering various surveying technologies, we were confident that laser scanning offered the speed and accuracy we required, whilst minimising the disruption to road and river users,” CDDV's project manager, Dr Lyn Wilson commented. “Ultimately, the digital models of the bridges that we will create will support a broad range of development and educational goals, including conservation and management, the development of engineering talent in Scotland and the promotion of the area and its rich industrial heritage across the world.”
Mark Reid, Renishaw's UK/RoW Sales Manager for Mapping Systems said: “Mobile laser scanning makes data easier and quicker than ever to acquire, but it is CDDV's ambitious plans for the modelling of this data to achieve their very worthwhile conservational and educational goals that make this project stand out for us. Accurate data enables better planning and decision-making, and that is exactly what CDDV understand. We look forward to working with them again in the future.”