Capturing one of the world's longest tunnels
Author: Monica Miller Rodgers
When the Gotthard Base Tunnel officially opens in June 2016 as part of the New Rail Link through the Alps (NRLA), a construction project 20 plus years in the making at 9.8 billion Swiss francs will be one of the world’s longest and deepest railway tunnels. At 57 kilometres long and with a rock overburden of 2,300 metres, the tunnel increases the total transport capacity across the Swiss Alps while reducing passenger travel time between northern and southern Europe by one hour. With minimal gradient and wide curves, the route is also a flatter, lower-level journey at only 550m above sea level. The whole tunnel system measures a total of 152 km, plus almost 50 km of new built outdoor tracks.
When Grunder Ingenieure AG, a leading Swiss engineering firm specialising in rail surveys and long-time user of Leica Geosystems solutions, was sub-contracted by the Alptransit Gotthard AG, the firm knew it would be a challenging task but one for the history books. One of the main tasks, before the tracks open for the test operation, was to capture all the infrastructure of the tunnel for as-built documentation.
“There are several stakeholders working on the overall project, and we were tasked with registering the entire infrastructure to collect for the infrastructure database of the Swiss Federal Railways. All these users can now access this information,” said Gilbert Roulier, Grunder’s director of Imaging, Laser Scanning and Mobile Mapping. “Entering the underconstruction tunnel and outdoor tracks also presented organising challenges that we needed to account for with our engineers and surveying instruments.”
The firm selected the Leica Pegasus:Two to safely and efficiently capture the entire infrastructure of the newly-built open tracks. In combination with Leica Geosystems total stations, Grunder was able to provide a complete database of 3D imagery and point clouds covering the rails, signage, posts, electrical lines, and further installations and structural elements.
On the fast track
Facing a very short and divided up timeframe of only a few weeks, Roulier and his team knew they needed a fast and efficient method to capture all the available data. They found this in the Leica Pegasus:Two’s seven cameras providing full 360-degree dome imagery combined with the scans of the onboard LiDAR profiler.
Easily attaching the capture platform to the prototype of the firm’s specially-designed rail trolley, the engineers were able to quickly and effectively maneuver over the outdoor tracks to collect a few billion points. By constantly capturing data on the move without disrupting ongoing construction, safety increased for Grunder and other employees. No longer were the surveying engineers required to trapeze through a risk-filled construction site, and construction workers no longer needed to worry about avoiding surveyors or instruments set up in the midst of their site.
“This non-contact and kinematic measurement ability allows us to record everything without interruption, significantly decreasing risks," said Roulier. “This mobile method also reduces the effort, saving the entire project on costs and time, with benefit for all working stakeholders.”
With the complete 3D surround capture of the Leica Pegasus:Two’s images and point clouds, no critical information is forgotten, either. With only one pass, all important documentation is made. The need to return to site on multiple occasions for data collection is eliminated, saving vital resources.
Sensor merging for digital reality
With the combination of imaging and scanning data, all visual information is brought to reality. The Leica Pegasus:Two and reality capture solutions marry traditional surveying technology, such as positioning systems, laser scanning and radar imagining, into one convenient and easy-to-use platform. A complete and fluid workflow follows reality capture of calibration, post-processing, object extraction and GIS storage.
Enabling the engineers to work with the most accurate and current representation available, the open tracks were presented in 2D and 3D display for maximum manipulation capability. In the rail industry, working with highly realistic models translates into safer design, faster production and reduced costs.
“Being able to provide such a detailed dataset to the stakeholders enabled all interested parties to conduct their work swiftly and successfully,” said Martin Baumeler, Grunder’s managing director. “The Leica Pegasus:Two increases our business and ensures we provide quality deliverables to our customers.”