Tunnel Business Magazine

OCT 2018

TBM: Tunnel Business Magazine is the market leader for North America. TBM is written for leading professionals in all aspects of tunneling and covers project stories, design elements, contracting strategies, legal issues, new technology and more.

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Page 32 of 47

TUNNELINGONLINE.COM 3 3 TBM: TUNNEL BUSINESS MAGAZINE // OCTOBER 2018 F E AT U R E S T O R Y Preparation Having the right technol- ogy was critical. Sirguey had used Trimble products in his classes and after talking with scanning expert Gregory Le- pere in Trimble's France office determined the Trimble TX8 3D laser scanner would be ide- al for the project. The TX8 can collect 1 million points per sec- ond, producing 3D coordinates with millimeter precision. It has a photographic capability that assigns real color to any point, enabling high-density color data and realistic textur- ing of a 3D model, even in the dim light of the tunnels. Sirguey and Hemi envi- sioned LiDARRAS as a bicul- tural project, with resources coming from universities in ealand and France in a collaborative effort. The Uni- versity of Otago was already committed, and Sirguey con- tacted the École Supérieure des Géomètres et Topographes (School of Geometers and Topographers) in L France. Between the two schools, five students were chosen, with a lead student from each country committed for the long term. Safety was a primary con- sideration. Some of the net- work had been reinforced during the Cold War as fallout shelters and were deemed stable, but Sirguey's team met with archeological experts from the city of Arras for a walk-through to assess the network. They confirmed that out of 2.3 km of tunnels, at least half of the area could be safely accessed. While the tunnels were well venti- lated by natural air currents, the team was still required to carry gas detectors as part of a strict health and safety plan. The temperature stayed at a consistent 10°C with 100% hu- midity. There was a technical learning curve as well. Some students had used Trimble's TX5 for scanning projects, but not the latest generation of TX8. In addition, Lepere provided training on using the TX8 with a on D7100, which would capture imag- ery at 90-degree intervals. A fish eye lens provides overlap between photos to create a single panorama at each scan station. While the scanner can measure in total darkness, researchers needed sufficient lighting for photography. The additional illumination came from battery-powered spot- lights placed under the in- strument tripod at each scan- ning station. Three different exposures were captured from each sta- tion, with a total of 12 individ- ual photos used to colorize a single scan station point cloud. To reduce error, each group of 12 photos was imported to- gether. The software would use these to render a pan- orama. This process was com- pleted for all 814 scans. The RealColor function in Trimble RealWorks 10.1 software was used to colorize each scan. "The pictorial quality was excellent," Sirguey said. "The TX8 made things so much eas- ier. We captured everything possible to create photo-realis- tic renderings. Given the chal- lenging light environment, we never thought we would get such quality." The Project Progresses Students, with supervi- sion from staff from each sur- veying school, worked eight hours a day and sometimes Beginning in April 1917, members of the New Zealand Engineers Tunneling Company (NZETC) began creating a 2.3-km long subterranean passage under enemy lines.

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