Surveyors achieve great accuracy

Masterly surveying performance in the world's longest railway tunnel: only eight centimetres horizontally and one centimetre vertically were the deviations at the final breakthrough of the Gotthard Base Tunnel on October 15, 2010. At a professional conference held at the Swiss Federal Institute of Technology (ETH) in Zurich, some 300 surveying experts from Switzerland, Germany and Austria paid tribute to the precision that was achieved.

The focus was on the challenges that are presented to geomatics, and particularly surveying, by a major project such as the Gotthard Base Tunnel. Hilmar Ingensand, Professor of Engineering Geodesy, outlined the huge developments that have taken place in the sensors and methods used in surveying in the last 20 years. He emphasised the interrelatedness between the progress of the AlpTransit Gotthard project and the positive influence on the broad professional field of geomatics. The Chief Project Leader of the Gotthard Base Tunnel Surveying Consortium, Roland Stengele, explained the diverse surveying tasks from the point of view of the owner. By reference to examples, he showed how for a project of these dimensions important theoretical principles can be put into practice on site in the tunnel.

In the Gotthard Base Tunnel project, a total of around 100 geomatics specialists are deployed on behalf of the owner as well as the construction contractors. The surveying challenges in the AlpTransit project are highly diverse: the numerous construction sites, their complex interconnections, and the round-the-clock construction activity make surveying particularly demanding. Clear visibility and absence of vibrations, two further success factors for high precision in surveying, are not always easy to obtain on a tunnel construction site.

"With millimetre accuracy through the Gotthard"
The professional conference on October 29, 2010, was organised by the geomatics group of AlpTransit Gotthard Ltd, owner of the NRLA Gotthard axis, and the Institute of Geodetic Metrology and Engineering Geodesy of the Swiss Federal Institute of Technology (ETH) Zurich (Head: Professor H. Ingensand). AlpTransit Gotthard Ltd is tasked by the Swiss government with construction of the Gotthard axis of the New Rail Link through the Alps, with base tunnels through the Gotthard and Ceneri.