Gotthard Base Tunnel Geodetic and Geo-monitoring Challenges of the longest railway tunnel in the world

In June 2016, the opening of the longest railway tunnel of the world has been officially celebrated in Switzerland. This article summarizes the surveying challenges of the Gotthard Base Tunnel Survey Consortium from 1995 up to present. The contractual requirements, the geodetic basis and the establishment of the reference geodetic networks for construction of this tunnel with 57 km length are briefly described. The tunnel surveying concept of the project, the performance and processing of tunnel controls and the survey of the related vertical shaft are shortly presented. The analysis of survey data and the appraisal of accuracy and reliability levels are explained. Furthermore the automatic Geo-Monitoring of large dams in the Swiss Alps during the construction of the Gotthard Base Tunnel showed that the impact of the tunnel construction is to be significantly measured at the earth’s surface.