The Anneberg-Skanstull tunnel is part of the so-called City Link project by the Swedish National Grid - Svenska kraftnät and serves to improve the power supply in the Greater Stockholm area. At a length of around 14 km and a diameter of 5 m, the tunnel is being driven approx. 50 - 100 m below the Swedish capital using a tunnel boring machine.

Until completion in 2024, DMT surveying experts will carry out tunnel orientation measurement campaigns using DMT’s unique GYROMAT surveying gyroscope in order to achieve the necessary route orientation accuracy in the narrow tunnel network, which is being constructed by Implenia and HOCHTIEF.
 
DMT offers one-stop tunnel orientation services with a word-class surveying team and expertise from more than 3500 successful gyro campaigns. DMT has been active in underground mining and tunnels project around the world e.g. Eurotunnel, Brenner Base Tunnel, Gotthard Base Tunnel and major European and Middle East metro line tunnels.
 
https://www.dmt-group.com/news-info/press/press-release/archive/dmt-performs-high-precision-tunnel-orientation-survey-for-city-link-project-anneberg-skanstull-tunnel.html