Issue link: https://geospatial.trimble.com/en/resources/i/1480686
Fa , accurate su eying of unde ater and mountain tunnels The need to survey an undersea tunnel in Norway saw one surveyor look beyond conventional survey tools and practices and instead employ Trimble's SX12 Scanning Total Station imble's SX12 Scanning tal Station is being used to do the surveying work needed r the renovation and upgrading of the Maursund and gen tunnels in Norway N orway is well known for its many road, rail and waterway tunnels that travel through mountains and under the sea. According to the latest report, Norway has over 1,200 roadway tunnels and count less more rail and waterway tunnels. The maintenance and expansion of these tunnels is a considerable line item in every transport plan. The NOK211 million (US$24 million) project to renovate the Maursund and Kagen tunnels is one such project. The two vital road tunnels connect the cities of Nordreisa on the mainland to S erv0y on Kagen Island. Built in 1991, the tunnels are about 2km long. The Maursund tunnel travels under the Maursundet Strait between the mainland and the island of Kagen in Tram about 92.Sm below sea level. Some sections of this tunnel have a 10 per cent gradient. The Ka gen nnel passes through the Kagen mountain. Managing survey tasks for the expansion of this undersea tunnel while the roadway remains open to travellers required one surveyor to look beyond conven tional survey tools and practices. AN ACTIVE RK ZONE The Maursund and Kagen tunnels renovation project includes extensive upgrades to each tunnel, including the widening of the carriageways as well as installing new LED lighting, CO/NO 2 gas meters, new water and frost protection and new drainage systems, plus paving new road surfaces. Survey needs include: • Geodetic control • Initial site surveys to guide construction • Ventilation, road and radio signs, emergency lights and boxes, and other bolt markings • Reference points along steep gradients • As-built conditions to design intent comparisons • Earthwork volume calculations • Final inspection Familiar underground chal lenges include poor lighting, a GNSS-restricted environment, long linear underground distances in cramped conditions. Adding to the complexity, the Maursund tunnel needed to remain open for traffic 24/7 when avalanche conditions were present. Renovation of the tunnel began in January 2021. Initially, Mesta had a two-person survey team using a total station trading off, but the demand would require night and day work with near continuous setup-measure-set out requirements and virtually impossible to provide same-day response to field crews. TECHNICAL VER TILI Mesta AS's professional surveyor Sylvia De Vuyst is responsible for the entire survey scope. With an eye on versatility and working with imble supplier Norgeodesi, she opted to use a total station and scanner combination, namely the imble SX12 Scanning Total Station, a multi-purpose solution particularly well-suited for underground survey projects like tunnels. The imble system combines the high accuracy of total station March 2022 G D lling International