February 23rd 2015

Detailed maps of the seabed

Sigrid Elvenes, aboard Seisma, is mapping the seabed in southern Sunnmøre.
The Geological Survey of Norway (NGU) has begun to prepare new maps of the seabed in southern Sunnmøre. The base maps available from the Norwegian Mapping Authority have very high resolution and show details of the seabed which no-one has seen previously.
This is a shade relief map of Åramsundet, where two Second World War wrecks can be seen on the seabed. The Norwegian Mapping Authority is already aware of them and they are shown on existing charts. The shipping lane follows narrow gullies in the seabed and the strong current forms wave patterns in the sand on the sea floor.

“The depth data from the Norwegian Mapping Authority will form the basis for a number of maps which NGU is preparing in cooperation with the local authorities of Hareid, Ulstein, Herøy, Sande and Vanylven. Such data mark a fantastic advance for being able to manage the coastal zone to benefit society as a whole,” Sigrid Elvenes and Oddvar Longva, researchers at NGU, tell me.

NGU has bought the terrain models from the Norwegian Mapping Authority. “We are using them as the basis for mapping the distribution of sediments on the seabed and constructing a series of maps of the seabed showing terrain forms, hardness of the seabed and sediment distribution, and to construct thematic maps,” the researchers continue.

Important for society

The terrain models are constructed by the Hydrographic Service of the Norwegian Mapping Authority, which is responsible for acquiring, processing and disseminating depth data in Norway, and publishing and updating official nautical charts for navigation.

“Detailed depth data from the Norwegian Mapping Authority are essential to produce modern maps for navigation and many other aspects that are vital for society. NGU is keen to help the Authority have sufficient funds allocated to give its mapping higher priority,” adds Oddvar Longva.

The new maps cover most of the seabed in the boroughs concerned. Runde Environmental Centre is responsible for coordinating the project. NGU covers 50 per cent of the cost and the local authorities and the County Governor of Møre & Romsdal take care of the rest.

Approved for publication

The Norwegian Armed Forces has approved the publication of the terrain models. In Norway, depth data with a higher resolution than a depth specification per grid of 50 x 50 metres are confidential for defence reasons. Southern Sunnmøre is the first area in the country where maps of the seabed with a resolution of 1 x 1 metre have been released.

“The Norwegian Mapping Authority has pressed hard to get the system which classifies such data revised so that data that are valuable for society can be made available for public use throughout the country. NGU fully supports this effort,” says Morten Smelror, the managing director of NGU.