Seabed mapping, for safer shipping

The time is 04:40 when the speaker system crackles and calls out "Battle stations!". Half of the crew jump out of their beds and get dressed on the hoof as they run towards their battle stations. The mine-sweeper HMS Koster is in the highest state of combat readiness, Battle stations. The starboard watch, who was asleep a few minutes ago, may not be quite as keen and alert as the port watch, but everyone knows that sleep is not given high priority during the exercise.

Fredric Leufstadius is second-in-command on board HMS Koster. Photo: Magnus Jirlind/Försvarsmakten
Full personnel on the rear deck during the mooring procedure. Photo: Magnus Jirlind/Försvarsmakten
The ship is controlled with high precision. Photo: Magnus Jirlind/Försvarsmakten
The half deck on HMS Koster is soon cleared after mooring. Photo: Magnus Jirlind/Försvarsmakten
For a layman, information about the seabed in the sonar image looks like yellow and blue fields. Photo: Magnus Jirlind/Försvarsmakten
A trained sonar operator spends many hours in front of the screens. Any deviations from the normal image are immediately noted and are examined further. Photo: Magnus Jirlind/Försvarsmakten
The exercise took place under almost ideal weather conditions. There have been moderate winds and almost no waves. Photo: Magnus Jirlind/Försvarsmakten

Mine clearance vessels are now working to create a map of the seabed off the west coast to document it.

"The Swedish Armed Forces have a commission in this particular case to map the seabed off the west coast. We haven't had a major exercise here for some time, so it's a good thing that the SWENEX is on the west coast this year," says Fredric Leufstadius, second-in-command on HMS Koster.

"Many people probably imagine that it's not very difficult to find things under the surface, but in fact the seabed looks similar to the land surface. There are hills and valleys, rocks and stones, vegetation and many other features that make it difficult to find mines or even a submarine." The waters around the Gothenburg archipelago hold another challenge, too.

"The salt content of the water is quite a lot higher than on the east coast. Ships' sonar can't easily present a clear picture of the bottom due to the salt and temperature. Sonar is the technology we use to search the seabed," says the second-in-command.

Ensuring safe passage for shipping

A mine is fairly easy to drop without being detected, and does not require advanced equipment. If a port such as Gothenburg were to be closed, it would put a lot of pressure on society since about 90% of Swedish imports and exports are by sea.

"In 2005 a fishing vessel had a mine in its trawling net and unwittingly took it into Gothenburg port. The port and parts of the city of Gothenburg had to be cordoned off. The mine was dealt with by the Swedish Armed Forces, who transported it out to sea and disposed of it safely.”

The task for mine-sweepers in this exercise is to ensure that the shipping routes into a port are safe. It is a time-consuming job and there are no margins for missing threats. Swedish defence relies heavily on mapping the seabed.

When the speakers on board crackle again at 04:45, all 28 of the crew are now at the ship's battle stations. "Attention all hands! We are drawing fire from nearby islands. No personnel are injured". There are many hours of the exercise left and the men are really on their toes. There will no doubt be another awakening in store for the crew from the speakers calling out "Battle stations!".