On coastal aids to navigation – sea marks

Based on text by Jo van der Eynden

Sea marks

Along the Norwegian coast there are a number of daymarks that help seafarers navigate during daylight hours because it is difficult for those in unfamiliar waters to know which inlets are navigable. For visitors, the archipelago can seem like a maze, where an overview of waterways between shallows and reefs requires extensive experience and local knowledge.

The illustration on the 200-krone note shows a lateral mark indicating direction of buoyage. These marks traditionally consist of a wooden grid on an iron pole mounted in the rock bed of a reef. The mark indicates the side of the shallows on which to navigate. Such sea marks can have one or more "flags" indicating direction of buoyage for a waterway.

There are also traditional iron stakes without a grid or "flag" that indicates shallows or a reef that can be sailed around on several sides. In the 1800s, these stakes were often made of cast iron and had a diameter at the bottom of approximately 20 cm. To secure them to the rock bed, a deep hole of at least equal diameter had to be chiselled by hand. This was done manually by three men on a simple rig of pipes. Such work could only be done in calm weather. One man held the chisel, while the other two took turns swinging their sledgehammers. It is estimated that around 35 000 blows were needed to chisel a hole for such a stake.

Landscape formations and characteristics and place names were originally used to navigate along the coast. Pilots and fishermen memorised these, or they compiled the information in books containing descriptions of the underwater landscape and waterways based on cross bearings and manual soundings taken using lead lines.

The large number of sea marks contracted with the development of the network of lighthouses during the 1800s, when the government took overall responsibility for the establishment of aids to navigation along the coast. Some key sea marks were, however, already mentioned in the Sagas. The fact that very many of the burial mounds from the Bronze Age are situated near important coastal waterways is also indication that marking waterways past archipelagic islets and inlets goes far back in history. The location of inland burial mounds can often make much more sense when post-glacial rebound is considered. What were once historical waterways now appear as dry land because of the change in sea level.

Cairns and wooden sea marks

After the burial mounds, stone cairns and wooden (later concrete) sea marks were built at several points along the coast, both on promontories and along inland waterways. Their construction was often a private initiative, usually by local pilots. They were locality-specific and would provide seafarers with reliable land sighting as they approached from the open ocean. Others were constructed along inland waterways to indicate navigable inlets and shallows that needed to be avoided.

There is an account of an Italian crew in the 1430s that became stranded on the island of Røst, furthest out in Lofoten. After having wintered there, the crew were provided passage south to Bergen. The account enthusiastically conveys how the waterway was made navigable by establishing a system of cairns to show the way.

Modern daymarks

Today, the Norwegian Coastal Administration (NCA) is responsible for sea marking and the rest of the maritime infrastructure along the Norwegian coast. The NCA, which is a specialised government agency under the Ministry of Transport and Communications, administers a total of more than 14 000 daymarks along the Norwegian coast.

Published 27 July 2017 10:19