On lighthouses and sector lights
Based on text by Jo van der Eynden
Illuminating the way into our land
From isle to isle, from cape to cape
A legion of will-o'-the-wisps
Guarding the narrow passages
Leading to our homes
Terje Stigen: "De faste lys" (en norsk reise) ["Abiding lights" (a Norwegian journey)] 1975
Lighthouses are usually divided into three categories based on their function in navigable waters: landfall lights or shore lights, leading lights and harbour lights. Large shore lights are primarily intended to give mariners a sure means of sighting land, ie a warning of approaching landfall, and an indication of their position relative to the shoreline. Leading lights are intended to facilitate nighttime passage through inland fairways along the coast, where channels are often narrow and foul. Harbour lights are intended to safely guide ships through narrow breakwater openings in rough weather and in the dark of night.
From the mid-1800s, a number of smaller, manned leading lights were erected along the coast. But they could not help ships to navigate through foul waters at night by merely flashing a white light. To guide them safely through narrow straights and between islets, reefs and skerries, varying the light signal, called the "phase characteristic" was necessary.
Light in different sectors were assigned various colours: red, green or white, in order to provide more detailed and delimited guidance in fairways. It is the interplay between an individual light's phase characteristics and the sector colour and positioning on nautical charts relative to other lights that make nighttime navigation by sector light possible.
The need for sectored lights varies according to the complexity of the coastal landscape. In order to achieve a precise and accurate delimitation of the light, bearing and distance measurements and angle calculations must be made, in the same way as for land surveys and cartography. This is painstaking work, requiring detailed knowledge of local waters.
Today, all lighthouses along the Norwegian coast are automated and have been renovated to run on cost-efficient and environmentally friendly solar power. Digital charts have virtually absolute precision. The signals from global positioning satellites that orbit the earth make it possible to digitally track both one's own and other vessels, without the need for lighthouses or visual observation. Nevertheless, traditional navigational aids are maintained. The growing number of recreational boats is increasing the importance of seamarks, which serve as an important back-up system in the event that technology fails.
The Norwegian Coastal Administration (NCA), which is a specialised government agency under the Ministry of Transport and Communications, is responsible for administering maritime infrastructure along the Norwegian coast. Several vessel traffic centres have been established to monitor shipping traffic, while a number of light signals remain operational as navigation aids: approximately 2 000 lighthouses, 4 000 lanterns, of which approximately 700 use indirect lighting, and 2 000 buoys, of which 100 are lighted.