Digital Guide to Lights and Fog Signals

Introduction

The Digital Guide to Lights and Fog Signals is a specialist nautical reference for identifying the lights and sound signals used as aids to navigation at sea. It complements nautical documentation by providing precise information for each light or signal, including its position, light characteristics, range, elevation and, where applicable, its fog signal.

Essential for both coastal and offshore navigation, the List of Lights enables navigators to identify a lighthouse, light tower, lighted buoy or other maritime navigational aid observed from a vessel. It is particularly useful during night navigation, in reduced visibility or when approaching a harbour.

The digital documentation published by the SHOM – French Hydrographic and Oceanographic Service includes the publications “Feux et signaux de brume L1” for metropolitan France and “Feux et signaux de brume L2” for overseas territories and foreign areas. These publications are currently distributed exclusively in digital PDF format.

What is a Digital Guide to Lights and Fog Signals used for?

A List of Lights identifies maritime navigational aids encountered along the coast and at sea. It allows navigators to find a light according to its geographical area, name, number or characteristics.

For a navigator, it can answer very practical questions:

• Which light am I observing?

• Where exactly is this lighthouse or light tower located?

• What are its light characteristics?

• How many flashes does it produce and at what interval?

• What is its nominal range?

• What is its elevation?

• Does it have a fog signal?

• What is its international number?

• Is it located on land or on a floating mark?

This information makes it possible to compare a visual or audible observation with official nautical documentation.

The Guide to Lights is therefore an identification and verification tool, particularly valuable when several navigational lights are visible at the same time.

What information is included in a digital List of Lights?

Depending on the publication, a List of Lights may provide:

• the international number of the light;

• the national number, where applicable;

• the name and location of the navigational aid;

• geographical coordinates;

• the light characteristic;

• its colour;

• its rhythm and period;

• its intensity, where available;

• the elevation of the light;

• geographical and luminous range;

• a description of the structure;

• the presence and characteristics of a fog signal;

• information relating to associated navigational aids.

The SHOM publications are organised geographically according to the route followed by the navigator. They may also include correspondence tables between international and French light numbers, index maps and different indexes facilitating searches.

This organisation is particularly useful for navigation because the navigator can identify the successive lights encountered along a route rather than searching only for the name of a particular lighthouse.

Understanding light characteristics

Identifying a light does not simply mean observing that a light is visible. Its light characteristic acts as a genuine signature that helps identify it.

A light may be fixed, occulting, flashing, isophase or display a group of flashes. Its colour can also be an important identification element, particularly where a sector light distinguishes different approach directions.

For example, a navigator approaching the Brittany coast at night may observe several lights around Brest, Pointe Saint-Mathieu or the entrance to the Goulet de Brest. Comparing the flash rhythm, colour, range and position can help determine which navigational aid is actually being observed.

The same method can be used in the English Channel around Cherbourg, Cap de la Hague, Dieppe or the Pas-de-Calais, where the density of maritime traffic and navigational aids makes accurate identification particularly important.

Fog signals

The guide does not only concern lights. It also lists fog signals, which provide information when visibility is severely reduced.

Depending on the installation, signals may use different technologies and have their own characteristics. Their descriptions allow navigators to compare an audible signal with the information contained in nautical documentation.

Knowledge of fog signals is particularly useful in areas where fog, sea mist or reduced visibility are common, including the English Channel, the North Sea, parts of the North Atlantic and the approaches to many ports.

Under these conditions, identification no longer relies solely on visual observation. The vessel's estimated position, radar information, electronic navigation aids, buoyage and audible signals must be interpreted together.

SHOM L1 and L2: two areas of coverage

The SHOM digital Lists of Lights are organised according to geographical coverage.

The SHOM L1 – Lights and Fog Signals publication describes maritime navigational aids in metropolitan France.

It covers the coasts of the English Channel, Brittany, the Atlantic and the Mediterranean. Navigators can therefore find navigational aids in areas including Dunkirk, Calais, Boulogne-sur-Mer, Dieppe, Le Havre, Cherbourg, Saint-Malo, Brest, Lorient, La Rochelle, Bordeaux, Bayonne, Marseille, Toulon, Nice, Ajaccio, Bastia and Bonifacio.

The SHOM L2 – Lights and Fog Signals publication covers overseas territories and foreign areas. It is therefore relevant to navigation around the French Caribbean, French Guiana, Réunion, New Caledonia, French Polynesia and the foreign areas covered by the corresponding documentation.

This distinction makes it easier to select the appropriate publication according to the navigation area.

Admiralty Digital List of Lights

For international navigation, Admiralty publications constitute another major reference.

The Admiralty Digital List of Lights, or ADLL, contains official information on more than 90,000 fixed light structures worldwide. Its coverage includes lighthouses, lightships, fog signals and certain floating marks equipped with lights.

The worldwide coverage of Admiralty publications is particularly suitable for ocean and international navigation: the English Channel, North Sea, North Atlantic, Mediterranean, Red Sea, Indian Ocean, Asia, Pacific, South Atlantic and the Americas.

For example, a navigator sailing from Brest to Gibraltar and the Canary Islands may successively encounter navigational aids along the European Atlantic coast, the Iberian Peninsula and the Atlantic archipelagos. For a longer voyage towards the Caribbean or the Panama Canal, international documentation becomes even more important.

The ADLL provides the main information contained in the corresponding paper publications while allowing electronic searching and regular updating.

Using the Guide with nautical charts and navigation instruments

The List of Lights should not be considered in isolation. It forms part of the wider set of nautical documentation used to prepare and conduct a voyage.

When approaching a harbour, the navigator can compare:

• the vessel's position;

• charted information;

• observed buoyage;

• light characteristics;

• the coordinates of the light;

• radar information;

• GNSS data;

• information provided by electronic navigation systems.

Nautical charts published by SHOM, Admiralty, NV Charts and other national hydrographic offices therefore provide complementary information depending on the area being navigated.

In the English Channel and along the French Atlantic coast, SHOM documentation is particularly important. In the North Sea, Mediterranean waters or during ocean passages, Admiralty publications and national hydrographic services can complement the available documentation.

Coastal, professional and offshore navigation

The digital Guide to Lights is intended for a wide range of users:

• sailors preparing coastal passages;

• offshore navigators;

• skippers and ocean-racing crews;

• professional merchant seafarers;

• commercial fishermen;

• shipmasters and navigation officers;

• maritime schools and training centres;

• crews undertaking international voyages.

Its usefulness is particularly evident during night navigation and harbour approaches.

In the Bay of Biscay, for example, identifying lights along the French and Spanish coasts can help confirm the vessel's position. In the Mediterranean, the numerous navigational aids around Marseille, Toulon, Ajaccio, Palma, Barcelona, Genoa or Gibraltar also make detailed light documentation particularly useful.

In northern waters, such as the North Sea, Norway or approaches to the Baltic, the density of navigational aids and the possibility of reduced visibility can likewise make accurate identification essential.

Why choose a digital version?

The digital version offers several advantages for modern navigation:

• rapid searches within the document;

• consultation on a compatible computer or tablet;

• direct access to the required information;

• practical organisation by geographical area;

• the ability to carry extensive documentation without taking several paper volumes on board;

• access to updates where these are provided by the publisher.

For SHOM digital Lists of Lights, the publication can currently be downloaded during the 12-month period following the initial purchase, with users notified of updates and able to download updated versions during this period.

Admiralty also provides a digital version of its List of Lights, with regular electronic updates and search functions designed in particular for ship crews.

A particularly important document for night navigation

Night navigation transforms coastal visual aids into genuine position references. A lighthouse or lighted buoy can provide essential information provided that it is correctly identified.

The List of Lights allows the navigator to move from a simple observation — “I can see a light to port” — to a documented identification: position, number, colour, rhythm, range, elevation and, where applicable, audible signal.

This approach is particularly useful when several lights are visible simultaneously or when weather conditions make identification more difficult.

Conclusion

The Digital Guide to Lights and Fog Signals is a specialist nautical reference for identifying lighthouses, lights, lighted marks and sound signals used for the safety of navigation.

SHOM publications, particularly L1 for metropolitan France and L2 for overseas territories and foreign areas, meet the needs of navigation within the areas covered by the French hydrographic service. Admiralty digital publications provide extensive international coverage, suitable for coastal, professional and ocean navigation.

Used carefully alongside other nautical sources, the List of Lights enables navigators to interpret the signals encountered at sea more effectively, confirm an identification and access structured documentation for both daytime and night-time navigation.

FAQ – Digital Guide to Lights and Fog Signals

What is a Guide to Lights and Fog Signals used for?

It is used to identify lighthouses, lights, lighted marks and fog signals used as navigational aids. It provides information such as their position, light characteristics, range and, depending on the publication, audible characteristics.

What is the difference between SHOM L1 and SHOM L2?

L1 primarily covers maritime navigational aids in metropolitan France. L2 covers overseas territories and foreign areas.

Is the SHOM List of Lights available in digital format?

Yes. SHOM L1 and L2 Lists of Lights are currently distributed exclusively in digital PDF format.

Does a List of Lights indicate the range of a lighthouse?

Yes. These publications include information relating to the range of lights. Admiralty documentation also provides information allowing geographical and luminous ranges to be distinguished.

Does the List of Lights include fog signals?

Yes. Lists of Lights include installations producing fog signals and their characteristics where documented.

Which List of Lights should be used for navigation in the English Channel?

For the French coast, SHOM is a major reference. For British waters and international navigation, Admiralty publications are also particularly important.

Is a List of Lights useful in the Mediterranean?

Yes. It can be used to identify navigational lights and signals around ports such as Marseille, Toulon, Nice, Ajaccio, Bastia, Barcelona, Palma, Genoa or Gibraltar, depending on the publication and area covered.

Is a List of Lights useful for an ocean crossing?

Yes. For transatlantic or around-the-world navigation, international publications allow navigators to identify navigational aids encountered along different coastlines and in port approaches.

Are digital Lists of Lights updated?

The arrangements depend on the publisher. SHOM provides updates for its digital publications during the download period associated with the licence. Admiralty also provides regular electronic updates for its digital documentation.

What is the difference between a List of Lights and a nautical chart?

A nautical chart represents the maritime environment and its navigational aids geographically. A List of Lights provides detailed information about the characteristics of lights and signals. The two types of documentation therefore serve complementary purposes when preparing and conducting a voyage.