Select Page

Sector lights, directional lights and leading lights guide vessels safely through hazardous waters or narrow channels at night. These lights are used when approaching or leaving harbours and are marked on charts and in nautical almanacs. How do they differ from one another?

A typical sector light has three arcs of light coloured red, white and green. In order to stay safe, as a vessel approaches the light it has to stay in the white sector. If the vessel moves into the red or green sectors, then this indicates that the vessel is no longer in the safe channel. If the vessel is within the IALA A system, it needs to alter course as follows:

  • red sector – indicates the port side of the channel. The vessel needs to steer to starboard to return to the white sector.
  • green sector – indicates the starboard side of the channel. The vessel needs to steer to port to return to the white sector.
  • white sector – indicates safe water.

Sector lights guide vessels through hazardous channels or into harbours with narrow entrances. The boat shown here would only be able to see a white light, as it is in the white sector. 

Sector lights are shown on charts with their light characteristics. The light characteristics in the diagram above are IsoWRG3s9m8M. This means: isophase, white, red and green, flashing every 3 seconds, height 9 metres, range 8 miles. 

Learn all about buoyage and lights in our reference app IALA Buoys & Lights at Sea for all navigators at sea. The app includes a quiz to test yourself.

Directional lights

Directional lights are similar to sector lights. A directional light guides a vessel into harbour in a very narrow channel. There is less margin for error than with a sector light as the channel is so narrow. The light beam is usually flanked by darkness rather than coloured light sectors, as is the case with sector lights.

The correct angle of approach for a directional light is given as a compass bearing on charts. Unlike sector lights, directional lights are marked on charts as single, unbroken lines, with the angle also marked on the line.

Once the navigator has seen the light, they are on the correct bearing and are safe to enter the harbour.

The directional light in the diagram here flashes on a bearing of 220.5º. Its light characteristic is Fl(2) 5s 10m 12M. This means it flashes twice every 5 seconds, is at a height of 10 metres above MHWS and can be seen from a distance of 12 miles. 

Learn all about buoyage and lights in our reference app IALA Buoys & Lights at Sea for all navigators at sea. The app includes a quiz to test yourself.

Leading lights

Leading lights are pairs of beacons that help navigators keep on the correct line of approach into harbour. They work in the same way as leading marks do during the day, where two day marks or shore features give the correct course, if lined up. 

While leading lights are excellent aids to night time navigation, it is important you have identified the  correct two lights to line up, which is not always easy.  

Leading lights show the safe line to take. Here, you are too far to port if the lower light moves to the right and so you need to steer to starboard. If the light moves to the left, you need to steer to port.

Learn all about buoyage and lights in our reference app IALA Buoys & Lights at Sea for all navigators at sea.  The app includes a quiz to test yourself.

Happy boating and stay safe on the water!

Marine engine oil system maintenance

The regular maintenance of a marine diesel is key to preventing engine failure at sea. This means doing regular checks of the fuel, cooling, electrical and oil systems.

Boat interior varnishing

Most boat interiors have a combination of varnished and painted surfaces including solid wooden joinery, plywood laminates with thin hardwood veneers and glass reinforced plastic. When making your assessment of what you are going to do, bear in mind that the varnishing process consumes a lot of time, especially if the existing surfaces are in poor shape.

Safety Equipment Checklist for Boats

Safety Equipment Checklist for Boats   Liferaft line attached The liferaft will not work unless the trigger line is...

Understanding tide tables and tidal curves

There are many factors that influence local tidal patterns and it’s essential for every sailor to have a good understanding of tide tables and tidal charts to ensure they can calculate the level of tide at any given time.

Keel design – options to consider when choosing a yacht

Keel design is constantly evolving and nowhere is this more apparent than in modern racing yachts such as the Imoca Open 60...

Boat decks and superstructure

The deck of a boat is constantly exposed to the elements and should be inspected on an annual basis. Particular attention needs to be given to the overall condition of deck fittings such as the stanchions, cleats and chainplates.

Essential Knots: Reef knot

Essential Knots: Reef knot Use: Tying two ends of rope together, often used for tying up a bundle of loose sail around the boom. Step...

Peer to Peer yacht charter – How can you monetize your boat?

There is a growing trend in peer to peer yacht charter. How does it work? People already rent rooms, cars and bikes from one...

Safe Skipper – crew management tips

Effective crew briefings are a vital part of the good on-board communication that helps everything to run smoothly on a sailing vessel at sea, whether it is cruising or racing.

Avoiding collisions at sea – how to stay safe on the water

Boats have many blind spots, including the headsails of sailing boats. Always keep a lookout, stay safe and remember that...

Dag Pike’s Boat Survey

We're really pleased to be working with Dag Pike on some great new apps for iPhone & Android. Here'a a bit more about the first app: Dag Pike's...

Essential Knots: Round turn and two half hitches

Essential Knots: Round turn and two half hitches Use: Tying a rope to a pole or a ring. Step 1. Pass the end around the object. Step 2....

Sailboat rig checks – Part 2

In part two of Sail boat rig checks we run through some useful rig maintenance tips and then finish with a brief look at what a professional rig check involves.

Understanding tides

If you are used to sailing in tidal waters, you will know that tides can be both a benefit and a hindrance to the sailor. In many ways,...

Top Ten Tips For Learning The ColRegs Boating Rules Of The Road

Colregs Boating Rules Of The Road Skippers struggle to learn and remember the ColRegs Yachtmaster and Day Skipper course...

Boat maintenance – what does it involve?

The maintenance of a boat involves things like cleaning, varnishing, painting, polishing, antifouling, servicing the engine, servicing the seacocks, and maintaining the gas and plumbing systems. It all amounts to a fairly considerable amount of work that can’t be ignored if you are to keep your boat in a safe and good condition.

Essential Knots: Figure of eight

Essential Knots: Figure of eight Use: Stopper knot, prevents a rope from being pulled through a hole e.g. through a block or...

Essential Knots: Clove hitch

Essential Knots: Clove hitch Use: Tying a rope to posts, bollards, rings or a guardrail. Step 1. Make a turn around the object and lay...

How to predict wind direction and strength by reading a weather chart

Weather charts, also known as surface pressure or synoptic charts, contain a lot of information that helps weather...

Passage Planning Advice & Safety for skippers

Passage planning helps you to: • Decide where to go • Calculate how long it will take to get there • Avoid bad weather •...

Engine failure at sea – common causes and how to avoid them

Many engine failures are caused by lack of maintenance, resulting in fuel filter blockages, water pump failures, overheating and other breakdowns. Indeed, one of the most common reasons for marine rescue service call outs is for one of the most basic reasons possible – boats that have run out of fuel.

Getting a tow for your sail or power boat at sea or on inland waterways

FREE tips from the Safe Skipper App for iPhone/iPad/Android: Getting a tow for your sail or power boat Plan how to secure a...

Stress cracks on GRP boats

It is quite common to find cracks in the gelcoat when inspecting the deck and superstructure of a GRP boat. It is important to differentiate between a gelcoat crack and a scratch.

Tidal terms and definitions

Getting to grips with tidal terms and definitions can seem a little daunting, even to the most experienced sailors! Here we look at some of the key terms and definitions associated with the language of tides.

Boating emergency – how to broadcast a MAYDAY emergency call

How to broadcast a MAYDAY emergency call   How to broadcast a MAYDAY emergency call if a vessel or person is in grave...