Physical Aids to Navigation

The General Lighthouse Authority’s strategy is to provide an appropriate mix of Aids to Navigation (AtoNs) for general navigation in our waters. This mix includes a range of physical aids, such as Lighthouses, Buoys and Beacons and electronic navigation such DGPS, AIS and eLoran.

We provide over 200 navigation lights, ranging from substantial Stevenson designed structures containing lights of over 20 miles nominal range, to lit beacons marking ferry routes. The lights are distinguished by their colour and character:


Continuous. For example, F.G (fixed green)


On for less time than off. For example, Fl 5s (flashing one (white) light every 5 seconds)

Quick flashing

Flashing at a rate of 50-60 times per minute. For example, Q.R (quick red)

Group flashing

More than one flash. For example, Fl(3) R 10s (three red flashes every 10 seconds)


On and off for equal periods. For example, Iso 8s (on for 4 seconds and off for 4 seconds)


On for more time than off. For example, Oc 8s (on for 6 seconds, off for 2 seconds)

All lighthouses in our estate were automated in the second half of the last century and are monitored on a 24 hour basis. The emphasis now is on modernising the lights themselves and, in particular, converting those without mains powers to solar energy. 


We currently provide 174 lit buoys. We also have a legal responsibility for the inspection of 647 third party buoys in our waters. Pursuing a policy of using renewable energy sources, combined with a desire to reduce risk to the workforce, we completed solarising our statutory buoy inventory.

Our buoys conform to the IALA Region A model and comprises 6 principal buoy types:

Lateral Marks – for example, Port (red) & Starboard (green) buoys

Cardinal Marks – yellow/black marks depicting the safe side of any hazard

Isolated Danger Marks – red/black horizontal stripes

Safe Water Marks – white/red vertical stripes

Special Marks – yellow with an ‘X’ topmark

New Danger Marks – blue/yellow vertical stripes

As a general rule, reliance can’t be placed on floating aids always maintaining their exact positions. Buoys should therefore be regarded with caution, especially when in exposed positions or after poor weather. Buoys should generally not be used as a primary source of vessel position but rather for situational awareness. In circumstances where they are the only source of visual positional reference, caution should be used. The majority of NLB buoys display their name and the NLB website address.

We currently provide 25 beacons around our estate. Beacons range from unlit/lit pole beacons to substantial, lighted structures for the purposes of leading lines, hazard and channel marking

The General Lighthouse Authorities’ (GLAs) Navigation Policy, requires that all aids to navigation meet the requirements of the present and changing needs of mariners.  We therefore review AtoN provision on a regular basis to assess current and future requirements and undertake an operational review every five years.

Each GLA reviews the AtoNs in its own area of responsibility and joint consultations are conducted where there are areas of common or overlapping interest. The latest review was completed in 2015, and work is ongoing for the 2020 publication.