A note about Lateral marks:
IALA = International Association of Lighthouse Authorities
IALA A = UK & rest of the world excluding areas noted in IALA B
IALA B = USA, Japan, North & South Korea and the Phillipines
The system consists of lateral, cardinal and other buoys, such as isolated danger and safe water marks. Buoys can be distinguished from each other by
- the colour of their light and flashing sequence
- the colour and combination of colours on the buoy
- the shape of the topmark
This marking scheme is designed to enable mariners to identify a buoy if the light is extinguished and /or the topmark is missing.
Lateral buoys mark well defined channels and indicate port and starboard hand sides of the route to be followed, for port hand marks the buoy and light are coloured red, for starboard marks these are green.
Cardinal buoys are used in conjunction with a compass to indicate where a mariner may find the best navigable waters. They are coloured yellow and black and have white flashing lights.
Indicating safe water
Light sequence: White light either Quick or Very quick flashes continuously.
Light sequence: White light either Quick or Very quick flashes x 3.
Light sequence: White light either Quick or Very Quick flashes x 6 + 1 long
Light sequence: White light either Quick or Very quick flashes x 9.
Mark the edge of channels
Port Lateral Mark
Light Sequence: Flashes Red (various sequences (other than 2+1), dependant on area - refer to chart)
Starboard Lateral Mark
Light Sequence: Flashes green (various sequences, dependant on area - refer to chart)
Preferred Channel to Port
Red Flashes (2+1)
Preferred Channel to Starboard.
Green Flashes (2+1)
Isolated Danger Mark
Light sequence: Flashes white x 2
Temporary Wreck Mark
Light sequence: Alternating blue and yellow 1 second flashes with an interval of 0.5 seconds.
Safe Water Mark
Light sequence: White (various sequences - check chart for details)
Light sequence (if it has one): Yellow flashing (various sequences depending on area - refer to a chart