How Cardinal Marks Indicate Safe Water Directions

Cardinal marks are navigational aids used in maritime pilotage to indicate the position of a hazard and the direction of safe water. They are named after the cardinal points of the compass (North, East, South, and West) and use specific colors, topmarks, and light patterns to convey information about the surrounding waters. 

Key features of cardinal marks:

• Color: Cardinal marks have distinctive black and yellow horizontal bands, with the specific arrangement indicating the cardinal direction. 
• Topmarks: They often feature black double cones as topmarks, with the cones’ arrangement (pointing up, down, or towards each other) indicating the cardinal direction. 
• Lights: At night, cardinal marks display white lights with specific flashing sequences that correspond to the cardinal direction. 
• Safe Water: The cardinal mark indicates that the deepest and safest water is located in the direction of the cardinal point it represents. 

How to interpret cardinal marks:

• North Cardinal:. Black above yellow bands, two black cones pointing upward. Safe water is to the north. 
• South Cardinal:. Black below yellow bands, two black cones pointing downward. Safe water is to the south. 
• East Cardinal:. Black at the top and bottom, two black cones pointing away from each other. Safe water is to the east. 
• West Cardinal:. Black in the middle, two black cones pointing towards each other. Safe water is to the west. 
• Lights:. North: continuous quick or very quick flashing. East: 3 flashes. South: 6 flashes + 1 long flash. West: 9 flashes. 

Purpose: Cardinal marks are used to: 

• Indicate the location of a hazard.
• Show the direction of safe water to navigate around the hazard.
• Mark a bend, junction, or end of a shoal in a channel.
• Indicate the deepest water in a specific area.

The easiest way to remember the shapes- two triangles face North to indicate that direction, same for South. West has two opposing triangles, resembling a hula dancer, the East mark is what’s left. The flashing lights correspond to the numbers on a clock face.