Module 12 - Visual Aids to Navigation
Fog Signals
Some lighthouses and aids have charted sound signals such as horns, sirens, bells or gongs. A notation such as Horn(2) 30s describes two blasts in a complete 30-second period. Check the current chart or light list because equipment and service status can change.
Sound can be refracted by temperature and wind gradients, reflected by land or structures and masked by vessel noise. Apparent loudness and direction are therefore poor measures of range and bearing. Hearing the expected character is supporting evidence, not confirmation of proximity or a precise position.
In restricted visibility maintain the required lookout, safe speed and collision-avoidance actions, use radar and other available aids competently, monitor depth and position, and follow the pilotage plan. A shore fog signal does not replace the vessel's COLREG sound-signal duties.
- Fog signals: diaphones, sirens, horns, bells
- Character shown on chart (e.g., Horn(2) 30s)
- Sound over water is unreliable for distance/direction
- An expected character corroborates identity but not precise range or bearing
- Shore/aids signals do not replace the vessel's COLREG duties
Optional quick check
Section 6 of 6
What is the safest use of a matching shore fog-signal character?
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