Module 15 of 17
Precautions and limitations imposed by fog and restricted visibility.
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Fog is one of the most dangerous conditions for small-craft sailors. Visibility can drop to metres with little warning. Your ability to see hazards, other vessels, and navigation marks is...
Fix your position immediately while you can still see landmarks. Switch on navigation lights. Start sounding fog signals (one prolonged blast every two minutes for a power vessel, one pro...
Rule 35 of the COLREGs specifies sound signals in restricted visibility. A power-driven vessel making way: one prolonged blast (4–6 seconds) every 2 minutes. A power-driven vessel stopped...
Without visual references, you must rely on instruments. GPS provides your position — plot it on the chart regularly. The echo sounder gives depth — compare it with the chart to confirm y...
Rule 19 applies to vessels not in sight of one another in restricted visibility. The stand-on/give-way rules (Rules 12–18) DO NOT APPLY in fog — every vessel must take its own avoiding ac...
Radar is one of the most valuable tools in fog. It transmits microwave pulses and displays returning echoes on a screen, showing the range and bearing of targets such as other vessels, la...
AIS (Automatic Identification System) is a powerful complement to radar in restricted visibility. AIS-equipped vessels broadcast their identity (MMSI number and vessel name), position, Co...
When fog descends, you need a systematic plan executed quickly. The priority is to transition from visual navigation to instrument navigation before you lose all references. Every second...
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