20/08/2026
⚓ Maritime Essentials #3
GPS FAILURE AT NIGHT
Coastal Navigation Scenario
The situation:
“GPS has just failed. It’s nighttime, and radar shows multiple coastal targets within 3 NM. You’re the OOW. What do you do?”
The priority: Stay safe. Don’t panic.
1. Call the Master
If you are in doubt about the safety of navigation, call the Master without delay.
2. Reduce Risk
Proceed at a safe speed appropriate to the prevailing visibility, traffic and navigational conditions. Arrange an additional lookout and ensure the engines are ready for immediate manoeuvring.
3. Revert to Alternative Position Fixing
Use all appropriate available means, including:
📡 Radar ranges & bearings
🧭 Visual bearings & transits
🌊 Echo sounder / soundings
📍 Dead reckoning
Where possible, verify the ship’s position using independent methods rather than relying on a single fix. Visual and radar position-fixing techniques are particularly important in coastal waters.
4. Maintain Collision Awareness
Continue using radar and other available aids to assess surrounding traffic. AIS should support situational awareness, not replace proper radar observation, visual lookout or COLREG-compliant decision-making.
5. If Position Becomes Uncertain
Take immediate action to keep the vessel clear of danger. If necessary, reduce speed or alter course to increase the available sea room while establishing a reliable position.
6. Record & Monitor
Document the failure, actions taken and relevant times, and continue frequent position checks using the most reliable methods available.
# The Key Lesson
GPS is a powerful navigation aid —
but it should never be the only source of confidence in your position.
⚓ A good navigator doesn’t just know how to use navigation equipment.
They know how to navigate when that equipment fails.
Maritime Essentials #3
Stay tuned for more practical maritime knowledge from SENA Ship Management.