ISM News

From ISM News Update nr. 139: Safety Improvement Sheet No.14

July 2026

Safety Improvement Sheet No.14: Disrupted GPS Signals

The Safety Improvement Sheet alerts the maritime industry to the increasing occurrence of GNSS/GPS interference, including signal jamming and spoofing, which can significantly affect the safe navigation of ships.
The guidance emphasizes that:

  • GPS/GNSS should never be the sole means of navigation.
  • Masters and bridge teams should remain alert for signs of unreliable positioning data.
  • Navigation should be continuously verified using independent methods, such as:
    • Radar and radar parallel indexing;
    • Visual bearings;
    • ECDIS cross-checks;
    • Echo sounder;
    • Terrestrial navigation techniques;
    • Other available position-fixing methods.
  • Bridge teams should be familiar with the symptoms of GNSS interference and take appropriate action when unreliable position information is suspected.
  • Companies should ensure that bridge procedures, training, and the Safety Management System (SMS) adequately address the risk of GNSS disruption.
  • Suspected GPS/GNSS interference should be reported through the appropriate reporting channels to improve situational awareness.

Please refer to the NATO Shipping Centre reports on GNSS disturbances for current information on affected areas.

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