Confidential Human Factors
Incident Reporting Programme
The Charity
Aviation
Maritime
M2433
Initial Report
Indications and markings for the GPS 1 and GPS 2 antennas were incorrectly displayed on both the bridge antenna arrangement plan and the compass deck. Incorrect markings, in the event of specific issues, can lead to misunderstandings regarding which equipment needs checking and repair. A complete survey of the ship’s antennae was conducted and the plans were updated accordingly.
CHIRP Comment
This report illustrates how a minor error, such as incorrect labelling, can lead to significant issues. The GPS 1 and GPS 2 antennas were wrongly marked on both the bridge plan and the compass deck. If a fault had occurred, the crew might have checked the wrong antenna, wasted time, and possibly overlooked the real issue.
The antennas were installed in the correct place, but the signs and drawings did not match. This indicates that no one properly checked the labels after installation was completed.
For something as crucial as GPS, all information, including markings and drawings, must be clear and precise. If the crew cannot trust what they see, it can cause delays or mistakes during fault-finding.
This case serves as a reminder that when antennae are installed during the new build phase or at dry dock, any new equipment must be rigorously checked. The area/antenna plan should also be updated and cross-checked to ensure accuracy.
On a critical and operationally practical note, an antenna position must be correctly marked and located so that the navigation system can apply the correct offset from the vessel’s centre line. e.g. on a 60-meter beam vessel, a 20-meter error in recording can put you outside of a navigable channel!
It is essential that, during the annual or five-year radio survey, aerial verification of all bridge equipment is physically carried out. This also applies after any refits at dry dock, where bridge equipment is renewed or replaced.
Key Issues relating to this report
Situational Awareness – During technical troubleshooting, bridge teams rely on plans and labels to quickly isolate faults. Incorrect markings can easily mislead the operator and prolong a problem that requires urgent attention.
Communication – Poor information flow between design, installation, and operations teams likely contributed to this discrepancy. Without effective feedback loops, errors can persist unnoticed until they lead to failure.
Teamwork – The eventual resolution required a coordinated review of all antenna locations and documents. This highlights the importance of collaboration across departments in identifying and addressing safety risks.
 Key Takeaways
Seafarers – Check, do not assume. Don’t rely unthinkingly on diagrams or deck markings — especially during fault-finding. Visually confirm the actual installation and speak up if you notice any discrepancies.
Managers – Danger lurks in the small details. Include signage and documentation checks in post-installation and maintenance routines. Even minor labelling errors can cause significant operational delays.
Regulators – Test assumptions – not just systems. Ensure that commissioning and inspection processes verify not only the functionality of equipment but also the accuracy of associated markings and plans, particularly for critical systems such as GPS.