GMDSS (Global Maritime Distress and Safety System)
The system that connects a ship in distress to the whole world: what changed with the modernisation in force since 2024, and how to stay compliant with the new RMSS terminology.
Operational Explanation
GMDSS is the integrated system of radio communications that guarantees, in every sea area, the ability to raise a distress alert and receive assistance. Until 2024 the system referred almost exclusively to Inmarsat as the satellite provider; the modernisation of Chapter IV has made the regulations independent of the individual provider.
1 January 2024 update: amendments to SOLAS Chapter IV enter into force replacing specific references to Inmarsat with the generic term Recognized Mobile Satellite Service (RMSS). Since 2020 the IMO has also recognised, alongside Inmarsat, Iridium as a GMDSS satellite provider: installing an RMSS-SES Iridium unit as an alternative to Inmarsat remains subject to flag State policy. Sea Area A3 is also redefined (based on RMSS coverage) and the NBDP (Narrow Band Direct Printing) function is removed for MF/HF equipment.
Regulatory Reference
SOLAS Chapter IV (Radiocommunications), as amended with entry into force on 1 January 2024: generic, provider-independent requirements, RMSS terminology, consolidation of VHF and SART provisions, updated Sea Areas A1-A4.
Scope of Application
Every ship subject to SOLAS Chapter IV; the specific equipment required depends on the Sea Area (A1-A4) in which the ship operates.
Procedure / How to Complete It
- Verify that the GMDSS equipment installed on board is consistent with the operating Sea Area and with the RMSS provider approved by the flag State.
- Carry out the daily test of GMDSS equipment per the required procedures (battery test, DSC check).
- Carry out the weekly test of EPIRBs and SARTs per the manufacturer's instructions.
- Check the battery expiry dates of portable GMDSS devices and EPIRBs.
- Update the radio log with every test, safety communication and anomaly found.
- Verify the GOC/ROC (General/Restricted Operator's Certificate) training of the officers responsible for GMDSS communications.
Practical Example
Example radio log entry: "Daily DSC test VHF/MF/HF carried out on 10.07.2026, positive outcome. Weekly EPIRB and SART test carried out, batteries within expiry. No anomalies."
Real Cases
Common Mistakes Mistake Library
| Mistake | Consequence | How to avoid it |
|---|---|---|
| Onboard documentation still referring exclusively to 'Inmarsat' instead of RMSS | Inconsistency with updated SOLAS terminology, possible PSC requests for clarification | Update onboard manuals and procedures to the post-2024 RMSS terminology |
| Weekly EPIRB/SART tests skipped or not recorded | PSC deficiency, risk of malfunction in a real emergency | Systematically schedule and record weekly tests in the radio log |
| GMDSS personnel without a valid or up-to-date GOC/ROC certificate | Serious deficiency, possible detention | Track radio certificate validity alongside the crew's other statutory certificates |
PSC Observations
Operational Tips
- Update crew training on the new RMSS terminology, to avoid confusion during inspections.
- Never skip the weekly EPIRB and SART tests, even when the operational workload is high.
- Check flag State policy before installing or replacing an RMSS-SES Iridium unit in place of Inmarsat.
Checklist
- GMDSS equipment consistent with the operating Sea Area
- Daily DSC test carried out and recorded
- Weekly EPIRB/SART test carried out and recorded
- GOC/ROC certificates of designated personnel valid
- Radio log updated with current RMSS terminology