Operational Guide · Registers & Logbooks

# 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.

SOLAS Chapter IV GMDSS RMSS radio

## 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

1. 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.
2. Carry out the daily test of GMDSS equipment per the required procedures (battery test, DSC check).
3. Carry out the weekly test of EPIRBs and SARTs per the manufacturer's instructions.
4. Check the battery expiry dates of portable GMDSS devices and EPIRBs.
5. Update the radio log with every test, safety communication and anomaly found.
6. 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

In several PSC inspections, the crew's lack of understanding of the new RMSS terminology (in place of previous specific references to Inmarsat) has caused documentary confusion, with radio certificates or equipment labels not updated to the new nomenclature, leading to requests for clarification from inspectors.

## 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

PSCOs check the radio log, the validity of the GOC/ROC certificates of designated personnel, the status of the EPIRB/SART, and the consistency of the installed equipment with the declared Sea Area.

## 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

## FAQ

What is RMSS and why did it replace 'Inmarsat' in SOLAS texts?
RMSS (Recognized Mobile Satellite Service) is the generic term introduced by the amendments in force from 1 January 2024 to make the regulations independent of the individual satellite provider, given that since 2020 Iridium has also been recognised by the IMO as a GMDSS provider alongside Inmarsat.
Can a ship freely install Iridium instead of Inmarsat?
Installing an RMSS-SES Iridium unit as an alternative to Inmarsat is technically possible but remains subject to the ship's flag State acceptance policy.
What was removed from MF/HF equipment by the 2024 amendments?
The NBDP (Narrow Band Direct Printing) function was removed, considered obsolete technology as part of the Chapter IV modernisation.
🎬 Additional photos, videos and interactive diagrams for this topic will be available in a future version of the platform.

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