Module 9 - GMDSS & Safety Equipment
AIS and NAVTEX
What you will learn
Separate live traffic awareness from maritime safety information and use both as aids rather than collision-avoidance guarantees.
AIS exchanges identity and movement data; NAVTEX broadcasts maritime safety information. Neither service replaces a proper lookout, current notices or voice coordination.
AIS can display reports such as identity, position, course and speed from suitably equipped stations. Data can be absent, delayed, entered incorrectly or attached to a target that is manoeuvring. Not every vessel carries or transmits AIS, and a plotted symbol is not permission to stop looking outside.
NAVTEX is a direct-printing or display service for maritime safety information such as navigational warnings, meteorological warnings and forecasts, and other urgent safety information. The receiver uses transmitter and subject identifiers to control routine selection while protecting mandatory safety categories.
Use AIS to support the developing traffic picture and NAVTEX to update the passage risk picture. Then verify with sight, radar, charted information, official warnings and radio traffic appropriate to the circumstances. Technology adds evidence; it does not take command.
| System | Useful evidence | Critical limitation |
|---|---|---|
| AIS | Reported identity and movement | Missing or inaccurate targets and data |
| NAVTEX | Broadcast maritime safety information | Selection, coverage and reception must be managed |
| Voice VHF | Direct local coordination | Range, watchkeeping and language still matter |
Fuse information instead of obeying one screen
AIS shows no target near the harbour entrance, while visibility is poor and a NAVTEX gale warning applies to the passage area.
1. Treat absence honestly
No AIS symbol is not evidence that the entrance is clear.
2. Apply the warning
Reassess the route and departure decision using the actual forecast and sea room.
3. Keep independent watch
Use lookout, sound, radar if fitted and appropriate radio watch.
Sense check: If the plan would become unsafe when one receiver or transmitter fails, the information sources have not been combined defensively.
Common mistake or limitation
- Assuming every vessel appears on AIS and every target report is current.
- Treating NAVTEX as live traffic information.
- Allowing either system to replace lookout, collision regulations or passage judgement.
Recap
- AIS reports traffic data; NAVTEX broadcasts maritime safety information.
- Both systems have coverage, data and equipment limitations.
- Combine electronic information with independent observations and judgement.
Optional quick check
Section 3 of 10
What does a clear AIS display prove about nearby traffic?
Sources and factual review
Reviewed 20 August 2026 - Compass Revision editorial review.
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