Maritime Safety
Information Under
the GMDSS
Background
 The
GMDSS makes specific
requirements with regard to radio
equipment, and ships must be able to
carry out several different functions,
one of which is the ability to
TRANSMIT and RECEIVE Maritime
Safety Information (MSI)
Maritime Safety Information (MSI)
Navigational reports
 Meteorological reports
 Weather Forecasts
 Messages of General Importance

MSI is transmitted via the ff:
NAVTEX
 Inmarsat EGC system
 Radio Telex (NBDP)
 Radio telephony (Safety Messages)

Navtex system MSI
The NAVTEX System
Navtex system could reach up to a
distance 600 nm offshore.
 518 kHz is the International navtex
frequency
 24 Navtex stations in one NAVAREA
 The 24 stations are divided into 4
groups consisting of 6 transmitting
stations.
 Every group is allowed one hour
transmission time. (10mins/4 hours)

 There
Navareas
are 16 Navareas worldwide.
 Navtex stations are geographically
separated.
 Every Navtex station has its own
identification character (A-Z).
 Navtex stations coverage is shown in
the ITU “List of Radio Determination
and Special Service Stations”
 The Navtex coordinator in each Navarea
decides which MSI messages the system
is to broadcast.
Navtex Stations Worldwide
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The Navtex Coordinator
• Coastguard
• Buoyage authority
• Electronic Navaids
• Offshore Operator
• Government dept.
• Ship reports
• NAVAREA co-ordinator
• National Coordinator
Navigational
warning
co-ordinator
Initial distress
message
SAR
co-ordinator
NAVTEX
coordinator
Transmitter
Ice Monitoring
meteorological
offices
Meteorological
message
co-ordinator
Building up a Navtex message
-----------------------------------------------------------ZCZC
B1 B2 B3 B4
Message Origin …….
……………………..
NNNN
-------------------------------------------------------------
The Subject Indicators (B2)
A = Navigational Warnings (cannot be rejected by the
receiver)
B = Meteorological Warnings (cannot be rejected by the
receiver)
C = Ice Reports
D = Search and Rescue information (cannot be rejected by
the receiver)
E = Meteorological Forecasts
F = Pilot Service Messages
G = DECCA Messages
H = LORAN Messages
I = OMEGA Messages
J = SATNAV Messages
K = Other Electronic Navaid Messages (messages concerning
radio navigation services)
L = Navigational Warnings for mobile drilling rig movements
(cannot be rejected by the receiver)
V = Amplifying navigational warning information initially
announced under “A”
Z = No messages on hand
-----------------------------------------------------------ZCZC
GA20
GL67
PB68
NETHERLANDS
ORKNEY
RIGMOVE.
ISLANDS
SOUTHERN
COASTGUARD
NORTHSEA.
GALE
“CHARLESNR.
WARNING
ROWAN”
55 180630
AT FEB
54-19N 02-07.7E
LOTHER ROCK RACON 58.44N 02.49W
CANCELTHAMES
DOVER
THIS MESSAGE
– SOUTH121020
8
Z FEB 25
TEMPORARILY
OTHER
DISTRICTS
OFF–AIR
NO WARNINGS
NNNN
NNNN
-------------------------------------------------------------------------------------------------------------------------