Maritime Safety Information: NAVTEX, SafetyNET and MSI reception
MSI and its two main carriers
Maritime Safety Information includes navigational warnings, meteorological warnings and forecasts, SAR information and other urgent safety information. SOLAS requires ships to receive MSI for the areas they sail. NAVTEX is a terrestrial, automatic direct-printing service on 518 kHz (international English), with 490 kHz and 4209.5 kHz used nationally. SafetyNET is the Inmarsat EGC service for ocean areas and some coastal areas. A ship may use NAVTEX, SafetyNET or both; the certificate and area determine the required fit.
Reading NAVTEX
A NAVTEX message begins with ZCZC, then a station identifier, message-type letter and serial number; it ends with NNNN. Type A is a navigational warning, B a meteorological warning, D SAR information and E a meteorological forecast. The receiver can be set to accept selected message types and transmitter stations; do not switch off types A, B and D if you need them.
Worked example
A NAVTEX receiver shows 'ZCZC IB12' followed by a gale warning, then 'NNNN'. Reasoning: the header identifies the station and message type; B is a meteorological warning, so it is a safety-critical message for the area. The watch officer should note it, plot or act on it and ensure the bridge team is informed. It is not a routine message to file unread.
Traps
Do not assume NAVTEX covers the open ocean; it is coastal, typically about 200–400 nm. Do not rely on SafetyNET without checking the correct ocean region/NAVAREA and that the EGC receiver is logged in. Do not mute all NAVTEX alarms. Do not ignore messages for a nearby area that affect your route.