GMDSS is an international system which provides "911" or emergency communications for ships in distress. GMDSS was adopted by the International Maritime Organization (IMO) in 1988. The global implementation of GMDSS became fully effective on 1 February 1999.

Thales Systems Canada (Thales Systems) is a company that specializes in the design, development, integration, installation, set-to-work, and life cycle support for the shore based communications infrastructure of GMDSS solutions. We are supplying systems in Canada, Latin America, and Africa.

The Global Maritime Distress and Safety Service utilizes a combination of VHF, MF/HF and Satellite communications channels to facilitate the exchange of short digital messages between ships and shore stations and between ships using Digital Selective Calling (DSC). The messages are formatted and error checked to minimize errors that could lead to false alarms or incorrect information.

As indicated above, GMDSS combines various communications subsystems into one overall system. The GMDSS equipment carried by ships varies with the distances that they travel away from the shore. The shore based GMDSS infrastructure that is installed is in turn partly determined by the type of vessels that transit a country’s waters and the emergency communications services that they need for safe operations. GMDSS divides the oceans into four sea areas that are identified as A1, A2, A3, and A4. These areas are defined as follows:

Area A1--The area within range of a VHF DSC coast station, which is about 20-30 miles.

Area A2--The area which is beyond A1, but, within the range of a MF DSC coast station. The distance is about 100 miles from shore.

Area A3--This area is beyond A1 and A2 but it is within the coverage footprint of a geostationary communications satellite which is the area between the latitude lines of 70 degrees north and 70 degrees south.

Area A4--These are the sea areas outside the A3 zone, it encompasses the polar seas.

Coastal vessels carry VHF radios but may also carry satellite communications equipment. Ships moving outside A1 need to carry MF equipment and VHF radios or satellite equipment. Ships operating beyond MF range must carry VHF, MF, and satellite communications equipment. Ships operating in A4 must carry VHF, MF and HF equipment.

Coastal communications station facilities are installed to provide coverage using dedicated signaling channels followed by correspondence on one of a number of working channels. VHF (A1) coverage is provided on channel 70 and MF/HF (A2/A3 & A4) coverage is provide on up to six channels as required by ionosphere conditions. Satellite coverage of the A3 region is also provided via INMARSAT.

In addition to DSC emergency messages the GMDSS service can include other services such as NAVTEX, a broadcast service of safety notices to mariners, Narrow Band Direct Printing (NBDP), a two way telex type service, and on VHF only, a direct dial public correspondence radio telephone.

The design of an optimum system is a trade-off of many technical, operational, coverage, service and cost factors. Thales Systems specializes in performing the required trade-off studies so that the systems supplied and integrated by the company best suit the specific requirements of each of our customers. Thales Systems does not build communications equipment. The company is therefore an independent system integrator with no hardware bias. The company can choose equipment from many original equipment manufacturers (OEM) from around the world to ensure the GMDSS systems we deliver suits the economic, logistics support objectives, and other preferences of our customers.

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