Safety communications are not confined to the GMDSS requirements alone as there are other areas of SOLAS where communications that relate to safety are mandated and beyond that there are voluntary equipment that can be used to enhance safety some of which will interact with GMDSS.
Included among the various equipment and systems outside of GMDSS are personal locator beacons (PLBs) which transmit alerts on emergency frequencies and also mandatory radar equipment which makes use of the communications spectrum. Technically ships’ radar systems operate using radio transmissions although they are not considered as communication devices, but another collision avoidance system is because it transmits information intended to be used by other vessels and shore stations.
The Automatic Identification System (AIS) was initially developed purely as a response to the issue of collision avoidance and as a corollary to aid shore-based VTS operators as well as navigators on ships to properly identify radar targets. AIS consists of a transponder system in which ships continually transmit their ID, position, course, speed and other data over VHF. The data transmitted is derived from ships equipment as regards position, course and speed, from initial input for the ID which comprises ship’s name and call sign and from direct manual input for other details such as port of destination and type of cargo.
Updated information is transmitted at regular intervals of very short duration. When received on the other ships, the data is decoded and displayed for the officer of the watch, who can view AIS reports from all other AIS-equipped ships within range in graphic and text format. The AIS data may optionally be fed to the ship’s integrated navigation systems and radar plotting systems to provide AIS “tags” for radar targets. It can also be logged to the ship’s Voyage Data Recorder (VDR) for playback and future analysis.
In 2000, IMO adopted a new requirement as part of a revised new SOLAS Chapter V for all ships to carry AIS capable of providing information about the ship to other ships and to coastal authorities automatically. The regulation requires AIS to be fitted aboard all ships of 300gt and upwards engaged on international voyages, cargo ships of 500gt and upwards not engaged on international voyages and all passenger ships irrespective of size. The
requirement became effective for all ships by 31 December 2004.
The IMO regulation requires ships fitted with AIS to maintain AIS in operation at all times except where international agreements, rules or standards provide for the protection of navigational information. The regulation requires that the AIS must provide information – including the ship’s identity, type, position, course, speed, navigational status and other safety related information - automatically to appropriately equipped shore stations, other ships and aircraft and to receive automatically such information from similarly fitted ships.
AIS transmitters can also be attached to navigational marks or to hazards and transmit information that will complement the sight/ sound signals that may be present. These fixed AIS transmitters can also be used to give other information such as current strength and direction.
Although initially intended only for navigation use by ships and shore authorities, AIS data is now regularly disseminated by commercial operations either to subscribers or on a gratis basis allowing almost anyone to determine any specific ship’s current whereabouts and operational status. The IMO does not condone this use but appears powerless to prevent it.
Because AIS operates on VHF radio, there is a natural limit to the distance over which it can be transmitted. However, there is a small but growing number of service providers using satellites that can receive AIS signals when ships are out of the range of shore stations. These
services are generally referred to as satellite AIS or S-AIS. Most of the service providers say that their services are targeted purely at national security organisations but others make no secret of the fact that their customers are often commercial organisations including commodity traders and analysts.
It is fair to say that AIS has not been universally welcomed by navigators or ship operators. Many believe that its introduction was rushed and insufficient thought given to its use under operational circumstances. Officially AIS is an aid to navigation and not a collision avoidance method in its own right. Some seafarers believe that AIS overrides COLREGS but official advice from some flag states makes clear this is not so.
Just as with radar in its early days, AIS has been blamed for causing rather than helping to avoid collisions. One of the factors that many say was ill considered was the fact that by being obliged to transmit its identity, cargo and destination, a ship can easily be identified by those with criminal intent or even terrorists. Some operators address this by either transmitting false information at certain stages of a voyage or by switching the device off except when in very close traffic situations.