Shipping has traditionally been slow in integrating technological developments, but maritime communications are certainly not a representative case. From flag semaphores, as a primary means of ships’ communication, to the GMDSS, the evolution of maritime communications has been long.
Ship communications involve both ship-to-shore interactions, such as voyage instructions, notices of arrival contact with ports, etc., and ship-to-ship interactions, such as safety of navigation matters. In an era of increased connectivity, shipping legislation is expected to increasingly mandate vessel communication and information reporting (see the IMO DCS and EU MRV). But what have the key means of communication been over the years?
Maritime signal flags
Dating back to ancient times, this is a system under which a series of flags can spell out a message, each flag representing a letter. Individual flags have specific meanings, e.g., when diving support vessels raise the “A” flag, they indicate they cannot move from their current location because they have a diver underwater, warning other vessels to keep clear. As such, maritime signals are the most effective way to send messages without the use of technology.
The principal system of flags and associated codes is the International Code of Signals, an international system of signals and codes for use by vessels to communicate important messages (e.g., regarding safety of navigation), especially when language difficulties arise. Signals can be sent by flaghoist, signal lamp (“blinker”), flag semaphore, radiotelegraphy, and radiotelephony. The Code is currently maintained by the IMO, which published a new print edition in 2005.
In the early 19th century, the radio enabled ship-to-shore communication by means of Morse Code or other coded signals. Morse code is a method that encodes text characters as standardized sequences of two different signal durations (dits and dahs). The International Morse code encodes the 26 basic Latin letters (A through Z), one accented Latin letter (É), the Arabic numerals, and a small set of punctuation and procedural signals (prosigns). However, the fact that every letter had to be transmitted individually was adding to the vessel communication expenses, eventually making the technology obsolete.
The integration of VHF radio resulted in a drastic transformation of marine communications, making ship-to-ship communication a reality and improving the safety of everyone involved. Using uses FM channels in the very high frequency (VHF) radio band, marine VHF radio involves two-way radio transceivers on ships enabling voice communication, not only from ship-to-ship, but also ship-to-shore (e.g., with harbormasters). The marine VHF is implemented worldwide since the early 1900s, shortly after Guillermo Marconi invented the radio technology. However, providing under 1GHz in frequency, it is understood that the VHF technology brings several daily challenges related to radio limitations.
Did you know?
The first significant marine rescue enabled by radio technology occurred in 1909, when 1,500 people were saved from the sinking of the luxury cruise ship RMS Republic. In addition, the Titanic tragedy, three years later, brought the field of marine radio to public awareness, and marine radio operators were regarded as heroes.
To overcome the disadvantages associated with VHF radio, the IMO in 1979 encouraged all member nations to establish Maritime Mobile Satellite Communication (MMSC) systems. As enablers of modern ship communications since the late 20th century, the satellite antenna is a tenuous link to systems ashore.
Ship communications are often challenged by the large quantities of data that most satellite communication systems generate. This is what the VSAT (very small aperture terminal) seeks to address. Subscribing to VSAT services for a monthly fee, operators can exclusively use satellite channels for sending and receiving voice and data, enabling a network that permits the transmission of large quantities of data.
A new era for ship communications arrived in the early 1990s with the implementation of the Global Maritime Distress and Safety System (GMDSS); an integrated communications system using satellite and terrestrial radiocommunication systems. The full implementation of GMDSS came on 1st February 1999, officially eliminating the Morse Code as a means of maritime communication.
Under SOLAS in Chapter IV, all passenger ships and all cargo ships over 300 GT on international voyages are required to carry specified terrestrial and satellite radiocommunications equipment for sending and receiving distress alerts and maritime safety information, as well as for general communications, according to IMO. The GMDSS offered communication by email as an option that did not exist before.
Earlier in 2022, the IMO approved a modernization plan of the GMDSS with respective amendments expected to enter into force by 2024.
The Digital selective calling
As part of the GMDSS, Digital Selective Calling (DSC) allowed for greater communication capabilities including remote control commands that could transmit and receive distress signals, place urgent safety calls, and put out routine messages. Today, DSC controllers are often integrated with the VHF radio, under SOLAS. Transmitting predefined digital messages via the VHF, DSC was developed to replace the voice calls used in conventional procedures.
The Automatic Transmitter Identification System
Under the Basel agreement, European inland waterways mandate the use of an Automatic Transmitter Identification System (ATIS), as part of the VHF radio, which conveys the vessel’s identity, in the form of a ten-digit code, after each voice transmission.
As expected, the increasing digitization of maritime communications has brought respective cyber vulnerabilities, which requires constant vigilance from satellite communication providers and operators and which prompted the IMO in 2017 to recommend ship operators to address the issue in their SMS.
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