Before AIS
By observing celestial bodies, ancient mariners could determine latitude and plot a rudimentary course. Near the shore, prominent features like headlands, mountains, or even constructed towers served as guideposts for sailors, ensuring that they could find their way to safe harbors.
The 20th century marked a significant shift with the advent of radio communications. Ships were able to send distress calls and communicate with other vessels and shore stations over long distances. The use of Morse code and later voice transmissions allowed ships to share positions and navigational warnings. Ships could now reach out for help or coordinate with others to avoid dangerous areas.
Introduced in the 1940s for commercial use, radar systems used radio waves to detect other vessels and land obstacles even during low visibility conditions such as fog or darkness. It could show where other vessels were, but it didn’t provide any specifics about them. Information such as the type of vessel, its cargo, destination, or actions it might take in navigational situations was not available. While radar could alert a captain to the presence of other ships, it offered no insight into their intentions or identity—which sometimes made avoiding collisions and navigating busy waters a complex task.
Busier shipping lanes and larger vessels required a more sophisticated system capable of providing detailed information about the surrounding marine traffic. The marine community sought a solution that would ensure safety in increasingly crowded waters and minimize the risk of maritime accidents.
Mariners had to manually calculate their vessel’s position, speed, and course alterations, relying on skills honed through practice and experience. While these methods had supported navigation for centuries, they were not foolproof and left room for human error—especially under pressure or in changing conditions.
The Birth of AIS
In 1998, the IMO’s Maritime Safety Committee adopted a new requirement as part of the Safety of Life at Sea (SOLAS) Convention to develop an automatic identification system that would be carried by all sizable ships on international voyages. The system was designed to be capable of providing key information, including the ship’s identity, type, position, course, speed, navigational status, and other safety-related data to appropriately equipped shore stations, other ships, and aircraft.
The AIS was intended to operate in an automatic and continuous mode, regardless of external conditions, and to be intrinsically intuitive so that when information was exchanged, it could be effectively used by the ship’s officers without placing additional strain upon them.
AIS technology works by using VHF radio channels to transmit and receive encoded data over the airwaves. When the conventions for AIS were first established, their inclusion in the SOLAS Convention meant that they became part of a global regulatory framework that would facilitate widespread adoption and standardization.
The early technical challenges were significant as this system required a robust method of data transmission and reception that could function in the often harsh maritime environment. International collaboration among maritime authorities, navigation safety experts, and technology developers led to the establishment of performance standards and the rapid progression of AIS technology.
The deadline for the deployment of AIS technology was set by amendments to SOLAS and started with implementation by the end of 2004, applying to passenger ships, tankers, and all ships over 300 gross tonnage. The regulations specified that AIS devices should have the capability to automatically provide information to appropriately equipped shore stations, other ships, and aircraft. Receive such information; monitor and track ships; and exchange data with other ships and shore stations.
Early Version of AIS
The early version of AIS was developed as a simple yet powerful ship-to-ship and ship-to-shore communication system. It functioned by automatically transmitting and receiving vessel information to nearby ships and AIS base stations located along coastlines.
The first iteration of AIS, often referred to as AIS 1.0, was designed to broadcast key pieces of information including a ship’s identity—signified by its Maritime Mobile Service Identity (MMSI)—its position, speed, course, and other navigational data. This data was transmitted at regular intervals using VHF radio frequencies. There was no need for manual input from the ship’s crew, which helped in reducing human error and workload.
AIS units were equipped to handle a range of data processing functions and operated using standardized communication protocols. This ensured compatibility and facilitated the exchange of information among all vessels equipped with AIS, no matter their origin or make of equipment. The information sent by AIS transceivers could be displayed on various devices, including dedicated AIS screens, radar screens, or Electronic Chart Display and Information System (ECDIS) screens.
The early versions of AIS were mandated to have certain functionalities such as:
The ability to operationally interface with shipborne navigational equipment.
A self-checking capability that alerted users to any operational problems.
The capacity to handle a significant amount of data traffic without data loss.
Early AIS had a limited range, based as it was on VHF radio technology. It was effective within Line of Sight (LOS) distances, which could lead to gaps in monitoring vessels on high seas. There was concern about data congestion in heavily trafficked sea lanes where the volume of AIS communications could strain the system’s capacity.
Capacity issues were addressed through the AIS communication protocol’s time division multiple access (TDMA), which organizes data transmissions to prevent overlap. Areas with dense maritime traffic continued to challenge the system’s efficiency, leading to further refinements in bandwidth management and data handling.
Enhancements and Global Integration
The main enhancements after the initial rollout of AIS technology were the development and standardization of AIS message types. This involved defining various message formats used to communicate different types of information, such as static vessel information, dynamic navigational data, and voyage-related details. Improving the diversity and specificity of data transmitted by AIS gave vessel operators a more comprehensive understanding of their surroundings and improved decision-making capabilities on the sea.
To increase reliability, the VHF data link (VDL) used by AIS was improved to manage the growing volume of data being transmitted as adoption increased. Advanced error-checking mechanisms and communication protocols were developed to ensure the integrity of data despite the noisy maritime environment and potential for signal interference.
Regulatory bodies around the world needed to adopt AIS and integrate it within their existing maritime laws and regulations. Mandating the use of AIS on international voyages, as per the directives of the International Maritime Organization (IMO), provided a standardized approach to vessel tracking and monitoring.
To extend the benefits of AIS beyond the reach of coastal AIS stations, space-based AIS (S-AIS) technology emerged. Satellite constellations equipped with AIS receivers enabled the tracking of vessels over open ocean waters, filling the gap where terrestrial AIS could not reach. The global coverage achieved by satellite AIS meant that vessels could be monitored across the entirety of their voyages, enhancing the capabilities for search and rescue, piracy prevention, and environmental monitoring.
By sharing data internationally, maritime authorities could monitor global shipping traffic more effectively. This collaboration facilitated a more coordinated response to maritime incidents and improved the efficiency of maritime traffic management.
AIS data became an integral component of Vessel Traffic Management Systems, which play a vital role in managing vessel traffic in busy ports and waterways. AIS allowed VTMS operators to visualize and manage traffic with precise vessel identification and location data, minimizing the risk of accidents and optimizing waterway resources.
With the establishment of AIS as a global standard, it allowed for integration with other existing navigational tools such as the Electronic Chart Display and Information System (ECDIS) and the Global Positioning System (GPS). This kind of technological convergence created a robust suite of navigational aids for mariners, further enhancing maritime situational awareness.