AIS: A tool for VTS



J. Carson-Jackson, Technical Coordination Manager, International Association of Marine Aids to Navigation and Lighthouse Authorities, St Germain-en-laye, France



Automatic Identification System (AIS), as we know it today, is quite different from the original imaginings of a ‘transponder’ for ships. It was in the late 1980’s, early 1990’s that the concept of a transponder for ships began to surface, to aid in identification of vessels in Vessel Traffic Services (VTS). This idea was really brought to the forefront by the wide-spread acceptance of ‘positive control’ areas in air traffic control. In the 1960s the aviation world began successful testing of a system where aircraft in certain ‘positive control’ areas were required to carry a radar beacon, called a transponder, that identified the aircraft and helped to improve radar performance. Although there are many areas where parallels between VTS and air traffic control (ATC) cannot be identified, this appeared to be one area where VTS could learn from the lessons gained in ATC.

At the International Association of Marine Aids to Navigation and Lighthouse Authorities (IALA) VTS Symposium in Rotterdam, 1996, many references were made to these ‘transponders’ for ships. The emphasis at this time was on the ship – shore benefits gained through positive identification of vessels and enhanced display. Indeed, in his 1994 report ‘Safer Ships, Cleaner Seas,’ Lord Donaldson urged the United Kingdom Government to “press for the introduction of a world-wide system of transponders”.

In the following years, at many international forums, the concept of ‘transponders’ for ships went through various evolutions until AIS, as we know it today, came into existence. When we look back at how AIS evolved, it is easy to see how AIS and VTS fit together. The very concept of positive identification for ships was, initially, as a tool to aid VTS. The other benefits, and the system which is now known as AIS, have followed a natural evolution as the benefits of the system were more clearly identified.


The International Maritime Organization (IMO) Assembly Resolution A.857(20), Guidelines for Vessel Traffic Services, established that the following tasks should be performed by a VTS: “A VTS should at all times be capable of generating a comprehensive overview of the traffic in its service area combined with all traffic influencing factors. The VTS should be able to compile the traffic image, which is the basis for the VTS capability to respond to traffic situations developing in the VTS area. The traffic image allows the VTS operator to evaluate situations and make decisions accordingly. Data should be collected to compile the traffic image. This includes:

1. Data on the fairway situation, such as meteorological and hydrological conditions and the operational status of aids to navigation;

2. Data on the traffic situation, such as vessel positions, movements, identities and intentions with respect to manoeuvres, destination and routing;

3. Data of vessels in accordance with the requirements of ship reporting and, if necessary, any additional data required for the effective operations of VTS.”

What a VTS does is improve port efficiency and reduce the risk of marine accidents by providing timely, accurate, and relevant information to mariners and allied services.

According to SOLAS Chapter V, Regulation 19 – AIS shall:

• Provide automatically to appropriately equipped shore stations, other ships and aircraft information, including the ship’s identity, type, position, course, speed, navigational status and other safety-related information

• Receive automatically such information from similarly fitted ships

• Monitor and track ships

• Exchange data with shore-based facilities

According to the IALA Guidelines on AIS as a VTS Tool (published December 2001), AIS is an important supplement to existing communication systems and provides information to:

• Identify vessels

• Assist target tracking

• Simplify information exchange

• Provide additional information to assist collision avoidance

As we look at the implementation of AIS, we can see that it provides many benefits as a tool for VTS. In addition to the benefits envisioned in 2001, AIS provides valuable assistance in situational awareness and statistical analysis for overall traffic planning.

AIS: A tool for VTS

VTS performs three basic tasks relevant to the provision of its services – information (data) collection, evaluation and dissemination. Within the evaluation of the information, overall situation awareness is developed, and the various tools used by VTS assist in providing this picture of the waterway. In addition to these basic tasks, VTS can provide an ideal location for collection of statistical data that can be used in the overall provision of aids to navigation services.

While the ship-shore/shore-ship aspect of AIS is often overlooked, AIS can and does assist VTS. Indeed, as indicated in SOLAS Chapter V, to realise its full potential, AIS must be able to exchange data with shore-based facilities. Although the tool is very different from what was first imagined, AIS provides valuable information to VTS, including the originally envisioned positive identification of vessels.


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