What is AIS?

The Universal Shipborne Automatic Identification System (AIS) is a system of transponders installed on vessels which transmit over two dedicated digital marine VHF channels. The data is sent from each vessel every few seconds and contains position and movement information such as course, speed, latitude, longitude, and rate of turn. Static information about the vessel is sent every few minutes and includes the name, type of ship, length, beam, draft, etc. Nearly all commercial ships are mandated to carry AIS transponders and each year more yachts, launches and work boats are fitting AIS equipment.

AIS Transponders: An AIS transponder receives and translates the AIS digital radio signals. It also sends AIS signals, making your vessel visible to others with AIS equipment. There are two types of transponders, Class A intended for SOLAS vessels and Class B for fitting on non-SOLAS category vessels. AIS transponders are sometimes referred to as transceivers in the marine industry.

AIS Receivers: An AIS receiver operates in the same way as transponder but is a receive only device. If your vessel has a receiver you are able to view vessels in your area but other vessels will not see you on their AIS equipment.

AIS Display: An AIS display interfaces with either a transponder or receiver to display the AIS radio signals in a useable format. A dedicated AIS display is very useful to allow critical safety information to always be available at a glance and can include features that aren’t normally found in plotters or computer programs. If the transponder or receiver is WiFi enabled, you are able to use your smart phone, tablet or computer as an AIS display.

AIS Aerial/Splitter: A dedicated AIS aerial is used to pick up and transmit AIS signals only. A AIS/VHF splitter can be installed in order to share an existing VHF aerial between your VHF radio and AIS transponder or receiver.

For another excellent introduction to AIS, take a read of this article, How AIS Can Improve Your Navigation & Safety. It's written by Tim Bartlett who is acknowledged as a worldwide authority on marine electronics.  This article was published in the March 2011 Yachting Monthly magazine.  It answers some of the most asked questions about AIS such as:

  • Can ships filter out Class B AIS?
  • Is AIS complex to use?
  • Is AIS useful on a yacht?
  • Is AIS Class B as powerful as AIS Class A?
  • Do all ships use AIS?
  • What is the benefit of the target list?
  • What is the benefit of a separate AIS display versus an AIS data box?
  • What is the benefit of the graphic display?
  • How do I know if they have seen me?
  • How do I install AIS?

Who has AIS Equipment?

Every year, more and more vessels are voluntarily installing AIS equipment due to the enormous safety benefits. During the 73rd Session of the IMO's Maritime Safety Committee, the following vessels were identified as requiring AIS equipment as a mandatory requirement.

All ships of 300 gross tonnage and upwards engaged on international voyages and cargo ships of 500 gross tonnage and upwards not engaged on international voyages and passenger ships irrespective of size shall be fitted with AIS, as follows:

  • Ships constructed on or after 1 July 2002
  • Ships engaged on international voyages constructed before 1 July 2002
  • In the case of passenger ships, not later than 1 July 2003
  • In the case of tankers, not later than the first "safety equipment survey" after 1 July 2003
  • In the case of ships, other than passenger ships and tankers, of 50,000 gross tonnage and upwards, not later than 1 July 2004
  • In the case of ships, other than passenger ships and tankers, of 10,000 gross tonnage and upwards but less than 50,000 gross tonnage, not later than 1 July 2005
  • In the case of ships, other than passenger ships and tankers, of 3,000 gross tonnage and upwards but less than 10,000 gross tonnage, not later than 1 July 2006
  • In the case of ships, other than passenger ships and tankers, of 300 gross tonnage and upwards but less than 3,000 gross tonnage, not later than 1 July 2007

United States Coast Guard Rule Change

The United States Coast Guard issued new AIS rules in January 2015 requiring nearly all commercial vessels of 65 feet or more to install AIS transponders by March 2016. The new rule applies to all self-propelled commercial vessels of 65 feet or more operating within all U.S. Navigable Waters. Certain towing, passenger and dredges are also included. Read more...