Issue Date: Sunday 1 January 2023
Aid: All AIS
The General Lighthouse Authorities (GLA) are continuing to provide AIS AtoN at selected fixed and floating stations on the coasts of Great Britain and Ireland.
AIS AtoN are Aids to Navigation under the Merchant Shipping Acts and as such Statutory Sanction for their provision is required from the General Lighthouse Authority for the area in which they are established.Application forms are available at
It is considered appropriate at this time to repeat some guidance to mariners on the purpose of AIS AtoN and what they may expect to see on some of the available displays.
Displays & Symbology
The IMO mandatory carriage requirement for Class A AIS display is the Minimum Keyboard Display (MKD) which displays the data in alphanumeric form.
The information available to mariners will be dependent on their display system and not all transmitted information may be displayed. Mariners are encouraged to install systems that provide AIS overlay on ECDIS and Radar.
It is important to bear in mind that not all vessels are equipped with AIS. Of those vessels that are AIS equipped the displays available can range from no display on some Class B units, through the mandatory Class A MKD, to full ECDIS and Radar overlay. In the absence of ECDIS or Radar overlay users will not be able to fully utilise AIS AtoN functionality. There is also a variance on information that will be displayed by different manufacturers on ECDIS or Radar equipment.
The symbology that may be displayed on nautical charts, display systems and MKD is summarised below.
On nautical charts, AIS AtoN are indicated by a magenta circle, surrounding the existing AtoN symbol and an adjacent legend stating AIS. The font will be straight for fixed AtoN and italic for floating AtoN.
Symbol of a Virtual Aid to Navigation marked on a nautical chart. The topmark
indicates its navigational purpose.
|Where AIS is provided as an overlay on ECDIS, Radar or other display systems, AIS AtoN are indicated by a Diamond shape with crossed lines at the reported position of the AtoN.|
Where the AtoN is on station the diamond will be Blue and where the AtoN Off Station flag has been activated the diamond will be Red.
In the case of a Virtual AIS AtoN there will be a V below the crossed lines.
In the case of a Virtual AIS AtoN the diamond will be drawn using a thin dashed line. If available a symbol indicating the navigational purpose should be included e.g. a North Cardinal Virtual mark will include two triangles, pointed
Minimum Keyboard Display
The mandatory Minimum Keyboard Display (MKD) is only required to display data in alphanumeric form. Some MKD units are supplemented by a small graphical display. Exact presentation will vary but the layout opposite would be typical of MKD displays.
AIS stations provided by the GLA will transmit Message 21 – Aids to Navigation Report
Message 21 – Aids to Navigation report. This message will provide details of the Name, MMSI, Type and Position of the AtoN. In addition there will be an indication if the AtoN is off station, and of the status of the light, Racon or other equipment.
Other messages providing additional data may occasionally be broadcast. These would normally be binary messages 8/10 or short safety related messages 12/14.The Commissioners of Irish Lights provide live wind and sea state data from a number of AIS AtoN and also provide this information over the internet and Twitter, see www.irishlights.ie. Details of AIS AtoN are set out in Volume 2 of the Admiralty List of Radio Signals.
Irish Lights are continuing to expand our Met/ Hydro Service as per Commissioners of Irish Lights Notice to Mariners No. 05 of
2014. Mariners are requested to contact the General Lighthouse Authorities regarding their experience of AIS and in particular the extent to which AIS AtoN data is available to them.
¹ The General Lighthouse Authorities (GLA) consist of Trinity House (England & Wales), Northern Lighthouse Board (Scotland) and the Commissioners of Irish Lights (Ireland).
² Class A AIS units are those meeting the mandatory SOLAS carriage requirements (SOLAS Chapter V, Rule 19) for vessels over 300GRT. Class B AIS units are for use on craft that are not covered by the mandatory carriage requirements.
³ Virtual AIS AtoN are used to mark new dangers / wrecks or in circumstances where a physical AtoN is not appropriate. The AtoN does not physically exist and therefore will only be visible on display systems.By Order, Yvonne Shields, Chief Executive