We all know what an AIS is: an Automatic Identification System which sends a signal that “labels” the ship, showing data such as name, IMO number, port of departure and of arrival, even a picture… Nowadays there are a lot of webs where you can track, through their AIS signal, the routes of ships throughout the oceans: one, two, three, four, and even more…

Then main utility of the AIS comes when it gets integrated into other navigation aids. Hence in our multifunction display we not only see a tiny dot signalling that vessel in front of us, but the AIS identifies her and tracks her course. And, more important, we are seen by others! AIS displays as well navigation marks such as buoys and lighthouses. And all this in our electronic chart, and live.

But one picture is worth a thousand words:

Screenshot of electronic chart with AIS, Menorca Channel


Screenshot of electronic chart with AIS, Barcelona port entrance. The label initially displayed when hovering the mouse over the ship, shows only a small part of the data from the AIS

Be aware that the AIS does not replace the radar; rather it complements the radar. Mainly because AIS is not mandatory to all ships (or maybe it is off, or out of order): not being displayed on the screen doesn’t mean it may not be out there.

Hence one of its most important applications: as commercial ships seldom see small boats, at least being displayed on their screen as a small pink triangle is something. One point in favour of safe navigation for everybody.

AIS: colour code as per ship type

The AIS works using GPS data (i.e. satellite channel) and with the register (name, IMO number, MMSI…) and operation information (port of arrival, speed, if she’s under way or anchored…) of the ship. All these data are transmitted through VHF, automatically every 2 seconds approx.

AIS is mandatory for ships bigger than 500 GT (and 300 GT if on international voyage); and not mandatory for pleasure boats lesser than 45 m.

That is why there are two types of AIS:

  • AIS Class A: with more features, with requirements under IMO and governments rules; for ships where AIS is mandatory
  • AIS Class B: simple, shorter range, for boats having installed AIS on their own free will; the signal is sent every 30 seconds, and it includes less data

The AIS is purely a transceiver that receives and emits signals (some older models didn’t receive, only emit). Depending on the model, they include a screen to display the data. But it’s better to integrate it into a multifunction display, with the electronic charts. Some models have a WiFi, hence you can use your mobile or a tablet to display.

The installation is quite simple:

  1. Install the transceiver box on a protected place (not outside!); connect it to the boat batteries
  2. Connect the transceiver to the GPS antenna (most of the AIS will include that antenna in the pack)
  3. The transceiver has to be connected to a VHF antenna as well; you can use the one you already have by using a splitter, with which we can double the signal to the AIS
  4. Connect the transceiver to the equipment on the bridge, e.g. your plotter multifunction display

(The transceiver is not very bulky; just like a number 27-kid-shoe box.)

Once installed and connected to the electronic equipment, there’s nothing else to do but watching the screen to get the displayed info. Moreover, most of the AIS have an option to save the data via an SD card, so you can register your route while the AIS is on.

All the websites linked on the firs paragraph, and others, offer a service to track your boat via internet, showing all the data provided by the AIS. For when a friend borrowed your boat.

In a few days we, at Medenisa, are going to supply and install an AIS for a nice 32 m Leopard built in 2006. Apart from this AIS, we have just installed a BNWAS watchkeeper to this yacht.

As you may know, ships must have always a radio watchkeeping, in order to get emergency calls so that help can be sent asap (this regulations come from the Titanic disaster: some ships did see her SOS flares, but they mistook them for fireworks; those ships had their telegraph stations off). The BNWAS (Bridge Navigational Watch Alarm System) is a system that detects when there is no watch on the bridge, meaning the ship is sailing by herself and there is no watchkeeping. But we’ll talk about this system soon…

Sketch of the yacht


Any doubt about AIS? Ask us, we’ll be delighted to assist you!