Passage Nautical: Yacht News & Know-How

What is AIS and do you need it?

Jul 8, 2019 8:09:30 PM / by D Reynolds

What is AIS?

AIS (Automatic Identification System) was developed to help commercial vessels see who is operating in a given area. AIS works with a combination of GPS, VHF radio, and an AIS transponder.  On commercial vessels, the transponders broadcast both static and dynamic information. Static such as the ship’s length and beam, name, and port of origin, dynamic such as the ship’s position, course and speed over ground and its navigational status, for example, if at anchor, underway by engines or engaged in fishing. This information is updated continuously and can be viewed by any other ship or boat equipped with a designated AIS unit as well as on any computer or smartphone linked to the internet.

The main attraction of AIS is safety. When equipped with AIS, you'll know all of the commercial vessels nearby, and the course of a ship that appears to be getting a little too close for comfort. You'll also know if someone is nearby in case you need to call for help and the name and type of ship you need to hail. At the same time, the captains of nearby vessels will be aware of your position, unless you have only passive AIS (an AIS receiver or apps). It puts you "on their radar," whether your boat would normally show up on their radar or not.

On the day of this post, this screenshot shows a live map of ship traffic from Marine Traffic so you get an idea of ship's traffic.

Further advancements in AIS in the areas of safety include AIS MOB (man overboard) or PAIS (Personal AIS) devices. These small units generally attach to a lifevest or life raft and transmit a MOB notification with GPS coordinates over the AIS system. Anyone in the water is electronically visible to any AIS-equipped boat within approximately 4 miles.

Do you need AIS?

The answer to this question for most recreational boaters depends upon your location and ocean going plans.  For boaters who regularly navigate through heavily congested areas or busy harbors or are planning for long-distance cruises, the safety advantages of AIS make it a yes. The same goes for boaters who boat at night or in the fog, when moving lights and distant sounds can be deceiving.  One thing for sure is that with AIS aboard, your boat will be a safer boat.

What are affordable AIS Options?

  1. Passive AIS, via Smartphone or Computer

There are sites and apps that let you access vessel data so now AIS data can be as simple as downloading an app onto your smartphone.

The the least expensive way to harness AIS data is from your computer and visiting the website marinetraffic.com and bring up a world map showing AIS vessel data. Zoom in, click, and learn.

If using a phone is more your style, apps are also available for iPhone, Android, and Windows. The AIS apps include Boat Beacon (iPhone, Android) Ship Finder (iPhone, iPad, Android) and Vessel Finder (iPhone, Android). It’s recommended that third-party-produced websites and apps should not be expected to be as accurate as designated units and be considered supplements to navigation, as opposed to something to be solely relied upon.

With the smartphone apps and AIS websites you can watch vessel traffic but other boats can’t see you on their chartplotters, You can see where your boat fits into the traffic by using these apps and websites at a reduced cost.

To display your boat’s AIS information using these apps and sites, install Mobile AIS (mAIS), a free app from MarineTraffic, register your email address, and enter your vessel’s MMSI number. The app will broadcast AIS information over the web using your smartphone’s GPS position and cellular data networks. Once you load, click “Start” to begin reporting your position, with status, course and speed.

Once you do this you can view your vessel on MarineTraffic.com, which maintains a worldwide network of AIS receivers.  In theory, the data is shared by a number of AIS sites, though there may be delays or vessel information may be out-of-date. Again, since data is not transmitted through VHF radio frequencies, your AIS information will not display on the chartplotters of nearby vessels, only on websites. Remember you are not visible on AIS on nearby boats.

  1. VHF’s with AIS

All major electronic companies make VHF’s with built in AIS which allows you to track nearby vessels (receivers) so you can see all traffic in your area. This only allows you to see, not be seen by nearby traffic. If you want to be able to transmit your information (position, MMSI number, vessel data...), the addition of a transponder will accomplish this.  VHF’s also come with GPs that can be integrated and displayed on your onboard electronics.  The cost for this technology toady is very affordable. 

See: B&G VHF AIS Products

        Raymarine VHF AIS Products

D Reynolds

Written by D Reynolds

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