AIS (Automatic Identification System) is a tracking and identification system used in the maritime industry to enhance navigational safety, collision avoidance, and situational awareness. It allows vessels to transmit and receive real-time information such as position, speed, course, and other data.

AIS is great for increasing your “look-out” capabilities on small yachts, specifically at night or when sailing shorthanded. Setting a radius around your yacht of, say, 5 nm, AIS will warn you audibly when a vessel enters this radius. Furthermore, it will tell you whether you are on a collision course! Loving it…

How AIS Works

AIS operates via a combination of VHF radio signals and GPS technology:

1. Transmission: AIS-equipped vessels broadcast information over dedicated VHF frequencies.
2. Reception: Other AIS-equipped ships and shore stations receive these transmissions, providing a real-time overview of nearby vessel traffic.
3. Integration: Data is often displayed on chart plotters, electronic navigation systems, or standalone AIS receivers.

AIS Information Transmitted

AIS broadcasts two main types of data:

1. Static Data (entered manually):
   • Vessel name
   • MMSI (Maritime Mobile Service Identity) number
   • IMO number (if applicable)
   • Vessel type
   • Length and beam (dimensions)
2. Dynamic Data (updated automatically via GPS or sensors):
   • Vessel position (latitude and longitude)
   • Course over ground (COG)
   • Speed over ground (SOG)
   • Heading
   • Navigational status (e.g., anchored, underway)
   • Rate of turn

Types of AIS Devices

1. Class A AIS:

   • Mandatory for larger commercial vessels.
   • Higher transmission power and frequent updates (every few seconds when moving, every few minutes when stationary).
   • Transmits both static and dynamic data.

1. Class B AIS:

   • Designed for smaller vessels (e.g., recreational boats, smaller fishing vessels).
   • Lower transmission power and less frequent updates.
   • Provides similar information but with a smaller impact on VHF traffic.

1. AIS Receivers:

   • These can only receive AIS signals; they do not transmit. Used on smaller vessels for situational awareness.

1. AIS-SART (Search and Rescue Transponder):

   • A specialised AIS device for emergencies, allowing rescue teams to locate lifeboats or people in distress.

Benefits of AIS

1. Collision Avoidance:

   • Provides real-time tracking of nearby vessels, including their direction and speed.
   • Alerts crew members to potential collision risks.

2. Improved Traffic Management:

   • Helps ports and authorities manage vessel movements efficiently.
   • Assists in coordinating safe passage through busy waterways.

3. Search and Rescue (SAR):

   • Helps locate vessels or individuals in distress by providing accurate position data.

4. Enhanced Security:

   • Monitors vessel activities, aiding in identifying unauthorised or suspicious movements.

Limitations of AIS

1. Range:

   • VHF-based, the range is limited to approximately 15–20 nautical miles, depending on antenna height.

2. Data Accuracy:

   • Relies on user-input data for static information; errors can occur if the data is outdated or incorrect.

3. Visibility:

   • Not all vessels must use AIS (e.g., smaller recreational boats), so not every nearby vessel will appear.

4. Signal Clutter:

   • In busy ports, AIS data can become overwhelming without filtering.

Applications of AIS

• Commercial Shipping: Navigation and compliance with international regulations.
• Recreational Boating: Situational awareness for safety.
• Fisheries Management: Monitoring vessel activity for regulatory purposes.
• Search and Rescue: Locating vessels or individuals in emergencies.
• Marine Conservation: Tracking shipping activity to reduce environmental impacts.

AIS has become a cornerstone of modern maritime navigation and safety, helping vessels avoid collisions, aiding search-and-rescue missions, and supporting efficient maritime operations. I highly recommend AIS to those cruising our coastlines, particularly at night.

Please feel free to leave a comment below about your good/bad experience with AIS…

How does AIS compare with RADAR

AIS vs. RADAR