AIS, or Automatic Identification System, is a VHF-based radio tracking system used by ships and small craft to automatically share information about their identity, position, speed, course, and other data with nearby vessels, shore stations, and sometimes satellites.

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⚓ 1. What Information Does AIS Share?

AIS broadcasts a digital signal containing key vessel details, such as:

• Vessel name and type

• MMSI number (a kind of unique vessel ID)

• Position, heading, course, and speed

• Navigational status (e.g. “Under Way,” “At Anchor,” or “Not Under Command”)

• Dimensions, draught, destination, and ETA (if input)

This information can be extremely useful for nearby vessels, allowing skippers to identify traffic and better assess collision risks or communicate directly via VHF if needed.

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📶 2. AIS Types

There are two main types of AIS transponders:

• Class A – Mandatory for large commercial vessels. Higher power and more detailed data with longer range.

• Class B – Designed for leisure craft and yachts. Lower power (typically 2W), usually providing around 5–10 nautical miles of range.

Some AIS systems are transmit-and-receive (transceivers), while others are receive-only, which allow you to see other vessels’ positions but don’t broadcast your own.

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€ Compass; 3. AIS and Collision Avoidance

AIS is a support tool, not a replacement for proper seamanship. You should never rely on AIS alone to avoid collisions. Use it in combination with:

• Visual lookouts

• Radar

• Sound signals

• Navigation lights

• VHF radio communication

In fact, if you rely only on AIS and something goes wrong, you may be found negligent. Many vessels (especially smaller boats and fishing craft) don’t transmit AIS, so they simply won’t appear on your screen.

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🚩 4. AIS for Man Overboard (MOB) Situations

One of the most exciting advances in recent years is the use of personal AIS beacons. These are small units that can be attached to a lifejacket and will automatically activate if someone falls overboard. When triggered, they transmit the person’s position to nearby AIS-enabled vessels — exactly the boats most likely to assist quickly.

This feature can make a major difference in a MOB situation, especially in low visibility or at night.

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⛿ 5. Practical Use on a Yacht

• Monitor other traffic on your chartplotter or AIS screen, especially in busy channels or restricted visibility.

• Check vessel details if you're unsure about the course or behavior of a nearby ship — use the MMSI to hail them directly by VHF if necessary.

• Program your own vessel’s details into your AIS unit before sailing, and check your transmission settings.

• Keep it updated — if your AIS unit allows you to input voyage information (e.g., destination, ETA), do so. It helps other vessels understand your intentions.