About AIS

What is AIS (Automatic Identification System)?

AIS (Automatic Identification System) is a real-time vessel tracking system that enhances maritime safety and navigation. It operates using VHF radio signals to transmit and receive vessel information, allowing ships and coastal stations to track nearby traffic and avoid collisions.

How AIS Works

AIS-equipped ships automatically transmit their data, such as position, speed, course, and identification details, at regular intervals. Other vessels and shore stations receive these signals and display the information on electronic charts or radar systems.

AIS uses two VHF frequencies:

• AIS Channel 1 (161.975 MHz, VHF Ch 87B)

• AIS Channel 2 (162.025 MHz, VHF Ch 88B)

It employs TDMA (Time-Division Multiple Access) technology to organize transmissions and prevent data collisions.

AIS Classes

1. Class A AIS

   • Mandatory for large commercial ships (SOLAS vessels).

   • Transmits at higher power (12.5W) with more frequent updates.

   • Uses SOTDMA (Self-Organizing Time Division Multiple Access) for efficient data management.

2. Class B AIS

   • Used by smaller vessels and recreational boats.

   • Transmits at lower power (2W) with longer update intervals.

   • Uses CSTDMA (Carrier-Sense TDMA), leading to less frequent transmissions.

3. AIS Base Stations

   • Operated by coastal authorities for monitoring and managing vessel traffic.

4. AIS Aids to Navigation (AIS AtoN)

   • Used for virtual or physical navigation aids like buoys and lighthouses.

5. Satellite AIS (S-AIS)

   • Uses satellites to track ships globally, even in remote ocean areas beyond terrestrial AIS range.

AIS Data Types

AIS messages contain different types of information, including:

• Dynamic Data: Position, speed, course, heading (updated every few seconds to minutes).

• Static Data: Ship name, MMSI number, IMO number, call sign, vessel type (updated every 6 minutes).

• Voyage Data: Destination, estimated arrival time (ETA), cargo type, draught.

• Safety & Alert Messages: Weather warnings, distress signals, or navigation hazards.

Uses of AIS

✅ Collision Avoidance: Helps vessels detect and avoid each other, especially in poor visibility.
✅ Maritime Traffic Monitoring: Coastal stations and authorities use AIS for vessel traffic management.
✅ Search & Rescue (SAR): Assists in locating ships in distress.
✅ Environmental Protection: Helps monitor and prevent illegal fishing, oil spills, or unauthorized activities.
✅ Fleet Tracking & Management: Shipping companies use AIS to monitor their vessels in real-time.