Types of AIS Equipment

Types of AIS (Automatic Identification System)

AIS is classified into different types based on functionality, transmission method, and application. The main AIS types include:

1. AIS Classes (Based on Vessel Equipment)

Class A AIS

• Mandatory for large commercial ships (over 300 GT) and passenger vessels (SOLAS-compliant).

• Higher transmission power (12.5W) with more frequent updates.

• Uses SOTDMA (Self-Organizing Time Division Multiple Access), ensuring efficient message scheduling.

• Provides more detailed voyage-related data.

• Continuous broadcasting even in congested areas.

Conclusion

AIS plays a crucial role in maritime navigation, safety, and fleet management. The type of AIS used depends on the vessel size, location, and purpose.

Class B AIS

• Used by smaller vessels, recreational boats, and fishing vessels.

• Lower transmission power (2W) with less frequent updates.

• Uses CSTDMA (Carrier-Sense TDMA) or SOTDMA (for Class B+), making transmissions less frequent.

• Less priority in crowded signal environments compared to Class A.

AIS Class B+ (SOTDMA-based Class B)

• Similar to Class B but uses SOTDMA instead of CSTDMA, improving transmission reliability.

• Higher power output (5W) than standard Class B, leading to better range and tracking.

• More frequent updates compared to standard Class B AIS.

2. AIS Base Stations (Shore-Based AIS)

• Operated by coastal authorities and port management.

• Collects AIS data from vessels and transmits information about navigation safety.

• Provides traffic management and aids search & rescue operations.

3. AIS AtoN (Aids to Navigation)

• Used for virtual or physical navigation aids like buoys, lighthouses, or offshore platforms.

• Helps mariners identify hazards, safe passage routes, or port entry points.

• Can be real (installed on physical objects) or virtual (broadcast via AIS without a physical presence).

4. Satellite AIS (S-AIS)

• Uses satellites to receive AIS signals from vessels beyond coastal station coverage.

• Global tracking capability, especially for remote ocean areas.

• Used for maritime security, environmental monitoring, and fleet management.

• Examples: ORBCOMM, Spire, exactEarth satellites.

5. AIS SAR (Search and Rescue) Transponders

• Used for emergency beacons and man-overboard devices.

• Helps rescuers locate distressed ships or crew members in emergency situations.

• Operates on standard AIS frequencies and sends distress signals.

6. Inland AIS (I-AIS)

• Adapted for use in inland waterways (e.g., rivers, canals, and lakes).

• Provides additional navigation data specific to inland shipping routes.

• Uses different message types tailored for inland vessel operations.