Understanding AIS: How It Works and Enhances Maritime Safety

 

 

How do massive ships navigate crowded waterways, busy ports, or conditions with poor visibility safely? In addition to radar and visual lookouts, modern vessels rely on advanced technology that allows ships to "talk" to each other electronically. This revolutionary technology is the Automatic Identification System, or AIS. AIS has fundamentally changed maritime navigation and safety, providing unprecedented levels of situational awareness. This article will explain what AIS is, how it functions, its various types, its vital real-world applications, and how integrating this technology into distress beacons significantly enhances safety at sea. HZH Marine, a provider of comprehensive maritime solutions, understands the crucial role of reliable AIS safety devices in modern navigation and emergency response.

 

What is AIS? The Basics
 

AIS is an automated tracking system used on ships and by Vessel Traffic Services (VTS). It utilizes transponders installed on vessels to transmit and receive electronic information about them.

The primary purpose of AIS in maritime navigation is to:

• Identify vessels: Broadcasting static data like a vessel's name, MMSI number, call sign, IMO number, type, and dimensions.
• Track movement: Transmitting dynamic data such as a vessel's current position, speed over ground (SOG), course over ground (COG), heading, and rate of turn.
• Facilitate information exchange: Enabling ship operators and shore authorities to exchange crucial data for collision avoidance and traffic management.
• Enhance situational awareness: Providing a clear picture of surrounding traffic, even when visibility is poor or radar returns are cluttered.

 

How Does AIS Work? The Technology Behind It
 

The core of AIS technology lies in its use of standard marine VHF radio channels. AIS operates on two dedicated frequencies: AIS 1 (161.975 MHz) and AIS 2 (162.025 MHz). Vessels and shore-based stations use these channels to broadcast and receive AIS messages.

AIS utilizes a sophisticated communication method called Self-Organizing TDMA (SOTDMA) or Carrier Sense TDMA (CSTDMA) for Class B. This technology allows multiple users to share the same radio channel simultaneously without centralized control, automatically managing time slots to avoid interference and ensure reliable data transmission.

The information transmitted by an AIS transponder is gathered from various onboard sensors, including the vessel's GPS/GNSS receiver (for accurate position, speed, and course data) and gyrocompass (for heading information).

 

Types of Information Transmitted
 

AIS transponders transmit different types of information:

• Static Data: This includes fixed information about the vessel (Name, MMSI, Call Sign, IMO Number, Vessel Type, Dimensions). This data is transmitted less frequently as it does not change during a voyage.
• Dynamic Data: This is real-time information about the vessel's movement (Position, SOG, COG, Heading, Rate of Turn, Navigational Status). This data is transmitted frequently, with the rate depending on the vessel's speed and whether it is maneuvering.
• Voyage-Related Data: This data is manually entered by the crew and transmitted periodically. It includes details like the vessel's destination, Estimated Time of Arrival (ETA), and current draft.

 

Know Your AIS: System Classifications
 

AIS systems are classified based on their capabilities and the types of vessels required to carry them:

• Class A AIS: Mandatory for larger vessels under SOLAS regulations, typically those over 300 gross tonnage engaged in international voyages and all passenger ships. Class A transponders have a higher power output (12.5W) and transmit more detailed data more frequently.
• Class B AIS: Designed for smaller non-SOLAS commercial vessels, fishing boats, and recreational craft. Class B transponders have lower power (2W for Class B/CS, 5W for Class B/SO) and transmit less data less frequently than Class A units.
• AIS Base Stations: Shore-side stations operated by authorities (like VTS centers or Coast Guards) that communicate with vessels, monitor traffic, and manage the AIS network in a specific area.
• AIS Aids to Navigation (AtoN): These are devices that broadcast their position and status via AIS. They can be physical (like buoys or lights) or virtual (representing features like wrecks or hazards).
• AIS Search and Rescue Transmitters: These are specialized distress beacons that utilize AIS technology to aid in locating individuals or survival craft in emergency situations. (We will discuss these in more detail shortly).

 

AIS in Action: Real-World Scenarios & Benefits
 

The implementation of AIS has brought significant benefits to maritime operations:

• Collision Avoidance: One of the primary benefits. A ship's officer can see other vessels equipped with AIS on their navigation displays (ECDIS or Radar), identify them, track their movement, and calculate crucial information like Closest Point of Approach (CPA) and Time to CPA (TCPA). This is invaluable for making safe passing arrangements, especially in congested areas or reduced visibility.
• Vessel Traffic Services (VTS): Port and coastal VTS centers use AIS to monitor all traffic within their area of responsibility. This allows them to provide advisories, manage vessel movements, and prevent accidents within harbor limits and approaches.
• Search and Rescue (SAR): During a distress incident, rescue coordination centers can use shore-based AIS data to identify vessels in the vicinity that might be able to provide immediate assistance.
• Fleet Management: Shipping companies can use shore-based AIS tracking services to monitor the real-time positions, speed, and progress of their entire fleet globally, improving operational efficiency and logistics.

 

Beyond Navigation: AIS for Enhanced Distress Alerting
 

While standard Class A and Class B AIS transponders are excellent for situational awareness and collision avoidance, they primarily show where vessels are. In a distress situation involving a person overboard or a survival craft, relying solely on standard AIS is insufficient. Traditionally, distress alerting has relied on EPIRBs (Emergency Position Indicating Radio Beacons), which transmit a distress alert via the 406 MHz satellite system to global rescue authorities, and SARTs (Search and Rescue Transponders), which are detected by ship's radar.

The integration of AIS technology into dedicated AIS distress beacons significantly improves rescue outcomes:

• Local Alerting: AIS-SARTs and AIS EPIRBs transmit a dedicated AIS distress message. This message is immediately visible to all AIS-equipped vessels within VHF range, appearing on their navigation displays with a specific icon indicating a distress situation.
• Precise Localization: The AIS distress message contains the precise, real-time GPS position of the beacon. This allows nearby vessels and rescue assets to pinpoint the exact location of survivors or life rafts directly on their navigation screens, enabling faster response and recovery, which is crucial in the critical first hours of an emergency.
• Multiple Layers of Detection: Modern AIS-enabled beacons often combine AIS with traditional 406 MHz satellite alerting and 121.5 MHz homing signals, providing multiple layers of detection for rescue authorities and nearby vessels.

 

HZH Marine: Your Partner in AIS Safety Technology
 

HZH Marine is a trusted provider of essential GMDSS and safety equipment, understanding the importance of reliable communication and distress signaling at sea. We offer a range of advanced AIS-enabled safety products designed to enhance your vessel's safety preparedness:

Conclusion

AIS is a vital technology in modern maritime operations, revolutionizing navigation, traffic management, and collision avoidance. The integration of AIS technology into EPIRBs and SARTs provides a significant enhancement to distress alerting, offering local, precise localization that can dramatically improve the chances of a successful rescue. Investing in reliable AIS equipment, both standard transponders and AIS-enabled safety beacons, is an essential step for ensuring maritime safety and compliance.

For further information on these AIS safety devices or any other marine products from HZH Marine, please contact our expert team:

Email: info@hzhmarine.com

WhatsApp: +86 133 6056 0504