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Integrating Marine Communication with AIS- The world of AIS (Automatic Identification System) can be perplexing at times, with many questions like “What is AIS?” “Why do I require it?” and “What form of AIS does my ship require or possess?”
An automatic Identification Device (AIS) is a tracking system that automatically displays other ship details in the area. It is a portable transponder system that works in the VHF band.
There is no information interchange on plates via AIS if AIS is not installed or turned on. Unless the Master determines that it must be turned off for security or other reasons, the AIS operates in a continuous and self-contained manner.
What is the purpose of AIS?
It is used to identify ships and navigational markings installed on boats. However, it should only be used as a navigational aid and not for collision avoidance. AIS is used by ashore Vessel Traffic Services (VTS) to identify, detect, and monitor vessels. The Panama Canal employs the AIS to send information about rain and wind in the locks and the canal itself.
Requirements of SOLAS
The International Maritime Organization (IMO) mandates that all vessels with a gross tonnage of 300 GT or more engaged in international voyages, as all passenger ships of any size, carry AIS.
Types of AIS
Class A: Requires all vessels with a gross tonnage of 300 GT or more and all passenger ships to operate on international journeys.
Class B: Provides limited functionality and is designed for not SOLAS compliant vessels and primarily used for pleasure ships and other vessels.
AIS uses two specialized frequencies, or VHF channels, to communicate:
AIS 1 (Channel 87B) operates on 161.975 MHz (Simplex, for the ship to ship) 162.025 MHz, Channel 88B, AIS 2 (Duplex for the ship to shore)
It employs Self-Organizing Time Division Multiple Access (STDMA) technology to accommodate the high broadcast rate. This frequency is limited by the line of sight, around 40 miles.
How Does AIS Work?
What precisely is AIS, and how does it work? How are we going to get all of this information?
AIS was first employed on land, which meant that the signal was sent from the boat to land and had a range of around 20 miles (also taking into account the earth’s curvature). As ships sailed further away from land, they began transmitting signals to low-earth orbit satellites, which sent data back to land. This meant that ships might travel as far as they pleased, and we’d always know where they were and how they were doing.
A VHF transmitter, two VHF TDMA receivers, a VHF DSC receiver, and a conventional marine encrypted communications link to shipboard screen and sensor systems make up the AIS system. An internal or external GPS receiver is typically used to obtain position and timing data. Other data transmitted by the AIS is collected electronically from shipboard devices via regular marine data connections.
Despite the fact that only one radio channel is required, each station sends and receives data over two channels to reduce interference and communication loss from ships. Every 60 seconds, a location report from one AIS station is slotted into one of 2250 time slots. To avoid slot broadcast overlap, AIS stations constantly coordinate with one another.
It’s also simple to set up, as AIS is usually linked with ship bridge systems or multifunctional displays, but setting up a standalone system is as simple as plugging in a few cables and turning on the socket.
Data Transmitted
1. Static data (every 6 minutes and on-demand):
- MMSI and IMO numbers
- Call and Name Length and Beam of the Sign
- Type of vessel
- Antenna for determining the position
2. Information that is constantly changing (Depends on speed and course alteration)
- Position of the ship with accuracy indication
- timestamp for the position (in UTC)
- Overground Course (COG)
3. Information on the voyage (Every 6 minutes, when data is amended or on request)
- Draught of a ship
- Cargo Type, Destination, and Time of Arrival
- Plan your route (Waypoints)
4. Safety-related warnings that are brief
- A text message in any format is sent to one or more destinations or to all stations in the region. This content could include things like a missing buoy or an iceberg sighting.
As a surveillance tool, AIS
Shoreside authorities in coastal waterways may set up automated AIS stations to track the passage of vessels through the area. The AIS channels can also be used by coast stations to relay information about tides, NTMs, and local meteorological conditions to ships. Coastal stations can utilize the AIS to track the transit of dangerous cargo and regulate commercial fishing in their waters. AIS can also be used for SAR operations, allowing authorities to assess the availability of other vessels in the area of the incident using AIS data.
AIS as a collision avoidance aid
AIS makes a substantial contribution to navigational safety. All of the data that is provided and received improves navigational efficacy and can considerably increase situational awareness and decision-making. The AIS’s surveillance and monitoring of targets, as well as determining information on the CPA and TCPA, helps a lot to the overall safety of navigation as an aid to the OOW. However, for collision avoidance, the user should not rely only on the information provided by the AIS. AIS is merely a supplement to the OOW’s information and is only used to aid in the navigation of the vessel. On bridges, AIS will never be able to replace human competence!
AIS’s Limitations
The AIS, like any other navigational and technological device, has limitations:
- The accuracy of AIS received information is only as good as the accuracy of AIS transmitted information.
- It’s possible that the position displayed on the AIS display isn’t referenced to the WGS 84 datum.
- The OOW’s over-reliance on the AIS can lead to complacency.
- Users must be mindful that the AIS may send incorrect information from another ship.
- AIS is not installed on all ships.
- The OOW must be informed that AIS, if installed, may be turned off by a specific vessel, effectively nullifying all information received from that ship.
- It would be unwise for the OOW to presume that the information obtained from other ships is entirely reliable and precise in comparison to what is available on their own vessel.
To summarize, the AIS only enhances navigational safety by supporting the OOW/VTS or whatever entity is in charge. It’s also simple to set up, as AIS is usually linked with ship bridge systems or multifunctional displays, but setting up a standalone system is as simple as plugging in a few cables and turning on the socket. There’s a lot more to AIS than meets the eye, and the accompanying manual delves further into the subject for both novices and more experienced AIS users.
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