Background

AIS (Automatic Identification System) is the mariner’s most significant development in navigation safety since the introduction of radar. The system was originally developed as a collision avoidance tool to enable commercial vessels to ‘see’ each other more clearly in all conditions and improve the helmsman’s information about his surrounding environment. AIS does this by continuously transmitting a vessels identity, position, speed and course along with other relevant information to all other AIS equipped vessels within range. Combined with a shore station, this system also offers port authorities and maritime safety bodies the ability to manage maritime traffic and reduce the hazards of marine navigation.

Due to the great safety benefits offered by AIS, this technology was made compulsory throughout the world in 2002 for all passenger ferries and vessels over 300 gross tonnes.

How AIS works

The Automatic Identification System was developed to allow ships and coastal stations to accurately locate and identify one another. An AIS transceiver uses VHF radio and GPS technology to communicate with other nearby ships.

An AIS transponder determines its own position, speed and course using a built in GPS receiver. This information is combined with other important navigation information and automatically communicated between AIS equipped vessels without any user interaction.

AIS transponders on other vessels and coast stations receive this information and use it to build up a live graphical display of traffic in the area. The transponder can be connected to many types of chart plotter or PC charting software to give a RADAR type display of vessel positions. AIS does not require a radar, but can offer similar capabilities and even enhance a radar image if a radar has already been fitted to the vessel.

The range or coverage of the system is similar to a VHF radios. The system also has the advantage that VHF radio signals will travel around bends and over islands giving better coverage than RADAR or enhancing a RADAR picture when used together.

Benefits of AIS

• “See and be seen”.
  A Class B transponder continuously receives information form all Class A and Class B equipped vessels around you and displays this information on your standard chart plotter or PC. At the same time your Class B will transmit your position to all AIS equipped vessels automatically.
• Safety at night and in poor weather conditions
  The class B AIS is a vital navigation tool in poor visibility conditions. The information received from other AIS ‘targets’ provides the user with vital navigation information and the position transmission alerts other vessels to the users location.
• Combined with radar, AIS gives you the best possible picture of your situation in all conditions
• Safety in high traffic / commercial shipping areas
• Position transmission to authorities / nearby vessels in case of emergency
• Best possible picture of a dynamic environment (moving vessels)
• Graphically view your position in relation to other vessels when connected to suitable display
• Ability to ‘see around the corner’
• Track vessels of interest such as friends/ colleagues“See and be seen”.

AIS Classes explained

Two types of AIS transponder are available, Class A and Class B.

Class B transponders have been developed to provide the safety and navigation benefits of AIS to smaller vessels with lower cost and simpler installation when compared to Class A. As the Class B system was developed after the introduction of Class A it was designed to be compatible whilst protecting the safety critical operation of the Class A system for big ships.

AIS receivers are also available; these units will pick up broadcasts from both Class A and Class B AIS transponders but don’t transmit their own position. A receiver allows you to see the position of other vessels however your position won’t be visible to them.

The following diagram shows what information each type of transponder will receive from the other.

Please note that in the last example ‘Class B- Class A’ there are some instances when a class A user may not see the name, call sign and vessel type- however the users vessel will still be displayed in it’s correct position. In this circumstance, the receiving vessels display may default to showing the MMSI rather than the vessels name.

Class B AIS

Despite the huge safety benefits of commercial (Class A) AIS the cost of this advanced technology has previously been a barrier to introducing AIS to leisure craft and light commercial vessels. To overcome this problem the class B AIS transponder has been developed to provide all the benefits of AIS in a cost effective, reliable and user-friendly product for users that do not need the comprehensive data required for commercial shipping.

The class B product has been designed with the light commercial and leisure users budget in mind, yet still offers all the advantages of AIS. The device can be easily installed and connected to most chart plotters or PC based navigation software.

Comparison table

A Class B AIS transponder can be fitted to any non-SOLAS vessel. A Class A transponder is only required on ships in excess of 300 gross tons on international voyages.

Receive only AIS units are available however these lack the ability to broadcast your vessels position to others. Receive only units aren’t subject to international standards so don’t necessarily have the same ability to receive all AIS messages on all channels.

* Some Class A transponders and receive only devices may require software update to receive the latest Class B vessel details messages.
** All Comar AIS receiver products have 2 parallel channels and can receive messages on both channels simultaneously.

Product detail

The CSB 200 Class B transponder is a fully compliant AIS Class B transponder providing all the benefits outlined above and meets the strict international standards. The following are some of the key feature of the Comar CSB 200

• Silent Mode
  The CSB 200 can be fitted with a simple toggle switch to put it into ‘silent mode.’ This function allows the user to stop transmitting their position when required. This function may be useful when fishing at a ‘secret spot’
• Water Resistant
  Robust, coated aluminium case suitable to the hash marine environment. The device is designed to operate from -25 to +55 degrees and meets the IP67 standard for water resistance
• Internal GPS
  The class B includes an internal GPS module to facilitate ease of installation and use
  
• Standard NMEA interface
  The CSB 200 Class B is designed to be compatible with all modern plotters and PC’s. The NMEA interface is the standard in marine connections and ensures simple installation
• Designed to internationally recognised IEC standards
  Tested and approved by BABT, BSH, USCG (US Coast Guard)

Installation

A Class B transponder can easily be integrated with your existing equipment. A dedicated VHF and GPS antenna is required, along with a connection to your boat’s power supply.

Information received by the transponder can be used by your chart plotter or navigation PC with a simple NMEA data connection. Check with the manufacturer of your chart plotter to see if it is AIS ready.

To use the Class B AIS to transmit your position it should be programmed with your vessels MMSI number. If you don’t already have one (e.g., for a VHF DSC radio) it can easily be obtained from the local radio licensing authority.

For further installation detail refer to the product manual and quick installation guide available here

If you still have unanswered questions do not hesitate to contact us here