By clicking on a target you will see the information that is provided by an AIS signal. This ship is Liberian based and is leaving Ney York en route to Seven island. This ship is underway, 245m long, speed is 14.1 knots and course 99 degrees.

 

Benefits & features

The basic benefit of AIS is safety and navigation. AIS signals include course, speed and graphic displays showing AIS targets make navigating in crowded channels less stressful.

The Marine Accident Investigation Branch,(UK). MAIB has a report of a mid channel collision between a commercial Ferry and a small sailing vessel which resulted in the sailboat sinking and loss of life. The reports conclusion showed the sailing vessel did not appear on radar and because of the height of the bridge the sailboat was not seen by eye. The recommendation was for better radar reflectors so the sailboat could be seen on the ferries radar and or the use of AIS.

One of the many features of the AIS system is that it has the potential to notify you well in advance of an oncoming ship, along with potential collision avoidance alarms.

CPA, or closest point of approach tells you how close a approaching vessel comes to your course. From this you can decide if you need to alter course. TCPA - The Time to Closest Point of Approach tells you how much time you have to work with.

Also in addition to CPA class A signals includes rate of turn. With this it is possible to predict the path of a ship which is turning. Rate of turn ROT information looks like this ROT L>5 degrees. The ship is turning left at a rate of turn under 5 degrees.

AIS also includes information about the target including call sign and ship details. With this you can call a vessel knowing you have the right vessel. Instead of calling hey ship coming toward me, you can call the ship by name. If you have a VHF with DSC you can type in the ships MMSI number and call the bridge directly.

Filtering of AIS messages is possible with some devices. If the area is crowded with signals you can filter some of the AIS signals by choosing say CPA and speed, range and TCPA to prioritize targets.

Additional benefits include, Safety related Message (SRM) i.e. a mayday or Pan Pan call. The SRM will contain the vessels details and position. Another development is channel markers with AIS transponders, and now SARTS.

 

Equipment needed to receive AIS

You need an AIS receiver or transponder, then you need a display, an antenna, power, and GPS (some transponders have integrated GPS). These are the basic needs and you can use a PC as a display or a chartplotter, or have a standalone AIS display which just needs an antenna and power. Another recent development is combination VHF and AIS devices.

The most basic is an AIS receiver, which receives the AIS signals which can then be displayed on your boats existing chartplotter, repeater or PC.

Standalone displays look like Radar plots (see ICOM right). You are centered on the screen and AIS targets are shown relative to you. This is different to seeing a AIS signal on a chartplotter or PC, which shows the target at its Lat & long with its speed and direction.

If you decide on sending your AIS signals you will need a transponder either a class A or class B. Class B is for recreational boaters.

Antenna or splitter

You will need an antenna, either a dedicated antenna or using a splitter to your VHF antenna. VHF antennas work across a wide range of frequencies, while AIS works on two frequencies and 2 watts. AIS frequencies; 161.975 and 162.025 MHz in marine band.

if you are using your VHF at the same time as a transmission is scheduled the AIS signal may get lost. So if you use the VHF a lot a dedicated AIS antenna may be worth it.

Choosing a VHF and positioning the antenna should take these requirements into account. line of sight, gps and ais 5m apart interference, not on same plane as other antenna, 360 deg view of horizon

MMSI number

If you elect to get a Class A or B transponder you will need to program the unit with certain information including your MMSI number. If you have not already got one You will need to apply for a MMSI number just as you do for DSC radios. Someone receiving your AIS signal will have important information about you and be able to call you by name and call sign.

 

Register here for MMSI numbers

Once you have a AIS device you will need to get programmed into the transponder include; Ship's name (20 characters maximum), Vessel's radio call sign (7 characters maximum), MMSI number, Vessel type  and certain vessel's dimensions.

 

Types of AIS devices

The simplest AIS device is a receive only device, either single or dual channel. A "receive only device" allows you to receive AIS signals and display those signals on a chartplotter. You do not send your AIS data.

"Receive only devices" do not have the regulations, that cover transponders.

If you elect to broadcast your AIS data you will need a transponder and you have the choice of Class A or Class B transponders. Transponders need FCC approval.

Class A

Class A is intended to meet the IMO mandated carriage requirements for commercial ships. Class A AIS transponders transmit, via 2 channels and typically are fully integrated into the ships navigation systems.

Class A transmits at 12 W and receive all types of AIS messages. Class A has a range of 20 miles, and transmits every 2 seconds,.

Shown is Comars Class A AIS for recreational boats. The Comar Class A costs around $2,500.

Class B

Class B transponders are for smaller vessels. Class B signals are sent every 30 seconds, compared with as frequent as 2 seconds for Class A. Class B transponders are also dual channel. range is around 10 miles and 2 watt power.

Class B can be set to receive only. This maybe to avoid clutter in a crowded channel or to avoid being seen, Fishing boats unfortunately are in this category, so are Pirates.

The Class B is nearly identical to the Class A, except the Class B:

• Has a reporting rate less than a Class A (e.g. every 30 sec. when under 14 knots, as opposed to every 10 sec. for Class A)
• Does not transmit the vessel's IMO number
• Does not transmit ETA or destination
• Does not transmit navigational status
• Is only required to receive, not transmit, text safety messages
• Is only required to receive, not transmit, application identifiers (binary messages)
• Does not transmit rate of turn information
• Does not transmit maximum present static draught
• another interesting feature of B is that transmission spots are not reserved as class A. instead class B listens for a empty slot, so there is no chance of crowding out Class A signals

AIS or Radar

 Which is best for navigation aids, Radar or AIS or both?

Radar can show vessels in your vicinity, it can also show weather and land masses. These are the good features, however a Ship may not see you as passive radar reflectors (carried by small vessels) are not that efficient. If you do not show on a ships radar you better keep out of their way.

Radar is complicated to read and takes skill to use, Also weather and rain can clutter the screen. You can use rain clutter or FTC, but this will weaken representation of other targets.

AIS can provide similar benefits to radar and some better ones. If you are in a rain squall AIS will still give you the information of vessels course and speed. The information received in an AIS massage contains valuable information. AIS is not an expensive upgrade and cheaper than radar.

The negatives to AIS is that not all vessels are not required to transpond. Fishing vessels are one example and they may like to keep their location secret.

Bottom line both AIS and radar have their merits. Its is now a requirement for new ships radar be able to display AIS targets. So this is the best of both worlds. If everyone had AIS then we could just use that, however it would get awful crowded on your screen.

 

AIS and man Overboard

SARTs

SART stands for Search and rescue transponder. New SART devices are now on the market that use AIS signals to locate device.

McMurdos Smartfind S10 AIS Beacon uses AIS signals to track the device. The Smartfind beacon is carried on each person onboard and is manually activated.

If a person falls overboard, they can activate the device and anyone with a AIS receiver in range will see the distress signal and therefore be able to assist in rescue. The diagram right shows a SART active with range and bearing on a chartplotter.

 

RT650 VHF DSC, AIS & MOB radiotelephone

How many acronyms can you have in one device?

This new VHF from Navicom combines VHF, DCS, AIS and MOB functions in one device. What sets the VHF apart not just the DSC and AIS capabilities, but a MOB function, not seen on any other VHF.

The RT650 MOB will not alert search and rescue teams, however in the case of a MOB, the watch like transmitter will activate and send a signal back to the base unit onboard the vessel. When a crewmember falls overboard, the watch transmitter actives (automatic or manual activation) and sends a signal to the base VHF unit activating an audio signal.

As a skipper with crews lives in your hands you can be rest assured that if anyone falls overboard you will have immediate audio notification. There are not too many details on the Navicom web site, but this is an interesting idea. The unit can handle up to 16 wristbands and cover 100 meters.

The VHF radio is DCS capable with integral AIS. Couple this with your chartplotter or PC and you have a very comprehensive display.

 

 

 

AIS devices

 

The simplest AIS device is a "receive only device". This will give you all the information from Class A and Class B signals so you can act to keep clear of shipping in a safe manner. If you choose to broadcast your AIS data, it is no guarantee that vessels receiving it will act to keep clear, you hope they will, but its no guarantee.

Below you will find examples of AIS devices. There are many more examples in each category, be it receive only ot transponder. This list gives you an idea of options.

"Receive only AIS", single channel

Smart Radio SR161, AIS Receiver is a well respected and cheap option if you are looking for an AIS receiver, but not interested in broadcasting.

The SR161 costs around $190.

Sending an AIS signal lets other vessels know where you are but many believe its better to know the other vessels in your area and navigate defensively. 

The SR161 is a single channel receiver, flipping between channels and hence will not report as fast as a dual channel receiver. This can be an issue if you are tracking fast craft.

SR161 features
Receive only
Hears Class A & B vessel reports
Sends the information to be mapped on a PC or chart-plotter
AIS2 162.025 MHz default(software programmable to other frequencies),dual channel scan receiving.
Also available upgrades to the SR162 and the SR162G
SR162 includes an additional dual channel receiver.
SR162G includes an additional Integrated 12 channel GPS module.

NASA AIS Engine - latest Version 3 model

Sometimes you will see an AIS receiver described as an engine; Cost around $200

Specification
Select 161.975 or 162.025 MHZ operation or switch automatically every 36s
Uses standard NMEA 0183 GPS input
Supply voltage 12 – 15v DC

Additional requirements

GPS connection
VHF antenna with BNC connector (not supplied)
A suitable chartplotter system - dedicated unit or PC/Mac-based

In the box
AIS engine (not waterproof)
Fused power cable with plug
Serial plug to serial socket data cable
A blue fly lead for GPS data connection **
'Software On Board' by Digiboat chart plotter software CD
Installation instructions

 

Receive only AIS, dual channel

 

ICOM make some very good VHF and navigation units. So it no surprise they are entering the AIS field as the same VHF airwaves are used. The MXA-500 is a AIS Duel Channel receiver, which is fine with many boaters. Being able to plot AIS targets on your chartplotter aids your navigation.

Cost around US$600

The MXA-5000 dual channel AIS receiver allows boat owners to receive AIS information (both Class A and Class B AIS signals) on two channels simultaneously and outputs this real-time information on a computer, radar or a chart plotter, thus aiding navigation and collision avoidance.

The MXA-500 was first shown at the London Boat Show 2009.

MXA-5000 Features:
Receive Only Dual Channel
receives both Ch. 87B (161.975MHz) and Ch. 88B (162.025MHz) simultaneously
Includes dedicated antenna splitter to share common antenna with VHF radio
RS-422 balanced connection for third party navigation equipment.
RS-232C unbalanced connection for PC connection
Included Equipment: DC power cable, mounting bracket & screws
Draw: 0.25A
Antenna impedence: 50Ω
Not waterproof

 

Nauticast dual channel receive only

This new little AIS receiver is a cheap way to get AIS signals. The "receive only" AIS device picks up reception of all AIS transmissions from both Class A and Class B AIS systems. The simple device can be connected easily to existing systems via NMEA 0183 device or direct to chartplotter or laptop.

To connect to your chartplotter check your plotters manual. Usually connections are NMEA data at 38400 baud (also referred to as NMEA HS). For a PC use the USB connection.

You will also need an antenna. It is possible to use a VHF antenna to receive both AIS and VHF signals

List price $320 for receive only AIS.

 

Standalone AIS display

 

Sail magazine recognized 15 sailing products for its 2009 Pittman Innovation Awards. One of Peter Nielsen’s Cruising Gear awards went to Vesper Marines AIS WatchMate.

AIS WatchMate is a repeater connected to an AIS receiver and is a stand alone display showing AIS data from all shipping in the area.

Cost around US$500

This like other standalone displays look like Radar plots. You are the center on the screen and AIS targets are shown relative to you. This is different to seeing a AIS signal on a chartplotter, which shows the target at its Lat & long and its speed and direction.

This device would work well if you do not want to clutter up your chart screen with loads of AIS data and keep it solely for navigation, while looking at the WatchMate to see AIS traffic.

 

Features:
Purchase receiver separately
Works with most AIS engines like SR161
Display Type: 5" grayscale FSTN, 320 x 240
Alarms: Closest point of approach  (CPA), Guard, GPS failure alarms
Antenna: Requires GPS receiver (outputs NMEA 0183 RMC sentences), AIS receiver or transponder, dedicated VHF antenna or antenna with AIS-compatible splitter.
Draw: less than 100mA at 12V
Interface: NMEA 0183, 2 input, 1 output port
Waterproof: Rated waterproof (IPX-67, CFR-46)

 

VHF radio w AIS

Matrix AIS GX2100

New from Standard Horizon is a combination VHF and AIS. GX2100 MATRIX AIS has a dual channel AIS receiver and the data is displayed, radar like circles, on the backlit LCD screen. MATRIX AIS is Class D class DSC VHF with a separate Channel 70 receiver, and is capable of entering and saving up to 100 waypoints. Only one antenna is required.

Needs GPS.

One feature of DSC in a VHF unit is the ability to share position information with other DSC equipped vessels using the ” Position Polling, position request ”  functions. You will need to connect the VHF to an external GPS and then your friends can have your position on their chartplotter by simply plugging in your MMSI number into the VHF.

MATRIX AIS features Clear Voice Noise Reduction Technology eliminating unwanted background noises like engines and wind during transmission.

Transponders class A & B

Class A transponder

Comar have in the CSA 300 class A transponder an AIS device that will take class A AIS beyond Commercial shipping and into larger pleasure craft and Fishing vessels. With the advent of class B AIS for small boats, Class A units have been deemed too expensive by many. However the new unit from Comar brings down the price of a fully blown Class A device.

The Comar CSA-300 provides a vessel with: Class A AIS transmission of vessels own position, speed and heading to other vessels within VHF range. The ability to plot heading and speed of other AIS vessels on a Chart Plotter, Radar or PC program.

Suitable for use on; Commercial vessels, police and Coats Guard vessels, larger leisure craft, commercial and passenger vessels needing to meet AIS carriage requirements.

The CSA-300 outputs AIS data in standard NMEA format so that information can be shared with other devices such as AIS compatible radar, PC navigation programs and chart plotters.

Information that can be received by the CSA-300 ;

1. Transmissions from both Class A and Class B vessels
2. Base Stations
3. Aids to Navigation
4. AIS SARTs

Class B transponder

Nauticast B AIS
Class B Automatic Identification System FCC Approved

The Nauticast is an example of a receive and transpond AIS unit which has received FCC approval for the US.

The ACR Nauticast-B Class B AIS Transponder kit includes the following items: Class B AIS transponder unit, Product manual, GPS antenna with 20 foot cable GPS mount VHF ACR A-3200 AIS antenna with mount and 15 foot cable Power/ECS/PC interface cable (4 foot).

ACR Nauticast features:

Transmit and receive AIS

Plug and Play

GPS Receiver

Water Resistant

Remote SRM Switch

Small in Size

Cost around $799

The Nauticast B AIS RS232 and RS422 NMEA electrical interface communicate data directly through the users chart plotter or laptop. All in all Nauticast B is one of the best AIS class B units on the market.

 

 

 

Conclusion

 

 

Most manufactures of navigation software ENC, support AIS receivers. The ability to show the AIS targets can be brought to your PC as well as your chartplotter. Many of the AIS devices we mention here are from independent manufacturers. If you have a Garmin, Raymarine or Simrad system you can purchase their AIS device. It does seem however these are more expensive than many of the independent deviceds.

 

AIS is not an expensive upgrade and cheaper than radar, while giving you the security of knowing what is going on around you.

 

 

 

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