Wednesday, 15 October 2008

Automatic Identification System (AIS) for Sailboats/Cruisers

Cruising the oceans of our planet brings us many times in close proximity to many large commercial vessels. Naturally, by comparison, we are like the flea on an elephants' derriere and wish to give these behemoths of the sea as wide a berth as possible! Hence keeping a good lookout, radar and radar reflectors (see my blog 22 September) are all part of the package to assist in these events.

Like Formula One, new technology is tried out in the heat of Grand Prix racing and eventually trickles down to mainstream auto production. The marine industry is no different.

The latest innovation to come along is AIS(Automatic Identification System).

AIS has been around for several years now and it is law for all vessels over 300 gross tonnes to be fitted with this system. It is only recently however that this technology has been available for recreational use with a range of units coming on the market. It has been embraced enthusiastically by the yachting world and is appearing more and more on the list of equipment to be included on new vessels and fitted for any sailors planning extended passagemaking.

Here is an article from a marine website dedicated to testing new equipment: www.

AIS provides data exchange—both boat to boat and boat to shore. AIS can increase safety at sea by providing your position to other boats (if you have an AIS transmitter) and by informing you of other boats’ positions (if they have an AIS transmitter). This is particularly true in low visibility or high traffic conditions. AIS displays this information on your Chartplotter. The Simrad-Navico unit to the right is a typical unit.

It is important to realize that AIS is not a substitute for Radar, some vessel do not transmit their positions or intentions. Therefore relying solely on AIS could mean you are unaware of potential hazards.

There are 3 implementations of AIS: Class A, Class B, and receive-only units.

Class A transceivers transmit and receive AIS signals and are required on large commercial vessels. Class A provides a great deal of data including the ship’s name, type, MMSI number, call sign, IMO number, length, beam, GPS antenna location, draft, cargo, destination, ETA, ship’s posi­tion, COG, SOG, heading, rate of turn and navigational sta­tus. Not all ships transmit all of this information.

Class B transceivers are designed for boats under 65 feet. Class B AIS provides the boat’s name, position, SOG, and COG.

AIS receive-only units receive messages from vessels carrying Class A or Class B transceivers. These products do not transmit vessel information to surrounding traffic.
AIS is not required on recreational boats. AIS does not detect land­masses or navigational beacons, so it does not replace Radar.

The Navigate-us selection guide addresses receive-only AIS units.
An AIS receiver requires a VHF antenna, a GPS input, and a data output to your Chartplotter. Since standard NMEA communications are used, the AIS device does not need to be provided by the same manufacturer as your marine network. Provide a dedicated, clean source of 12 VDC power for your radio that can supply 10 amps.

AIS information is displayed on your Chartplotter. It’s worth considering how the Chartplotter manufacturer presents the data on the chart. Keeping a clean display with only the most important information is key to ease of use.
Choosing Your AIS Receiver:
If you want other boats to know your vessel’s data, buy a Class B Transceiver. If you only need to know the position of other boats, buy a receive-only unit. Review the Comparison guide for units that meet your requirements.

This is a new category of marine electronics and the products being offered are changing quickly. However the underlying technology remains the same, so there is no need to worry about obsolescence.

Reproduced courtesy

If you were contemplating going the whole hog or re-equipping your vessel, you could look at the latest offering from Furuno. This exciting arrival is chartplotter, radar, GPS, AIS all rolled into one stylish system which also includes a celestial compass and fishfinder.

There are a number of other useful sites you can look up on the net by tapping in 'AIS for sailboats'.

You can read more about radar, identification with commercial shipping and sailing on passage at night in my ebook 'Voyage of the Little Ship 'Tere Moana' downloadable from my website

1 comment:

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Very good technology this is what The marine industry was looking for because they need new ideas to increase their business, I'd like to read more about this implementations.m10m