About AIS (Automatic Identification Systems)

About AIS. (Automatic Identification Systems)

Cruising is a great way to explore new places and make new friends. Wouldn’t it be great if you had the peace of mind of knowing that you were visible to other vessels using AIS? Thankfully, this system is available to cruisers and can help you stay safe while sailing. In this article, we’ll explain about AIS and how Automatic Identification Systems benefit the cruising sailor.

Freedomafloat is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to Amazon.com. As an Amazon Associate, I may earn from qualifying purchases.

What is AIS?

AIS (Automatic Identification System) is a system that uses the vessel’s instruments like position, speed and their navigational status to broadcast a vessel’s position, and its VHF to transmit (and receive) that data. It has been developed for use by the maritime community. The AIS system is designed to assist in the navigation, tracking and identification of ships and boats. The vessel is identified by its preprogrammed MMSI number and radio callsign which is issued by the relevant maritime safety organisation.

What are the different types of AIS?

There are a three types of AIS in use nowadays, they are:

  1. Class A (used on commercial ships)
  2. Class B, (used on smaller vessels like yachts and motor boats.
  3. Class B+ (is an upgraded version of Class B with a slightly greater range and a guaranteed transmission slot).

Class A

Class A AIS Transceivers consist of A VHF transmitter, two TDMA VHF receivers and a single DSC receiver. They are are requirement on vessels over 300 tonnes, or if the vessel carries more than 12 passengers. These transmitters transmit greater detail than the lower class units and at a much higher wattage. As this class of unit is generally reserved for shipping, the details are virtually irrelevant for the cruising sailor/boater.

Class B

Raymarine AIS350 Dual Channel AIS Receiver

as of 10 August 2022 06:16

Class B transceivers are smaller, simpler and lower cost than Class A transceivers. A VHF transmitter, two VHF Carrier Sense Time Division Multiple Access (CSTDMA) receivers, and an active dedicated GPS antenna. RS232 and/or NMEA formats are used to transfer the standard AIS data stream at 38.400 kbit/s. With A 2watt limitation on transmission power subject to atmospheric conditions will generally give a coverage of around 5–10 miles. This limitation is designed to avoid bandwidth overload.

Class B+

About the only difference between Class B and Class B+ is timing. The Class B Transceivers use the SOTDMA system and basically have a guaranteed timeslot to transmit their data. The power is also set at 5w and could therefore be more of a benefit for offshore cruising as well as fast boats.

Digital Yacht AIT5000-5W SOTDMA AIS Transponder

as of 10 August 2022 06:16

How does AIS help cruising sailors?

AIS helps by providing real-time vessel tracking information. This system helps sailors stay informed about the vessel’s whereabouts, which can help avoid any potential accidents. Additionally, the system can also help sailors coordinate with authorities in case of any emergencies.

What are the different benefits of using AIS?

AIS (Automated Identification System) is a system that helps identify and track maritime vessels. It is a mandatory requirement for all ships over 300 gross tonnes that sail in international waters. The system helps to identify and track vessels by using a variety of data sources, including radio, radar, and satellite. There are a number of different benefits of using AIS, including:

  1. Enhanced safety and security for maritime vessels and crews.
  2. Improved navigation and tracking capabilities.
  3. Improved response to maritime emergencies.
  4. On smaller vessels there is no need to have a radar in constant use.

There are a number of limitations to AIS.

Limitations include:

  • weather conditions,
  • ship speed
  • Distance of transmission/Reception based on the capability and usability of your radio’s VHF Aerial.

There are a few concerns with AIS. One is that the system could be used to track ships and other maritime activities. Second, the data could be used for piracy or illegal fishing.

AIS helps maritime safety by providing collision warning and avoidance services to ships and coastal communities worldwide. In some cases, this information, if known to the search and rescue organisations can assist in the locating of a vessel much faster.

A transceiver is capable of transmission and reception of broadcast AIS signals and would be my personal recommendation. If however you only wish to be able to see other vessels then a receiver will do just fine, just be aware of what type of unit you are buying though, most VHF radios are only able to receive AIS signals, very few are actually AIS transmitters.


If you’re a cruising sailor looking for a reliable and affordable way to track your vessel’s movements, AIS (Automatic Identification System) is the system for you! This system provides real-time tracking of a vessel’s location, speed, and direction, making it a vital tool in ensuring safe navigation. So, whether you’re a experienced sailor or just starting out, make sure to check out AIS and its many benefits!

Suggested Video’s

How AIS Works - Operation of AIS

How AIS Works - Operation of AIS This section should give a short introduction to: Operational aspects of AIS Functions and ...

Should I Have an AIS Transponder or an AIS Receiver on My Boat?

"I just moved my boat to an area that has a lot of ship traffic so I am looking into installing an AIS transponder. " writes Keith.

Leave a Reply

This site uses Akismet to reduce spam. Learn how your comment data is processed.