Understanding MMSI, AIS

VHF Marine Band radios, protocol, radio communication theory, practical advice; AIS; DSC; MMSI; EPIRB.
HandsenSten
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Understanding MMSI, AIS

Postby HandsenSten » Tue Mar 08, 2022 6:10 pm

I want to learn about an MMSI, and also how the Automatic Identification System (AIS) works.

jimh
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Re: Understanding MMSI, AIS

Postby jimh » Wed Mar 09, 2022 7:40 am

AIS is an acronym for Automatic Identity System, a radio communication protocol.

MMSI is an acronym for Maritime Mobile Service Identity, numerical identity for ship radio stations.

There are many websites that explain the Automatic Identification System (AIS) in great detail. I recommend you read more about AIS on websites whose purpose is to describe AIS in detail. Here are links to some good resources on fundamental information about AIS:

https://www.navcen.uscg.gov/?pageName=AISworks

https://en.wikipedia.org/wiki/Automatic ... ion_system

Information about Maritime Mobile Service Identities can be found at

https://en.wikipedia.org/wiki/Maritime_ ... e_Identity

Also, you should read about Digital Selective Calling:

https://en.wikipedia.org/wiki/Digital_selective_calling

HandsenSten
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Joined: Tue Oct 19, 2021 2:09 pm

Re: Understanding MMSI vs AIS, and signal transmission

Postby HandsenSten » Wed Mar 09, 2022 11:25 am

Thank you so much for help, and for posting this information here. This is very helpful.

I am trying to learn more about accessing data from the stations and mapping the data.

jimh
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Re: Understanding MMSI vs AIS, and signal transmission

Postby jimh » Wed Mar 09, 2022 11:29 am

HandsenSten wrote:I am trying to learn more about accessing data from the stations and mapping the data.
If you read the cited articles on AIS you will learn the answer to your questions.

The AIS system is a radio system. To receive AIS information you have to receive radio transmission from the ship sending the information.
This means the ship typically must be not farther away from you than about 20-miles, that is, you must be within the range of reception by your receiver of the radio signal sent from the vessel sending the AIS transmission.

To receive VHF Marine Band AIS transmissions you need an AIS receiver and a proper antenna. The AIS receiver will receive, demodulate, and decode the transmitted signal, and should also produce a data output signal according to NMEA-0183 or NMEA-2000 communication protocol containing the information that was sent by the ship.

You can then connect the AIS receiver data output signal to some sort of chart plotter display or other display device which supports the necessary AIS data groups being sent out from the receiver data connection. Then the display or whatever device you connect can use the data for whatever purpose its designers have provided. If the device that receives the AIS data payload is an electronic chart plotter, then the chart plotter MAY be able to create an indication of the ship position on the chart. Exactly how this will be presented depends on the chart plotter and what data was provided to the chart plotter from the radio that received the radio broadcast transmission from the ship.

If interested in the detail of AIS transmission, you can find complete descriptions of the methods employed in the applicable recommendations of the International Telecommunications Union document:

ITU-R M.1371 : Technical characteristics for an automatic identification system using time division multiple access in the VHF maritime mobile frequency band

You can download a PDF version of the recommendation at no cost from the ITU website at

https://www.itu.int/rec/recommendation.asp?lang=en&parent=R-REC-M.1371-5-201402-I

jimh
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Re: Understanding MMSI vs AIS, and signal transmission

Postby jimh » Wed Mar 09, 2022 11:48 am

This website has much more information about boating and radio communication than just the forum. Here are some links you might find useful:

https://continuouswave.com/whaler/reference/

Then read these articles listed under the sub-headings

Automatic Identification System (AIS)

AIS SHIP SPOTTING
https://continuouswave.com/whaler/refer ... otter.html

AIS ANTENNA FOR SHORE STATION
https://continuouswave.com/whaler/refer ... tenna.html