Where the Ships Are: AIS and MMSI

You never know where the tangents will take you. My cruise ship schedule experiments began when a newspaper ad led me to a not-helpful-enough web page and, in learning about cruise ships and how and where they move around, I learned a lot that I hadn’t planned on learning.

Like about the Automatic Identification System (AIS), for example, wherein ships of a certain size broadcast digital information about themselves, in the clear, over VHF frequencies. Using a decentralized network of AIS receivers, websites like Google Maps APRSVessel FinderAIS Hub, MarineTraffic.com, VesselTracker.com that aggregate ship position information onto maps and other feeds. It’s an interesting example of data that needs to be free and open — it’s primarily intended as collision avoidance data — can be shared in unanticipated ways.

One of the important components of the AIS system is the MMSI — Maritime Mobile Service Identity — which is a 9-digit unique identifier assigned to each vessel. Not only is a ship’s MMSI broadcast as part of its AIS data, but it it’s also used to allow voice and data connections to vessels

If you know a vessel’s MMSI, and you’re set up to monitor AIS broadcasts in your area, you can tell when a vessel comes into range.

I added the MMSI to the XML data file of cruise ships coming into Charlottetown this year — Maasdam, which arrives tomorrow, has an MMSI of 244958000, for example. If you Google that number you can find all manner of interesting information about the ship, from myriad photos (there is, apparently, an entire sub-hobby called “ship-spotting”) to its current position.

One can imagine — or at least I can imagine — an interesting hack that would monitor AIS data for Charlottetown and when a cruise ship was about to dock would sound some sort of klaxon to alert we citizens that the streets would soon be fully of horses pulling wagons, double decker buses, and rove bands of costumed fathers and mothers of Confederation.


Rob's picture
Rob on May 28, 2012 - 21:10 Permalink

I use MarineTraffic.com to keep tabs on a close friend who is First Officer on a big private superyacht. I also recently located another friend doing saturation diving from a vessel in the North Sea. Unfortunately, there is no AIS station in Charlottetown. I contacted the manager of the Charlottetown Harbour Authority about this and he responded that he’d look into it.

Peter Rukavina's picture
Peter Rukavina on May 28, 2012 - 21:18 Permalink

It would be great to have the Harbour Authority install an AIS repeater, doubly great if they contributed their data in an open format.

I have discovered that the Harbour Authority uses the abbreviation CHAI in its internal documents. Can it be long before there is some sort of exotic tea-themed rebranding effort?

Peter Rukavina's picture
Peter Rukavina on May 28, 2012 - 21:21 Permalink

MarineTraffic.com appears to have gone off the air today. Perhaps it’s only temporary? Every URL on the site returns ”The requested service is unavailable.” for me today. Google Maps APRS seems like an able replacement.

Heather M's picture
Heather M on May 29, 2012 - 01:21 Permalink

Fathers & *Ladies of Confederation. I was once in those hoop skirts.

Peter Rukavina's picture
Peter Rukavina on May 29, 2012 - 13:26 Permalink

I’ve just sent in the paperwork requesting MarineTraffic.com provide a free AIS repeater station for installation here at Reinvented HQ.

Olivia Rukavina's picture
Olivia Rukavina on May 29, 2022 - 12:00 Permalink

10 years!