Crappy Class A AIS data, some stats


I’m still hoping someone will tell us more about the FCC and Class B AIS, but in the meantime Dan sent a great link to The Nautical Institute’s AIS Forum. It’s not a forum in the usual sense but rather a collection of Reported Problems and Technical Feedback papers. An interesting piece in the latter section is a PDF called Automatic Identification System (AIS): A Human Factors Approach, which strongly confirmed my notion that lots of user entered data is bogus. For instance, of nearly 31,000 AIS transmissions examined in one study 49% “showed obvious errors in the fields of destination and ETA.” Which reminded me of the screen shot Russ sent a while back, showing BoatingSF’s neat AIS tracker on Feb. 8, more than a month after the Pilot Vessel Golden Gate’s ETA! The boat, a violet target headed SW toward its namesake bridge, is also going 22 knots even though its Navigation Status is “moored”.
  The good news is that user entered data isn’t very important (unless maybe you’re filtering targets based on their nav status), but the paper also confirms a rumor I’d heard that certain Class A transponders can broadcast a default MMSI in certain circumstances, leading to possible duplicates that really mess up the System. Well, it’s true, the MMSI is 1193046, and there’s a link to details about the units, causes, and remedies. We need to remember that AIS is a relatively young technology (and Class B is an infant).

Ben Ellison

Ben Ellison

Panbo editor, publisher & chief bottlewasher from 4/2005 until 8/2018, and now pleased to have Ben Stein as a very able publisher, webmaster, and editing colleague. Please don't regard him as an "expert"; he's getting quite old and thinks that "fadiddling fumble-putz" is a more accurate description.

2 Responses

  1. bobetter says:

    That Nautical Institute site is a great resource. The AIS info is a bit old and possibly outdated tho. The most recent docs I have seen are from 2005, an eternity in this day and age.
    I am also hungry for some furthur info regarding the FCC cert. I see that it only covers Part 80, doesn’t it also have to pass Part 15 tests?
    I received a Comar CSB 200 last month, got it programed with my MMSI number and call sign (a very easy process, I might add) and am chomping at the bit to put an antenna on it and start transmitting.

  2. norse says:

    The website mentioned above has several animations of the Cosco Busan hitting the Bay Bridge on 7 November, created from AIS data.
    Some other websites I’ve stumbled upon which show live AIS data:
    Google “ais live” for more.

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