Another AIS Class B glitch, & a parser in a pear tree


When Class B AIS finally gets going, there’ll be yet another issue to deal with: not all existing AIS plotting systems are going to fully understand the Class B messages. Apparently separate messages were anticipated in the original Class A standard but the slotting and details were changed in the final B standard that went official just this spring. I understand that the dynamic data—position, speed, etc.—will likely show, but the static stuff—boat name, etc.—may not until the plotter, ECDIS, radar, or whatever is updated.
  A good place to see exactly how AIS messages are structured is Brian Lane’s Among other resources is a neat demo that let’s you turn your own raw AIS strings into targets plotted in Google Earth. Brian is even running a sort of Christmas sale on his AISparser SDK, which I’d guess to be quite good. (Imagine the look on her face!)

And here’s some more good/bad B news: An AIS expert at the U.S. Coast Guard told me that two of the Class B transponders now awaiting USCG approval will “retail for under $900”. But he could not say whose, or when approvals may be issued. Neither could the FCC.

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.

3 Responses

  1. GPSNavX says:

    That is exactly right. Without sample [approved] Class B transponder messages to test with yet it makes it difficult to support at this time. Class A messages are formatted a bit different then Class B so what ever AIS plotting software you use will have to be updated to support the approved B messages. That being said I am most interested in Class A as Class B is going to be a lot of clutter.

  2. del says:

    The changes to the Class B static data messages (24A and 24B) are not really new – the standard was approved for publication in August 2005, so manufacturers have had over a year to get their software updated (assuming that they take an active interest in the standards process – but even if they don’t, it has been publiclly available since April 2006 – how slow can they go?).

  3. Ben Ellison Ben Ellison says:

    I’ve heard that from a few people, Del, and don’t doubt it; but I do wonder how many Class A transponders, even recreational AIS plotters, have been updated to understand 24A & B?

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