I hate to be a scold, but an otherwise fine new article about AIS in Cruising World contains this flawed paragraph:
Once an AIS signal is received by the antenna, it's sent to a black box that translates the data into NMEA streams that can be sent at 4,800 or 38,400 baud. The lower baud rate works with electronics suites still using the NMEA 0183 communication protocol; the higher baud rate works with proprietary networks, such as RayMarine's, and devices using the more capable NMEA 2000 communications protocol.
Every AIS transponder and receiver I know of outputs the same way—NMEA 0183 data messages at 38,400 baud. The 38.4k speed rate is called NMEA 0183–HS (high speed) and is included in the current standard. As far as I know there is no AIS using the NMEA 2000 standard or a proprietary communications protocol, though the new Furuno receiver does do Ethernet in addition to 0183–HS and the junky NASA unit apparently filters out some AIS messages before it sends them down the 0183 pike (though NASA claims it uses N2K, God knows why).
I’ve heard a very ugly rumor that the Class B delay at the FCC may be something serious and long term. Can anyone elaborate?
A big thanks to Shine Micro for providing some useful detail about how the FCC is handling Class B AIS. First of all, the MMSI’s will be just like those used in DSC VHF’s (in fact, should be the same one already programmed into your boat’s radio). So, if your vessel requires an FCC station license, then you use the included MMSI. Otherwise you can use a free MMSI for a Class B transponder. And programming the MMSI is going to be left up to the manufacturer, who can do it themselves or pass it on to the dealer or user. However, the FCC is mandating that manufacturers preprogram all Class B devices with a unique unit identifier in the Vendor ID field of Static Data Message 24, and that field must be verified when the MMSI number is programmed during unit activation. Now, I don’t quite understand how that last part will work in practice but the concept of every transponder having, besides an MMSI, a second fixed unique user ID that also identifies the manufacturer sounds to me like smart security, and a useful trouble shooting tool, without undue burden on anyone.
PS: If your company wants to get into the Class B transponder business, Taiwan manufacturer Alltek Marine has units purportedly ready to hit the approval circuit. They come either with or without a display, the former (below) expected to retail for about $1,000.
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).
A reader (thanks, Dan!) tipped me to this FCC approval issued last Thursday for Software Radio Technology’s Class B AIS transponder. Does that mean units using SRT’s circuit board can now be sold here, or do they need additional approval for their particular configurations? Will units from ACR, Shine Micro, Furuno, and Simrad be close behind (I don’t see applications in the FCC database, but I may not be looking in the right place). And what did the FCC decide about the MMSI numbers needed to activate a transponder; can boats in U.S. waters use the free ones easy to get—or already gotten for DSC radios—from BoatUS, SeaTow, and others, or will a user need to get an FCC license? Will a user be able to program a transponder with his MMSI number, or must a “qualified technician” do it? Inquiring minds want to know!
PS 4/12: So why does the “FCC approval” link now yield: “This application currently is not in final status”? Apparently the Government temporarily pulled SRT’s approval! My source says that this unusual move is only because the FCC accidently issued the certificate before publishing its own rules about Class B. Both rules and approval(s) should be out in a few weeks…for real.
Panbo friend John C. came back from more sailing aboard Solent Blue to discover that his overview photo of English Channel AIS traffic had stirred up quite a conversation. So he adds this:
The original photo was intended to show the number of AIS targets received from a 22 metre aerial whilst sailing across some busy shipping lanes. I don't routinely operate the equipment on 48 mile range other than to get a quick view of what is coming my way. Actually I do have some other photos taken in the same few minutes which depict a more normal operating practice at least for me.
Geez, this morning I found myself confused about Class B AIS details touched on yesterday, and realized that my sources are somewhat sketchy. The USCG AIS site is pretty informative generally, but its Class B particulars seem suspect, the statement “IEC has begun work on a Class B certification standard, which should be completed by 2003” suggesting that it has not been updated in a long time. I am grateful for the Documentation section of AISParser.com, which is where I found the following message info, much edited and with a few notes added:
Message 18 - Standard Class B CS Position Report: UserID/MMSI, Time, SOG, COG, Longitude, Latitude, True Heading. {CS, or Carrier Sense, integrates “politely” with the Class A protocol known as Self-Organizing Time Division Multiple Access or SOTDMA, illustrated above}. Message 19 - Extended Class B Equipment Position Report: Same as 18, plus Ship Type and Dimensions {measured bow/stern and port/starboard relative to GPS, which may be why they are often screwed up}. Message 24 - Class B CS Static Data Report: UserID/MMSI, Boat Name, Ship Type, Call Sign, Dimensions, and Vendor ID {i.e. transponder manufacturer, to help track down problems}.
While I don’t understand the purpose of #19, which seems redundant, I think that the list includes every significant data field that a Class B can transmit. But I could be wrong!
Ever wonder why the U.K. and Western Europe are such AIS hot beds? John C. send in this shot of his zoomed out screen, taken as he sailed across the English Channel yesterday:
I was heading northwest just about right angles to the main shipping routes. Those going northeast are heading up Channel to Hamburg, Rotterdam, Antwerp, Kiel Canal etc, and those heading SW in the other lane are heading to the rest of the world. A couple of cross channel ferries are more north/south. Equipment is a Raymarine E-80 with additional VGA screen (in photo) and Easy AIS receiver.
I wonder what this picture will look like with class B's as well! I am planning to upgrade to class B soon - please lets get some real user experience on this subject on your site soon! {I hope so too, but we don’t even have B over here yet—ed} BTW: with the class B's, do you know how I might differentiate between Underway Sailing, and Underway Motoring? {Anyone?}
PS I’d bet that if the 47’ Wahkuna, making a similar crossing in 2003, had had an AIS receiver like John’s, it might still be afloat. I wrote about the accident here, and the amazingly complete MAIB report is here.
PPS Regarding Underway status (and thanks to Marinate’s input below), apparently Class B can not send out Nav Status, but will see the Nav Status of Class A transponders.
Simrad introduced a Class B AIS in Europe today, and it looks very cool indeed. Besides the obvious, if unique, color plotting screen, this unit has a “Buddy Tracking” feature whereby you put in a list of your friends’ MMSI numbers and if they show up within AIS range, the A150 will highlight them. And if you have a “suitable SimNet equipped” DSC radio attached, you can cursor over an AIS target, select “DSC”, and the radio will initiate a call. I don’t know if the A150 outputs target data to other displays, via SimNet (aka NMEA 2000) or otherwise, and I also don’t know its price, but I’m guessing that it will get some serious attention. Mind you, of course, that the A150 is not for sale in the U.S. (see FCC languarge below, and click here for more on that subject, here for more on Class B in general).
This device has not been authorized as required by the rules of the Federal Communications Commission. This device is not, and may not be, offered for sale or lease, or sold or leased, until authorization is obtained.
How cool is that? In this cropped screen shot, Coastal Explorer is plotting a SAR aircraft that’s using the special AIS message discussed here the other day. Rosepoint’s Jeff Hummel, who sent the screen, says they’ve never actually seen message 9 data before, but this function was already built into CE, as are other obscure AIS and DSC capabilities. Jeff’s also proud that “Coastal Explorer works just fine on VISTA”, unlike the competition (and alma mater) he likes to tweak. By the way, Rosepoint can see AIS targets cross country because they’ve got CE tapped into the IP feed of Shine Micro’s receiver network. Coincidentally I just learned more about this CE ability yesterday, even tried it, thanks to Penobscot Bay pilot Skip Strong, who’s responsible for the series of Shine Micro receivers that I’ve been enjoying via Shine’s public live AIS site. Strong is a big fan of AIS in general and this setup in particular, as he and his associates use it to avoid wasted time waiting offshore for a ship that’s forgotten to call in late. The CE screen below, bigger here, shows the Penobscot Pilot which may have just put Strong aboard the Alouette Arrow (off screen). I’ll have more one day on this gentleman, and also on a trip aboard the pilot boat which I’m looking forward to, big time.
C.A.P. Major Tim Strickland wrote in: “In my free time, I'm doing an experiment to track Civil Air Patrol Search & Rescue aircraft using the AIS SAR Aircraft Position Report (AIS Message 9) in maritime environments. There's interest in other SAR air assets doing the same, and curiosity on whether vessels can (they should) see these aircraft when they're transmitting. Have you seen much regarding the use of AIS Message 9? I've gotten one aviation AIS transponder company to loan a unit to test/demonstrate this and perhaps pursue migration to AIS Message 25 (BFT). I'm looking for a low-cost receive, display & chart (with land, not just marine maps).” I know nothing about this SAR Aircraft message, but am hoping someone can educate us in the comments section (or you can email Tim directly). Meanwhile, if you’re thinking about building AIS transponders, CML Microcircuits wants you to check out their dedicated CMX processors. Their site is mostly above my head, but I think it’s another sign that AIS may get smaller and less expensive at a rapid rate. By the way, PMY has started to post my columns again, including my March one on Class B.
PS 3/13 Good question from Tim Flanagan, now at Navagear.com, who’s writing an article on the potential value of “Synthetic AIS”: “Is anybody broadcasting aids-to-navigation, hazards-to-navigation, or vessel-in-distress info from equipment NOT installed upon the affected vessel or object? By the way, have you encountered any nomenclature to describe this, besides Synthetic AIS and Virtual AIS?”
