Listen: Maritime and Trade Talk | Episode 2: The Basics of AIS

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Welcome to IHS Markit's Maritime & Trade Talk podcast. I am [ Shiraya Abrahams ]. And today, I am bringing to you our second episode, the Basics of AIS Part 2, following up from last week's Part 1, a conversation between George Devereese and Richard Hurley.

Question and Answer

George Devereese

So Richard, thank you for that very in-depth explanatory part as to what -- as to how areas of the world that we can't see and continue -- you managing further to Message 27 and the areas of the room putting their hands up to have to say their piece. What is that piece that the vessels have to say? What is that data that is transmitted from the ship? And is it standardized?

Richard Hurley

Yes. The data is standardized. As we said, there are 26 messages in the AIS standard, excluding the Message 27, which we've just talked about, which is a special one. The majority of them are not used commonly. There are, in fact, 6 messages which are used primarily for getting over there the message data. And they fall into 2 main groups.

The first group is what we call a dynamic message. And there are 4 dynamic messages, different ones for Class A, Class B, but they contain details and it's rapidly changing, such as position, course, speed, rate of term, et cetera. And these messages are broadcast over 2 to 10 seconds for a vessel underway and every 3 minutes for a vessel alongside or at an anchor.

That's all they contain. And the only linking message -- linking piece of information they contain is the MMSI, which is the Maritime Mobile Service Identity, which is the sole identifier, which is used in all the messages in the AIS spectrum, okay? It's automatically assigned by the radio authority to a ship, and every ship with radio equipment on board will have an MMSI. So that's why it's there.

The MMSI is then -- is used to link to the other type of message, which is the static message. And again, there's a different static message for Class A and Class B. But this static message just gives the information which is not frequently changing. And so this is the name, the call sign, the IMO number, perhaps the ship's destination and the ETA. And this message to, again, to save bandwidth is only broadcast every 6 minutes. It's not changing. Therefore, rather than every 2 to 10 seconds, it's broadcast in 6 minutes.

But the key thing to note is this business about the MMSI, because the MMSI is the only linking field in all these messages. So you, for example, in a dynamic message, you will not have the ship's IMO number or name. It's not necessary. You already know it from a static message, you just link the 2 messages together. So whenever you see a processed message for an AIS message and it contains position information and the ship's name, call sign, et cetera, that is concatenated from these 2 types of messages. So they are taking the dynamic message and adding data from the static message to give you that full information. So that's an important thing to understand.

We did mention Message 27. That's a different thing. As I say, it's very much a cut-down message. It has far less information in it. It just gives you effectively the dynamic data message, so position, call speed, heading, navigational status. And that -- and it also uses a slightly lower precision for its position messages because, again, it's used for long-range tracking at -- in the mid oceans, not for precision tracking in harbor or piloted situation.

George Devereese

Understood. Thank you, Richard. So I think if we may, we'll just look to unpack that MMSI number a wee bit. As we know, the IMO number, the International Maritime Organization number is a unique identifier for vessels, which are issued by IHS Markit on behalf of the International Maritime Organization. But the MMSI is, as you said, is issued by the radio authority, often, if I'm correct, the flag state of the vessel. So the flags to which the vessel is attributed. Is this, like the IMO number, is this a unique number? Or can it be allocated to other vessels? Are they recycled, for example?

Richard Hurley

Yes. As I said, the Maritime Mobile Service Identity, MMSI number is allocated by the radio authority of the individual flags. The advantage of it is that every ship, as I said, that has a VHF installation or radio installation will require an MMSI number in order to identify the transmitter. And that's why it's been used in the AIS standard, because every vessel with a VHF transmitter will have an MMSI number, it's universal.

The IMO number, as we said, is only really for vessels covered under SOLAS. So a lot of the vessels have adopted AIS as a nice-to-have, but not mandatory because they're not covered by SOLAS. So all the vessels, all the smaller, in the water ways craft, the trugs, harbor trugs, et cetera, will have an MMSI but may not have an IMO number. So that's why MMSI was chosen.

So -- but the disadvantage from point of view of ourselves, who want to look at the ship over its history, is that the MMSI is not unique. It's unique at the time of transmission. In other words, a flag authority should not be issuing the same MMSI to numerous ships. But when a ship, for example, is either broken up or sold or moved to another flag, it will get a new MMSI or the MMSI will be relinquished. And so if it goes from Spanish flag to a Panamanian flag, it will lose its Spanish MMSI, it will gain a new Panamanian MMSI.

And so the problem comes in historical tracking of being able to associate an MMSI with a vessel at a particular time. It's further complicated with some of the larger flags, and I mentioned Panama in that the number of MMSIs available to these registrations may be relatively limited either by the sheer number of MMSI groups that are allocated or by their policies on the formats of MMSIs for the different types of ship, et cetera. And as a result, certain authorities will reissue a relinquished MMSI quite quickly after it has been relinquished. And Panama is a case in point where we have seen ships reappear with the same MMSI as a previous relinquished ship within 6 months of that change happening.

So it is very important when you're trying to do tracking over a period, if at all possible, to be able to relate an MMSI to an IMO number, and keep a historic track on when these changes take place. So it is the only -- the MMSI is the only identifier in all these messages. I say, the IMO number or any other local number, there is a provision in the static data message, for example, to put in a local number, which may be a local fishing number or whatever. It's only in this static data message and it can only be linked to the MMSI. And the other problem with it is when you receive a message in, there is no other way of checking the originator of that message on receipt other than just by looking at the MMSI, which hopefully is correct.

George Devereese

That's very interesting thing. Thank you, Richard. So I think by now, our listeners will have a very good understanding there, thanks for your explanation, Richard, of what AIS is, why it was incepted and what -- in the -- what is contained within that message. So my next question to you, Richard, is who inputs this information into the message? Who inputs this data into the AIS? How accurate is it? And can it be trusted?

Richard Hurley

By and large, most of the data, particularly in the dynamic message is input directly from one of the ship's navigational aids. In most cases, this will be a GPS system or equivalent of a global navigation system, navigation system. So for example, position, core speed, heading, is usually automatically input. And as long as the GPS is accurate, then that information will be coming into you accurately.

Navigational status, which is whether the ship is underway, anchored, not in command, et cetera, is normally input manually. And that can have a little bit of mismatch with the rest of the data, usually because a ship may, for example, leave harbor. And the navigational status, obviously, will be moored or anchored. It will leave harbor, and the ship staff did not update the data straight away. So for a short period of time, you may see a ship that's supposedly anchored doing 10 knots, because the GPS system is reporting the information in real time, the navigational status is manual.

With the static data message, there's a lot more of the information is entered manually. So for example, the name, the call sign, the IMO, the dimensions, the destination and ETA. The setup of the system is designed in such a way that it is not easy to change, for example, the MMSI. It normally requires a level of information deeper than is available generally on the bridge, for example. To change that, you need to get into the maintainer side of the AIS system.

So manipulation of the MMSI is -- accidentally is rare. Obviously, the name and the call sign and the IMO number, a lot of that depends on the diligence of the ship staff in maintaining that to date. But as I said before, the whole thing about it is, as a navigational safety system, a well-honed ship, responsible master and ship's crew have every legal and safety reason to try and maintain this data as accurate as possible. That's the great thing. There is a commercial and legal driver behind the system, which means that legitimate users should endeavor to maintain this information up to date.

So that's what I will say on the subject of how much you can believe this. Obviously, like any system, and the one thing I will say about it is that the AIS system as it was set up originally is never designed to contain extensive security and checks in it. It's designed to be as open as possible to ensure that people use it. And therefore, if you were designing a security system, you would put a lot more checks and balances than there are in there. The biggest security from one view of how good the data is, is this legal and moral reason behind maintaining the safety of your own ship and others in the area.

George Devereese

Yes. Thank you, Richard. Given my time at sea and especially when I was working for a container shipping company, I can certainly attest to when vessels are busy doing port calls over 12 hours, they certainly may not update their correct port call. I've certainly seen vessels moored doing 10 knots plus. And I have seen some truly shocking spellings of different ports and trying to decide sometimes where these vessels are actually going based purely on the destination does certainly sometimes lead to one getting quite imaginative when you're trying to decide for some of these spellings.

Richard, you touched upon it briefly there about the legality of the system and where it comes on -- and you've mentioned SOLAS previously in this podcast. Who is responsible for the standards of the AIS and its enforcement?

Richard Hurley

The overriding standard, obviously, is the IT, IMO with the Safety of Life at Sea Convention, Chapter V is the one that mandates AIS. It lays down the rules should be obeyed by the shipping. And the technical standards are developed by the ITU. And again, there's a big technical document, which gives you all the technical standards and also the formats for all the messages, et cetera.

So they are the people mandating the design or technical standards and the actual legal standards. The implementation is very much down to the flag states. And again, the flag states are also able to extend the requirements for AIS to other users other than mandate under SOLAS. So ITU and IMO specify the system, but the individual flag states are the ones responsible for maintaining and policing it in a local level.

George Devereese

Thank you, Richard. I think that's very important for our listeners to understand the standards and where it gets enforced as we -- as you said and I've said, it obviously comes and stems from that safety and navigation primarily and has therefore snowballed. With that, we've talked about how often AIS transmits from a vessel every 2 to 4 seconds whilst underway, et cetera. Is there any time therefore, when a vessel would legitimately not transmit on AIS?

Richard Hurley

Yes, there are. Broadly speaking, in the requirement is for the vessels to transmit at all times when navigating. Obviously, when a vessel is alongside, there may be occasions when it was to switch off. It can also switch off, for example, if it was a tanker and it was alongside a berth way or its load is discharging, the local radio regulations may require to power down or switch off equipment.

So it's quite legitimate alongside, long-side berths for ships [ to spear ], although in most cases, ships are quite happy to leave them on. You have a container vessel going alongside a container, berth will not switch its equipment off, it will just leave it running. And we normally can see sort of 95% or so of the vessels at any one time, the bigger vessels that we know of.

And that -- the only other time -- sorry, the other place they could switch off, for example, is if a vessel goes into refit or go for breakup briefly or lay-up, ship may be laid up for several months. It obviously will not leave its AIS transmitting, but it will be secure in a location.

There is allowance in the standard for masters to switch off their AIS when they think the ship's safety is endangered by -- so typically, what we're talking about here, most people understand, is areas of potential war and conflict where, obviously, you don't want to make yourself a target. And also piracy areas. Piracy was quite problem, particularly in the Arabian -- sorry, the Horn of Africa area. And the bridge was there to switch off so that you wouldn't be a target for the pirates.

In actual fact, in many cases, they found it was actually the opposite way around. You should really have it on because if the pirates couldn't find you, neither could the good guys, neither could the law enforcement agencies, the warships in the areas. So it was obviously a lot easier to find you if you had your AIS on or at least they knew where your AIS disappeared, which is likely to be where you'd been subject to the pirate instance. So there is a provision on safety. There is no provision in the rules for switching off because you don't want people to track you, you don't want people to know that you're fishing in an area. That's not a legitimate reason. It's got to be a genuine reason for safety.

George Devereese

Yes. I will just attest to that, having done antipiracy operations off the Horn of Africa in sort of 2010, 2011. When a master turns off his AIS and all your left with is a rather garbled transmission over VHF, while he's -- while the pirates are boarding his vessel over latitude and longitude, it sometimes is rather hard to try and find them and rescue them. So certainly, it is a double-edged sword.

But Richard, I think now we're running -- rather coming up to time on this first, very interesting and very informative podcast, which I hope our listeners have enjoyed listening to as much as I have. Is there anything you would finally like to just bring to the listeners' attention before we do wrap up this podcast?

Richard Hurley

I think obviously, there's a lot more to be said regarding where in the world you may have problems locating a ship. I think what I always say to people is if you are trying to identify where a vessel is in the world, and you believe the vessel will be operating is perfectly well found and operating legitimately, if you do not see it, then there is usually a very good technical reason why the vessel is not there. The least likely issue is that the vessel has switched its AIS off because, as we said, the key thing is safety.

The whole of the AIS system is built around safety. People that often talk about it as a tracking system, it's not, understand, a safety system. If you cannot see a vessel and you think the vessel should be visible, the first thing to do is to look for reasons why that vessel may not be an area where you can pick it up.

So for example, these high-traffic zones 200 miles off the China coast stop Message 27 capability, there may be a good reason why you can't see it. So before you start looking for reasons and why people have switched off, ask why you may not be able to see that vessel. And that's -- usually, you can find a reason. And then eventually, the ship will pop up, and you'll say, yes, obviously, the reason is correct.

George Devereese

Yes. And I think that's a fantastic point to end on, Richard. It's just a reinforcement of AIS as a safe navigation system. And ultimately, the seafarers use it to get home safely to their families and their loved ones.

Richard, thank you ever so much for joining me today on our first podcast. I truly hope that the listeners have found as interesting as I have and look forward to working them back for our next in the series. Richard, thank you, and thank you to our listeners.