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Maritime and Trade Talk | EP1: Part 1 - The Basics Of AIS


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Maritime and Trade Talk | Episode 19: The EU’s 11th Package on the Circumvention of Sanctions and Vessel STS Transfers


Maritime and Trade Talk | Episode 18: Right Place, Right Time - Q3'23 Trade and Supply Chain Outlook


Maritime and Trade Talk | Episode 17: Striving for Normality – Q2’23 Trade and Supply Chain Outlook

Listen: Maritime and Trade Talk | EP1: Part 1 - The Basics Of AIS

What is AIS, what it’s designed to do, how does it work? The Basics of AIS Part I and Part II intends to assist users new to AIS to make informed decisions on the consumption and interpretation of AIS data. 

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Sheraer Abrahams

Welcome to IHS Markit's Maritime and Trade Talk Podcast. I am Sheraer Abrahams. And today, I am bringing to you our first episode, the Basics of AIS Part 1.

George Devereese

Hello, everyone. Welcome to this, the first of the new IHS Markit Maritime and Trade Podcast series. My name is George Devereese. And I am the product manager for our Maritime & Compliance -- correction, Maritime Risk & Compliance suite of products. Today, I am delighted to be joined by Mr. Richard Hurley, who I'll let introduce himself in a minute, to talk through AIS, what it is, what it does and what you as the consumer of our data needs to know about it.

A little bit of background of myself. I joined IHS Markit in February 2020. Previous to that, I was an officer in the Royal Navy for just shy of 8 years before working for a number of shipping companies and the maritime insurance sector. And Richard, I'll hand over to yourself for a brief introduction. And then we'll crack into the subjects.

Richard Hurley

Thank you, George. Right, my name is Richard Hurley. I'm a principal maritime analyst at IHS Markit. And I've worked here for nearly 30 years now. And I've been working primarily in recent years with AIS from its very inception up to the present day.

Prior to joining IHS Markit, I also was an officer in the Royal Navy, not for quite as long as George, and then an officer in the Naval Reserve. So I have a background in navigation as well as the technical issues. And that's where I come from. So I've got the long-standing in AIS.

Question and Answer

George Devereese

Thank you, Richard. So let's get stuck into the subjects. And I suppose the first question that our listeners will be keen to hear of is what exactly is AIS? And what is it designed to do?

Richard Hurley

Yes, very simple. AIS stands for automatic identification system. And it's officially classed as primarily an aid to navigation, which may confuse some of our listeners who think of it as a tracking tool. But it was designed primarily for improving vessel safety by increasing situation awareness of vessels regarding nearby traffic.

It also had a secondary function of allowing the monitoring of traffic by vessel traffic systems and port authorities and the government agencies. And it's this secondary monitoring function which IHS Markit and other companies have further developed and exploited to ride the global vessel tracking systems we use today.

George Devereese

Yes. Thank you, Richard. I have to say, I remember the first time we got the IHS Fairplay laptop put at the back of a bridge that showed us the AIS network and especially going through the Davis Strait, seeing the other ships that are coming towards you or traveling in the same part of the traffic separation scheme, which is absolutely phenomenal for that situation awareness and to help avoid those navigational instances that you can sometimes get into in busy shipping lanes.

So going on from that, obviously, it's like a very interesting system. How does it work? What system does it use to operate on?

Richard Hurley

Well, basically, it's a VHF radio system. And what it does is by allowing the individual vessels to broadcast automatically a regularly set, updated series of structured messages pertaining to navigation and identity information to other vessels in their immediate vicinity.

These messages are broadcast on two main VHF channels. And the message themselves conform to 1 of 27 predefined formats. So the whole thing is predefined and standardized. It's also designed to be self-organizing with the individual transmitters in an area synchronizing themselves with each other to avoid overlapping their transmissions.

So each ship is transmitting in its immediate area in a clear transmission slot, so their message can be got through to vessels in their local area. And when we're talking about local areas, typically for a big ship, this will be out to 20, 25 nautical miles maximum from their position. So it is a very local system or that's how it was designed.

George Devereese

Yes. And I think as you touched upon, and I'm sure as we'll touch upon later, where it originally started and where it is now has come on leaps and bounds, maybe not always for the better. So it all sounds fairly standardized, Richard. Is therefore all AIS equipment the same?

Richard Hurley

It is in the formats of the messages that are sent and received. What is different is the equipment that's fitted on the individual vessels. And broadly, it falls into two main groups and a couple of subcategories. The first main group is what we call Class A equipment. Now this was the original primary class specified as a mandatory fitment when AIS was first developed.

And it was developed for -- by the IMO for ships under SOLAS, Safety of Life at Sea Convention, particularly [ Chapter V ], which is regarding safety at sea. And this specified this Class A equipment was being mandatory for vessels of a certain size on international voyages. So this is the standard equipment. It's the most powerful and capable version. And it is the only one that is actually mandated for carriage on specific types of vessels.

The advantage of AIS in providing situational awareness and navigational safety was rapidly realized. And so a second type of equipment was created called Class B. Again, this is using exactly the same message format, but it's a lower-power version designed primarily for the voluntary use by small commercial vessels, private users, yachts, pleasure craft, et cetera. It's less powerful, it's less capable. But it will read all the messages from the larger ships in Class A.

Coming on from that, when we say the specification of AIS develops over the years, and there is now a newer version, which is called Class B+ or Class B SOTDMA. The acronym doesn't really matter at this point. But it's a development falling in power between the Class B and the Class A equipment. But it uses a slightly more powerful time slot-sharing system, which is used by Class A, which means vessels with Class B+ equipment are slightly more visible than the Class B.

So Class A is the primary equipment. The main difference is the power of their transmissions and the priority according to their messages. So Class A, this is what SOLAS is all about. This is what AIS is all about. It's the primary and most powerful system, which has a priority. Class B+ is next down the priority level. And finally, Class B itself is at the bottom of the priority level. But there's no difference in the performance regarding reception between any of the three types of equipment.

George Devereese

Yes, thank you for that clarification, Richard. So it's rather interesting. Obviously, I suppose a lot of our listeners would sort of interpret AIS as something that every single vessel has to have. And it's interesting to hear of those different classes, and especially, when you talk of voluntary AIS. Therefore, who has to use AIS? And are there any certain sort of vessels that are excluded, it's not mandatory for?

Richard Hurley

As I mentioned, the primary driving force behind the adoption of AIS was the IMO Safety of Life at Sea Convention under Chapter V. And this, for the first time, specified not only the design of the AIS system but also its mandatory use and fitment to all vessels over 300 gross tons and upwards engaged on international voyages and cargo ships of 500 gross tons and upwards not engaged with international voyages and all passenger ships, irrespective of size.

And these regulations started back in December 2004. Now that was the internationally mandated carriage. On national level, the -- it was left open to the individual sovereign nations that they could also enact local regulations requiring the fitment of AIS equipment, either Class A or Class B, to certain categories of ships in their own waters.

So for example, when we saw the European Union in 2010 extend its compulsory use to most commercial fishing vessels operating in European waters but also to vessels operating on the European inland waterways, so not seagoing, not oceangoing but in the inland waterways of the Rhine and the Danube and that, they specified that the commercial vessels would need to use AIS.

We touched earlier on the navigational advantages and the safety advantages. A lot of adoption has been voluntary adoption, particularly the Class B equipment by smaller vessels. Obviously, if you're navigating in a waterway where there are large vessels navigating, it's nice to have the information about who's moving around you. At the same time, it's also nice to point out to these big vessels where you are as they might not be that well aware.

So one of the big driving forces behind the adoption of AIS, not just by the vessels mandated for by the IMO, is this safety. And there is a really strong safety reason why vessels would like to fit and to use and maintain up to date their AIS equipment and their transmissions.

George Devereese

I think, Richard, I can attest to that safety and navigation piece, both having been an Officer of the Watch in warships but equally being rather a keen sailor, especially out in the Baltic, where you've got some of the larger container vessels doing their container runs and you're sailing around at night.

It certainly does give you a sense of safety knowing that you're transponding -- transmitting on your AIS to let them know you're here rather than having to shine a big, old torch on your sail to stop yourself getting run over. So I definitely attest to the benefits of broadcasting AIS. So we have...

Richard Hurley

Yes, I'd also point out that I didn't quite answer your question regarding who wouldn't use AIS or may not what use AIS. One of the big areas that is left out of the AIS standard is the use by naval, government or other vessels, which don't fall inside the SOLAS categories. Use of AIS by these sort of vessels is not mandatory.

A lot of them do use it because it has a very good safety reason for it. But you cannot assume that government vessels, naval vessels will be using AIS even in restricted waterways. So they are the big area of oceangoing vessels that may not be using AIS at all times.

George Devereese

Thank you for clarifying that, Richard. And I think those listeners that operate in the insurance sector will be aware of incidents with naval vessels that have happened, collisions such as the Swedish vessel -- a frigate that came stuck in the fjords and the Americans when they tried to do some overtaking in the traffic separation schemes, not transmitting on AIS.

Richard Hurley

I think it's been interesting on that, in that navies, for obvious reasons, do want to maintain their secrecy at times. But sometimes they've been overzealous with this. And we have actually seen regulation being brought on, notably with the U.S. fleet, telling the ships to use AIS in navigational situations wherever because of the safety implications and incidents which have happened with not using it.

George Devereese

Exactly so. And I think that points to the constantly evolving nature of this topic and of AIS as a whole. So I think we touched upon it very briefly at the beginning of this podcast about the technology that AIS is based upon. Obviously, the VHF regulators is an old system, which has a limited line-of-sight transmissibility.

And listeners will know that there is also satellite receivers of AIS. So Richard, is there different equipment that is required on the vessels to be able to transmit both terrestrially over that VHF but also to satellite receivers?

Richard Hurley

The beauty of it is that there is, by and large, no need for the ships themselves to change their equipment. As you say, VHF is traditionally line of sight, which on the surface of the Earth with curvature means, depending on the height of the transmitter and the receiver, with a big ship, you'd probably see 25 to 30 nautical miles reliably.

Obviously, if you're talking about a satellite receiver, the satellites that are used now to pick up AIS transmissions are usually in a low Earth orbit, which is about 120, 130 miles, 150, 160 kilometers up. They have a very large footprint. It can be 1,500 nautical miles across plus. They obviously pick up a lot of data from a lot of areas.

But they are using exactly the same types of receiver, obviously more sensitive because of the distances involved, as the conventional terrestrial equipment. So by and large, they will pick up all the messages or have the capability, should I say, to pick up all the messages, which are transmitted. Now we'll probably go on, there are some issues with satellite monitoring because of its -- the large footprint. But we'll talk about it in a moment.

But there is actually no requirement for a small yacht to change its equipment, for example, to be picked up by satellite. The mere fact it's transmitting on VHF should give it a possibility being detected from a satellite. You may then say, "If satellites can pick up all the transmissions, why do we need a terrestrial network?"

The simple answer is the most reliable form of receiver is a terrestrial receiver. It's on 24/7. As long as it's with line of sight of the vessel, it should have continuous ability to pick up and detect those signals. The problem with satellites is they're low Earth orbit. Physics dictates that those sort of satellites cannot be geostationary. So they're not just sitting there over one part of the Earth. They are orbiting.

And typically, their orbits are around about 100 minutes, 110 minutes. So they are sweeping the Earth. And depending on how many satellites there are on a constellation and their locations and their specifications, it means that they will pass over typically a vessel for no more than about 5 or 6 minutes at a time. And then they'll disappear over the horizon. So they are not able to provide a continuous coverage.

And there are other aspects of the way that they pick up that the -- of the coverage pattern that they have, which means they don't always have the same chance of picking up a vessel in different parts of their footprint. So they are much more transitory. They will pick up perhaps one or two positions every time they go over a vessel. But they are not able to provide 24/7.

So that's the main reason why satellite -- it's very good for the deep oceans, very good for the poles, where you can't get terrestrial antennas, but not so good when you start getting into very high traffic areas. And we'll talk about that in a moment.

George Devereese

Yes. Thank you, Richard. So obviously, with the overlay of both terrestrial networks with the antenna and also with the satellites' overwatch, so to speak, obviously we spoke originally about AIS not being a global tracking tool and very much an aid -- a safety aid to navigation, is it fair to say that now with those overlays of both the satellite and terrestrial that AIS covers globally? Or are there areas of the world that aren't covered?

Richard Hurley

The coverage from the point of view of satellite is now global insomuch as that there will always be a satellite that will be able to cover or to sweep over an area of the Earth. The problem with satellites, and I started to touch on it, but I will now explain what my comments were about, is its footprint is so large that, for example, a satellite flying over China -- and this is a classic example, it could have 40,000 vessels in its footprint, all of which are transmitting.

Now the problem there is that the AIS system, being designed for vessels within sight of each other, it organizes itself, so the vessels in a little cluster, they actually listen to each other. They wait for a transmission. They work out when the next transmission is going to be from a particular ship. And then they will pick a transmission slot. Between that, they can broadcast there. So they're organizing their messages amongst these little 25-, 30-nautical mile cells.

And the way I describe it, it is a bit like being in a very large concert hall or a meeting, where you've got lots of people meeting. You're all in your little cells having your conversations. And you organize amongst yourselves so that in your little cell, you're talking to each other, but nobody is talking over. You wait for a polite pause and you talk. And that's fine. And it works brilliantly in these very small cells.

With a satellite, you're trying to effectively listen to a whole room and all the little cells in that room. At the same time is you're literally going through there only for 3 or 4 minutes and you're walking through the room, you're trying to listen to every conversation. The problem is if there are too many people in the room, you are not going to hear these individual conversations. You're only just going to get a babble.

And that's what happens with satellites. There are not enough transmission slots and the ships are not organized themselves on a scale of 1,500 nautical miles. And so effectively, when you go over these areas with a satellite, then you'll just hear a babble. You can hardly pick out any message at all. Not to say you won't get any messages, but you'd only get a very small subset in a really high-density area.

And a classic example is, say, China, South China Sea, the Mediterranean, the U.S. Gulf, the Persian Gulf, there are so many vessels there, such a high density, that you will have very little pickup of the individual ships. And that is why in those areas, traditionally, the solution was to try and get a terrestrial antenna in the area, which, of course, can listen to a much smaller area.

But the problem was that a lot of these areas, the main shipping routes, the main areas of shipping activity was well out to sea. So unless you could actually get an antenna onto a platform or an island in the area, very often they were well beyond the reliable reception range of a terrestrial AIS station. So there are areas of the world where reception is problematic.

Now I think I should go on from that and say this obviously is a recognized problem with the original specification of the system as laid back in 2004, when it was all being put out together. What has happened since then is two things. First off, the specification has now been amended. And what has being created as a new message called Message 27. And this is specifically designed for long-range tracking. It's designed to get over this problem of high-density areas and the long-range tracking by satellite.

The way it does it is to take the Message 27, which is a brand-new message, and to transmit this message on two completely new dedicated VHF frequencies, so it's not fighting with the other traffic on the main frequencies. At the same time, it is using a much shorter message, which is designed just to give you literally the position, course, speed. And it is being broadcasted at a much lower data rate, so it requires less bandwidth.

So it's only being broadcast every 3 minutes whereas a message from a vessel underway could be broadcast every 2 to 12 seconds normally. So by reducing the frequency of the message, reducing the size of the message and by giving it two dedicated channels, there is now this Message 27 that is designed to aid long-range tracking in high-density areas.

The disadvantage with this approach is, at the moment, this is not a mandatory message transmit. And to transmit it, you obviously need the equipment which can transmit on the two new frequencies. So it's not necessarily being retrofitted to vessels that have already got an AIS transponder.

It is not mandatory even for new vessels to have it, although the vast majority of the larger vessels are now fitting it. We're seeing it. At the same time, we're also seeing certain market sectors retrofitting. And for example, the cruise industry, all the bigger cruise ships have been retrofitted to broadcast Message 27 to enable long-range tracking.

The other disadvantage is, of course, it requires a dedicated receiver. And particularly with satellites, some of the satellites and the older satellites were obviously put up before the Message 27 specification was -- [ came to ]. Therefore, they don't have this receiver onboard. The modern satellites do, but the old ones don't.

So Message 27 is, at the moment, a partial solution because it is one that requires dedicated equipment. But it is already in use. There are something like 30,000-plus vessels that have been identified using it. And so these vessels are now much more visible than they were using just the standard Class A and Class B transmissions. So Message 27 is one advantage.

The second thing that we are also seeing is a move now towards being able to get AIS transmissions from ships. And this is where we use the ships themselves to transmit their local AIS picture via satellite or other means to give us effectively like a roving data station. And that is also starting to address these areas of high-density traffic.

Obviously, if it's high-density traffic, there's likely more of these ships that operate in the area, we'd like to get more coverage. So both of these are starting to remove these dark areas, these areas where, for technical reasons, I stress it is a technical reason rather than in the original specification, we were not previously able to get coverage.

George Devereese

Thank you, Richard. I think the listeners will find that very comprehensive explanation very insightful. And if I can continue on your analogy, just to sort of unpack the Message 27, I suppose, with the satellite running through the room of the meeting of those cells, I suppose Message 27 is rather like one of the cells putting their hands up to say, "Please come pay attention to us and hear what we've got to say." Would that be fair?

Richard Hurley

I think it's more of somebody sort of saying to the room, "Right, everybody, quiet and then, everybody, slowly explain who you are, where you are." It's cutting the bandwidth down or cutting the transmission rate down and giving much more time for the individuals to be heard. So rather than just gabbling away, everybody is waiting a longer period before they say their sentence, for using the room analogy.

Sheraer Abrahams

Thank you for listening. Make sure you don't miss the Basics of AIS Part 2. Until next time, stay safe.

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