Pilot vs Processor: The Strive for Zero Latency UKC.

This episode explores the invisible hydrodynamic forces of restricted waters—such as bank cushion, ship-to-ship interaction, and the devastating "2D trap" of reduced under-keel clearance that triggers exponential squat and violent sheer. We then expose the severe fragility of modern navigation, detailing how the UK's critical infrastructure is exposed to state-driven GNSS removal, localized signal jamming, and silent spoofing attacks, while also breaking down why augmentation systems like RTK and SBAS offer only a false sense of security. Finally, we contrast these vulnerable computational systems with the unmatched zero-latency sensory fusion of an experienced maritime pilot.

Barry draws on his years of piloting to highlight the factors and ultimate benefits of a pilots' zero latency experience driven intervention.

Come and Visit our Website

https://www.captainbarrysadler.com/

At Captain Barry Sadler Maritime Training & Consultancy we deliver industry-leading online courses, oral exam preparation, and professional resources for deck officers, cadets, and maritime professionals. Fully aligned with UK MCA standards, our training helps you build knowledge, confidence, and a successful career at sea.

Check Out Our MCA Questions Apps 

https://captainbarrysadler-colregs-quiz.base44.app

Follow us

Linkedin

Instagram

X

Facebook

Transcript

Copy Transcript Copied

SPEAKER_00 0:00

A warm welcome once again, everyone, to the Maritime Education Podcast. My name is Barry Sandler and uh welcome back to those of you who are regulars to our podcast. It's great to have such a huge following. To those of you that have just discovered us, welcome. Welcome to a podcast that deals with all matters maritime and helps explain some of the fundamentals behind maritime business, ship handling, and seamanship in general. I hope you guys find what we're going to discuss today both interesting and educational, depending on whether you work in the industry or are literally just intrigued by how it works. In our last podcast, I discussed at length the benefits of a dynamic underkill clearance and how this compares to a static underkill clearance. What I'd like to do today is build on that a little bit further and talk about water hydrodynamics and how they affect the ship, the the shock of unexpectedly having a reduced underkill clearance below the ship, some of the vulnerabilities of our satellite navigation systems that may result in this happening, how these systems can be corrected, and how a pilot reacts compared to how a portable pilot unit or other source of pilotage information displayed electronically, how they compare when it comes to reacting to things and times when a ship may not behave the way it expect we expect it to due to the fact it's got too little water under the keel. Before we discuss these topics, let's say first of all, that a pilot will always produce a passage plan the same way as a captain will produce a passage plan. A pilot will analyze the intended voyage, will analyse the ship, the weather, the berth that we're going to, the channels that we are taking, and produce a plan based upon the information given to him or her. The information given will also all will of course be the type of ship, the draft, the size of the vessel, the berth that we're going to, and any other factors that may be of interest to the pilot, such as the number of tugs that we're taking in the expected time of boarding the vessel. All these factors are taken into account by the pilot and the pilot will produce a passage plan. And one of the key elements of that passage plan is calculating the underkill clearance, ensuring that before the act of pilotage is undertaken, that at all times that the ship is under the conduct of that pilot, it has sufficient underkill clearance to allow the pilot to handle that ship in a way which the pilot can semi-predict how the ship's going to behave and avoid any unexpected movements or trends in the vessel's manoeuvre that may occur when there is insufficient underkill clearance. If a pilot produces a passage plan and that passage plan shows that the underkill clearance is not what the pilot requires, then the pilot will obviously contact the VTS station and request that the boarding time of the ship be adjusted to allow for better underkill clearance, obviously, based upon the times of high and low water, especially. So a reduced underkill clearance has a real issue when it comes to handling ships. Now there are some very very common things that the ship will do with a reduced underkill clearance, which are are well documented, well known about, and are sometimes easily avoided by avoiding excessive speed when the underkill clearance of the ship reduces. Underkill clearance is basically the measurement between the hull of the ship and the seabed. In other words, it's a measurement of the space available for the water around the ship to flow. If the distance between the bottom of the ship and the seabed is too small, then this restricts the water's ability to move around the ship as the ship moves through the water. Bernoulli's theory of sorry, not Benooli, we'll talk about Bernoulli in a minute. Archimedes theory of flotation says that a body will displace its own weight in water, and any body that displaces its own weight without sinking contains what we know as buoyancy, an upward force that keeps the vessel floating. Now we talk about this because a huge ship will displace a huge amount of water. Now the ships that we have coming into the Port of Salems and the biggest ships that we have are what we call category seven container ships, and they are displacing anywhere in the region of between 220 and 280,000 tons of water. That's a huge displacement. A displacement created by the mass of these massive ships. And that amount of water moving around the vessel is a huge amount. In other words, if we take one of these monster ships and we push it through the water using the engines and the thrusters and the rudder, and we do not allow sufficient underkill clearance to allow the displacement of these vast sums of water, then the hydrodynamic effects can really be detrimental. Now there are some hydrodynamic effects that are well documented, which as I say are based around the ship's speed, really. One of them is what we call squat. Now squat is basically where water cannot flow fast enough under the hull of the ship. The ship's going too fast, and so the water is squeezed between the hull of the ship and the seabed, creating a low pressure, and this causes the ship to displace the water away from it, meaning that the underkeel clearance, the distance between the hull and the seabed, reduces even further. Squats are easy to deal with as a pilot, you just reduce the speed. Although, unless the ship is stopped, squat will always be there, its effects will be minimal if you've got control of the speed. The other well-documented hydrodynamic effect is what we call bank cushion and suction. This is where the water flowing between the ship and the bank of a river or a key is again squeezed in between the ship and the key, and the same effect happens. Now this does produce a drop in pressure. This is Bernoulli's theorem of fast flow low pressure, a drop in pressure between the ship and the key wall, which will attract the ship to the key wall. But because the ship is moving, there are other hydrodynamic effects in play, one of which is a pressure wave at the front of the ship. Because the ship's moving ahead, the pressure of the water ahead of the ship increases as the ship displaces it. And if this bounces off the riverbank or bounces off a key, this is going to deflect the bow away. Conversely, at the stern and towards the midship section of the ship, we get this negative effect caused by Bernoulli's theory, which can cause the ship to be drawn in. So if you're passing a berth too fast, the bow will be rejected, the midship's part of the stern and the stern will be pulled in, and the effect will be that the ship uncontrollably swings its back end towards the key. Ship-to-ship interaction is something else that is exacerbated with a reduced underkill clearance. Now, this is because the high pressure values of the ship's bow, the water around the ship's bow, deflect off one another, causing the ships to initially be deflected away as they pass one another. But again, when they get alongside one another and both ships have their negative pressure bands alongside each other, they can be drawn in. The sterns may inevitably touch. There are other forms of ship interaction from overtaking, but I won't go into that just at the moment. What I want to talk about really is the effects of a sudden unexpected reduction in this underkill clearance. Let's assume that we have this sudden reduction in underkill clearance when the ship speed has been moderated. In other words, as part of the pilot's passage plan, he or she identified reduced underkill clearance and has moderated the speed accordingly. Let's talk a little bit now about what's going to happen in just handling the ship when we have a reduced underkeel clearance. Because we now have very, very little distance between the ship's keel and the seabed, the water can no longer escape under the keel. So the flow of water is really flattened into almost a two-dimensional horizontal plane which instantly multiplies all the hydrodynamic forces that I've talked about. This means that particularly shearing away or towards a berth can be exacerbated, passing another ship can be exacerbated, and this is even with our speed moderated. Shears can happen, so the ship can suddenly start to head off in a direction that we do not expect it to. Again, even if we are manoeuvring at a relatively low speed. Now, another problem with squat and with a reduced flow of water underneath the ship is that we start to get problems with the rudders and the propellers. This is caused by twofold. One, water that is squashed between the ship and the seabed or the ship and another ship can get aerated. So as the propeller and the rudder are flowing through this liquid, if there are air bubbles in the liquid, that makes the propeller and the rudder less effective. If the propeller becomes less effective, then obviously the rudder will become less effective as well. If the propeller becomes less effective, the speed will reduce, and when the speed reduces the flow over the rudder reduces, and this can again create problems in the handling of the ship. Because of these limitations that are placed upon the rudders and the propellers, this literally increases things like turning ability. So where you would expect to be able to make a turn with a certain rate of turn and a certain diameter, that can increase if we have a sudden reduction in underkill clearance. The other problem with reduced underkill clearance, which I touched on briefly in the previous podcast, is the wave wall or the necessity to push large amounts of water out of the way when we are manoeuvring a ship. Not just when a ship is going ahead, but if we're pushing a ship sideways with tugs, for instance, to berth it, we are trying to push water out of the way. The ship displaces this huge amount of water, and as we are pushing the ship, let's talk about going sideways towards the berth, as we're pushing that ship sideways, we're having to displace that water away from the ship. If we try and push the ship too hard, what happens is we build up a wall of water. In other words, we're trying to push the ship with too much power towards the berth. The water cannot escape because we have this sudden reduction in underkill clearance, and therefore, literally, it builds up against the hull as we push the hull sideways. This means that we may need extra thruster power, extra tug power, extra engine power, more rudder to achieve the same movement of the ship than we would have done if that water could have freely flowed. When I talk about a sudden reduction in underkill clearance, what I'm focusing on really is a reduction in the underkill clearance that we did not plan for. In other words, if we were perhaps using a dynamic underkill clearance system that hadn't met its calculation potentials, or we have a weather event that can cause the tide to cut, or human error, let's not neglect human error, you've taken a ship in and uh you've uh perhaps got the time of the tide wrong, you've got less dynamic underkill clearance than you think you have, or perhaps one of the greatest vulnerabilities of both the dynamic and the fixed underkill clearance is the actual position of the ship, and this throws up some really interesting thought processes about global navigation satellite systems and how we use them. Ships are now huge. I gave you the dimensions earlier on. A Cat 7 container ship is 400 meters long, 62 meters wide, has a draft somewhere in the region of between say 12 and 16 meters, and the containers are stacked up on deck sometimes 13 or 14 containers high. This means that as a pilot stood on one side of the ship, whilst you can see down the side of the ship, and you've got a good overall view of what that ship is doing, it's almost impossible to tell where the rest of the ship is that we cannot see. And for that reason, we furnish ourselves with what we call portable pilot units. These are units that we take with us on board ships that run off global navigation satellite systems and enable us to see where the ship is in relation to the hazards and obstacles around us. It will give us not just a course and speed over the ground but a predictor to show where the ship's going to be in one minute, two minutes, three minutes. And predictors are normally ship-shaped, so you can see that based upon the speed of the water, the transverse movement of the ship, and the rate of turn, the PPU will show you where it expects the ship to be in 30 seconds, one minute, three minutes, whatever. These predictors are highly useful to pilots when navigating these huge ships because you have that three-dimensional view but of just one half of the ship. So we rely to a certain extent on these PPU units, and these PPE units rely in turn on the accuracy of the satellite navigation systems that are used to drive them. The rate of turn of the ship, in other words, how fast the ship is turning, that comes from an independent unit that the pilot has. The dimensions of the ship are drawn from the ship's AIS transmitter. In other words, the length and breadth and draft of the ship are obtained from the ship's own output. So we combine some independent position fixing systems with this, some independent heading systems, so a portable pilot unit that I use will not only tell me the ship's position, but it'll use satellite to derive the ship's heading as well. This combined with the built-in rate of turn indicator and the size of the ship given by the AIS system furnishes me with a half decent predictor. But that predictor is only accurate if the position given to the equipment is accurate in itself. In other words, the precise location of the position pod on the ship, and I've told my system where that position pod is positioned within the ship itself, so that the ship's model can be based around it. But the critical thing is the actual position on the earth's surface of that portable pilot unit pod, how accurate is that, and how can that be subject to error, which can, if we're not concentrating as a pilot, put us into an unexpected underkill clearance situation. The vulnerabilities of satellite navigation systems are well documented. UK infrastructure, for instance, if we talk about what we use these satellite navigation systems for within a UK infrastructure, their importance is absolutely critical. Position, navigation and time, PNT, critical infrastructure, is what the UK focuses on when it talks about its vulnerabilities to the loss of a satellite navigation system. One of the most important parts of that is the T, the timing standard. In other words, GNSS systems have built-in clocks, hyper accurate clocks that effectively are used to synchronize the United Kingdom's time. So if we lose our GNSS provision or it becomes inaccurate, then things like power grid phases can desynchronise, cellular network towers can drop connections, financial market time stamps can fail. Estimates on global navigation system blackouts in the UK suggest that if we lose our timing from our satellite systems for seven days, it would cost the UK economy somewhere in the region of 7.6 billion pounds. Now that's an estimation based upon the inability to trade accurately, but nonetheless it goes some way to showing you that national infrastructure is tied very, very closely to GNSS systems because of the timestamp that they give us. There is the growing threat of state driven removal of these satellite systems. So the threat isn't just a localized signal loss. Hostile foreign states already possess the capability to actively remove. This GNSS architecture and includes kinetic anti-satellite weapons, in other words, weapons that take out literally the satellites themselves. States can create cascading space debris fields in medium Earth orbit that the satellite systems can career into. And of course, there is the highly documented, sophisticated cyber attacks on terrestrial ground control stations that upload orbital data to the satellites, which can affect the satellite's ability not just to fix a vessel's position, but can affect this timing ability, which can affect national infrastructure as well. Don't forget, signals from navigational satellites are very, very fragile. They transmit with the power of around a 50 watt light bulb from almost 12,000 miles away. And by time the signal reaches a ship, then it's fairly weak in comparison. So it's easy for it to be jammed out by very, very cheap localized jammers or perhaps severe solar weather. Spoofing is another problem that we have seen recently, particularly with recent warfare, where a jam signal will trigger an alarm, but a spoof signal will make your satellite receiver think that it's got a good signal, but will spoof it into thinking it's in a different position. Doesn't matter which one of these uh happens, or whether it's just one of the well-known errors of the GPS system, such as a multi-path error, which is where the signals bounce off somewhere else, affecting the timing of the reception of the signal and therefore the position, or whether it's a uh a satellite almanac area error, sorry, where the satellites perhaps aren't in perfect orbit around the receiver. Whatever it is, we are not immune on our pilot PPU unit from errors that can creep in with the position of the actual pod that our system is based around. We do have, in general, when it's working, and when nobody's spoofing it, nobody's trying to bring it down, when it's working, we do have the benefit of corrections coming to our units which make them hyperaccurate, hyper accurate to within just a few centimetres, which enables a pilot to use his or her PPU in order to achieve the maneuver within a uh a very very confined water, taking into account these forces that we discussed on a reduced dynamic underkill clearance. The two most commonly used forms of correction now are what we call a real-time kinetic connection and satellite-based augmentation. Real-time kinetic tends to be the most accurate way of correcting a position fixing satellite signal by basically using a base station, a shoreside base station, to compare the signals that it's receiving from the satellites to its actual position and bang out corrections from there. As long as you're within 20 to 30 kilometers of said station, you will receive hyperaccurate corrections, sometimes over cellular data or a radio link, which, when combined with your GPS receiver, will give you an accuracy of literally centimeters. The trouble with RTK is that if a cellular data link goes down, you lose your RTK signal, and therefore you've lost the benefits of that localized correction station. Satellite-based augmentation is different. This uses satellites to literally correct the signals coming from the GPS satellites themselves, the uh the GNSS satellites themselves. I said GPS there, but don't forget we've got several systems now. Uh, the American system, GPS, uh, we've got Glonas, which is the the Russian system, the European system, Galileo, is there, the uh the Chinese system, Badoo, is there, so the system or the dropping out of one system is now not an issue. GPS used to be a standalone system on its own 10-15 years ago. It's not now, there are other systems, so a single use GPS was to fall out, we've still got, for instance, Galileo to back us up. But these providers can all be corrected by satellites themselves, so they all park um what we call geostationary satellites up there, which will receive corrections from ground stations and then they will directly correct the signal coming from the navigational satellite itself. So RTK that corrects the received position, whereas satellite-based augmentation corrects the transmitted signal from the satellite, again giving us very, very good accuracy. Trouble with satellite-based augmentation is that they are geostationary satellites, they aren't polar orbiting. So, in other words, if you're not within a decent elevation of one of these geostationary satellites, i.e., it's fairly close to the horizon, then that can make reception of these uh augmentation signals very, very difficult. So, S-BAS and RTK are there to make things accurate. But both systems augment the underlying GNSS signal. If a local jammer or state actor knocks out the frequency of both RTK and S-BaS, then these will fail alongside the core GPS. So, in other words, although these correctors are there to give us this accurate position and tell us where the ship is and confirm our underkill clearance, it's possible to take out not just the GP the GPS or GNSS signal, but to also take out the benefits of both RTK and S-BAS by doing so. So, we've now got an issue. We've got a ship that is not in a position that we think it's in, with a underkill clearance that is much smaller than we expect to, and we are struggling now to handle the ship. But we have the pilot on board. And reading the ship, i.e. detecting a problem without screens, is where an experienced pilot comes in. Visual cues, tactile feedback, auditory cues, these are all things that an experienced pilot is tuned into. An experienced pilot will have transits, in other words, two poles in line will indicate that the vessel's in a good position. When we back a ship out of the container terminal in Southampton, as we come off the berth, there's a pylon that lies directly astern. If we line that pylon up with the side of the ship, we know we're a good distance off the side of the quay. Doesn't matter what the GNSS is telling us, if we can see that pylon in line with the side of the ship, we know we are the correct distance off. That's a visual cue which will outweigh any kind of inaccuracy given by a satellite navigation system. Tactile feedback is something that a pilot often relies on, particularly when the ship is perhaps doing a bit of speed. If the ship starts to vibrate, this is indicative of the fact that the ship may be entering shallow water, and the shallow water effect of squat may be kicking in, and one of the symptoms of squat, as well as an increased bow wave, increased stern wake, is vibration of the ship, as that water is forced between the ship and the seabed, the aeration can cause the propeller, especially to start to vibrate. Auditory cues are there as well. Um, engine loads that can sometimes suddenly come on may cause a change in pitch of the engine as it's turning over, and this can happen when you've entered shallow water, where the engine is struggling to push the ship through that shallow water because of the wall of water ahead and forcing the water in between the ship and the seabed. Don't forget, we can't compress water. So when this happens, if we're trying to force the same amount of water between the ship and the seabed, we've just got to force it through quicker. Yeah, if we can't force it through quick enough, this is what causes the water wall. That's a principle worth bearing in mind. So we are now pitting the pilot against the processor. We're now saying what advantages does the pilot have over the processing of the pilot's PPU unit taking into account any potential inaccuracies that may creep into the GPS system due to regular errors or due to unexpected state or other interference. What we've got to remember about GNSS is that a lot of it is based on history. In other words, computational predictors that I've talked about rely on past data. The software must effectively collect multiple coordinate fixes from the past, run them through a smoothing algorithm to remove signal noise and to remove, shall we say, the sensitivity of a predictor and then calculate this trend. This can build a delay into the predictor on the screen. A pilot watching a visual cue will detect a problem with the movement of the ship quicker than the predictor will detect it itself because the pilot's able to compute his line of sight quicker and react before the prediction process has been completed. So the pilot uses physical geometry as an amplifier. In other words, when we see the bow swinging or we see our transit closing, we know very, very quickly that the ship is moving in a direction that we don't want it to go in, and we can react to that. Zero latency sensor fusion is basically before the GNSS antenna registers a coordinate change, an experienced pilot will feel, as I've said, the deck vibrate, the engine load shift. Okay, this is before the GNSS has had a chance to change its predictor based upon its history. And don't forget, predictive versus reactive, the computer waits for displacement to happen before it updates on the screen. In other words, the computer waits for the course over the ground to change based upon the accurate GNSS position before it changes the predictor. The pilot can detect the physical movement of the ship instantly by looking. A lot of a pilot's sensors are of course visual, and if you take the visual away, i.e. navigation in fog, that does level the playing field somewhat. But in general, an experienced pilot and having an experienced pilot on the bridge of a ship when manoeuvring in areas with reduced dynamic underkill clearance will be able to detect problems with the position of the ship and the handling of the ship much quicker than a position derived from a satellite navigation system corrected, complemented, smoothed up, and predicted by a portable pilot unit. I often back up a lot of what I say in these podcasts with my personal experience. And a couple of days ago I was backing a 300-meter container ship out of the container port to swing it. The winds had just kicked in. We are uh out of uh the uh the British uh summon out, the uh the high pressure system seems to have been uh pushed southwards, and although this is great because we're no longer in these ridiculous extraordinary heat waves that we've had, it does allow low pressure systems to come in, and it was a breezy day when I was backing this ship, so I was very, very conscious of the fact that as I swung the ship, the ship was going to be blown across the swinging ground during the swing. I had my PPU unit set up and I had it set up reading from the ship's own equipment. In other words, it was using the ship's own GPS. I didn't have an independent uh sensor set up for this. Uh, the position of the ship alongside the berth was accurate when I set it up, so I was happy with the fact that the position given to me by the ship into my PPU equipment was good. That gave me the confidence to use it as a piece of equipment that wasn't standalone from the ship's equipment but integrated into the ship's equipment. So we are backing into the upper swinging ground at Southampton, and the ship came round the corner a little bit faster than I would normally do it, just a bit over three knots, going a bit faster because the wind was having an effect and pushing us a little bit, so the faster I could get through the cut, the less lateral movement the ship would have based upon the wind on the side of the ship. As I entered the swinging ground, it was time to slow the ship down in preparation for swinging her. So I gave the engine a kick ahead. As I gave it a kick ahead, I noticed on the GPS speed, the four and a half GPS speed given to me on my PPU wasn't reducing, so I increased the engine to slow ahead. I was going dead slow ahead. I was taught at a very early stage of my career to judge the speed on the beam, so I looked on the speed on the beam to confirm that the speed was coming down, having given this slow ahead kick. The portable pilot unit showed me still going astern at nearly two knots, and I became a bit concerned at this. But when I looked on the beam, I could see that the ship was rapidly slowing. I stopped the ship's engine, I asked the captain to ask his man on the front of the ship, on the forecastle of the ship, to confirm that the ship was swinging clear, as I suspected that the predictor given to me by my PPU was uncorrect was incorrect because the PPU was still registering 1.7 knots of sternway, whereas visually I could see that the sternway was always was almost off. The officer confirmed that the bow was swinging clear, albeit by only 40 metres, and I would normally swing 60 or 70 meters clear up forward, and this was because the sternway of the ship had been checked by my movement ahead, and I hadn't allowed the ship to come back far enough. So there was a problem there. There was a problem with the PPU telling me that the ship was still making 1.7 knots astern when in reality the ship was almost stopped and the bow swinging closer to danger than I had planned or anticipated. Had I have not used my eyesight, had I have relied on the PPU's four and aft speed and perhaps kick the engine ahead even further to try and make the PPU speed go down, I would have inevitably touched the front of the ship on the beach. But my line of sight on the beam, watching the transits of the crane legs, I was able to deduce very very quickly that something was wrong. I ignored the PPU, switched completely to line of sight for the swing, swung the vessel without incident and got the vessel going. Now I then bought out a second pod, connected it up to my PPU, put it on the bridge ring as an independent position fixing sensor because I now knew that the feed from the ship's GNSS equipment was poor. An independent position fixing system corrected to S-Bass gave me a much better indication of speed. So I was lulled into a false sense of security, if you like, by the accuracy of the vessel's position showing on the PPU when I first set it up to just the vessel systems, and that when I came to back the ship round, caused a massive error in my PPU, which I spotted with sight and was able to correct. Underkill clearance is critical, critical for the movement of ships when they are on passage, and exceptionally critical for the movement of the ships when we are swinging, berthing, pushing huge ships sideways in order to achieve intricate manoeuvres within very, very restricted waters. Dynamic underkill clearance systems and other systems designed to minimize your underkill clearance rely heavily on accurate position fixing systems, and sometimes those systems can let you down. The pilot, the pilot's ability to calculate and manage the underkill clearance based upon experience, the pilot's ability to detect a departure from the intended plan much quicker by watching what's happening with the ship outweighs the ability for the technology to spot it first. This means that dynamic underkill clearance systems that rely heavily on position fixing technologies may be flawed if those position fixing technology errors are not detected at an early enough stage to prevent the ship from wandering into an area where the dynamic underkill clearance is not what we expect it to be. A pilot has more than likely built in a safety factor to account for things as I did the other day not coming in visually against the equipment. Whereas a dynamic system relies heavily on the ability to move the ship at a speed and direction governed by the electronic systems on board the ship itself. Thanks a lot, guys, for uh listening to this podcast. I hope you found it engaging, and I hope you found that, like me, the value of an experienced pilot on the bridge of a ship manoeuvring in and out of port should never ever be overlooked. Pilots and the experience that they bring to a ship handling scenario is invaluable in ensuring the safety of the ship, the safety of those on board, protection of the marine environment and the port infrastructure itself. Have a great day, everyone. Look forward to welcoming you back to the next podcast. In the meantime, take care and sail safe.