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Old 07-06-2014, 09:03   #1
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Thoughts about AIS

I've now had my new electronics for a little more than a year. During that time I've sailed West out of the English Channel and down into the Bay of Biscay and back, I've crossed the Channel about a dozen times, and I've sailed East out the Channel via the Dover Straits and made a full transit of the North Sea, Kiel Canal, and the whole Baltic Sea right up to the Russian border, from where I'm writing this.

In doing this I've passed through a number of the world's busiest seaways and I've had plenty of time to think about how this wonderful tool, AIS, works.

First of all, I want to say that I now consider AIS to be practically indispensable on any boat of any size which sails anywhere where there is any commercial traffic. It is truly revolutionary. Before having it, I had expected that it roughly duplicates the function of MARPA, with less technical overhead, and a bit more functionality, but that's really not right. MARPA requires very active use -- acquisition of specific targets, etc. AIS automatically presents all targets, with those of particular interest arranged according to your own criteria in a list. MARPA, even with a high end heading sensor like I have, even with a really good radar, is very inexact -- probably because radar inherently cannot be very accurate in determining bearings (it is very accurate for range). AIS is as precise as the GPS system. MARPA cannot track more than a few targets at once, and the operator has to regularly re-acquire targets as they drop on and off the radar screen. MARPA doesn't identify the targets, so you have to keep up with them yourself. AIS shows you the name and MMSI, so you can call them on the radio if you need to.

It's so good that with all the will in the world, you just stop spending a lot of time working MARPA targets. Which means that other vessels which are not broadcasting AIS automatically become low priority targets. Is that the way you want to appear to a ship bearing down on you? After staring at a screen with radar and AIS displayed on it for a few thousand miles, I can now say for sure that I never again want to be a subtle, maybe unnoticeable red blob on a ship's radar screen, rather than a bold triangle with my COG vector coming out of it. There is just no comparison how much more attention it evokes. It makes all the difference, in the operator's consciousness, between -- (a) a vessel, which I know by name already, and which I need to pay attention to and maneuver well in advance; and (b) some inconsequential floating object, which I will dodge if necessary when I get to it, and if I remember to, because it's surely not worth working in MARPA this far out. I tried and tried to avoid this mentality, but I found it unavoidable.


AIS revolutionizes the way you get through areas of dense traffic, but I have some complaints about how the information is displayed on my Zeus system.

The main problem is that you have no good way of determining whether a target is passing ahead or behind. This information is crucial in determining what kind of maneuver you need to make in order to create a safe crossing with the target.

In areas of dense traffic where it was necessary to track multiple targets at once, I found it impossible to do from the helm. I left my crew at the helm and retired to the nav table with a good old fashioned pencil and paper, and started writing down bearing, range, and CPA at regular intervals. This is really inefficient, and it is frustrating because it would be totally simple to present this data electronically.

In my opinion what is needed is the following. Along the right hand side of the Zeus radar screen, there is a list of the top three AIS targets, showing SOG, COG, CPA, TCPA, RNG and BRG for each. Would it be so hard to display the dynamic of each of these data? The most absolutely essential is the dynamic of the bearing, but dynamic of the CPA would also be extremely useful. This could be easily represented simply by showing the BRG number in green (for increasing) or red (for decreasing), in three different shades to show the speed of increase or decrease. Or, chevrons, say, next to the number -- one pointing up means slowly increasing, two pointing up means increasing somewhat faster, three means increasing fast; down chevrons means decreasing. Or both color and chevrons.

Then you instantly see what's going on with each target, rather than having to write them down over a period of time. Having to use paper and pencil with a sophisticated electronic navigation system seems kind of ridiculous.


The crucial bearing dynamic data might also be displayed in the target triangle on the radar (and chart) screens -- the triangles themselves might be colored red or green, or there could be a red or green dot in them, or something, with varying levels of intensity of the color showing the speed of change.

A somewhat useful workaround is to set the COG extension lines for both vessels and own vessel to 30 minutes (must be the same time horizon!!). Then you can see whether a vessel is passing ahead or behind by comparing the end points of the respective COG extension lines. This is good, but it's fairly rough, and it works only in chart view. And in chart view, you don't get a list of AIS targets!

So please, Navico, could we have something like this, pretty please?


Two other complaints:

The list of three AIS targets might be plenty in some places, but it is not nearly enough in the English Channel! I know that screen real estate is limited, but there should be some way to choose to display more.

And there is no way to display a list of AIS targets in the chart view! I actually find the chart view to be easier to understand when dealing with AIS targets, which probably shows that I am a poor radar operator . It is frustrating that there is no way to monitor AIS targets in chart view other than by clicking on them one at a time.


I would be curious to know what others think about all this, and whether people have the same problems with Furuno and Raymarine AIS displays. Maybe if there is enough consensus, and if we get enough signatures, we can get the makers to produce a software update!
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Old 07-06-2014, 09:23   #2
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Re: Thoughts about AIS

More good information is always better than less information.

I have no problems with my Furuno AIS transceiver. It works quite well on both my Furuno MFD Blackbox and my Nobeltec chart software.
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Old 07-06-2014, 09:46   #3
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Re: Thoughts about AIS

No doubt that AIS is revolutionary, and is certainly vastly superior in many aspects to MARPA. But MARPA is a broken version of ARPA, which doesn't have all the deficiencies you describe. Hence, IMHO, a good ARPA system provides tremendous value. Using both tools at the same time coupled with human eyes and ears provides a valuable set of navigational tools. We're years away from, or probably never, being able to rely on a single tool.

I can't comment on your UI woes, I don't frequent areas with the quantity of traffic you do.
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Old 07-06-2014, 09:50   #4
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Re: Thoughts about AIS

The Vesper AIS displays allow you to easily figure out whether a target is passing ahead or behind--great piece of gear.
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Old 07-06-2014, 09:54   #5
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Re: Thoughts about AIS

My Garmin won't show whether a vessel will pass in front or to my stern, but it does show which ones are going to cause a collision by drawing a rather obvious red line and giving a "time to impact". This is in addition to the alarms which previous could be permanently turned off but now need to be turned off each time the GPS is switched on. Why turn off the alarms? well in a busy waterway the situation is changing by the minute so its just easier. Well offshore however, it would be a boon. Interestingly the red lines only appear if you give the Garmin a way point to go to or follow a route. So it doesn't calculate a possible collision on your current course and a speed but on you proposed course. These could be and are likely to be different especially if there is a tide to consider.

The other annoying problem I put down squarely to the Americans. After the last upgrade you can only have depths in feet by choosing the imperial distance measurement nautical miles option. If you want depths in meters then you must have distances in km So 300 million Europeans who have been using the sea for 10 centuries now have to change. I will be writing to Garmin in the strongest possible terms

Overall I too think AIS is a boon and one reason I am not rushing to fit radar (that should draw a deep intake of breath from a few on the forum).

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Old 07-06-2014, 10:05   #6
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Re: Thoughts about AIS

OpenCPN shows how you will pass - plus you have full charting. I quite agree that it's probably the greatest advance in collison avoidance for a long time!
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Old 07-06-2014, 10:13   #7
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Re: Thoughts about AIS

AIS provides good additional information, BUT... it's no substitute for radar and knowing how to use it.

There are still many large ships which either don't broadcast or have their transmitters turned off.
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Old 07-06-2014, 10:47   #8
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Re: Thoughts about AIS

Dockhead,

That is a fine presentation based on sound experience and observation.

Since it is so valuable, I recommend you consider writing it up as a technical paper (edit out the "emotions" parts ) and send it to the manufacturers by snail mail, registered letter as well as electronic copies.

There are undoubtedly other significant boating forums that would welcome copies of your OP just as it is to get more insight from other experienced boaters, too.

Good luck, great post, a classic along with the CTS one!
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Old 07-06-2014, 10:54   #9
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Re: Thoughts about AIS

On the Furuno, targets that are outside of user-set thresholds are green, while those that trigger the thresholds turn red and get bolder. I find this very useful. One can also independently set the own ship's predictor line and the target predictor lines. I too find this very useful. I "think" ships that will pass behind you are given a negative number for either CPA or TPA. This may be how Coastal Explorer treats them, so I might have it mixed up - one of them do this - possibly both.

Coastal Explorer dynamically lists all ships in a sidebar along side the chart display with regard to the closest CPA/TPA's being on the top. The text also changes color along with the icons and the icons "pulse" when the user threshold has been tripped. I find this very useful - one quick glance and I have a great mental picture of the situation. Non-moving boats are grey, moving ones green and "dangerous" ones red and pulsing.

I have mentioned this before - I find it very easy to navigate crowded AIS traffic without using any audible alarms at all. We go in and out of the Panama canal zone often, where hundreds of ships are anchored, underway, doing circles, steaming out at full throttle, etc. With the AIS thresholds and handling set up correctly, we simply eyeball navigate around and through this type of shipping using quick glances down at a colored graphic display to provide us with a synthesized "whole" picture of the dynamics without needing any list of static or dynamic data numbers or tracking by hand, etc.

In other words, once you have the thresholds set up properly and enough experience operating, and give up needing the numerical data and manually tracking every single target and start to view the graphic as a dynamic composite, you begin to navigate the "picture" instead of all the individual ships. I'm probably not explaining this well, but it is similar to navigating around and through close islands, where the land, safe water and unsafe water are marked with different colors and you simply navigate by eye with quick glances at the changing "picture" on the chart plotter ignoring the numerical depths, names, etc.

Mark
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Old 07-06-2014, 11:03   #10
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Re: Thoughts about AIS

Dockhead, does the Zeus only provide MARPA, where targets have to manually be acquired? And only tracks a few targets?

Our Furuno automatically acquires targets and can track 30 simultaneously. As for accuracy, the Furuno ARPA (they call it this) tracks AIS targets and seems to give the exact COG/SOG/CPA/TPA as the AIS for all but those ships that are constantly changing speed and direction - where the ARPA takes longer than the AIS to adjust its calculations.

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Old 07-06-2014, 11:25   #11
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Re: Thoughts about AIS

Quote:
Originally Posted by donradcliffe View Post
The Vesper AIS displays allow you to easily figure out whether a target is passing ahead or behind--great piece of gear.
How? Does it show the rate of change of target bearing? Or what?
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Old 07-06-2014, 11:38   #12
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Re: Thoughts about AIS

Quote:
Originally Posted by colemj View Post
On the Furuno, targets that are outside of user-set thresholds are green, while those that trigger the thresholds turn red and get bolder. I find this very useful. One can also independently set the own ship's predictor line and the target predictor lines. I too find this very useful. I "think" ships that will pass behind you are given a negative number for either CPA or TPA. This may be how Coastal Explorer treats them, so I might have it mixed up - one of them do this - possibly both.

Coastal Explorer dynamically lists all ships in a sidebar along side the chart display with regard to the closest CPA/TPA's being on the top. The text also changes color along with the icons and the icons "pulse" when the user threshold has been tripped. I find this very useful - one quick glance and I have a great mental picture of the situation. Non-moving boats are grey, moving ones green and "dangerous" ones red and pulsing.

I have mentioned this before - I find it very easy to navigate crowded AIS traffic without using any audible alarms at all. We go in and out of the Panama canal zone often, where hundreds of ships are anchored, underway, doing circles, steaming out at full throttle, etc. With the AIS thresholds and handling set up correctly, we simply eyeball navigate around and through this type of shipping using quick glances down at a colored graphic display to provide us with a synthesized "whole" picture of the dynamics without needing any list of static or dynamic data numbers or tracking by hand, etc.

In other words, once you have the thresholds set up properly and enough experience operating, and give up needing the numerical data and manually tracking every single target and start to view the graphic as a dynamic composite, you begin to navigate the "picture" instead of all the individual ships. I'm probably not explaining this well, but it is similar to navigating around and through close islands, where the land, safe water and unsafe water are marked with different colors and you simply navigate by eye with quick glances at the changing "picture" on the chart plotter ignoring the numerical depths, names, etc.

Mark
Ah, I had thought of using negative and positive numbers for the CPA -- good to know that someone has actually implemented it! That should also be in every interface. I'm just curious -- what does a negative CPA mean? Like a decreasing bearing? Because a decreasing bearing can mean either behind or ahead, depending on what direction the ship is coming from. I'm not sure "ahead" and "behind" is always clear, depending on the relative angle of courses.

The Zeus does show the target triangles in bold when they become "dangerous", according to criteria you can set, and will gray out targets which are stationary (you can even hide them). This is useful, but we need to know which way the bearing is going! I think this is much better for those of us who learned navigation in the stone (non-electronic) age, because it corresponds to how we see potential collisions with a HBC. I think even for youngsters who've never used a HBC, it's useful to think about bearings when you see ships on the horizon.

As to AIS alarms: I had never used them until this last trip. I set them in open water and turn them off on approach to harbors. Like other alarms (especially my favorite, radar guard zone), I think its main purpose is when you're in open water out of sight of land and outside of shipping lanes and not keeping an intense visual watch. I know someone will be shocked by the irresponsibility of it, but I actually took a nap or two on deck last month, when out of sight of land and out of shipping lanes. I set a radar guard zone, set the depth alarm for 10 meters, set the AIS alarm, set alarms for large course changes and wind shifts, and went to sleep for half an hour at a time. Was a Godsend during the single handed part of my trip.
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Old 07-06-2014, 11:51   #13
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Re: Thoughts about AIS

Quote:
Originally Posted by colemj View Post
Dockhead, does the Zeus only provide MARPA, where targets have to manually be acquired? And only tracks a few targets?

Our Furuno automatically acquires targets and can track 30 simultaneously. As for accuracy, the Furuno ARPA (they call it this) tracks AIS targets and seems to give the exact COG/SOG/CPA/TPA as the AIS for all but those ships that are constantly changing speed and direction - where the ARPA takes longer than the AIS to adjust its calculations.

Mark
I'm not sure what the real difference is between MARPA and ARPA -- AFAIK it may be just a difference in specification and not necessarily functionality.

Yes, targets are acquired manually -- you have to point the cursor to a target then go into menu and "acquire targets". I thought ships' ARPA systems worked the same way. Interesting yours acquires automatically. How do you stop it from picking up a hundred meaningless blips and overloading itself?
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Old 07-06-2014, 11:53   #14
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Re: Thoughts about AIS

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Originally Posted by Pete7 View Post

The other annoying problem I put down squarely to the Americans. After the last upgrade you can only have depths in feet by choosing the imperial distance measurement nautical miles option. If you want depths in meters then you must have distances in km So 300 million Europeans who have been using the sea for 10 centuries now have to change. I will be writing to Garmin in the strongest possible terms
Those bloody colonials!!



In all seriousness, however, that this is one of the stupidest things I've heard about in ages.
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Old 07-06-2014, 12:07   #15
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Re: Thoughts about AIS

Quote:
Originally Posted by Dockhead View Post
Ah, I had thought of using negative and positive numbers for the CPA -- good to know that someone has actually implemented it! That should also be in every interface. I'm just curious -- what does a negative CPA mean? Like a decreasing bearing? Because a decreasing bearing can mean either behind or ahead, depending on what direction the ship is coming from. I'm not sure "ahead" and "behind" is always clear, depending on the relative angle of courses.

The Zeus does show the target triangles in bold when they become "dangerous", according to criteria you can set, and will gray out targets which are stationary (you can even hide them). This is useful, but we need to know which way the bearing is going! I think this is much better for those of us who learned navigation in the stone (non-electronic) age, because it corresponds to how we see potential collisions with a HBC. I think even for youngsters who've never used a HBC, it's useful to think about bearings when you see ships on the horizon.
It might be the TPA that goes negative - I don't remember which, just that a negative number means I don't have to worry about it.

And that was the point I was trying to make - when one is getting a good composite graphic of various data, one only needs to glance at it to have the situational perspective sufficient to augment your eyeballs. I don't care about the actual bearing numbers, if they are increasing or decreasing, etc. I have the AIS display thresholds set to complement my eyeball navigation. The composite graphic tells me instantly and dynamically the position of all ships relative to me and each other, their movements relative to me and each other, which ships are anchored, which are not an immediate threat and which are an immediate threat. All on a chart and all in a short glance! When I look back up, that composite picture is floating in my brain.

I have never found a need to take HBC, paper and pencil and start writing down numbers and plotting movements. Or even much care about that level of detail coming into the forefront of my consciousness. It certainly would not stay in my brain and I would then find myself in a slaved position with my head buried in a chart and table of names and numbers frantically trying to update everything and cross-check it with reality. It would be a dangerous way to navigate for just the two of us. You even said you had to put crew on the helm while you did this full-time.

If a really tight situation presents itself where my options for solving it dwindle or are not favorable, I pick up the remote mic at the helm, highlight the ship on its display and push "call". I then negotiate a solution directly.

Mark
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