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Old 09-01-2017, 07:38 PM   #1
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Use of AIS by the Big Boys

There is a very interesting discussion of use of AIS and Radar by commercial ships on gCaptain for those interested:

How are you using AIS? - Professional Mariner Forum - gCaptain Forum

Though it starts out about AIS, very good discussion on Radar use and abuse.

Also, I like that the also bring up Radar's limitations because of set-up or attenuation.
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Old 09-02-2017, 05:45 AM   #2
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That is an interesting article.. I was surprised by the "AIS is not for collision avoidance" mantra with that group.. Perhaps a different world where they have the bandwidth to tag and track targets.
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Old 09-02-2017, 10:17 AM   #3
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That is an interesting article.. I was surprised by the "AIS is not for collision avoidance" mantra with that group.. Perhaps a different world where they have the bandwidth to tag and track targets.


That struck me as well. They seem to have a huge (and healthy?) distrust of AIS position information. That is something that I've never considered.

That discussion has caused me to rethink how I use the radar.

I have used the radar for target tracking, instead of the AIS. I am fortunate to have two displays. I put AIS information on my chart display and use the other display for target information. I add targets manually only.

I do need to get better at tuning the radar however.
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Old 09-02-2017, 11:21 AM   #4
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Pilots in the Puget Sound turn off B class AIS and do all collision avoidance by radar. AIS is great at letting you know what's coming at you but the lag time will kill you in the fog.
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Old 09-02-2017, 12:25 PM   #5
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I just don't understand this blanket dismissal of AIS as a collision avoidance tool. Why wouldn't you use all tools available to you? In fact, you are required to do just that.

Any why wouldn't you cross check what your various tools are telling you?

And if you see a disagreement between what your tools are telling you, why wouldn't you want to understand why?

Yes, AIS can have errors and/or delays, but errors in position are very rare, and will be obvious instantly when comparing AIS to a radar return. Delays in AIS position updates definitely happen, but it takes about 2 seconds to see what's going on as the radar return advances, then the AIS target jumps to catch up. So I don't see how it's such a big deal.

ARPA can have issues too, not just AIS. Just use a Simrad Radar and you will see how wrong ARPA can be. And you can lose the target is rain or sea clutter. And you can get target "swap" when a target passes close to another object and the ARPA lock jumps to the other return rather than following the original return.

I think all this is just part of knowing how your equipment behaves, and learning how to use it. I actually find it quite disheartening that so-called professional captains actively ignore AIS when evaluating collision risk.
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Old 09-02-2017, 12:28 PM   #6
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Learning to use both as tools and not solve all boxes is the trick.
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Old 09-02-2017, 12:32 PM   #7
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Learning to use both as tools and not solve all boxes is the trick.
Agreed, but that seems to complicated for many of the gCaptain participants.
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Old 09-02-2017, 12:50 PM   #8
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Agreed, but that seems to complicated for many of the gCaptain participants.
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Old 09-02-2017, 01:21 PM   #9
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Agreed, but that seems to complicated for many of the gCaptain participants.
We often noted in shipboard aviation, the surface fleet had an odd way of complicating things.

Possibly understandable in combat, but almost dangerous in peacetime....maybe that almost is becoming actually.
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Old 09-02-2017, 02:43 PM   #10
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The IMO issued Resolution A.1106(29), adopted on 2 December 2015 entitled REVISED GUIDELINES FOR THE ONBOARD OPERATIONAL USE OF SHIPBORNE AUTOMATIC IDENTIFICATION SYSTEMS (AIS).

The following guidelines excerpted from it may, in part explain the "Blanket Dismissal" attitude referenced earlier.

"Users are therefore cautioned always to bear in mind that information provided by AIS may not be giving a complete or correct "picture" of shipping traffic in their vicinity. The guidance in this document on the inherent limitations of AIS and their use in collision avoidance situations (see paragraphs 40 to 44) should therefore be observed."

USE OF AIS IN COLLISION AVOIDANCE SITUATIONS

40 The potential of AIS as an assistance for anti-collision device is recognized and AIS may be recommended as such a device in due time.

41 Nevertheless, AIS information may merely be used to assist in collision avoidance decision-making. When using the AIS in the ship-to-ship mode for anti-collision purposes, the following cautionary points should be borne in mind:

.1 AIS is an additional source of navigational information. It does not replace, but supports, navigational systems such as radar target-tracking and VTS; and

.2 the use of AIS does not negate the responsibility of the OOW to comply at all times with the Collision Regulations, particularly rule 7 when determining whether risk of collisions exists.

42 The user should not rely on AIS as the sole information system, but should make use of all safety-relevant information available.

43 The use of AIS on board ship is not intended to have any special impact on the composition of the navigational watch, which should continue to be determined in accordance with the STCW Convention.

44 Once a ship has been detected, AIS can assist in tracking it as a target. By monitoring the information broadcast by that target, its actions can also be monitored. Many of the problems common to tracking targets by radar, namely clutter, target swap as ships pass close by and target loss following a fast manoeuvre, do not affect AIS. AIS can also assist in the identification of targets, by name or call sign and by ship type and navigational status.

Then, this article from The Maritime Executive entitled Collision Avoidance: AIS Versus ARPA makes a case for Data Segregation of AIS and ARPA data. Also, the Best Practices / Guidance are useful for those who use both systems.
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Old 09-02-2017, 04:13 PM   #11
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So it acknowledges

1) the value of AIS

2) that it should be the ONLY tool you use, which can also be said of any other nav tool.

3) that is can help track where ARPA may be challenged

That seems to say to opposite of "do not use it for collision avoidance"
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Old 09-02-2017, 08:16 PM   #12
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So it acknowledges

1) the value of AIS

2) that it should be the ONLY tool you use, which can also be said of any other nav tool.

3) that is can help track where ARPA may be challenged

That seems to say to opposite of "do not use it for collision avoidance"
#2 I think you left out 'not'. ie .....not be the only tool...
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Old 09-02-2017, 08:59 PM   #13
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#2 I think you left out 'not'. ie .....not be the only tool...
Yes, thanks.
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Old 09-03-2017, 02:08 AM   #14
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Well, this summer I was very happy to have AIS crossing Juan de Fuca. No fog this time, but I had to cross the VTS lanes and was fighting a two knot current. This meant that I was crossing very slowly. A container ship was coming out of Admiralty Inlet and I wasn't sure which way he was headed. A quick call on 13 got a reply from him and I was able to make an early course change to be well away from him.

Not easy without AIS. Being able to hail them by name makes a huge difference.
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Old 09-03-2017, 10:29 AM   #15
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I use AIS for long range planning and radar for avoidance. With in VTS, AIS can let you know if a ship has made a course change or is about to make a change, this gives you better knowledge for making that go or no go decision when crossing a VTS channel.
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Old 09-03-2017, 11:11 AM   #16
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Or a VHF radio transmission.
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Old 09-03-2017, 11:11 AM   #17
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I guess my point, and it's really not my point - it's engrained in the colregs - is that you should use both, not one or the other. For collision avoidance, use your radar, and your AIS, and your eyes, and your VHF, and anything else at your disposal. That's what it's all there for.
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Old 09-03-2017, 11:26 AM   #18
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The biggest threat of technology is complication of data that is easily resolved by one or other means.

If one becomes distracted by trying to obtain more than necessary data, therein lies the danger.

The average recreational boater I have instructed is certainly overwhelmed by 2 or 3 pieces of electronic gear...we keep adding.

So only to a point does more equal better...its where your training and practice improve situational awareness, not just adding gear....especially gear that has to be interpreted for its shortcomings in some regards.

The airlines, military and I bet many other high performance organizations agree.

Tools in a toolbox that are misunderstood can be as dangerous as not having them at all...better to rely on other means.

If one cannot cross a simple traffic separation zone or VTS zone without AIS, I really feel for you.

Places like the English channel and other extrodinarily high traffic areas are a different story, so are river systems with huge tows around a corner that you may not know of until the last moment without AIS.
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Old 09-03-2017, 11:42 AM   #19
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I see we have an expert here. Some one who is experienced at pulling a 3kt log boom across a busy VTS channel with 2 kts of current. Channel 14 tells me if there is traffic in the area. AIS tells me if I can consider the cross. AIS class B is turned off, to many icons on the screen, unable to see all the little fishing boats in the VTS lane other wise. Radar tells me if I am going to collide with any of the commercial, pleasure or rec fishing boats.

Yes, use all the tools, but use them in the correct order.

I like the way some people have all the answers for everyone even though they have never left their home port.
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Old 09-03-2017, 11:54 AM   #20
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I see we have an expert here. Some one who is experienced at pulling a 3kt log boom across a busy VTS channel with 2 kts of current. Channel 14 tells me if there is traffic in the area. AIS tells me if I can consider the cross. AIS class B is turned off, to many icons on the screen, unable to see all the little fishing boats in the VTS lane other wise. Radar tells me if I am going to collide with any of the commercial, pleasure or rec fishing boats.

Yes, use all the tools, but use them in the correct order.

I like the way some people have all the answers for everyone even though they have never left their home port.
You're presumably talking to psneeld and/or me. I haven't pulled a log tow, but he might have. And we have both been out of port once or twice.
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