AIS collision alerts ?

[baz]

Subject: AIS collision alerts ?

Now that I have my AIS 800 fully operational I was out the other day experimenting with its features.

One experiment was with me driving the boat at some 20 kts toward another boat that had AIS Tx. It was less than a mile in front of me and eventually my Chart plotter indicated I was on a collision course with this boat. Well that was a good experiment as it did tell me my AIS 800 was doing its job.

My question here is did this other boat's Chart plotter, who obviously had AIS 600/800, show my boat approaching on a collision course with his/her boat ? If so, should I have expected a radio call from the boat asking what my intentions were ?????? I mean to say, if I were to see on my Chart plotter that an approaching boat was on a collision course with me I could certainly take some evasive/defensive action and if the collision appeared to me to be intentional I could radio the boat to ask what their intention was in addition.

This other boat I was approaching at 20 kts took no action and I received no radio transmission from it, nor did it take any evasive course corrections.... I really hope I did not cause this other boat's captain any alarm! 😱 Should I have radio the boat to announce my intentions as being experimental and that there was no need for concern ?

 

[baz]

Another question or two about Collision alarms.....

When I get ready to leave my slip and turn on my Chart plotters I get AIS collision alerts because there are several boats close to me in the marina. So I quickly disable the Collision alarms by selecting OFF.

Now with the AIS collision alarm turned OFF am I in trouble when out on the waters with other boats whizzing around ?

If the AIS collision alarm is turned OFF at my slip just before I leave does this then stop me from receiving or being notified on the Chart plotter chart display that a collision is immement and for it to display the oncoming boat's corse and speed ?

The other day when experimenting, this seemed to be not the case, as when approaching this other boat at speed I was certainly warned on my Chart plotter I was on a collision course with it.... but I do recall there was no audible alarm being sounded. Thus, I conclude with the AIS alarm being OFF it simply removes the audio alarm that sounds for possible collisions.

 

[Bruce Moore]

My manual is on the boat, but the Garmin support site addresses this. They also explain how to set your safe zone and turn alarms on.

 

[Scuba Too]

A few thoughts on the experiment. What were the relative bearings of the two boats? If you were overtaking or approaching from the port side then he had the right of way, which in a boat means he maintains heading so that the other boat can do the evasive maneuvering. What was the size of the other boat? In Southern California we have large freighters which have the right of way based on maneuverability (i.e., yeah they're not changing course for a pleasure craft lol). With respect to interpreting a collision course as being intentional I suppose that this would only seem to be the case if he maneuvered away from the collision and you changed course to cause it again. Otherwise I'd assume that you were just on your way somewhere and we happened to cross paths.

Other option is the other captain simply wasn't paying attention lol. Or he felt that he had time to maneuver based on visibility. Last thought is he was going to go his way and it's up to other folks to watch out! I had this happen a few months ago out in open water. We were both cruising at 15-20 knots and he came at a right angle from my port side, so I had right of way. He didn't budge an inch! I was close enough to see him staying straight ahead and his wife looking at me apologetically...

 

[baz]

Thanks Bruce.... yes read this

If desired, the audible alarm can be disabled for the AIS system, though the alarm message will still show on the screen. To disable the audible alarm, please follow these steps:

...and for the Safe Zone...

Setting the Safe-Zone Collision Alarm
Before you can set a collision alarm, you must have a compatible chartplotter connected to an AIS device or radar.

The safe-zone collision alarm is used only with AIS and MARPA. MARPA functionality works with radar. The safe zone is used for collision avoidance and can be customized.

Select Settings > Alarms > Collision Alarm > On.
A message banner appears and an alarm sounds when a MARPA-tagged object or an AIS-activated vessel enters the safe-zone area around your boat. The object is also labeled as dangerous on the screen. When the alarm is off, the message banner and audible alarm are disabled, but the object is still labeled as dangerous on the screen.

Select Range.
Select a distance for the safe-zone radius around your vessel.
Select Time To.
Select a time at which the alarm will sound if a target is determined to intersect the safe zone.
For example, to be notified of a pending intersection 10 minutes before it will likely occur, set Time To to 10, and the alarm will sound 10 minutes before the vessel intersects the safe zone.

 

[baz]

A few thoughts on the experiment. What were the relative bearings of the two boats? If you were overtaking or approaching from the port side then he had the right of way, which in a boat means he maintains heading so that the other boat can do the evasive maneuvering. What was the size of the other boat? In Southern California we have large freighters which have the right of way based on maneuverability (i.e., yeah they're not changing course for a pleasure craft lol). With respect to interpreting a collision course as being intentional I suppose that this would only seem to be the case if he maneuvered away from the collision and you changed course to cause it again. Otherwise I'd assume that you were just on your way somewhere and we happened to cross paths.

Other option is the other captain simply wasn't paying attention lol. Or he felt that he had time to maneuver based on visibility. Last thought is he was going to go his way and it's up to other folks to watch out! I had this happen a few months ago out in open water. We were both cruising at 15-20 knots and he came at a right angle from my port side, so I had right of way. He didn't budge an inch! I was close enough to see him staying straight ahead and his wife looking at me apologetically...

Thank you... 🙂
The boat I was approaching was on my port bow. The other boat was quite large (maybe 40+ feet long). It did not change course as I approached at speed. MY only concern was --- did I in any way cause the other boat's captain any anxiety with my experiment ?

 

[BB marine]

I keep the audible alarm turned off unless I'm piloting at night or in fog. I find the audible to be a distraction during clear days especially when entering an inlet. When there is boat traffic navigating into a harbor or inlet and having an alarm sounding can be a distraction. When I am in limited visibility I turn the AIS alarm on and radar safe zone on. The only time I have found the AIS to be a valuable navigation devise was when cruising the inland rivers. I could pick up a tow that was around a bend. The tow would not be visible by eye or radar.I knew the speed, direction of travel and name of the vessel. I could call the tow by name on the radio request a one or two whistle before even seeing him. This was valuable on the Mississippi River. I know there are many other times it is useful and it is a required navigational safety devise for all commercial vessels. Other then the river trip from my experiences it's mostly a novelty to have. I hope I never change my mind on this. If I do it means I experienced an unpleasant event. I have it and use it ( but no audible).

 

[Matty]

In my opinion AIS, for recreational vessels, is very limited in its usefulness other than as a supplemental device. Most recreational vessels do not have it so you will not be warned of their position. Therefore you get more information by sight than through the AIS (as I am sure we all know). I believe both vessels need to have it turned on in order to send and receive information. Then you throw egos into play and you have two vessels playing chicken. I have run into that with Sailboats that are under motor power. Unfortunately, most boaters do not know the rules of navigation. I can see how it is useful both at night and where there are large shipping vessels and barges.
Having said all that - do I keep it on? Yes. Nice to have. Apparently quite a few recreational boats keep it on while in their slip. I pick up a lot of those.
I would suggest warning another vessel of your test. otherwise he is just going to scratch his head and wonder what this guy is doing. He will also assume you are looking where you are going and that you will soon turn or stop.

 

[Toki]

I notice your from Edmonds. Up here in the PNW, I have found AIS to be indispensable. Between freighters and tugs (real tugs) in the shipping lanes and ferrys criss-crossing the sound, AIS not only allows you to see their course and closest approach time/distance, but also allows you to hail them by name. My AIS is always on, and I'm always paying close attention to it.

Regarding collision course traffic, by following proper right-of-way procedures and a bit of common sense, it's been extremely rare that I've ever had to hail a vessel. Perhaps I'm an overly polite boater, but I'll typically make an exaggerated course change to make my intentions known, then settle back into a non-collision course. I've noticed most other boaters around here also use that tactic.

 

[aintmissb]

Interesting to see the previous two posters with diametrically opposite opinions on AIS. I had an AIS receiver on my last sailboat (before becoming a Tugnut) and found it very useful, particularly cruising down Lake Ontario at night and trying to gauge the course of Lake Freighters coming at you. Power boaters may not have thought of this but it is a valuable tactical tool in sailboat racing, because it allows you to see your rivals in real time (if they are transmitters) and make tactical decisions accordingly. This has been a major factor in recent editions of the Volvo Ocean Race. I wish I had it on my Cutwater 28!

 

[baz]

I do appreciate all the responses in this thread. Thank you.

My recent activities using my AIS was driven by the fact it had not been working as it should. The issues with my AIS 800 have now been resolved and thus I wanted to prove to myself it was working as it should. AIS offers a lot of features and seeing them in action is simply evidence for me that it is working correctly. This is much like employing all the features the Auto pilot offers. It's simply prudent to use all the various features a boat's equipment offers so that when needed they can be used effectively and to acknowledge their limitations.

BTW.... my Garmin VHF radio has a built in AIS 300 and during the time my AIS 800 was not working correctly I got confused thinking the AIS 800 was working as my Chart plotter was displaying red targets that falsely indicated to me the AIS 800 was receiving. I have since disabled the radio from using its built in AIS 300 to avoid any confusion as to what device is reporting AIS targets on my chart displays.

I now know a great deal more about AIS than before.

IMO.... AIS and radar are indispensable tools for my PNW cruising areas.

As an aside.... was cruising with a buddy when I owned my R27/OB with just AIS Rx. My buddy was close to a mile in front of me and visibility became poor, and I lost sight of him at times. I was following him and the AIS green triangle on my chart display helped me in knowing where he was in front of me and in what direction he was traveling. This was when navigating through the San Juan islands where fog can descend quickly/suddenly at any time.

How many times have you seen a boat in front of you at a distance and having difficulty knowing which direction the boat is going. The AIS provides this info nicely for you.