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Old 08-11-2016, 05:58   #1
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How Do You Use AIS?

OK, now that I've got the technical issues sorted and have AIS targets showing up on my OpenCPN display what do I do with them?

So far AIS is a neat toy. I can sit at my dock and look at the ships and big yachts moving around the bay. I understand that if I am under way and the other vessels are under way OpenCPN will use AIS to calculate the closest point of approach for me and warn me if there is a risk of collision.

Traffic in Tampa Bay isn't so bad that I've had any difficulty avoiding collisions in the past. The big ships especially are easy to avoid. They stay in the ship channels. I stay out of them. Simple and effective.

If I were traveling on a river with lots of bends it would be great to identify oncoming vessels before they became visible so I could negotiate a safe passing by radio. That's especially true of tows because their maneuverability is limited.

Since my AIS device (a dAISy) is receive only AIS doesn't make me visible to other shipping.

So my question is how do you use AIS? What advantages does it offer you that I may not be aware of? I'm looking for suggestions that will make having an AIS receiver aboard of more practical value.

Fabbian
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Old 08-11-2016, 08:49   #2
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Re: How Do You Use AIS?

I've found it very helpful. Anything to increase safety and awareness is a good thing.

In fog, it's been a great help. In ports with lots of shipping, and especially where there are traffic control authorities, it's allowed me to participate as more than just an obstruction. Maybe it even gets just me a little bit of respect from the commercial traffic.

As more recreational boats have it, I'm finding that helpful, too. I've shared information with other cruisers entering a remote harbor.

And, it's fun to know more about the ships that would otherwise just "pass in the night," or the new arrivals entering the anchorage.

I'm not a big fan of receive-only. If you're going to spring for AIS, get the whole package.
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Old 08-11-2016, 09:08   #3
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Re: How Do You Use AIS?

I cruise offshore North American west coast, and have been running an AIS transponder for four years so far. It is helpful to let the shipping know you are there, and it is helpful to know where the shipping is from their broadcast.

From a receive-only perspective, the values beyond simply knowing the ship's position are:

you can call a ship by name on the VHF radio - knowing the name of the ship is a big improvement over calling 'the northbound ship 20 miles north of San Diego'. A ship called by name usually comes back quickly on the radio.

you can look up ship's course and speed directly - saves lots of time over trying to figure out if they are headed your way or not, and how quickly they are likely to become an issue and how quickly they will no longer be an issue.

you can receive data from beyond your line of sight - reduces unexpected shipping encounters simply because your area of awareness has increased.

As a comment, running a transponder is a significant value to you and shipping as the ships can detect small boats more easily on their AIS display as compared to looking for small boats down below the horizon, or trying to dig small boats out of the sea clutter on the radar (particularly at night). If the ship knows what you're up to it's easier for both you and the ship to take avoiding action early and accurately.

That said, not everybody operates an AIS, particularly offshore fishing boats - so keep looking around!

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Old 08-11-2016, 09:28   #4
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Re: How Do You Use AIS?

I just got my dAISy working too. The first use I see is looking at OpenCPN while listening to Ch 16 and 13 I can predict movement of Ships, bridge openings, etc. Although I haven't yet, I figure it will help me hail nearby ships by name instead of some vague description of their location.

While I'm at it Yuge shout-out to Adrian for a great little product and helpful customer service. http://wegmatt.com/
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Old 08-11-2016, 09:43   #5
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Re: How Do You Use AIS?

Any ship under 300 tonnes is not required to have AIS. So, some ships have it and some don't. This means to me that I still have to maintain a watch on deck. You can read an example of what this means if you go back to the accident reports for the 2014 Vendee Globe.
I often read of big ships simply ignoring little boats regardless of the situation and danger. Many aids to navigation are useful in a specific situation but not in others. Sailors cruising in well known patches would soon see AIS as interesting but not essential.I have radar but never use it because I just don't sail where and when it's important to use it. If the forecast says risky then I just don't go. I keep well away from known big ship lanes. I stay out on deck. I rarely go out of a 100 mile radius of Home base and know the coast line. I reckon I could get by with a compass, but use a chartplotter and depth gauge fairly often mainly to feel comfortable. I have wind instruments but spend most of the time watching the telltales. The more gadgets I get, the more things I have that can go wrong.
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Old 08-11-2016, 09:56   #6
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Re: How Do You Use AIS?

And in OCPN you can use a very handy function to let the system view the closest point of approach, CPA. Then it's easy to decide whether I can continue as is or withdraw the genoa a bit to make the CPA not so close. (It's sometimes easier to trim the genoa than the windvane.) See: AIS | Official OpenCPN Homepage
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Old 08-11-2016, 16:40   #7
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Re: How Do You Use AIS?

I like it for locating and ifentifying the fast ferry particulsrly in fog. Also good at night with tugs and barges!
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Old 09-11-2016, 04:04   #8
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Re: How Do You Use AIS?

I use the AIS radar view plugin because is easy to see if you are in a collision route with another ship: anything that moves towards the center of the radar (that is you), is in a collision route. For me is easier to see than the CPA lines.

The range is something you should adjust: I set a value between 1-3 nmi depending the conditions, the traffic, open waters, crossing a route, etc.

I use it with a rtl-sdr dongle with a 5/8 wave antenna, at a heigth of 3m over the water level, with a consistent reliable range of 10 nmi (and some targets up to 20 nmi).

Quote:
What advantages does it offer you that I may not be aware of?
For example, you can use your VHF to annouce a manouver to a specific ship or ask a ship go port, or starboard, because the names and callsigns are there.
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Old 15-11-2016, 09:29   #9
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Re: How Do You Use AIS?

Since one of the advantages mentioned by many respondents is that AIS lets you know the ship's name I am a little concerned by a few targets that don't show a name. Why is the name missing? I have good information including MMSI, nation of registry, course, and speed, so why don't I get the name? My first thought was there was an error in the message, but more than one target without a name was a big ship (class A transponder) and I watched it long enough to get several messages.

Fabbian
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Old 15-11-2016, 10:33   #10
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Re: How Do You Use AIS?

Fabian,

there is an issue with some recent Class A transponders (version information, already addressed in Github/OCPN 4.5.0) which will result in not showing the static data of the vessel.
There has been a specific thread some time ago about it.

The target will stay "yellow" (or "light green" if the MMSI has been registered once before changing the transponder).

Hubert
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Old 16-11-2016, 01:59   #11
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Re: How Do You Use AIS?

Fabbian..
As of Hubert's info: See discussion here:
AIS shipname and callsign presentation
And the fix:
AIS shipname and callsign presentation
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Old 16-11-2016, 04:13   #12
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Re: How Do You Use AIS?

Links that might interest readers of this thread:

Danish Maritime Authority to Publish 2 Years of AIS Data

And:

A Definitive Guide to AIS

/Petter
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Old 16-11-2016, 07:23   #13
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Re: How Do You Use AIS?

Quote:
Originally Posted by fgd3 View Post
Since one of the advantages mentioned by many respondents is that AIS lets you know the ship's name I am a little concerned by a few targets that don't show a name. Why is the name missing? I have good information including MMSI, nation of registry, course, and speed, so why don't I get the name? My first thought was there was an error in the message, but more than one target without a name was a big ship (class A transponder) and I watched it long enough to get several messages.

Fabbian
We too have noticed for the past 10 years of using a AIS in our travels that some vessels do not transmit the vessel name. Some large ships we see on AIS that remain on the screen for 30-40 minutes or longer never transmit a name. All the other information comes thru just fine.

This was especially noticeable in places like the Panama canal area where the screen would be loaded up with 30-40 vessels.

Would be interested if Jeff from Vesper Marine could comment if he is onboard

Safe sailing

Chuck
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Old 16-11-2016, 09:20   #14
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Re: How Do You Use AIS?

Chuck...
There seems to be two issues here.
One is for rather new AIS versions, a year or two, as of my links above.
If you're talking 10 years that's another issue. The ships name is there because someone wrote it by any AIS initialization program or afterwords using for example MaxSea. It's up to every skipper to maintain it. If they for any reason don't want a visible name they take it away. But it's also rather easy to take the name away by mistake in MaxSea, while editing destination for example.
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Old 16-11-2016, 10:36   #15
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Re: How Do You Use AIS?

Quote:
Originally Posted by dlymn View Post
Any ship under 300 tonnes is not required to have AIS. So, some ships have it and some don't. This means to me that I still have to maintain a watch on deck.
This is changing around the world where Thailand, for one is requiring all vessels to have rx and tx AIS units. You're absolutely right about standing watch anyways as there is a lot of thing to bump into other than ships. I have seen kayaks 6+ miles offshore.
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