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  #11  
Old 11-17-2012
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Re: Caution: AIS Apps

Quote:
Originally Posted by mdbee View Post
Just curious about "...is posted to the Internet by volunteers who have receivers located in fixed positions (often far from water)." I noticed AIS data showing in the Antarctic, are there volunteers there? It seems they would have better things to do than to be feeding data into the Internet. Curious how that works?
Any AIS receiver can output the digital information to another system, so some ships with BGAN or other internet connectivity can re-broadcast signals to marinetraffic or other internet systems.
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  #12  
Old 11-17-2012
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Re: Caution: AIS Apps

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Originally Posted by patrickbryant View Post
I recently had a fellow sailor - who is just IN LOVE with his iPhone - show me an app that displays vessel positions received via AIS. He said: "Why should I buy an expensive receiver and chartplotter when I have this?"
I met a fellow like that on the ICW last year and later listened to the radio traffic as the USCG was going out to rescue him because he had just discovered in Masonboro Inlet that the touch screen doesn't work when your fingers are wet.

Last edited by Roger Long; 11-17-2012 at 07:26 AM.
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  #13  
Old 11-17-2012
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Caution: AIS Apps

Just a side bar commentary - - The iPhone device is so prevalent with the slick marketing, it is easy to understand how society in general see this device as the modern Swiss army knife; the magic bullet for any and all solutions. There are so many apps that everything is covered:

Think of all the apps available and those to be made, apps for:

Paying for stuff
Finding places and stuff
Buying stuff
Controlling stuff
Driving stuff
doing stuff to other stuff or other person's stuff

There may already be apps designed to take on military missions while making love to your spouse at the same time.

So of course some may be inclined to think an app is just as good as the real thing. AIS vs App.

Thank you for explaining the difference.


Disclosure: I write this from an iPhone. Oh yeah.
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  #14  
Old 11-17-2012
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Re: Caution: AIS Apps

I didn't think anyone was that dopey to think marinetraffic.com could be used as a real time AIS plotter.

For a start it doesn't calculate CPA.

But marinetraffic.com is very useful to those with an AIS Transponder because when in a port that has coverage you can check that you are transmitting.

Plus you can add a photo or two of your boat so other users can see what you look like.

And as a foreign flagged boat cruising the USA I like to have plenty of records of where I am to keep Big Brother happy. As I'm not an illegal drug running criminal I don't need to hide.

Proper AIS, the transponder, is the best advance in marine safety since GPS and should be a requirement for all vessels going offshore for more than a day sail.
I commend anyone who doesn't have one to start saving up for a proper transponder. The receivers aren't worth a pinch of poop IMHO.

Mark
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  #15  
Old 11-17-2012
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Re: Caution: AIS Apps

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Originally Posted by MarkofSeaLife View Post
...The receivers aren't worth a pinch of poop IMHO.
I think your opinion is too negative.

AIS receivers do what they were designed to do perfectly well. For small boats sailing in bays and rivers during the day they are fine. Freighters aren't going to steer around a 25 foot sailboat anyway. You can place DSC calls to make your position visible on an as-needed basis.
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  #16  
Old 11-17-2012
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Re: Caution: AIS Apps

Its amazing i lived this long and never even had a RADIO on the sailboat until 2008 ?

I did up it to a DSC handheld in 2012 after taking Safety at Sea

In all these decades of distance racing MOST of the stuff we need to worry about does NOT have a transponder and the Nuke Subs do not give out info
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  #17  
Old 11-17-2012
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Re: Caution: AIS Apps

Quote:
Originally Posted by mdbee View Post
Just curious about "...is posted to the Internet by volunteers who have receivers located in fixed positions (often far from water)." I noticed AIS data showing in the Antarctic, are there volunteers there? It seems they would have better things to do than to be feeding data into the Internet. Curious how that works?
There is one volunteer receiving station at Palmer Station, Antarctica (country code AQ). At the time of this writing, it has been feeding data only about 20% of the time. Not bad for Internet connectivity from Antarctica.

You can see a full list of the receiving stations (sorted by country) here: Stations Status & Performance - AIS Marine Traffic.

Note that at any given time, about one quarter of the stations are offline, and that only one station - a test system run by the system operator (probably a few feet away from the marinetraffic server) has 100% availability.

A description of how all this works (in answer to your question) is posted here: Cover your Area on the Live Ships Map. As you will see, the data is uploaded by unpaid volunteers - often using scanners bought at Radio Shack. Those scanners, by the way, can only receive one of the two AIS channels at a time, so 50% of the AIS message traffic can be lost. Have I poked enough holes in the reliability of this service for collision avoidance? I am using a dedicated dual-channel AIS transponder (the same one I use while underway), but I am in the minority.

I am participating as a volunteer because it gives me an effortless way to monitor the health of my AIS transponder when the boat is at the dock (marinetraffic provides some nice graphs of my receiver's performance), while simultaneously performing a public service by sharing the data. But I'm a Ham radio guy, and that sort of stuff turns me on.

As an side, for anyone curious about the maximum receiving range of an inexpensive AIS transponder with a simple store-bought masthead antenna 40 feet above the water: my record so far is 188 nautical miles - a fluke probably due to atmospheric ducting or meteor trail bounce. My "solid" reliable range for receiving Class A transponders (the Big Boats) is 30 miles.

AIS has saved my bacon more than once already! I just happened to have a camera rolling during one encounter with a Pilot Boat. You can see it here:
The video was shot with a fisheye lens - the boat is MUCH closer than it appears. I was able to call the boat specifically by name and get it to turn and slow down - when all I could see was a bow with lots of spray coming right at me. There's no chance I would have known its name until I read it off the stern ... post-collision. My chartplotter computed that the boat would have gone right through my hull and sounded the CPA alarm, and without that AIS collision alarm, I wouldn't have seen it until much later because it was hidden behind the jib. Previously, it had been on a parallel crossing course but then turned to a conflicting heading while behind my jib. Note the shadow from my mainsail: the sun was almost directly in the pilot boat helmsman's eyes. Had there been any delay at all (such as you'd get using an iPhone), my boat could have been reduced to floatsom.

Last edited by patrickbryant; 11-17-2012 at 12:57 PM.
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Old 11-17-2012
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Re: Caution: AIS Apps

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Originally Posted by TakeFive View Post
Freighters aren't going to steer around a 25 foot sailboat anyway. .
Of course they do!
ALL AIS targets are logged and the "black box" is used in court. There is NO WAY a ship will run you down when he knows its being recorded!

You just can't think that ships don't care about it. Look at the Costa sinking the AIS record was all over the Internet within hours. The ships company emailed the ship as soon as they saw it go off course, BEFORE it hit the rocks.

Also look at the words in my post: vessels going offshore for more than a day sail.

Boats in a river will need to get out of the way of large ships anyway as the ship will be constrained and/or in a shipping channel.

Most Class B transponders also have the ability to log all AIS traffic, and every ship would realize it. So really, who is going to play chicken with a sailboat when it means their job?

Especially when sailboats are undermanned, or some cockpit crew are less experienced the transponder is vital. It gives both vessels the chance to comply with Colregs, not just one vessel. And remember if the sailboat is the stand on vessel it should stand on. It makes it vastly easier for a ship to maneuver around a sail boat when he knows its course and speed, very much so when the boat is pointing one way but leeway or current is taking him the other way.

One final point is that AIS is so powerful that It can be picked up a long way away... Just because a captain can't see a third target on the screen it doesn't mean that his every move isn't being watched, and recorded, by some other ship.

The pic shows you the range of these things... The red circles are 10 nms and 20 nms. Marsh Harbor to Nassau is 90 nms. Sure, I dont always get anywhere near 90 nms, but normally always have 40nms. (Purple line is my track from Nassau)

Toomany witnesses to run down a boat. All are recording all AIS information.
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Last edited by MarkofSeaLife; 11-17-2012 at 10:38 AM.
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  #19  
Old 11-17-2012
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Re: Caution: AIS Apps

Quote:
Originally Posted by tommays View Post
Nuke Subs do not give out info
Twaddle. When the navy is in areas with other vessels you would be surprised how many turn their AIS on.



And fishing boats too!

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  #20  
Old 11-17-2012
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Re: Caution: AIS Apps

Quote:
Originally Posted by MarkofSeaLife View Post
...Also look at the words in my post: vessels going offshore for more than a day sail.

Boats in a river will need to get out of the way of large ships anyway as the ship will be constrained and/or in a shipping channel...And remember if the sailboat is the stand on vessel it should stand on. It makes it vastly easier for a ship to maneuver around a sail boat when he knows its course and speed, very much so when the boat is pointing one way but leeway or current is taking him the other way...
OK, another one of these "you must have missed reading my words" comments. Yes, I saw the words in your post. Don't forget the part where you said AIS receivers "aren't worth a pinch of poop" part. I saw those words too, and I still think that they are overly negative.

As for an encounter between a sailboat and a massive freighter or cargo ship, the sailboat is almost never the stand-on vessel. For this reason I don't expect those guys to steer around me, especially since they are constrained by a narrow channel in my area.
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