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Old 12-24-2010, 01:47 AM   #21
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Re: Ais

You're probably right, Traveller, however ...

I'm not sure that I'll be able to effectively process the*additional information from an AIS receiver, at least at my current level.* Although I've sailed 24' to 28' auxiliary sailboats in the Bay Area for 15 years (in the 60s and 80s), mostly in races where weather isn't chosen, I've never*piloted with electronic equipment: no radio, no radar, no depth finder, no GPS; only compass, *charts, and speedometer.* My trawler will have that stuff, but at this point I'll wait until I become accomplished with those instruments, and then reassess the need for AIS.

I wonder.* Is there an affordable radar that incorporates AIS data?* That is, objects transmitting AIS data are*described on the radar screen adjacent to the object on the screen?
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Old 12-24-2010, 10:40 AM   #22
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Ais

I understand your concern, but the data is simply over layed on your plotter screen.* You see an icon that show's the ships direction of travel right on the chart.* Nothing could be easier, no skill needed.* Some of the units with dedicated screens that look like small radars might be a another story,(and far more expensive) but with the inexpensive black box unit, you simply plug it into your plotter / computer and the info is displayed.* Should you want further info, simply place the cursor over the desired ship, and a box opens up that gives all the info, such as ship name, size, speed, heading etc.*** I think it works better than radar (for those ships that are broadcasting a signal that is)

Here's the unit I use (I have no connection with the company)

http://www.milltechmarine.com/Smart-...ver_p_167.html

Here's a screen shot of what you might see

https://milltechmarine.3dcartstores....ges/ce-ais.jpg


...............Arctic Traveller

-- Edited by Arctic Traveller on Friday 24th of December 2010 11:42:48 AM
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Old 12-29-2010, 03:07 PM   #23
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Re: Ais

My first boat was hit by an out of control tow and I got to sit a watch in slow motion as the 800 foot monster closed in on me and "T"Bone my sailboat, pushing it and its forward barges onto a rock jetty. I decided that day that my next sailboat was going to have AIS B. Now when I see the tows coming I hail them by name, thanks to the AIS. Knowing that they should be able to see me is also a comfort.

Yes I can see the future problem of clutter from tons of pleasure craft on a chart. The first thing people can do is turn them off while tied to the dock. My unit is also made so its transponder can be turned off any time I want.
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Old 12-29-2010, 03:27 PM   #24
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Re: Ais

As more and more pleasure boats have Class B AIS, the discussion on big boats being able to filter out the B's continues.

See the December 28th post on Panbo.***

http://www.panbo.com/archives/2010/1...rris.html#more
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Old 12-29-2010, 06:03 PM   #25
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Re: Ais

So, if the big boats could filter out small boats from their radar screens, would they opt for that?
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Old 12-30-2010, 05:06 PM   #26
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Re: Ais

Quote:
markpierce wrote:

So, if the big boats could filter out small boats from their radar screens, would they opt for that?
Being mostly fiberglass, they might not show up anyway.

*
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Old 12-30-2010, 06:42 PM   #27
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Re: Ais

I often call and advise someone whose radar image is poor or non-existent, so they will be encouraged to go get a better radar reflector. At least they will know their boat presents a poor target.
I was in a line astern of 6 boats going past Alert Bay in the fog, and had a fishboat going the other way past us call and report the quality of each of our returns. I found that a valuable call, as it identified the effectiveness of each of our reflectors and sent one of us to the store for a better one.
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Old 12-30-2010, 07:24 PM   #28
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Ais

I often wonder about the true effectiveness of radar reflectors. We have our radar on all the time we're running. It's been interesting to see the differences in boat targets. We often get a very strong return from a boat that has no reflector at all, and we often get weak returns from boats that do. And we often get returns from boats that have no reflectors that are just as strong as the returns from boats that do.

Many fiberglass cruisers we encounter have no reflectors at all, yet their returns are usually quite strong. I attribute this to the returns from the metal in the boat--- engines, galley equipment, outboard motors for their dinghies, power davits if they have them, anchors, and so on.

We often get very strong returns from the small sport fishermen that are running around. Perhaps from their outboard motors or inboard/outboard engines? None of them carry radar reflectors.

We very often get a strong return from a boat that is oriented toward us in one way, and then when that boat turns or passes us so it's oriented to us in a different way, the return gets much weaker.

We always get a strong return from Carey's lobsterboat even if it's a long ways away. I attribute this in large part to the heavy-duty aluminum davits he designed and installed to carry his Bullfrog dinghy over the transom. Also the outboard motor on this dinghy.

In at least one instance I recall, we were boating in thin fog and approaching Obstruction Pass and there were a number of strong returns ahead of us that proved to be sport fishing boats in the the 16' to 25' range. When a weaker return showed up on the far edge of this cluster of boats we assumed it was another sport fisherman. The return remained weak as it approached, so imagine our surprise when it proved to be a 45 or 50 foot cruiser, complete with radar reflector.

So I would not automatically assume that because a person's boat shows up strong or weak on another boat's radar that a radar reflector or lack of one is the cause. There seem to be many factors at work to determine the strength of a particular boat at a particular angle to you.

-- Edited by Marin on Thursday 30th of December 2010 08:24:57 PM
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Old 12-30-2010, 07:29 PM   #29
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Re: Ais

Marin, just*how strong are radar returns on all-steel boats?
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Old 12-30-2010, 07:52 PM   #30
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Re: Ais

Quote:
markpierce wrote:

Marin, just*how strong are radar returns on all-steel boats?
I'm sure we have enountered plenty of all-steel recreational boats but we have not picked them out as such by sight.

The only all-steel boats we have encountered that we knew were all steel are the Washington State ferries, various oil tankers and bulk carriers, tug and barge combos, and the big tractor tugs that escort the tankers.* Needless to say, their returns are rather noticeable.
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Old 12-30-2010, 07:55 PM   #31
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Re: Ais

Quote:
markpierce wrote:

So, if the big boats could filter out small boats from their radar screens, would they opt for that?
Washington State Ferries has already anounced that they have turned AIS B class reception OFF.* Some of the older AIS A class units do not have this option, and most commercial traffic would probably not choose to turn it off.

*
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Old 12-31-2010, 06:23 AM   #32
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Re: Ais

Quote:
Jay N wrote:
Washington State Ferries has already anounced that they have turned AIS B class reception OFF.* Some of the older AIS A class units do not have this option, and most commercial traffic would probably not choose to turn it off.

I would expect the ships to turn class B off once there are enough that it gets cluttered.* They are concerned with other large ships, tugs, pilot boats, etc.* They are not going to get out of our way anyway, it's our responsibility to stay out of their way.

That's a reason I would not bother with a transmitter, just a receiver.
*
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