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Old 20-08-2006, 18:23   #16
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Jim,

I have found only a handful in eastern LI Sound area
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Old 21-08-2006, 10:56   #17
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The lack of AIS equipped ships is surprising....I just did a quick lookup on the Port of Tampa and came across this bulletin that mandates AIS for port entry for most non-fishing commercial vessels greater than 65 feet.
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Old 21-08-2006, 11:28   #18
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Jim,
If you haven't received a single AIS broadcast you should check your installation. Although I wouldn't be too surprised at the lack of AIS data in New London as almost all of the large vessels are military.
With regard to the vessels turning off the AIS transponder, I suspect the Captain would need a good reason for doing so (i.e., the transponder is malfunctioning). All of my experience with AIS has been in Europe. I've listened to VTS operators call individual ships questioning their static data when it appears to not be current and request they update it. Its taken very seriously here. Of course it still doesn't help with the Tunny Nets and the fishing trawlers.

John
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Old 21-08-2006, 12:35   #19
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Having quickly scanned the other posts in this thread, I'll add one more comment (there is always one more). I don't use the warning features in the various AIS plotting products I have onboard (Raymarine C-Series, SOB, Fugawi, Yacht-AIS software, etc.). I use AIS data strictly for identification. As a matter of fact I turn off any alarms, when possible (wish Raymarine would let me turn off theirs). From my experience the alarms, even when they are well programmed, at best are not very usefull at worst distracting. They tend to alarm you to everything out there with very little filtering of the data. If the heading or COG of the target vessel will come within a danger zone you get an alarm. This is especially a problem when you enter a large commercial harbor with a lot of moored cargo ships (e.g. Algeciras Bay, Gibraltar). Even moored vessels will report a very slight movement. Consequently the AIS plotters keep alarming you to potential collisions with anchored vessels and it is difficult to sort out the moving targets from the anchored ones.
For me the value of AIS is the positive identification of vessels in my area so I can communicate with them and have a reasonable level of assurance that the guy I'm talking to is actually on the vessel I'm looking at. That alone is worth the entry cost to this technology.

John
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Old 23-08-2006, 07:02   #20
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AIS is another navigation tool which, of course, doesn't replace good old 'situation awareness' while sailing in congested waters. Milltech's version, for less than $200, is a super value when compared to other electronic aids. Here in the upper Chesapeake I can see more than 20 ships up to 20 miles away using the mast VHF antenna (with Milltech splitter). It helps keep track of these behemoths, and along with radar's MARPA, keeps us from sharing the same spot of water.
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Old 23-08-2006, 08:43   #21
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Only 20 miles from the mast head vhf - must be because of the splitter. I get up to 40 miles from the masthead without splitter and have had 17nm from the dedicated aerial mounted on top of the davits.

I am not a fan of splitters - it is an easy (but expensive) answer to the problem but creates another point of failure for one of your important safety systems (VHF)
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Old 23-08-2006, 08:46   #22
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I'm sure it will be great if and when all vessels are required to fit it and have it on. In the UK we've heard of oil tankers for commercial reasons switching it off to prevent reductions in oil prices, and indeed fishing boats doing the same to stop fishery protection people checking the landed catch.
As most of my close calls in restricted viz have been with fishing and smaller vessels who don't have it anyway - I still rely 100% on Mk 1 eyeballs, ears, and conventional radar.
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Old 27-08-2006, 14:22   #23
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AIS is also fun.
When having kids on board, they can play "guess the length" or speed of a ship.
Like said, as navigational aids it should be used with caution.
I saw freighters with the AIS Info "under sail".
Just for the fun of it, here is a screen dump of the northsea, to give an idea about the amounts of targets.


Ok, ships that are 20miles away are (not yet) interesting, but there are many targets.
I use the mast-top antenna with a splitter (18m high)

Michael
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Old 27-08-2006, 15:02   #24
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Michael,

Your screen shot didn't make it, but thanks for your "entertaining" post.

Just helps convince me even more I don't want AIS aboard :-)

Cheers,

Bill
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Old 27-08-2006, 16:59   #25
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Quote:
Originally Posted by Curtis
I know a group buy was proposed a few months ago. Did many of y'all install the receivers? Prices continue to drop: Milltech Marine is advertising the SR161 for $189US.
What's the difference between this AIS receiver and the blackbox AIS by NASA sold in Europe?

Can one use the SR161 in Europe or is it only for the US market?

Thx.

Manou
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Old 27-08-2006, 23:53   #26
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http://www.ekpp.de/personal/micha/ais1.jpg

I included it as a link now, maybe the picture was too big.
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Old 28-08-2006, 10:10   #27
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Next time I am down on the boat I will also do a screen dump, cause i found that display to be very poor. But then I dont like mixing the ais and nav functions. I believe the danger of missing something cause there is so much other data is far too high.
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Old 28-08-2006, 10:23   #28
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I agree, but on the other hand, if you would not have overlays, you would end up with 10 displays.
I have seen the standalone-display for AIS, i think it was NASA, and i did not like it.
Having all in one of course might add to the "all eggs in one basket" strategy.
If i am far out, i usually just fade out the depth-numbers, light-signals and just keep the bouys and AIS and Radar. The Radar as split-screen then mostly, since i agree that too many overlays are distracting. Also very small blibs on the radar can easily be overlooked when overlaying IMHO.
I overlay AIS on the radar then. The radarscreen for me is Head-Up, while i like the plotter to be North-Up.
But maybe i am stupid ;-)
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Old 28-08-2006, 11:19   #29
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@Michael
I think your screenshot is completely overlayed with too much infos. It's difficult to distinguish what is where.
I use GPSNavX on Mac computers, which can display BSB, Areal Photographs, navigation tracks, AIS/RADAR and other infos, either at the same time or only the infos one wants.
But the maps are always crips and clean.
The idea behind this programm was to have just the necessary infos on screen, without filling the screen with several windows, what most navigation apps do today.
The follower of GPSNavX is MacENC, the only navigational application that can display S63 ENC maps (these are the international vector maps) and S57 (US vector maps) and overlay them with BSB charts. The maiyn advantage of vector maps is that you can turn on and off different layers so that ony teh relevant infos are displayed.
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Old 19-09-2006, 13:06   #30
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Now back from a short Bahamas trip and have some practical experience with AIS:

Range: I could "see" targets as far as 26 NM out with the dedicated antenna mounted next to the bimini top over the cockpit.
Based on that, I don't see a need for mast-head mounting. 50 NM or more is overkill and way out of visual range anyway.

Found it quite useful to see course and speed early in the game and before we got close enough to try to judge it "manually".

The CP180i chartplotter I am using to display the AIS signals are very clear and not cluttered up with multiple targets: A good combo in my opinion.

Never once did I see the ships name or call sign out of the 30 or 40 targets I tracked over several days..
Either I have programmed something wrong, or the transmitting ships have not programmed their transmitters properly.....

The rest of the information came in good, including the MMI numbers, CPA, course/speed and all that.

Agree that the 161 is a bargain and seems to work quite well. The antenna was $50.00 or so and the cable another $30.00.

With all that being said, we still keep a careful look-out as most traffic around here don't carry AIS equipment.
Still useful to see the big guys below the horizon and I would not remove the AIS now that I have tried it...
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