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Old 27-10-2013, 14:12   #91
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Quote:
Originally Posted by Powerabout View Post
AIS only gives Heading and not CoG
????

Cog & sog are included in message 18, aren't they?

http://www.navcen.uscg.gov/?pageName=AISMessagesB
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Old 27-10-2013, 14:48   #92
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Re: New Inexpensive Ais Transponder

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The only commercial captain in the world who would see any truth in any of your statements is the Captain of the Costa Concordia.



Mark
I beg to differ with you Mark. Just outside the Golden Gate bridge small boats are rolled over by large container ships, tankers, frequently enough to indicate maybe there's truth to what was said.
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Old 27-10-2013, 16:15   #93
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Re: New Inexpensive Ais Transponder

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AIS only gives Heading and not CoG
Doesn't this depend on how your chart plotter processes the AIS Data?

AIS provides a stream of positions which yield historic COG. I typically am running a plotted course, and I am used to observing the difference between my heading and my COG. In the PNW there are numerous areas where significant "crab angles" result.

My chart plotter also displays a graphic representation of the track and position of my boat and that of a conflicting target at CPA with a line to represent the distance between the two of us. My experience has been that if we both maintain course and speed the resulting CPA matches the prediction very well.
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Old 27-10-2013, 16:42   #94
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Re: New Inexpensive Ais Transponder

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yes cpa will be the same
now look at the vessel that is underway and making way but at current speed so stationary to the seabed so AIS says stationary
another vessel drifting in the current and AIS says that is moving due to the GPS data
ARPA will give you the opposite situation
CPA will be the same, as will TCPA, relative course, relative speed, and any other parameter that matters in an approach. Yes, I should have allowed that with a boat being swept backwards by the current (or with any current) the values of the speed through the water will not match the SOG, but none of this matters when calculating the approach. The relative numbers are what matter, and these are the same. If you are saying that the rules for a stationary vessel are different than those for a moving one, then yes, you are correct. And how often does this become an issue?

And AIS does provide COG. It provides position, COG, SOG, Rate Of Turn, and in most but not all cases Heading. Where are you getting your information about AIS?
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Old 27-10-2013, 17:10   #95
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Re: new inexpensive ais transponder

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I was pretty surprised that I saw AIS contacts from > 95 miles away the other day. I was in Puerto Escondido and saw three ships (class A) in San Carlos pop up. My masthead is ~55' off the ground, and they're probably ~80' off the ground, but still, I was surprised to say the least.
Eric,

How often do you see an AIS equipped boat in the sea of Cortez? i assume it's just the larger ships, and not the shrimpers or other fishing boats?
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Old 27-10-2013, 17:38   #96
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Re: New Inexpensive Ais Transponder

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PS yes I have also seen the VHF work longer range than line of site, not sure how to explain that
Tropospheric ducting if very long range, ground wave if just over the horizon.

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Old 27-10-2013, 17:45   #97
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Re: New Inexpensive Ais Transponder

I just purchased a new AIS receiver, not transponder, as an aid to my eyes, ears, and radar. With that said, philosophically I would never ever trust AIS over my eyes and ears because like all technologies, even the most reliable ones, can fail when you need them most... To back up that personal philosophical statement in relation to AIS it's important that everyone know that the current AIS system is known to have serious security vulnerabilities which if completely relied on could cause serious collisions... Sail-World.com : AIS concern - serious vulnerability to hacking

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Old 27-10-2013, 18:22   #98
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Re: New Inexpensive Ais Transponder

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I just purchased a new AIS receiver, not transponder, as an aid to my eyes, ears, and radar. With that said, philosophically I would never ever trust AIS over my eyes and ears because like all technologies, even the most reliable ones, can fail when you need them most... To back up that personal philosophical statement in relation to AIS it's important that everyone know that the current AIS system is known to have serious security vulnerabilities which if completely relied on could cause serious collisions... Sail-World.com : AIS concern - serious vulnerability to hacking

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sv Sunny Sky hailing from Cold Bay, AK
Have you heard that NOAA is getting out of the paper chart business? Click here for the news.
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Old 27-10-2013, 19:46   #99
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Re: New Inexpensive Ais Transponder

At a moonless and rainy 3am bottom of watch on the 2nd day of a rough and restless passage going through shipping lanes with multiple cruise ships and local fishing boats, I absolutely trust AIS over my eyes (ears? what do they have to do with a ship 10 miles away?). I get confused easily with the lighting of cruise ships and local fishing boats even when I am sharp, rested and most attentive. AIS is a godsend for when I am not.

How paranoid must one be to think that people want to mess with your AIS out in the middle of the ocean? Even if they did, you still have your eyes and ears and radar.

Not to mention human eyes and ears have a far greater failure rate than todays electronics - I bet yours are nowhere near as calibrated and sensitive as you think they are, let alone reliable for 24/7 operating times!

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Old 28-10-2013, 00:06   #100
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Re: New Inexpensive Ais Transponder

NOAA getting out of the paper chart business has it's pro's and con's, but that's more a factor of government issues and technological improvements making Print-On-Demand paper charts in many ways superior to the standard large scale print run of charts. Obviously the popularity of electronic charting is the other major factor, and I fully admit I use electronic charts just about all the time, but trusting my eyes and ears trumps any electronic aid to navigation especially in regions that charts may be either not be of appropriate scale or inaccurate due to age of survey information or typographical error.

Assuming enough electrical generation capability, no water intrusion problems, and not being hit by lighting modern electronics are definitely very reliable especially as it relates to a constant 24/7 watch. Mark I am in no way opposed to electronic aids to navigation, but there is also a number of people that seem predisposed to trusting technology over their eyes and ears. I am lucky to still have good eyes and ears that I can trust whether it be seeing a ship's lights on the horizon or hearing a ship is in the vicinity. Regarding ship traffic, I relatively recently sailed offshore from Alaska to San Fransisco with plenty of ship and recreational traffic at the conclusion of a long passage, and given the increased naviational challenges of busy shipping lanes I anchored out for two nights to catch up on sleep and listened to Vessel Traffic Services as a complement to my eyes and ears. Yes, I will appreciate having AIS information at my disposal as an additional aid to navigation now but it would be foolish to go out at sea without good eyes, ears, and paper charts, with countless other additional tools both electric and non-electric being important additions such as GPS, radar, and binoculars (yes, mark it's amazing how much further I can see with good old fashioned binoculars and if I had to choose I would choose to have a good pair of binoculars over AIS any day ;-) )
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Old 28-10-2013, 00:29   #101
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Re: new inexpensive ais transponder

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Originally Posted by susswein View Post
Eric,

How often do you see an AIS equipped boat in the sea of Cortez? i assume it's just the larger ships, and not the shrimpers or other fishing boats?
Excluding pangas I'd say it's about 25%. A lot more of the sailing vessels have it but certainly not most. It's typical on the ferries and luxury yachts, but nothing on the shrimpers. They'll pay to put a chopper on the back but not $1000 for a transponder.

It's definitely on the rise though. If you look at marinetraffic.com you'll see tons of stuff on there.
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Old 28-10-2013, 01:21   #102
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Originally Posted by SunnySky View Post
I just purchased a new AIS receiver, not transponder, as an aid to my eyes, ears, and radar. With that said, philosophically I would never ever trust AIS over my eyes and ears because like all technologies, even the most reliable ones, can fail when you need them most... To back up that personal philosophical statement in relation to AIS it's important that everyone know that the current AIS system is known to have serious security vulnerabilities which if completely relied on could cause serious collisions... Sail-World.com : AIS concern - serious vulnerability to hacking

Dave
sv Sunny Sky hailing from Cold Bay, AK
That security exposť is a fraud. They basically hacked marine traffic.com. AIS is quite simply the greatest single advance in marine safety systems.

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Old 28-10-2013, 01:35   #103
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Originally Posted by SunnySky View Post
NOAA getting out of the paper chart business has it's pro's and con's, but that's more a factor of government issues and technological improvements making Print-On-Demand paper charts in many ways superior to the standard large scale print run of charts. Obviously the popularity of electronic charting is the other major factor, and I fully admit I use electronic charts just about all the time,
It's all to do with the arrival of IMO approved ECDIS then anything else and the decreasing use of paper chats aboard mandated vessels and hence a declining market.

Quote:
]but trusting my eyes and ears trumps any electronic aid to navigation especially in regions that charts may be either not be of appropriate scale or inaccurate due to age of survey information or typographical error.
Of course , but you can obviously see what's under the water or around that visual object that blocking your view then. !

Quote:

but there is also a number of people that seem predisposed to trusting technology over their eyes and ears.
Where has anyone ever said that


Quote:
but it would be foolish to go out at sea without good eyes, ears, and paper charts, with countless other additional tools both electric and non-electric being important additions such as GPS, radar, and binoculars (yes, mark it's amazing how much further I can see with good old fashioned binoculars and if I had to choose I would choose to have a good pair of binoculars over AIS any day ;-) )
Few boats today have more then a set of backup charts. Most are not carrying full charts of all ports along the route. This is especially so in non US areas where charts are expensive and sometimes hard to get. Hence many boats Re relying on chart plotters as the primary chart device , with some form of paper backup. There is nothing wrong with this approach.


As for AIS over binoculars. Can I humbly say , it's a nonsense comment , you can get a set of cheap bins for $50 , why compare the two systems. Furthermore to my knowledge no set of bins will give you the oncoming vessels MMSI. !!!

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Old 28-10-2013, 02:46   #104
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Re: New Inexpensive Ais Transponder

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That security exposť is a fraud. They basically hacked marine traffic.com. AIS is quite simply the greatest single advance in marine safety systems.
Most of the press has been from the perspective of marinetraffic.com, probably because people understand websites getting hacked. The article in MIT Technology Review (see paragraph 4) makes it clear that significant over-the-air spoofing is practical.

Similar albeit more expensive technology exists for spoofing GPS.

I can see hackers sitting around hacking into marinetraffic.com and other AIS display web sites. Script kiddies seem to love that kind of thing. It won't make any difference on the water. I don't see hackers loading up boats (or cars in some places) in the marine version of war driving. Bad actors on the international stage are a different issue. Even there professional mariners will be using radar and Mark I eyeballs. They are much less likely to depend on a single technology than recreational boaters.

Recreational boats aren't a target. If there is a spoofing event it's going to be a big deal.

In the meantime I'll continue to use AIS as a tool.
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Old 28-10-2013, 03:19   #105
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Most of the press has been from the perspective of marinetraffic.com, probably because people understand websites getting hacked. The article in MIT Technology Review (see paragraph 4) makes it clear that significant over-the-air spoofing is practical.

Similar albeit more expensive technology exists for spoofing GPS.

I can see hackers sitting around hacking into marinetraffic.com and other AIS display web sites. Script kiddies seem to love that kind of thing. It won't make any difference on the water. I don't see hackers loading up boats (or cars in some places) in the marine version of war driving. Bad actors on the international stage are a different issue. Even there professional mariners will be using radar and Mark I eyeballs. They are much less likely to depend on a single technology than recreational boaters.

Recreational boats aren't a target. If there is a spoofing event it's going to be a big deal.

In the meantime I'll continue to use AIS as a tool.
No I examined the Trend Micro claims and the tests they did

With the exception of a fake AIS messages , all the rest was either marinetraffic.com or supposition. They persistently claimed things about AIS that were factually wrong and noticeably their subsequent blogs " left" out the marine traffic stuff as its was laughable.

They simulated a fake AIS sart message , big deal , you could do that every day just by making a fake VHF call or fake dialling 999 etc.

It's utter bunkum and trend is in the business of " shock horror" claims cause it's sells Internet security solutions -go figure

They know nothing about AIs and it shows ( and they would not a accept my comments on their blogs either )

They were also rebuffed by the IMO and quite rightly so . Bunch of chancers

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