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Old 05-10-2015, 12:15 PM   #21
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AIS Transponders

Marine traffic has the same ability to show shore stations and their identity. None of the AIS has the ability to connect Photos to the programs. That is all done by the particular website you are looking at. I subscribed to the Lloyds of London website. It was the best coverage. But after a couple weeks they shut it off until you pay for it. AFAIK Marinettraffic is the only free one ( with a slight delay). Although the delay is often negligible in real life. As far as having others 'follow you' Marinettraffic is free.

@Capttom: The websites don't work like that. You enter your. Desired vessels name, If it's in range is shows up. If not it doesn't.

@Twistedtree: the more expensive ones use Satellite reception. But they are ALL for pay. Even Matinetraffic has the 'pay' option with up to date info derived from both satellite and shore stations.

Marinetraffic has an app you can download and hook up to your AIS unit to 'rebroadcast' your data o provide a 'moving hotspot'. Everything your machine 'sees' it uploads to MT to make a more complete view. Look for it under FAQS on MT for more info. Or they will send you a unit to use at home, as long as you agree to transmit constantly to them.
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Old 05-10-2015, 05:18 PM   #22
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BTW, starting in 2016 all commercial vessels must be broadcasting on AIS.
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Old 05-10-2015, 05:51 PM   #23
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I was under the impression that was already the rule
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Old 05-10-2015, 06:27 PM   #24
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I haven't seen that...got a link?

Many above 65 feet...as far as I read....but not "all" commercial vessels.

http://www.sailfeed.com/2015/02/more...-requirements/
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Old 05-10-2015, 06:32 PM   #25
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Our Raymarine AIS has a "silent" mode which can be switched on/off.

What about this: Marine Traffic has shown Lady Di in Ft. Meyers ever since she passed thru there in late September.

Have taken her out of Marco 20 times since then with no change. No, I'm not on "silent" and other AIS targets show up fine.

Just curious...
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Old 05-10-2015, 07:18 PM   #26
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Quote:
Originally Posted by twistedtree View Post
I always assumed the different sites were all using the same underlying data. I'm not sure if I read that somewhere or just assumed it out of thin air.
Quote:
Originally Posted by cappy208 View Post
@Capttom: The websites don't work like that. You enter your. Desired vessels name, If it's in range is shows up. If not it doesn't.
Twisted, I can confirm that they don't all use the same data, since when I turn on my AIS, even if I leave it on for hours, I show up on some sites, but not others. Looking more closely, other large commercial boats in the same area also show up on the same sites as me, but not on the ones I don't show up on. Moral of the story: not all sites have receivers near my marina.

Cappy, I tend to use the sites the opposite way; select an area of interest and see what ships are there. Some harbors show no ships on one web site, but a bunch of them on another. So again, I know the coverage is not consistent from site to site.

What I'd really like is some way to know which sites cover a given area of interest, like where I am right now (for the people ashore) or where I'm going (for me.)

As I said, one of the sites does allow you to display receiving stations, but I can't find that option on the others. The ideal would be a "coverage map" like you see for cell phone companies. But there's no competitive advantage for AIS web site companies to do that, so it would have to be a 3rd party.
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Old 05-10-2015, 10:17 PM   #27
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I haven't seen that...got a link?

Many above 65 feet...as far as I read....but not "all" commercial vessels.
http://www.navcen.uscg.gov/?pageName=AISRequirementsRev


The list is getting longer and longer, with fewer caveats.
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Old 05-10-2015, 10:31 PM   #28
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Quote:
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I can confirm that they don't all use the same data, since when I turn on my AIS, even if I leave it on for hours, I show up on some sites, but not others. Moral of the story: not all sites have receivers near my marina.

Cappy, I tend to use the sites the opposite way; select an area of interest and see what ships are there. Some harbors show no ships on one web site, but a bunch of them on another. So again, I know the coverage is not consistent from site to site.

.
What I've found is the 'paid' sights have more consistent coverage. They use not just user submitted data, but satellite info. I personally have not found the need to pay for the website info. The slightly delayed info I get on my Iphone suffices. Although, technically I am not supposed to be using the iphone data for navigation, I almost always use it to do a look around for other large commercial vessels in addition to my chart plotter with AIS overlay. The vessels in close are often shadowed by buildings, mountains (think Hudson River around Bear Mtn Bridge) You can be within 4 miles of someone and they are invisible on your own AIS, But go to Marinetraffic and whoosh, there they are! Regarding the updated AIS, I have not seen true real time ais displays on the internet that were free. None of the free ones are real time. My company pays for realtime ais info to the tune of 1200 per year. I just don't feel it's necessary to pay. One of the benefits to being a 'live supplier' of data to MarineTraffic is you are given free live streaming info as a reward. Maybe this is why some vessels hook up the data stream? Not sure.

Although the following is just my own anecdotal opinion, It does seem to be pretty consistent.

In use there does seem to be some errors in data reception, transmission and use. The AIS seems to 'blink'. This may help explain your 'gaps' in coverage. The transmission is every couple seconds or so Class A, or couple minutes on Class B. But there seems to be either a reception problem, or a transmission problem on a lot of vessels. It seems that many minutes go by sometimes until positions update. This shows up as 'jumpy' targets on the plotter. I have been on several vessels that have 'blind spots' in their AIS reception. One small tanker actually received almost NO ais info from vessels ahead of the beam, but had exceptional reception from abaft the beam. So there are antenna issues, and location issues.
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Old 05-10-2015, 10:51 PM   #29
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The different websites (ShipFinder, MarineTraffic, etc) are all private. They rely on users installing software on a PC with a land-based AIS receiver. It packages up the AIS data and sends it over their private API's to their servers where the data is then distributed for viewing. In return, the user gets special access to the full dataset for free or less money.

The US government has a satellite network that is recording all AIS traffic. It allows NOAA to pick an area and see the tracks of all vessels through it over a given span of time. I'm sure there are other governmental uses of the data for intel too. I've been told that all of the government satellite AIS information is confidential for commercial and private use. I've been on telephone calls with cartographers who looked up a particular spot to see where the bulk of vessels went. They can access that information instantly.
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