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Old 06-05-2018, 11:21 AM   #41
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Ausp stated “leaving AIS on at the dock is rude”. In my opinion if 80% of the useres leave it on can it really be considered rude?

I turn my off when tied to a dock but certainly don’t consider those who keep theirs on rude.
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Old 06-05-2018, 11:46 AM   #42
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Slow Lane, I see you clearly in a marina near New Squantum south of Boston, i guess it works! (I looked at Vesselfinder.com)

As for leaving On, it doesnt bother us too much though I understand the argument. Good example is entering a marina unknown to you with a narrow slot in a high breakwater where you cannot see movement very well beyond the wall to see if its clear to enter.
i.e.: Port Sidney BC we noticed this recently. When looking at the chartplotter, you just see a few dozen green triangles that may or may not be moving. Imagine if only the moving guys would light up... but as you say perhaps we can do that with our own filtering.
One other issue besides the time slot is that it shares radio spectrum with VHF communications. AIS is very low duty cycle so not a real big deal but from a purist standpoint, spectrum usage does add up in crowded areas.
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Old 06-05-2018, 12:18 PM   #43
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For those radio types out there:

AIS VHF uses GMSK FM. Which all means the transmitter, when it is actually transmitting, uses a constant power output, with a frequency shift protocol to send data. If you are a receiver much closer to one transmitter that is going at the same time as another, farther away transmitter, the close one captures your receiver.

So, yes, a multitude of local AIS transmitters can effectively mask AIS transmitters some distance away. This is not seen as an issue for anti-collision. You will still pick up the closest users.

I don't know how the sat based AIS works, in comparison. But, obviously not a lot of docked ships out where there is no terrestrial AIS.

should also add: update rate is speed dependent. Slow, docked, anchored systems transmit every few minutes.
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Old 06-05-2018, 12:33 PM   #44
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I remain surprised that people expect AIS to be their collision avoidance means of choice in the tight confines of a marina. Any target stationary in the marina will be displayed as such, on a modern receiver at least. The majority of pleasure boats moving in and out of a marina will not have an AIS transmitter, and will invisible. You should be traveling at dead slow pace so that you can stop in less than the distance you can see - that is required by the Colregs. Eye balls work best in these situations. If you are getting nuisance alarms, learn how to turn your alarm off, or adjust your filtering criteria.
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Old 06-05-2018, 02:09 PM   #45
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Originally Posted by South of Heaven View Post
Guys, on a side note. Can someone search for me on their app of choice, vessel name Slow Lane.

For some reason I can find my myself on the ShipFinder app but then on other AIS apps I dont come up. Or vice versa. My name won't come up in the search function but if I zoom into my harbor it will. Lol

I have a new Em Trak class b transceiver and a dedicated antenna.
On Marinetraffic.com I see a "Slow Lane" in roughly the middle of the bay south of Boston, says "out of range" and last reported position was 5/30 at 22:13:29 and underway at 1.2 kts.

Their nearest receive/relay station is named "Ferguson Light" (station ID 3194) just east of Hull, at the north end of that peninsula that runs northeastward. Suggests you're either too distant or your signal is blocked at that receive station.

Dockwa has a station in Cambridge (Station ID 49) but it's marked "low coverage."

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Old 06-05-2018, 02:37 PM   #46
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Thanks gentlemen.
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Old 06-05-2018, 03:53 PM   #47
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Originally Posted by South of Heaven View Post
Guys, on a side note. Can someone search for me on their app of choice, vessel name Slow Lane.

For some reason I can find my myself on the ShipFinder app but then on other AIS apps I dont come up. Or vice versa. My name won't come up in the search function but if I zoom into my harbor it will. Lol

I have a new Em Trak class b transceiver and a dedicated antenna.
Marine traffic shows a SL off Quincy Bay a few days ago. But nothing current, or boat details in the read out.
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Old 06-05-2018, 04:39 PM   #48
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Originally Posted by Hamrow View Post
Slow Lane, I see you clearly in a marina near New Squantum south of Boston, i guess it works! (I looked at Vesselfinder.com)

As for leaving On, it doesnt bother us too much though I understand the argument. Good example is entering a marina unknown to you with a narrow slot in a high breakwater where you cannot see movement very well beyond the wall to see if its clear to enter.
i.e.: Port Sidney BC we noticed this recently. When looking at the chartplotter, you just see a few dozen green triangles that may or may not be moving. Imagine if only the moving guys would light up... but as you say perhaps we can do that with our own filtering.
One other issue besides the time slot is that it shares radio spectrum with VHF communications. AIS is very low duty cycle so not a real big deal but from a purist standpoint, spectrum usage does add up in crowded areas.

What display are you looking at to see this? I have never seen one that doesn't distinguish between stationary and underway vessels such that it's immediately clear what's moving and what's not.
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Old 06-06-2018, 08:26 AM   #49
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What display are you looking at to see this? I have never seen one that doesn't distinguish between stationary and underway vessels such that it's immediately clear what's moving and what's not.
Just looking at the chart plotter, Garmin 5000-series. but if you've played with AIS, we've all seen places like big marinas or shipping channels where things can get filled with targets. I grabbed an example thats a bit severe from Singapore to make the point.
Click image for larger version

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So of course there can be filtering but the point is there are areas where less clutter would be helpful.
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Old 06-06-2018, 12:08 PM   #50
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Just looking at the chart plotter, Garmin 5000-series. but if you've played with AIS, we've all seen places like big marinas or shipping channels where things can get filled with targets. I grabbed an example thats a bit severe from Singapore to make the point.
Attachment 77133
So of course there can be filtering but the point is there are areas where less clutter would be helpful.
But you're not going to try using AIS to navigate an area like that. It's like using speed control in your car in midtown Manhattan.
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Old 06-06-2018, 12:16 PM   #51
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But you're not going to try using AIS to navigate an area like that. It's like using speed control in your car in midtown Manhattan.
Perfect analogy.
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Old 06-06-2018, 02:43 PM   #52
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Originally Posted by Hamrow View Post
Just looking at the chart plotter, Garmin 5000-series. but if you've played with AIS, we've all seen places like big marinas or shipping channels where things can get filled with targets. I grabbed an example thats a bit severe from Singapore to make the point.
Attachment 77133
So of course there can be filtering but the point is there are areas where less clutter would be helpful.

So on a Garmin chart plotter, it doesn't show different icons for stationary vs moving AIS targets? Perhaps you need to turn on heading vectors for targets? Also, does it highlight "dangerous" targets? "Dangerous" is typically adjustable based on CPA and target speed.
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Old 06-06-2018, 03:41 PM   #53
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But you're not going to try using AIS to navigate an area like that. It's like using speed control in your car in midtown Manhattan.
You are certainly not going to use it with it zoomed out to cover a 30 mile radius. Even in Singapore, zoomed to a useful level, it isn't that cluttered. If, zoomed to a useful level, it IS that cluttered, then be thankful that everyone has them on - your gonna need it.
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