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post #101 of 136 Old 11-06-2019
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Re: AIS Transciever

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Originally Posted by Damon Gannon View Post
I don't agree entirely. I still think radar is a more important navigation tool than AIS. Many vessels <65' still don't have AIS and many fishing vessels turn off their AIS transmitters because they don't want to advertise their locations to their competitors. But I do agree that relying on a smartphone app for AIS data is a really bad idea. Update times are slow and variable. In many situations, using an AIS smartphone app can be more dangerous than relying exclusively on a visual lookout.
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Originally Posted by Arcb View Post
Why?

Review rule 5


every vessel shall at all times maintain a proper look-out by sight and hearing as well as by all available means appropriate in the prevailing circumstances and conditions so as to make a full appraisal of the sit


Sight and hearing always apply, regardless of what navigation toys you have. How is increaseing situational awareness ever a bad thing?
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Originally Posted by outbound View Post
Definitely you dance with the lady you brought to the party. So if marine traffic is what you have and it helps fine. This has zero impact on my statement. The product was not developed as an aid to navigation, has inherent faults (time delay to update) that can lead you into trouble and mislead you.
For instance you download vessel at a certain course and sog. Before next update either speed changes or course. Your decisions are predicated on false information which place you at greater risk.

There’s no radar v AIS in my prior statements. Think this depends on vessel and use. When my concern is commercial traffic the AIS tend to benefit me more (i.e. nyc harbor), when in an active fishing grounds (north coast of PR) it’s the radar. In both cases the data from my eyes remain key.

Recreational vessels without AIS are small. Commercial traffic and mega yachts are big and all have AIS. If you had a choice which would you worry about more. Perhaps our fellow SN posters who have experience of ships bridges can chip in but my understanding is they watch AIS/radar but are less diligent about visual scans of the full horizon. Even with AIS on your stern rail you are usually seen by them 8-16m out. It’s nice to be seen.

So it comes down to how you use your boat, when you use your boat and where. Depending on that and your budget only you can determine the risk/benefit and if radar, AIS receiver or transceiver is worth the bucks for you. There can be little argument that the more types of data available to you is better. There’s a very decent argument that for the type of sailing you do it’s not worth the bucks. I’d like FLIR thermal cameras and forward looking sonar. CCTV looking down from the spreaders might help with docking. But for the type of sailing I do decided I don’t have the bucks for that. Need to spend what I have on other boat expenses.

In a few years (hopefully many) I’ll give up cruising. Get something smaller and easy to sail. Probably put in a chart plotter or maybe just use navionics on a iPad. Or quite possibly nothing as I know the area well. Have depth but likely skip wind instruments. Likely won’t have radar nor AIS unless so required. Boat be used to daysail on nice days in Massachusetts Bay. All that stuff isn’t necessary

We each present our perspective from how we are currently sailing so each perspective is valid within that caveat.
If I may interject another reason not to depend on Marinetraffic.com: I run a volunteer receiving station for Marinetraffic.com at Half Moon Bay, CA. During the recent power outages in Northern California, my station and commercial power, along with all Internet service, was down for days. If you relied on Narinetraffic.com for traffic data south of the Golden Gate Channel during that time it would have appeared as though there was no traffic at all. There are just too many dependencies (receiving stations, Internet connectivity, processing latencies, user cell service) to use that source reliably for traffic avoidance.

Last edited by patrickbryant; 11-06-2019 at 02:37 AM.
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post #102 of 136 Old 11-06-2019
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Re: AIS Transciever

^^^ here is the thing that I hope AIS users understand as well. The absence of data does not indicate the absence of vessel traffic. It indicates the absence of AIS transmissions. Same rules apply. You can't blindly rely on AIS for traffic avoidance either. If you do you will be running down people in small craft left right and centre. If you want a system to rely on for collision avoidance, start with eyes and ears. You want more information, get yourself an active sensor like RADAR. If you want additional traffic information, you can look into systems like AIS or, if you are inside cell range and lack the supporting systems to support an installed AIS, you could use an app like marine traffic to enhance your situational awareness.

You have to understand the limitations of any system you use, including AIS. Nothing in the above post would make me consider not using marinetraffic as an additional traffic check.
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Last edited by Arcb; 11-06-2019 at 07:25 AM.
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post #103 of 136 Old 11-06-2019
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Re: AIS Transciever

For those of you who seem to think AIS can be blindly relied upon for all collision avoidance situations, the curretnt international standard for AIS is commercial SOLAS vessels over 300 Gross tons. Which means, you could very easily have a 150 ton vessel cruising along at 15 knots in the fog ahead of you and your gadget would give no indication of the vessels presence what so ever.
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Last edited by Arcb; 11-06-2019 at 08:36 AM.
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post #104 of 136 Old 11-06-2019
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Re: AIS Transciever

Arcb makes the most salient point. AIS offers more information... but that it is incomplete means that it should not be relied on PERIOD.

First and foremost you need to stand watch and OBSERVE. Then of course use other tools to add to your situational awareness... RADAR, AIS and even sound and smell... all senses can inform you about what's around you.

AIS B only allows those with receivers to see you IF they are monitoring and that too is an unknown.

Be smart... try to stay out of known shipping lanes and things like ferry routes especially in conditions or poor viisibility.
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Last edited by SanderO; 11-06-2019 at 09:34 AM.
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post #105 of 136 Old 11-06-2019
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Re: AIS Transciever

So as I said in the beginning of this thread....AIS is great technology....can be relied upon for large vessels.
But because of the fact that most small recreational vessels don’t use it cannot be relied upon to cover most vessels out there.

To those who are day, weekend sailors who really are not in an area where large vessels impede your sailing it is a option not necessary. If you want you can spend zero dollars and use Marine traffic knowing it’s limitations.

To those who sail in areas where your safety depends on monitoring ships carrying AIS it is invaluable.

In this specific thread the OP who sails in my area , the Chesapeake was asking about buying it. The overwhelming majority of vessels in ( 95%) our area Do not have AIS. Marine traffic is available. It would drop on my list of priority items to outfit the boat. In this specific area the OP sails the newer radar would be a much better investment as it picks up ALL vessels. Today’s radar is not like radars of the past. It is very easy to use and shows all available targets .

Sometimes threads get sidetracked which isn’t necessarily bad, but back to the OPs original question is important too.
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Re: AIS Transciever

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Originally Posted by chef2sail View Post
I am currently looking at my AIS display narrowed to the Central Chesapeake. It is showing 24 boats equipped and present, however the number of boats off Annapolis right now exceeds 50 let alone the rest of the central Bay. So many more without AIS than with it. Virtually zero of the 20-30 ft power boats showing up.

In reality it is useless for the Chessie if it doesn’t show most / all the boats. It takes away from its purpose accident avoidance if the HUGE majority of the boats don’t and probably won’t ever use AIS.
Thanks, this is really helpful. I think I'm going to give up on the trying to broadcast for now at least and get one of the radios with an AIS receiver next spring.
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post #107 of 136 Old 11-06-2019
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Re: AIS Transciever

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Originally Posted by Pendragon35 View Post
Thanks, this is really helpful. I think I'm going to give up on the trying to broadcast for now at least and get one of the radios with an AIS receiver next spring.
I didn't actually intend to discourage transmit capabilities, but when a few folks became excessively critical of Marinetraffic type apps, it seemed relevant to point out that AIS isn't without its limitations as well.

Having said that, I did really like the Standard Horizon GX 2200 I had on my last boat. Inexpensive, easy to install (just swap it out with your current radio), easy to use. Integrate it with your electronic charts or use it as a stand alone system. It is worth taking a look
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Re: AIS Transciever

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Originally Posted by Pendragon35 View Post
Thanks, this is really helpful. I think I'm going to give up on the trying to broadcast for now at least and get one of the radios with an AIS receiver next spring.
Sounds like a good choice Jim. Do you have an MFD? You can hook it into the chartplotter. Is it based on NMEA 0183 or NMEA 2000?

The Standard Horizon which was recommended is a good one. If your VHF is in the salon, you would want to bring the info into the cockpit. The SH unit is a good one, but the screen for the vessels is quite small I think.


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post #109 of 136 Old 11-06-2019
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Re: AIS Transciever

Here is why AIS cell phone apps actually degrade your situational awareness. I just used Marine Traffic to look at the vessel traffic at the mouth of the Brunswick River in Georgia. The app showed 15 vessels underway (I ignored those that weren't underway). The position information of these 15 vessels was an average of 4 hours and 28 minutes old. The delay in position update varied from 1 minute to 18 hours and 48 minutes! Of these 15 vessels, only 7 had position updates that were received in 0-2 minutes. Position information for the remaining 8 vessels was between 38 mins and 18 hrs 48 mins old. In other words, position information for over half of the vessels was totally useless. Marine Traffic tells you how old the position information is, which helps you assess the quality of that information. But with such long and variable lag times in the position updates, you'd literally be better off not using it at all.

"Use all of the navigation tools that you have at your disposal, but trust none of them." AIS cell phone apps are just not trustworthy. They were never intended to be a navigation tool, and shouldn't be used as such, at least not until they can operate in real time.
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Re: AIS Transciever

Painfully, everyone should transmit AIS, just like everyone must have proper lighting or day shapes. Whether you choose to have the functionality to monitor others transmissions can be up to you. We have it backwards, solely because low cost marine recreational technology was offered backwards. Low cost receivers came first.

In all aircraft, you are required to have a transponder to be identified. It becomes even stricter this coming January. There are exceptions, but they make the use of your plane highly restricted. You are not required to have a collision detection system, unless you are large enough or flying under certain commercial purposes.

Marine adoption should be similar. At the least, you shouldn’t be allowed on the water at night or in reduced visibility, without transmitting. White, green, red and yellow lights are the dark ages. Cones, balls, cylinders...... please.


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