Is AIS isolated or linked?

[wrwakefield]

Originally Posted by sailon46

Let me add one item about AIS friend of mine got boarded by Venezuelan misfits on the way to Trinidad from Grenada. They pistol whipped him and mishandled his petite wife stole some items and left. He was 40 miles off chaguaramas by the oil rigs. Apparently they had picked up his AIS transmission so they knew what they were after. Sailors with AIS transmitters be wary bad guys close to you are watching and listening.

I'm sorry to hear about your friend's ordeal.

It is important to be prudent about broadcasting one's location via AIS or other means. Fortunately AIS transmission can be turned off when appropriate.

As more AIS capable satellites are launched, this will likely become an even more pervasive issue, similar to voluntarily publishing one's current coordinates to a publicly accessible online source... [Where are we?]

Thankfully these kind of bad guys aren't something we have had to worry about [to date] in higher latitudes...

No one should ever come here anyway... boating is miserable, and its always cold and dark... really...

Bill

[farm sail]

Originally Posted by wrwakefield

Chrisgo,

Others have provided you with qualified detailed answers.

I wanted to mention we often use our AIS transceiver independent of the VHF radios- mainly when we are sleeping at anchor.

When we anchor, I change the status in the AIS software to "Anchored."

This summer we had an experience that reinforced this habit: We were in a sleepy little bay that had what appeared to be an inactive logging operation at its head.

At 0400 the next morning the radar proximity alarm got me up in time to see a very large barge ghosting past us in the fog not 100 feet away. [They had no choice but to transit between us and a small island...] When the fog lifted later that morning I could see the barge being loaded with logs...

Would they have seen us anyway? Most likely: we were also lighted beyond the mast-top anchor light, and have a very good radar reflector high on the main mast. However, I feel better knowing that they knew precisely where we were, what we are, and that we were at anchor, many miles before they arrived...

This is our main reason for operating our AIS transceiver independent of the VHF radios.

Cheers!

Bill

Wait a minute you leave your radar, and your AIS on but you turn off your VHF while at anchor??? what benefits does that give you?

[Robin3]

Originally Posted by sailon46

Let me add one item about AIS friend of mine got boarded by Venezuelan misfits on the way to Trinidad from Grenada. They pistol whipped him and mishandled his petite wife stole some items and left. He was 40 miles off chaguaramas by the oil rigs. Apparently they had picked up his AIS transmission so they knew what they were after. Sailors with AIS transmitters be wary bad guys close to you are watching and listening.

This is why we specified an AIS transceiver where the transmit side could be disabled temporarily if required. ON the Garmin 600 it is a simple switch, installed between two wires, that when closed prevents data transmission, which we would only do in areas where we wished not to announce our presence to undesirables, especially with information on our precise position, course and speed.

[colemj]

Originally Posted by Robin3

This is why we specified an AIS transceiver where the transmit side could be disabled temporarily if required. ON the Garmin 600 it is a simple switch, installed between two wires, that when closed prevents data transmission, which we would only do in areas where we wished not to announce our presence to undesirables, especially with information on our precise position, course and speed.

I'm pretty sure that all AIS transceivers have the capability to disable the transmit function. On our Vesper, we can do it through a physical switch or wirelessly through a computer, a smart phone or a tablet.

I'm not sure pirates operating in the Tabago oilfield area are equipped with AIS receivers - nor can I explain how one would know an attack was planned through an AIS signal reception. Most likely, they were discovered in more traditional ways like eyeballs, probability, patrolling, etc.

Mark

[colemj]

Originally Posted by wrwakefield

However, since we standardized on AIS based MOB alarm devices [SafeLink R10] we have chosen to have redundant AIS receivers.

Yes, this will definitely work. We also have an AIS receiver on board that is smart enough to ignore ownship MMSI, but dumb enough to continue to send its signal to the MFD.

When that data feed is chosen, it looks like a ghost ship slowly falling behind us over 30 seconds and suddenly jumping on top of us, to again slowly fall behind, etc.

I keep shooting my gun at it, but it still keeps coming…

Mark

[wrwakefield]

Originally Posted by farm sail

Wait a minute you leave your radar, and your AIS on but you turn off your VHF while at anchor??? what benefits does that give you?

Hi Farm,

My original statement was "...when we are sleeping at anchor..."

In a quiet anchorage where no anchor watch is required the VHF is turned off when we go to bed because, although we are usually boating in some pretty remote areas, there is enough radio traffic- especially during the summer season- that we would not be able to sleep without interruption.

The AIS is left on for 2 main reasons, one of which I cited an example of:

1- An additional method to alert other vessels of our position
2- The AIS has a great anchor alarm
3- Quick 'eyes' on other AIS targets if awakened by something
Note: It only consumes a measured ~.2A or so when it is on...

The 4G radar is often on [depending upon circumstances] when we sleep to take advantage of the programmable Guard Zone function and so we have instant 'eyes' if awakened by anything. [Note I can view/control the MFD screen on my smart phone for a quick peek without getting out of my berth, silence the alarm, and go back to sleep if the cause is innocuous. e.g., another boat coming or going at a safe distance and speed, or like one night when we drifted close enough to a large crab pot buoy to set off the alarm...]

The most simple Guard Zone is a circle around the boat of a desired radius [say 200ft for the sake of discussion] If anything enters that circle [other vessels, we drift too close to land, etc.] the MFD sets off an alarm. This was the case in my story about the barge...

As an aside, we can also program a portion of a circle as a guard zone which we might do when there is a shore line downwind of us.

The radar also is pretty low draw at around 1 amp.

Those two electronic helpers, along with depth alarms, additional anchor drag alarms, excellent ground tackle, low level night lighting on deck for other vessels to see, bilge, smoke, propane and CO alarms, etc... all contribute to our comfort and relaxation affording us a great night's rest [or not when they go off!]

For perspective, 80+% of the time we are the only boat in the anchorage... That percentage will increase in the fall and winter seasons...

I hope this helps. Thanks for your question.

Cheers!

Bill

[wrwakefield]

Originally Posted by wrwakefield

I'm sorry to hear about your friend's ordeal.

It is important to be prudent about broadcasting one's location via AIS or other means. Fortunately AIS transmission can be turned off when appropriate.

As more AIS capable satellites are launched, this will likely become an even more pervasive issue, similar to voluntarily publishing one's current coordinates to a publicly accessible online source... [Where are we?]

Thankfully these kind of bad guys aren't something we have had to worry about [to date] in higher latitudes...

No one should ever come here anyway... boating is miserable, and its always cold and dark... really...

Bill

On the lighter side, it might be fun to play with pirates by changing one's AIS data to read something like "USS Nimitz, 1123 ft long, 140 ft beam, 34 ft draft, aircraft carrier" etc...

[Robin3]

Originally Posted by wrwakefield

On the lighter side, it might be fun to play with pirates by changing one's AIS data to read something like "USS Nimitz, 1123 ft long, 140 ft beam, 34 ft draft, aircraft carrier" etc...

Which I guess is why they made it near impossible for Cap'n Joe Average to do so, as in I believe, allowing the MMSI number to be inserted only one time and needing a master reset or more to remove or change it..


Of course even the dumbest pirate might just guess that Nimitz could not really be at anchor in that 10ft deep bay and just 25yds off the beach.

[colemj]

Originally Posted by Robin3

Which I guess is why they made it near impossible for Cap'n Joe Average to do so, as in I believe, allowing the MMSI number to be inserted only one time and needing a master reset or more to remove or change it..


Of course even the dumbest pirate might just guess that Nimitz could not really be at anchor in that 10ft deep bay and just 25yds off the beach.

The MMSI is not user-programmable, but the boat information, like name, beam, size, draft, type, etc is.

Mark

[Robin3]

Originally Posted by colemj

The MMSI is not user-programmable, but the boat information, like name, beam, size, draft, type, etc is.

Mark

BUt not on the display screen menus s it? maybe with a computer connected and the setup software but on mine I don't think I could do it easily or quickly, but I'm an old numpty and possible one of the grandkiddos could do it blindfold!

[colemj]

I don't know about yours. On our black box transponder (no display), I can easily do it wirelessly with an iPad or computer. Since these devices are also our display, the data field are right there in the program.

Mark

[Robin3]

Originally Posted by colemj

I don't know about yours. On our black box transponder (no display), I can easily do it wirelessly with an iPad or computer. Since these devices are also our display, the data field are right there in the program.

Mark

Ours is a Garmin AIS 600 black box with a display on the NMEA 2000 network 10" garmin MFD AFAIK it can only be accessed physically via a USB connection to the black box, which is itself hidden behind a panel at the chart table. No matter really, just idle curiosity.

[tanglewood]

Originally Posted by colemj

Yes, this will definitely work. We also have an AIS receiver on board that is smart enough to ignore ownship MMSI, but dumb enough to continue to send its signal to the MFD.

When that data feed is chosen, it looks like a ghost ship slowly falling behind us over 30 seconds and suddenly jumping on top of us, to again slowly fall behind, etc.

I keep shooting my gun at it, but it still keeps coming…

Mark

Yup, this is a huge hole in the NMEA specs for AIS. There is no standard for who filters out own-ship AIS reports, so everyone does it a little bit differently. Sometimes it works, but other times you are constantly crashing into yourself.

[DotDun]

Originally Posted by tanglewood

Yup, this is a huge hole in the NMEA specs for AIS. There is no standard for who filters out own-ship AIS reports, so everyone does it a little bit differently. Sometimes it works, but other times you are constantly crashing into yourself.

Or maybe the standards never considered that one would run both a transceiver and a receiver.

Is there a reason to run 2 receivers at the same time??

[colemj]

Is redundancy a bad thing with AIS, but not with GPS, VHF, etc? In our case, the AIS receiver is internal to the VHF. Since this was already wired to the chart plotter for DSC, the AIS input was already along for the ride. With the ghost ship problem from that receiver picking up the output of the transponder (even though they share the same antenna and the receive is shut down during transmit), I was forced to pull another set of nmea wires to the plotter for the transponder.

It would have been great if the plotter was smart enough to ignore own ship mmsi. Even better if the VHF didn't send out own ship data over nmea - it is smart enough to ignore it on its own display, but too dumb to not send it out to others.

Mark