AIS Question

[Lodesman]

Originally Posted by bewitched

using an example:

bad visability (lashing with rain at night)
no visual contact
I am travelling west to east
From AIS I see a power driven vessel traveling south to north

If I am sailing I am the stand on vessel, if I am motoring, he is the stand on vessel.

Rule 18 does not apply in restricted vis.

[bewitched]

Originally Posted by Lodesman

Rule 18 does not apply in restricted vis.

OK now i'm curious - why doesn't rule 18 apply in restricted vis?

[Lodesman]

Rule 18 is in section II - conduct of vessels in sight of one another. Section III - conduct of vessels in restricted vis consists of Rule 19 - there is no distinction between vessels that can't see each other.

[Paul Elliott]

There are some significant differences between Class-A and Class-B transponders.

Class-A units transmit quite a bit of Static data, some of which is never changed:Vessel name, callsign, dimensions, etc. Other Static data is supposed to be updated when appropriate: Ship Type and Cargo (combined in a single field), Destination, ETA.

For Class-A, the "Navigation Status" field is contained in the Dynamic position report. This is hand-entered, and often incorrectly.

Class-B units do not transmit any sort of Navigation Status, and there is no data in the Static report that is supposed to be changed. There is the "Shiptype/Cargo" field, but this is definitely not the same as "Navigation Status"

On a practical level, the software provided by the Class-B vendors is obvioulsy not designed for everyday use.

The Class-A "Navigation Status" includes values for "Under Way using Engine", "At Anchor", "Engaged in Fishing", and "Under Way Sailing", among others. I submit that if Class-B users were expected to provide this data, we would have been given a way to do so. Class-B doesn't have a NavStat message, so I think we're off the hook.

So what do we all do in a crossing situation when presented with this ambiguous/incorrect information? I suggest we do what we did before AIS was invented.

[edsailing]

Best bit of navigational kit I have come across is my eyes............. other aids only alert me to what to look out for!

[bewitched]

Originally Posted by Lodesman

Rule 18 is in section II - conduct of vessels in sight of one another. Section III - conduct of vessels in restricted vis consists of Rule 19 - there is no distinction between vessels that can't see each other.

I think I may have learned something!!.....

.....actually, to be quite honest, I can't get my head round it......

rule 19 applies in bad vis, until you can see each other, then rule 18 kicks in??

[btrayfors]

Just turn the damned thing OFF, and use your eyes, your senses, and your brain.

Geez....whatever did sailors do to avoid collision before AIS?

Sometimes I think all these "modern navigational tools" just make us plain stupid.

Bill

[donradcliffe]

I asked the same question on a different forum as soon as I read the manual on my AIS B transponder. The lack of dynamic status information on sailing vs under power is a definite shortcoming of the Class B AIS, and hopefully may get changed in the future after a few people have been killed and lawsuits filed. All we can do at this time is to use the static definition of a sailing vessel and publicize the shortcomings so that the ships and authorities understand we can't change it.

[Paul Elliott]

Originally Posted by btrayfors

Just turn the damned thing OFF, and use your eyes, your senses, and your brain.

Geez....whatever did sailors do to avoid collision before AIS?

Sometimes I think all these "modern navigational tools" just make us plain stupid.

Bill

Bill, I think you are being unnecessarily harsh. Nobody is suggesting that we ignore our eyes, ears, the rules of the road, and common sense. The question had to do with the appropriate configuration of a piece of gear.

It's kind of like wanting to know which running lights should be turned on when under power on your sailboat, and wondering what do to do if you see somebody else with what you suspect may be incorrect lights. So what do we do? We use the best information we have and sail with care. And make sure that, for our part, we are showing the proper lights.

I doubt that anybody here thinks that AIS (or radar, or running lights) will eliminate the need to be prudent.

But you knew that...

[rustypirate]

This difference between A and B AIS systems is exactly why I have an AIS A system on my boat.

BTW I don't use mine to keep watch for other boats, but rather to make others around me aware of my presence. The more visible I am to others the better, regardless of how good a lookout I keep.

Remember that the Titanic kept a 24/7 lookout, but that did not prevent them from striking that iceberg.

[btrayfors]

Paul,

Maybe you're right, but maybe not. I've seen/heard too many stories of "sailors" who -- enthalled, mesmerized, captivated, seduced by all the wonderful new technologies -- just throw common sense to the wind. Along with their (possibly underdeveloped or undeveloped) navigational skills.

The almost mystical properties some folks attach to GPS and, most recently, to AIS just leaves an old navigator scratching his head in wonder.

Don't forget, folks, AIS isn't synoptic, i.e., it doesn't show you everything out there that you're likely to bump into or is likely to bump into you. Radar does, though, so if you're going to go all ga ga about something, make it radar first.

Scenario: you're under sail on the port tack, making 7 knots. A big blip on the radar shows an (unknown) vessel approaching fast from your port side, on a possible collision course. Geez. What to do? Consult the AIS to find out who he is and try to call him on the VHF? After all, you're the "stand-on vessel". He's gotta give way to a sailboat, especially one on his starboard bow.

ARE YOU CRAZY? Why not just alter course 5 degrees to port and pass behind him?

Whew....couldn't done that without AIS!

JMO,

Bill

[btrayfors]

Originally Posted by rustypirate

.....

Remember that the Titanic kept a 24/7 lookout, but that did not prevent them from striking that iceberg.

Yeah, but remember, too, that the Captain was dumb enough to take direction from the ship's owners/managers who wanted to set a record...to the detriment of his own navigational skills, experience, and good judgment.

B.

[Paul Elliott]

Originally Posted by btrayfors

Scenario: you're under sail on the port tack, making 7 knots. A big blip on the radar shows an (unknown) vessel approaching fast from your port side, on a possible collision course. Geez. What to do? Consult the AIS to find out who he is and try to call him on the VHF? After all, you're the "stand-on vessel". He's gotta give way to a sailboat, especially one on his starboard bow.

ARE YOU CRAZY? Why not just alter course 5 degrees to port and pass behind him?

Whew....couldn't done that without AIS!

JMO,

Bill

And altering course is exactly what we do, unless there's a darn good reason to do otherwise. With AIS, we usually learn of this approaching ship long before it becomes a solid blip on the radar, or more than a tiny spec on the horizon, and we can start our maneuver that much earlier.

I think the bottom line is that stupid or inexperienced people will do dangerous things, with or without the fancy gadgets. Lack of experience can be cured. People, if you have AIS, practice using it! Learn what it can and can't do. Learn to make it a part of your kit.

Using AIS to let other vessels know of your presence is good manners, but not a guarantee that they will be paying attention. I know, that goes without saying.

There. I think we essentially agree.

[Lodesman]

Originally Posted by bewitched

I think I may have learned something!!.....

.....actually, to be quite honest, I can't get my head round it......

rule 19 applies in bad vis, until you can see each other, then rule 18 kicks in??

Yeah, that's pretty much how it is. I also learned something from this thread - about the limitations of class B AIS. That's why I like CF.

[Lodesman]

Originally Posted by btrayfors

Scenario: you're under sail on the port tack, making 7 knots. A big blip on the radar shows an (unknown) vessel approaching fast from your port side, on a possible collision course. Geez. What to do? Consult the AIS to find out who he is and try to call him on the VHF? After all, you're the "stand-on vessel". He's gotta give way to a sailboat, especially one on his starboard bow.

ARE YOU CRAZY? Why not just alter course 5 degrees to port and pass behind him?

There's a valid reason that power-driven vessels are advised against altering to port to avoid a vessel on their own port sides - this would also be valid applied to sailing vessels altering for power-driven vessels on their own port sides.