Bosun Higgs
N/A
Dodgy idea the captain has. What about the grey funnel line not to mention small fishing boats without an AIS and large fishing boats with it turned off because they arent where they should be?
AIS transponder. Now you need it?
- Thread starter NPMR
- Start date
Dodgy idea the captain has. What about the grey funnel line not to mention small fishing boats without an AIS and large fishing boats with it turned off because they arent where they should be?
tcm
...
yep, there are two sorts of things out there
1 Things that look like ships (i.e have got AIB B or A)
2 Thing that look like bit of junk in the sea (floating wood, anything with no AIS)
1 Things that look like ships (i.e have got AIB B or A)
2 Thing that look like bit of junk in the sea (floating wood, anything with no AIS)
MM5AHO
Well-known member
I have two AIS-like devices on board. They scan the sea and are able to tell the size and direction of travel, approximate speed, type of vessel, and their computer device can calculate to some accuracy the likelihood of collision.
They don't work well in reduced visibility, and are subject to distraction at times, and can be influenced by chemicals. They also sometimes make errors of calculation, but they are free, consume so little power that I can't measure it, and I don't need to install a special viewing screen.
I understand that this type of "AIS" has been in use for many centuries, and while not foolproof, they seem quite adequate for my use.
They don't work well in reduced visibility, and are subject to distraction at times, and can be influenced by chemicals. They also sometimes make errors of calculation, but they are free, consume so little power that I can't measure it, and I don't need to install a special viewing screen.
I understand that this type of "AIS" has been in use for many centuries, and while not foolproof, they seem quite adequate for my use.
sailorman
Well-known member
rich
Well-known member
Crossing the channel on a mates boat with AIS, he was worrying about ships we could not even see on a clear day! some were going in the other direction to what it said on the screen.
maxi77
Active member
I must admit I have never seen a ship going in the opposite direction to it's AIS info. Like all aids you have to apply some intelligence to the data presented. One of the main problems is that the filtering the operator can apply to the data in most implementations is very limited.
In general though I find it an excellent aid especially in more complex situations
Conachair
Guest
Going the other direction? Are you sure about that? Sounds very unlikely.
One of the best things ablout AIS i think is almost instantly being able to stop worrying about ships as you can see they aren't coming anywhere near you.
Echo others about transmitting, onshore anyway. Better to look after yourself rather than expect someone else to change course to miss you.
oldvarnish
Active member
I think an AIS RECEIVER is one of the greatest advances in small boat safety since the invention of satellite navigation.
To get the best out of it, you carefully observe any ships which may be a threat to you, and get the hell out of the way. No TRANSMITTER needed.
As for the vessels which do not have AIS, such as small fishing boats, your two eyes remain the safest option. In fog, use your ears. It's a tried and tested system.
To get the best out of it, you carefully observe any ships which may be a threat to you, and get the hell out of the way. No TRANSMITTER needed.
As for the vessels which do not have AIS, such as small fishing boats, your two eyes remain the safest option. In fog, use your ears. It's a tried and tested system.
ChrisE
Active member
I don't agree re ears in fog, in my scariest moment in a peasouper, I sailed right under the bows of a large ship in the channel who wasn't sounding his horn, I was unaware of the ship until we saw a large red 'wall' about 50m behind us. Without radar I won't cross the channel.
Regarding AIS transmitters you are then relying upon others to be aware of you. With radar you know who or what is out there and can make your own mind up as to what to do about it.
NPMR
Well-known member
We have an ais receiver and crossing the Channel a couple of times this summer it was brilliant to be able to see the data offered and therefore which ships presented a 'problem' to take note of. The others, which to the eye still needed to be watched, showed clearly as not a threat on the screen. There was, as a result, a very significant decrease in tension in the process. Knowing you only have to take action for a few of the ships made it much easier, so I too feel it is a wonderful piece of add-on security.
My thoughts are, that as we are small, quite probably invisible on the radars, perhaps the transponders will alert the ships to our presence, especially as down here in the 'west' they are beginning to exit the lanes as they head off into the Atlantic, I'm not convinced that watchkeeping is of the highest standards.
We have had to call up ships on VHF a couple of times and not had responses; not conclusive but not reassuring either.
We don't have the budget for radar (or maybe even the reserve electrical power) so we have to compromise somewhere. Maybe a 'see-me' type device for radar would help but as the cost is not dissimilar to a transponder, perhaps we're better with the AIS system?
Twister_Ken
Well-known member
BrianH
Active member
I too, in six years of AIS receiver use, have never seen a ship going in any direction other than that shown in it's AIS info. The only anomalies have been in the manually entered, static data such as 'moored' while charging along at 20 kts.
+1. I now consider it a prime assistance tool that I run in OpenCPN on a netbook PC on the chart table below, occasionally consulting it, especially when a potentially close encounter is indicated. I once posted an example of such a situation (when using OziExplorer running on a Dell Inspiron) here.
I had thought that the Luddites had at last given up with AIS as so many have tried it and been won over. However, from this thread, it seems that they are still alive and well.
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Wandering Star
Well-known member
westernman
Well-known member
Also the destination port often does not get updated. This might be what he was meaning about ships going in the opposite direction.
nigel1
Active member
A question for those with a Class B AIS transponder. I am intending to fit a Raymarine unit (as I already have the Raymarine plotter). With a Class B transponder, is it possible to change your own vessels Navigation Status, i.e. can you select Moored, Underway using Engine, Sailing vessel etc.
This can be done with Class A, but with units such as the Raymarine one, there seems little user interface, unless you hook it up to a PC.
This can be done with Class A, but with units such as the Raymarine one, there seems little user interface, unless you hook it up to a PC.
BrianH
Active member
Class B static data (message 24) is not so extensive as Class A and should not need any updating as it consists only of:
MMSI, boat name, ship type, call sign, dimensions, and equipment vendor id.
webcraft
Well-known member
On Mojomo we could see our own AIS B data and in addition to the above it always said 'Under Engine' - thereby making it a bit useless from a colregs POV as we were under sail most of the time.
Also - could people with transponders please switch the bloody things off when they are tied up? Howth marina was full of 'dangerous targets' when I went in there in August.
- W
onesea
Well-known member
At the risk of opening up a hole new can of worms... and applying some grey but I think sensible logic.
YES AND NO!
Depends so much on each situation. You must follow the rules once risk of collision is deemed to exist.
Many a time I have tweak my course "for a wind-shift" lets say in a situation where risk of collision MAY exist. If this will keep me out of other vessels way, better than to head full speed into a situation where risk of collision WILL exist.
Frequent example in Solent, I am reaching on Starboard tack and I see risk of collision MAY develop with a vessel beating on a port tack... It normally will costs me very little to bear off a bit more show him I will go behind him and not force him to make a big alteration.
If I stand on he will have to make large alteration of course or tack, if he does not I will be forced into a crash tack (at the risk of spilling by beer). Personally I would bear off a bit before risk of collision (or beer spillage) existed.
I do not want to start a argument about the rules I am sure they have been hammered more than once on here... I am just giving an opinion that I feel has some weight...
Oh and as for AIS when I get that far yes transmitting in open waters, but turn it off in Coastal waters. Then when Transmitting The above might not apply so well
as you would have to put more weight to the argument they had seen you and had a better assessed of risk of collision.Either way fire suit standing by
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onesea
Well-known member
Not uncommon, presently seen a rig that is "underway using engine" yet is anchored on 8 point moor and does not have its own propulsion.
Many a ship I have seen passing "Making way under-sail" without a stitch of canvas to be seen
User entered data all prone to error..
Or is it like fishermen who never take there day shapes down....
BrianH
Active member
Ah yes, of course, that must be the answer. One can never depend on the static data as someone on the bridge has to manually enter it. Its importance is measured by its frequency of transmission - only every six minutes.
However, all the dynamic data is automatically processed and output from the GPS and other active sensors and transmitted at intervals depending on the manoeuvring conditions, with only a few seconds between messages.