Bavaria Yacht Info
Member Forums => Modifications & Equipment => Topic started by: solar on January 25 2014, 10:49
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I want to add AIS on my 2008 38" Cruiser.
I got a Raymarine RC435i plotter and a Raymarine RAY54E VHF radio.
At the Dusseldorf boat show I was told at the Raymarine stand that my present plotter won't take&show AIS info and that I'll need to buy a newer plotter model.
Since my plotter is very common on BAV boats and works great,I would like to learn about more options to get AIS then just buying a new one...
Anyone did that? how? where?costs?
Thank you.
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If your chart plotter won't take the AIS then there are only two alternatives - a new plotter or a stand alone display such as the NASA unit. The new plotter could, if you just want it at the chart table, be a PC based charting system or a tablet. However, many people like the display at the helm, and a dedicated plotter is better for that. It really depends on your style of navigation and pilotage which is better for you.
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Found this from Raymarine on a US forum:
"Unfortunately, it is not possible to change the software in RC435, as this product did not feature the processing power and 38400 BAUD communications circuitry required to support communications with an AIS receiver/transceiver. The RC435/435i GPS Chartplotters were retired several years ago, and as such no further updates for this product will be forthcoming. Should AIS/chartplotter integration be required, then it is recommended that the RC435 be replaced with an A65 Multifunction Display which has a screen size approximating that of the RC435."
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Thanks.
Anyone have the NASA AIS installed on board? Opinion?
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Yes. Have had both stand alone display and an AIS engine linked to a PC. Stand alone is OK, but takes a bit of time to get used to the way it is displayed and it does not link to anything else. Having AIS linked to the chart plotter greatly increases its value as shows the data in real time on your chart.
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Important info.Thank you.
It looks like a new plotter is on the wish list...
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If you have ambitious sailing plans I would highly recommend getting an AIS transponder despite the higher cost. The comfort of 'seeing and being seen' are worth it!
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Thanks,yes. I'll do just that soon.
New plotter
AIS receiver
Splitter
New Navionics maps
Hummm...cheap hobby...
:)
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Ive just bought a Standard Horizon Gx2100 dsc radio with AIS , to link up with Standard Horizon CP300 plotter I allready have , apparantly supposed to work really well , standard horizon service and kit very good too, including price . Found that the VHF will slide into existing face mount for Simrad RD 68 that was fitted .
once you spot a ship you can then select it and call directly ,without entering mmsi numbers etc .
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Thanks ,but AIS in VHF radio deep down at my nav table won't help me at the helm where it's most needed...
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dont recollect saying plotter is at chart table , however one is :) , also have one at helm which can show ais info if I wire it in too , also the remote command mike can display same information .
Pain in the @rse joining up fiddly fragile data cables , took longer than anything else . now I find main aerial not so good , but tested with emergency aerial and very impressed .
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I recently purchased an iCom MA500tr AIS transponder to fit on my 2002 Bavaria 36, and have not yet completed the installation.
There are several parameters which I wish I'd thought about a bit more before buying the instrument, though the problems are not insurmountable. The first is that the instrument should not be placed within one meter of the compass. Next is that two antennae are needed, one to receive GPS position and the other to transmit your data for the benefit of other vessels around. These two aerials should not be placed within three meters of each other, and the transmitting aerial should also not be placed within three meters horizontally from any human and not within one meter vertically above their head.
On a sailing vessel this more or less rules out having the display being located anywhere where it can usefully be seen from the wheel, while the requirements for the aerials has meant buying an active aerial splitter £200 (ish) in order to be able to share the use the main VHF radio on top of the mast for the AIS transmissions. Using the mast top transmitting aerial gets over the safety issues as far as radio transmissions are concerned. As for seeing the display from the wheel, it looks like I'll have to upgrade my chart plotter to something new enough to accept the output from the icom unit.
As for where to fit the display, I've now opted to fit it inside the main cabin and recessed into a panel. The problem here is that the fittings supplied for flush mounting the unit are not able to accommodate the thickness of the plywood that Bavaria panels are made from, so the fittings are having to be modified.
I have an elderly Raymarine C70 chart plotter which is a very reliable instrument, but it will have to be changed if I want to see the AIS information from other vessels displayed near to the wheel. That will be another £600 or more plus the new SeatalkNG backbone and a few converters to allow my other Raymarine instruments to all talk to each other. I'm beginning to wish I'd kept my money in my pocket instead of splashing out on that AIS !!!
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Quick reply for the moment. Your C70 should be able to display AIS with the latest software.
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The two antennae for AIS are a) a GPS receiving antenna, usually mushroom shaped and usually included with the AIS unit, and b) a sending VHF antenna, usually not included. The AIS module can be mounted remotely from the displaying plotter, usually below deck. Addition of AIS functionality to an existing plotter mounted near the helm should not affect or be affected by the compass. The GPS mushroomcan be mounted almost anywhere but should have clear view of satellites. Some installations user a splitter for the existing VHF antenna. These are not too expensive but sometimes don't work well. A separate VHF antenna tuned for AIS is best. This antenna should not be located right beside the radio VHF antenna-a good option is to mount the AIS antenna on the rail with the radio unit at the masthead. There shouldn't be a concern with proximity to either the plotter display or the helmsman's head. This is a problem with radar. Radar antennae should located well above people! Rail mounting of the AIS VHF antenna does not cause problems with reduced range because there is little need to see or be seen by vessels further than 15-20 miles away. Further range just adds clutter. I strongly recommend a receive and send AIS transponder rather than receive only.
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Ref Moodymike.
Thanks for the feedback, I'll check again, but so far all the information I've seen and heard had pointed against being able to have AIS information displayed on my C70 plotter.
Ref ROBGS.
I think your reply has helped to highlight the difficulties that I had not been aware of prior to purchasing the Icom MA500tr AIS transponder. For those not familiar with this unit, it has its own built in display which coupled with my own chart plotter being unable to display AIS information was the reason for buying the Icom unit.
Firstly, the separation distances I quoted were those stated within the Icom user manual. The AIS splitter I purchased is a Raymarine active splitter unit which I anticipate will work properly as designed, or it will go back to them for a refund if it does not do exactly what they say it will do.
You say that a VHF antenna tuned for AIS is best, and I have no reason to doubt that, but you then say to mount that antenna on a rail. The question here is which rail do you have in mind ?? Remember it should be at least three metres away from humans (according to Icom), so in order not to turn the majority of the cockpit area into a No Go zone for humans, where exactly did you have in mind to place that aerial???? I can understand the difficulties in perceiving the dangers from radio transmissions when most people are quite happy to use a hand held VHF radio with the transmitting aerial right next to their head, but it is very unlikely that you are using that hand held unit to transmit every thirty seconds or so. Occasionally I have young children on my boat, and I'm not planning to fry them just yet!!
As for the distance that the Icom unit should be placed away from the compass, again this is Icom's recommendation, and I can only assume that something within the unit is likely to cause compass deviation.
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Just a quick update, the AIS installation was completed early in May, as described with the transponder being located within the panel above the chart desk. A Raymarine antenna splitter allows the mast head aerial to be used both for VHF transmissions and for AIS transmissions, and has worked so far with the kind of solid reliability and robustness that goes with the Raymarine name. Regarding connection to the chart plotter, I had described my plotter as a C70 when in fact it was an RL70C, different beast but still solidly reliable. Unfortunately I don't think it will ever be capable of displaying AIS information and will therefore need to be upgraded to a later model along with fitting Raymarine's SeatalkNG communication system. Apart from that and the fact that for the time being I cannot see the AIS display from the wheel it all works exactly as it should, and is very handy for checking on where your colleagues are when sailing in company. The upgrade on the display will come next winter. The GPS aerial for the AIS transponder was fitted to the starboard pushpit handrail with the lead being taken through a waterproof gland, then down through the steering flat and under the starboard quarter cabin bunk to the area below the main switch panel, then up to the enclosure above the chart desk to where the transponder is fitted.
The result is that my boat can now be seen by others fitted with AIS as can be seen from the photo below courtesy of MarineTraffic.
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The result is that my boat can now be seen by others fitted with AIS as can be seen from the photo below courtesy of MarineTraffic.
You'll be seen by other yachts, but most ships filter out Class B AIS transmissions, due to clutter caused by the proliferation of leisure AIS transponders. If you want to be seen by ships, an active radar transponder (Sea-Me, etc) is the answer, and much better value.
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The result is that my boat can now be seen by others fitted with AIS as can be seen from the photo below courtesy of MarineTraffic.
You'll be seen by other yachts, but most ships filter out Class B AIS transmissions, due to clutter caused by the proliferation of leisure AIS transponders. If you want to be seen by ships, an active radar transponder (Sea-Me, etc) is the answer, and much better value.
Unfortunately the suggestion that Class B transmissions can be filtered out is nothing more than a frequently touted myth.
In the first place the design specifications for both Class A and Class B AIS systems are that they will work properly alongside of each other,
Secondly the Colregs state "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 situation and of the risk of collision."
So filtering out information provided by an AIS system would be contrary to those regulations, and I for one would not want to be stood at a court of enquiry having to answer the inevitable question of why it was that I (if it were possible) had filtered out the signal from a vessel I had just run down resulting in the deaths of all onboard that vessel. I have attended a court of enquiry, fortunately I was employed by one of the lawyers as an expert witness, and I am very acutely aware of just how searching the courts questions were.
Thirdly as a ship surveyor during the period of introduction of AIS up until very recently when I retired, there were no such filtering systems fitted to any of the multitude of different AIS instruments on any of the last several hundreds of ships that I visited,
And fourthly if such a system had been fitted, for sure one of the questions that would have been included in the questionnaire that I carried onboard each vessel I visited would have asked whether the ships officers were aware of the system, whether they were familiar with its use, and particularly with the limitations that such systems use would have upon their ability to detect a vessel whose transmissions had been filtered out.
So I'm afraid that myth is nothing more than a myth put about by persons who are not familiar either with the systems or with the legally mandated requirements for how they should work.
Possibly part of the confusion is that on the more recent installations, the output from the receive side of the AIS instrument is required to be connected to the ship's radar display. Within the radar display there is a an anti-clutter facility to enable the user to tune the radar to minimise the returning radar signals from reflections from the waves and swell conditions. The user manuals for the radar recommend that whenever the anti clutter control is used that periodically the user should adjust the control up and down to ensure that targets are not lost in the clutter, neither is the control set so high that target returns rather than clutter are filtered out. That control however will not filter out the AIS signal from either Class A or Class B transmissions as they are not reflected radar signals, but are a received VHF radio signal that has been put into the radar set from the vessels AIS receiver, and which has been amplified in order for it to show clearly on the screen of that radar.
Lastly any system that helps other vessels to know of my presence and which helps me to know of their presence before either of us sees the other, is of benefit to us both and helps us to comply with the COLREG mentioned above.
The use as you suggest of a radar transponder will also help, but as I do not have radar on my boat yet, it would not tell me of the other vessels presence. Lastly as AIS is currently not a mandatory fitment for all vessels there will of course be some that don't have it, and for those vessels the last resort is to keep a proper lookout as described above, and keeping in mind at all times that they too might not have radar either.
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Shipping will receive all Class A and Class B transmissions, but this may well be on a small read-out display. AIS overlays on the latest radars can, I understand, suppress Class B data when required to reduce screen clutter.
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The result is that my boat can now be seen by others fitted with AIS as can be seen from the photo below courtesy of MarineTraffic.
You'll be seen by other yachts, but most ships filter out Class B AIS transmissions, due to clutter caused by the proliferation of leisure AIS transponders. If you want to be seen by ships, an active radar transponder (Sea-Me, etc) is the answer, and much better value.
Salty: I'm not sure where you are getting this (mis)information; I am a foreign going master and use various top-end IMO approved AIS systems, and not one that I have ever used has a filter option for such things. IMO would not allow this feature.
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The result is that my boat can now be seen by others fitted with AIS as can be seen from the photo below courtesy of MarineTraffic.
You'll be seen by other yachts, but most ships filter out Class B AIS transmissions, due to clutter caused by the proliferation of leisure AIS transponders. If you want to be seen by ships, an active radar transponder (Sea-Me, etc) is the answer, and much better value.
Salty: I'm not sure where you are getting this (mis)information; I am a foreign going master and use various top-end IMO approved AIS systems, and not one that I have ever used has a filter option for such things. IMO would not allow this feature.
It wasn't Salty, it was me - and it's not misinformation. Read this RYA summary if you don't believe me - http://www.rya.org.uk/cruising/Pages/AIStransmissionsfromsmallcraft.aspx
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Ref Maritimo and his posting on Oct 6 2014.
I too am a qualified but recently retired Foreign Going Master Mariner, also I have extensive and very recent experience working as both OCIMF and CDI accredited ship inspector. I have to thank Tiger79 for the matter that he has raised, and I agree that there does seem to be an issue here which seems to be at odds with all that SOLAS and the IMO have strived to put in place. However, I also agree fully with the comment made in the RYA article that he referred to, in which they note that no one system will ensure that one vessel is seen by another, although the writer did come down in favour of AIS. I too would still prefer AIS rather than a radar transponder, as it does identify clearly the name and other details of each AIS equipped vessel, thereby allowing vessels to communicate with each other in order to determine what course of action they intend in order to avoid collision.
I have already raised the matter of filtering with former colleagues who continue to work for OCIMF and CDI (for the benefit of those not familiar these are the Oil Companies International Marine Forum and the Chemical Distribution Institute). My colleagues will take the matter up with those institutions in order that they decide whether ships should have a procedure in place in regard to the use of such filtering systems, and where that decision is extremely likely to result in amendments to the inspection regimes. I feel fairly sure that in consequence this matter will also be raised with IMO and SOLAS, and from there it should be passed on to vessels outside of the tanker industry.
Maritimo's comment however is also very valid as the vast majority of existing ships will not have facilities onboard which would allow filtering of AIS signals, where it appears this is a relatively recent change fitted to only the latest Radar systems. Existing ships do not normally change their radar unless they have a problem with them that is not easily resolved. So let's wait and see what happens.
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Salty,
Thanks for your informative comments. Could you also clarify the issue that whereas ships over 300 tons (and all passanger ships regardless of size) are legally bound to carry AIS, I understand they are not legally obliged to have it switched on?
I have, over the past couple of years, had occurances where vessels not were not transmitting class A/B and therefore not visible on my plotter. These instances occurred whilst other vessels around them were 'visible' to me and further complicated my decisions on how to cross shipping lanes safely and without hindering other traffic.
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Hi Dawntreader,
The following is a copy of the IMO regulation, and from it you will see that ships are required to have the system in use at all times except in situations where ship security is at risk. Unfortunately we live in troubled times, and an AIS signal for example, would be a homing signal for the likes of Pirates operating off the Horn of Africa. In such circumstances ships are permitted to turn off their AIS, but if they did, as an OCIMF or CDI ship inspector, I would expect to see a log book entry clearly stating why the system had been turned off, and in the absence of such entry the ship concerned would have an observation raised which while having no legal standing would severely hamper the vessels ability to trade. It would also be seen by Port State Control Inspectors who have the legal right to detain the ship until they are satisfied that the regulations are being followed. Such detention would also have a detrimental effect on the vessels ability to trade.
A further situation also needs to be taken into account and that is in regard to vessels carrying flammable cargoes such as oil, gas and chemical tankers where the output power of any transmitter onboard was required to be below 1 watt (it might be 2 watts now), or it was to be switched off during all cargo operations. Those operations usually take place in port, but not always as ships often transfer cargo during a ship to ship transfer at some offshore location. Such operations happen very frequently. Most AIS class A transmitters that I am aware of transmit at 2 watts or more and would in the circumstances be switched off in order to prevent the possibility of incendive sparking. (Not a great thing to happen in places where flammable liquids and gasses are present).
Passenger and other ships periodically need to load fuel and gas oil (diesel fuel), and would be required to observe the same restrictions during the loading as tankers. People make mistakes and occasionally they might forget to switch on their AIS after such operation. That's not an excuse for not switching it on, just a reason.
Sometimes also the text message contained in regard to the vessels destination may not have been updated, such that occasionally you will see, for example, a ship where the text message says it is travelling towards a specific port, but where it's heading is clearly away from that port, and not just marking time while waiting for the tide or a pilot. So while not right, the information needs to be read with care and things like the actual direction of travel being taken into consideration.
The text of the IMO reg follows, I hope this helps:-
Radio Communications and Search and Rescue
Home » Our Work » Maritime Safety » Navigation » Automatic Identification Systems (AIS)
AIS transponders
Automatic identification systems (AISs) are designed to be capable of providing information about the ship to other ships and to coastal authorities automatically.
Regulations for carriage of AIS
Regulation 19 of SOLAS Chapter V - Carriage requirements for shipborne navigational systems and equipment - sets out navigational equipment to be carried on board ships, according to ship type. In 2000, IMO adopted a new requirement (as part of a revised new chapter V) for all ships to carry automatic identification systems (AISs) capable of providing information about the ship to other ships and to coastal authorities automatically.
The regulation requires AIS to be fitted aboard all ships of 300 gross tonnage and upwards engaged on international voyages, cargo ships of 500 gross tonnage and upwards not engaged on international voyages and all passenger ships irrespective of size. The requirement became effective for all ships by 31 December 2004.
Ships fitted with AIS shall maintain AIS in operation at all times except where international agreements, rules or standards provide for the protection of navigational information.
A flag State may exempt ships from carrying AISs when ships will be taken permanently out of service within two years after the implementation date. Performance standards for AIS were adopted in 1998.
The regulation requires that AIS shall:
provide information - including the ship's identity, type, position, course, speed, navigational status and other safety-related information - automatically to appropriately equipped shore stations, other ships and aircraft;
receive automatically such information from similarly fitted ships; · monitor and track ships;
exchange data with shore-based facilities.
The regulation applies to ships built on or after 1 July 2002 and to ships engaged on international voyages constructed before 1 July 2002, according to the following timetable:
passenger ships, not later than 1 July 2003;
tankers, not later than the first survey for safety equipment on or after 1 July 2003;
ships, other than passenger ships and tankers, of 50,000 gross tonnage and upwards, not later than 1 July 2004.
An amendment adopted by the Diplomatic Conference on Maritime Security in December 2002 states that, additionally, ships of 300 gross tonnage and upwards but less than 50,000 gross tonnage, are required to fit AIS not later than the first safety equipment survey after 1 July 2004 or by 31 December 2004, whichever occurs earlier. (The original regulation adopted in 2000 exempted these vessels.)
Maritime security - AIS ship data
At its79th session in December 2004, the Maritime Safety Committee (MSC) agreed that, in relation to the issue of freely available automatic information system (AIS)-generated ship data on the world-wide web, the publication on the world-wide web or elsewhere of AIS data transmitted by ships could be detrimental to the safety and security of ships and port facilities and was undermining the efforts of the Organization and its Member States to enhance the safety of navigation and security in the international maritime transport sector.
The Committee condemned the regrettable publication on the world-wide web, or elsewhere, of AIS data transmitted by ships and urged Member Governments, subject to the provisions of their national laws, to discourage those who make available AIS data to others for publication on the world-wide web, or elsewhere from doing so.
In addition, the Committee condemned those who irresponsibly publish AIS data transmitted by ships on the world-wide web, or elsewhere, particularly if they offer services to the shipping and port industries.
Further information
Resolution A.917(22) Guidelines for the onboard operational use of shipborne automatic identification systems (AIS) - available from your national maritime Administration or purchase Assembly resolutions from IMO Publications.
Resolution MSC.74(69) includes Recommendation on Performance Standards for Universal Automatic Identification System (AIS) available from your national maritime Administration
Related Documents
SN/Circ.227 Guidelines for the installation of a Shipborne Automatic Identification System (AIS) (197 KB)
Related Links
IMO Publications
So you will also see that this regulation does not allow for filtering of AIS a signals and hence the stances from my earlier posting as well as that from Maritimo, as filtering would clearly be contrary to the requirement of the regulation.
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Salty,
Thanks again for the extensive information on AIS. I have attached a screen copy taken from Raymarine's manual on the AIS500 (published in 2008) - this is where I saw the comment that there was no mandate to use AIS on 'larger commercial' vessels. ???
Regards,
Jim
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Bear in mind at all times that compliance with the rules might only mean that they have a rudimentary AIS display tucked away in the corner of the bridge. They don't have to look at it. And, most of the time, they have better things to do. The main issue today is with modern radar/plotters displays which have AIS display capability. That's when the Class B signals may be filtered out to avoid screen clutter.
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....and they may also give confused messages ;D
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Thanks Dawntreader, that is exactly the point !!
Further to previous comments, I've done a bit more digging on this subject, and would recommend readers to look at the "Specifications for Ships Radar Sets" as set out in a document drawn up by the Maritime Safety Committee, and is referred to as :-
Resolution MSC. 192(79) which was adopted on the 6th of December 2004 and which recommended Governments to ensure that Radar Equipment installed on or after the 1st of July 2008 conforms to performance standards not inferior to those set out in the annex to this resolution. The document is thirty two pages long, and I would recommend that all who have any concerns or doubts about the subject of filtering of AIS signals should read it. The following is a link to the document. www.imo.org/blast/blastDataHelper.asp?data_id=15568
It should be noted that although the standard was adopted in 2004, and recommended to Governments from July 2008, it is my understanding of the way these things work, that the relevant governments of the various countries would first have had to ratify the document and adopt it into the law of their respective countries. Once a certain percentage of countries all of which had ratified the resolution had been reached, it would then become international law. This would take a number of years to achieve, and could explain why there is so much misinformation at the present time regarding filtering of AIS signals and what it means.
It should also be noted that the so called "Annex" referred to in the resolution, is the essential part of the document and should not be considered as some apparent afterthought.
Whilst the whole of the document is of interest to seafarers, it is not until the reader gets to page 13, section 5.24 PRESENTATION OF TARGET INFORMATION that one reaches the area relevant to AIS.
At page 15 section 5.26, the reference to AIS filtering provides for only two possibilities, either the target is filtered to "sleeping" or it is "activated."
On page 16 at section 5.26.3 FILTERING OF AIS SLEEPING TARGETS, the document notes there should be a means to filter the presentation of AIS sleeping targets etc, but goes on to require, and I quote "IT SHOULD NOT BE POSSIBLE TO REMOVE INDIVIDUAL AIS TARGETS FROM THE DISPLAY." (For those not familiar with the use of the word "should," in a document such as this it means "must." i.e it must not be possible etc. Any manufacturer that tried to wheedle their way around that definition would find their equipment would not receive the all important "Wheel" mark seal of approval that is put on equipment that conforms to the required standard and the documentation that goes with it.
Page 22 Section 6.3.3 refers to radar manufacturers documentation which has to describe any factors that may affect detection performance, and it is required to describe the basis of AIS filter criteria.
Page 24 Section 7.6.1 states that the design should ensure that the radar is simple to operate by TRAINED USERS, and readers should note that there are strict requirements for ships officers to be trained in the use of new equipment, and with respect, this is more onerous than is required for many amateur yachtsmen and women !!
Lastly the meanings of terms contained within the Annex are explained in Appendix 2 where amongst other terms the meanings of activated AIS a targets and sleeping AIS targets are clearly described.
I trust the foregoing should now clear up any doubts regarding what actually happens when AIS targets are filtered, in that the targets are not removed from the display, they remain there until they go out of range, and are not hidden from view save only that the text included with an active target, is removed on the sleeping targets. Once the target enters the area that the operator is mainly concerned about, the target is automatically activated, and the text that was previously filtered now re-appears.
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Lots of words there, Salty, but you seem to have been rather selective in the bits you've quoted. In particular, there are various provisions which can clearly be used to filter out Class B targets.
In 5.26.1 it actually says "Reported targets provided by the AIS may be filtered according to user-defined parameters." This provides for filtering out Class B targets.
Then in 5.26.3 it says "To reduce display clutter, a means to filter the presentation of sleeping AIS targets should be provided, together with an indication of the filter status. (e.g. by target range, CPA/TCPA or AIS target class A/B, etc.)." This confirms that Class B targets may be subject to being filtered out.
Again, in 5.26.4 it says "In addition, sleeping AIS targets may be automatically activated when meeting user defined parameters (e.g. target range, CPA/TCPA or AIS target class A/B)." Once again, we're reminded that Class B targets may be filtered out.
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Lots of words there, Salty, but you seem to have been rather selective in the bits you've quoted. In particular, there are various provisions which can clearly be used to filter out Class B targets.
In 5.26.1 it actually says "Reported targets provided by the AIS may be filtered according to user-defined parameters." This provides for filtering out Class B targets.
Then in 5.26.3 it says "To reduce display clutter, a means to filter the presentation of sleeping AIS targets should be provided, together with an indication of the filter status. (e.g. by target range, CPA/TCPA or AIS target class A/B, etc.)." This confirms that Class B targets may be subject to being filtered out.
Again, in 5.26.4 it says "In addition, sleeping AIS targets may be automatically activated when meeting user defined parameters (e.g. target range, CPA/TCPA or AIS target class A/B)." Once again, we're reminded that Class B targets may be filtered out.
Far from being selective, I've referred the reader to the resolution in order that they can see its contents in its entirety, but I have tried to keep to the point by only including what are in my opinion the points that are relative. So to spell out those points in full for the benefit of Tiger79 who has also been selective, the sections of the annex to the resolution that he referred to read in full as follows:-
5.26.1 Reported targets provided by the AIS may be filtered according to user defined parameters. Targets may be SLEEPING, or may be ACTIVATED. Activated targets are treated in a similar way to radar tracked targets.
5.26.3 To reduce display clutter, a means to filter the presentation of sleeping AIS targets should be provided together with an indication of the filter status. (e.g. by target range, CPA/TCPA or AIS class A/B). IT SHOULD NOT BE POSSIBLE TO REMOVE INDIVIDUAL AIS TARGETS FROM THE DISPLAY.
And for good measure I'll include
5.26.4 A means to activate a sleeping AIS target and to deactivate an activated AIS target should be provided. If zones for the automatic activation of AIS targets are provided, they should be the same as for automatic radar target acquisition. In addition sleeping AIS targets may be automatically activated when meeting user defined parameters (e.g. target range, CPA/TCPA or AIS class A/B).
So what does that all mean, 5.26.1 talks of filtering by user defined parameters, and goes on to state that targets may be sleeping or activated. Sleeping or activated are the only choices available, and while the activated targets are treated in the same way as radar tracked targets, it does not say here what happens to sleeping targets where that is covered in 5.26.3.
5.26.3 talks about reducing display clutter, a means to filter the display of sleeping AIS targets along with the filter status (e.g. by target range, CPA/TCPA or AIS target class A/B)., but it also makes very clear (t79 please note) that IT SHOULD NOT BE POSSIBLE TO REMOVE INDIVIDUAL AIS TARGETS FROM THE DISPLAY. So, no matter how extensive the filtering is set, the target will remain displayed on the screen whether it be class A or class B. It's location on the screen will of course be determined by its geographical location, so no matter what the settings, if a class B target is getting closer it will be displayed closer until it crosses one of the other user defined parameters of Range, CPA/TCPA, and at which point it will then automatically become an activated target irrespective of whether it is class A or B.
This is further backed up by the wording in 5.26.4
Looking at the definitions which follow on at the end of the annex,
A Sleeping Target is defined as "A target indicating the presence and orientation of a vessel equipped with AIS in a certain location. The target is displayed by a sleeping target symbol. No additional information is presented until activated.
So keeping in mind that "IT SHOULD NOT BE POSSIBLE TO REMOVE INDIVIDUAL AIS TARGETS FROM THE DISPLAY" this means that no matter how much filtering has been applied, the target will show on the screen all the while it remains within discoverable range, but it's course, speed, destination and other blurb will not show until it becomes an activated target.
Activated Target - can I suggest that readers refer to the definitions contained within the resolution.
I'm sure by now it must be quite clear that while some filtering of AIS targets of whatever class is possible, they cannot be made to disappear off the radar screen by filtering alone. So Class B AIS signals will remain displayed whether users like it or not, and they cannot be filtered out on any radar or AIS system that meets the standards set in the resolution 😄😄😄
I also think this subject has now been flogged to death.
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[I also think this subject has now been flogged to death.
That's usually what people say when they think they're losing an argument!
I come back to the key wording in 5.26.3 - "To reduce display clutter, a means to filter the presentation of sleeping AIS targets should be provided, together with an indication of the filter status. (e.g. by target range, CPA/TCPA or AIS target class A/B, etc.)." This confirms that Class B targets may be subject to being filtered out. You say they'll still be shown on the screen. I don't share your confidence. Reducing the target symbol to the tiniest dimensions would be one way of still showing it on screen, but that isn't going to stand out particularly well.
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The resolution does not offer an option of reducing the size of the target. To suggest it does is to put something into the resolution that was never there in the first place. The only option it provides for is for an active target to become a sleeping target and for the removal of text from the target. It does not provide for filtering out as you put it. However, if you don't have confidence in the resolution to provide a full and properly working seamanlike solution then that is your decision and hopefully one that you can live with. Whilst any form of filtering brings risks that people might not check periodically to see that the filter is not hiding information that is important, I also have confidence in properly qualified ships officers doing their job in a proper, efficient and seamanlike manner.
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I thought it would be useful to find a little more evidence to substantiate my view that Class B AIS can indeed be filtered out on modern ship radar systems. I found an article by Dr Andy Norris, who amongst other things has chaired IEC Technical Committee 80, which was involved in drawing up the MSC192(79) regulations on ship radars. In 2010, Dr Norris wrote, in specific reply to the question as to whether Class B AIS could be filtered out:-
"Although AIS is a highly useful system for ships and small craft the warnings that I gave in 2006 to AIS Class B users still remain. You cannot rely on your AIS transmissions being picked up and appropriately reacted upon by any vessel. There are numerous reasons for this. The knotty problem of AIS Class B target filtering is only one of these and is probably near the bottom of the list in terms of the potential issues that can cause problems.
Since 2008 all new ship radars have had to include AIS display functionality. It is an IMO requirement that means for filtering of sleeping AIS targets are included on such radars 'to reduce display clutter'. In the list of example filtering modes 'AIS target class A/B' is mentioned. The requirements for filtering are not particularly explicit, especially with regards to its interaction with automatic activation algorithms, which are themselves left to manufacturers to decide upon. It may have been at the back of the mind of some legislators that innovation by manufacturers would be the best way to evolve both filtering and acquisition strategies in these relatively early days of AIS/radar integration. Maybe, in the future, more explicit functionality could then be statutorily defined. Until then, manufacturers will be implementing their own best ideas in these areas.
The problem with AIS Class B targets with regards to filtering is, depending on scenario, you may wish to have a filter that prevents all Class B targets being shown either as sleeping or activated, or you may wish to activate filtered targets under certain special conditions. Class B targets typically apply widely different safety zones compared to interactions between Class A targets, because of their differences in size and manoeuvrability. Particularly in busy areas, small craft often pass closer to ships than is generally considered safe for ship-to-ship encounters, even though needing particular alertness by the small craft skipper.
For this reason, especially in areas that are crowded with small craft but that also have appreciable shipping movements - such as in the Solent area of the UK - it could well be the case that any activation of Class B targets will cause almost constant activation of the Closest Point of Approach (CPA) alarm on the ship - continually distracting the navigating officer/pilot. A 1.0 NM CPA may be appropriate for ship-to-ship encounters in such an area, but many small craft skippers will be quite happy approaching ships at very much closer distances. Therefore, filtering of all AIS Class B targets, together with preventing their activation, may be the appropriate strategy in such areas to avoid possibly dangerous alarm distraction of the bridge team.
Many such areas are found around the world, justifying the inclusion of such a mode in manufacturers' equipment. It should not be forgotten that the bridge windows form the most widely used navigational aid. When operating in busy areas in reasonable visibility they normally form the primary collision avoidance tool.
In inclement weather in such waters it would generally be the correct practice to switch off the AIS Class B filter, considerably improving the probability of identifying small craft in poor visibility and bad radar clutter conditions. In general, there would be fewer Class B targets in such conditions. These would naturally wish to keep a greater distance from ships and, in any case, any detrimental over-alarming of the ships system would, in these conditions, be compensated by the benefits of increased probability of target detection. Of course, in other than crowded waters in good visibility, the AIS Class B filter should generally be switched off.
No normal ship would ever want to ignore the presence of small craft. In most situations AIS Class B transmissions are a useful additional detection aid. In some circumstances, however, Class B filtering is essential to avoid unnecessary and distracting alarms.
Over the next few years it will be interesting to see the strategies that evolve for AIS filtering and activation, especially when combined with evolving radar/AIS association algorithms. Combining radar and AIS data enhances navigational integrity. Used on their own, both AIS and radar have significant integrity issues but the overall integrity of navigation is greatly improved when used appropriately together - and can be enhanced by further integration with other navigational aids. Navigation sensor integration continues to form a highly interesting and relevant research area."
So, confirmation from the guy who wrote the rules.
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Good for you to have looked it up, but it makes no difference what his thoughts or hypothesis are if its not included in the MSC resolution. At the end of the day the radar manufacturers have to build according to the specification or they do not get the wheel mark of approval. Without that approval they can have the finest radar sets imaginable, but they won't find any ship owner that will buy them.
As for his comment that the requirements for AIS filtering are not particularly explicit, that is not true. The requirement for filtering states very clearly that "it should not be possible to remove individual AIS targets targets from the display, and that sleeping targets as a result of filtering, would continue to be displayed except that the text which might otherwise have accompanied the target would not be displayed.
So I suggest if you still want to argue the case, that you contact the MSC and tell them they have got it wrong.
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It's disappointing that you won't accept the views of the guy who was involved in developing the very rules which you keep quoting. Oh well, that's life I suppose.
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No, it's hearsay, hypothesis and scaremongering that I won't accept. But give me verifiable fact and back it up and I'll listen all day.
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No, it's hearsay, hypothesis and scaremongering that I won't accept. But give me verifiable fact and back it up and I'll listen all day.
So Dr Andy Norris, apart from helping frame the regulations, is guilty of "hearsay, hypothesis and scaremongering"? I think not.
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referring back then to Tiger79 posting on 15 October, you said, and I quote:-
"In 2010, Dr Norris wrote, in specific reply to the question as to whether Class B AIS could be filtered out."
You followed it up with some text which you have quoted as his reply, and finished with a statement saying, "So, confirmation from the guy who wrote the rules."
Now just so that we can all be entirely clear about this matter, can you please tell us which of the statements in his reply actually confirms that Class B AIS targets can be filtered out on radar displays that have been constructed in accordance with the MSC 192(79) Resolution where as you suggest, Dr Norris "wrote the rules."
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I see you're still in denial. :bang
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Firstly, I'm far from being in denial, though I note that you chose not to answer the question.
Referring readers to my last posting on this subject and the more recent comment from tiger79.
T79, as you are reluctant to explain how the posting you have attributed to Dr Norris helps your viewpoint, I will explain to the readers how that letter appears to me.
The posting is supposed to be an answer to a specific question as to whether Class B AIS signals can be FILTERED OUT, and is in relation to the Maritime Safety Committee Resolution MSC192(79).
Reading through the posting it is very clear that while it confirms that such signals can be filtered, IT DOES NOT CONFIRM that they can be FILTERED OUT.
The posting goes on to discuss situations where information overload might lead to a desire to have a system, as the writer hypothesises, that would Filter all Class B signals so that they did not show either as sleeping or activated targets. A filter that would achieve the writers hypothesis would be contrary to the requirement of the MSC resolution in its current form, where the resolution specifically requires that it should not be possible to remove an individual target from the display.
Dr Norris chaired the IEC Technical Committee that assisted the Maritime Safety Committee in order that the MSC could formulate the resolution, and a reasonable conclusion for their involvement would
be that the IEC TC could advise the MSC whether or not it was technically feasible for the filtering
system fitted to be able to work exactly as the MSC required, notably to ensure that targets could not be filtered to the point where they disappeared from the display.
Now this next bit is my own opinion, but if the posting had confirmed that Class B targets could be filtered out on radar equipment built according to the standard required by the MSC, and if it was actually written by Dr Norris, one would anticipate that some serious questions would be asked of that technical committee.
So, its not a matter of whether I accept Dr Norris' views, the fact is that what has been stated to be his views, do not confirm that Class B AIS signals can be filtered out, and where he hypothesises over what people might like to have by way of a filtering system, unless that system meets the very rigorous requirements of the MSC resolution, it simply will not get off the ground.
It therefore remains a complete myth and nothing more than scaremongering to suggest that Class B AIS signals can be filtered out on radar sets that have been built in accordance with the MSC Resolution until such time that there is clear and quantifiable evidence to the contrary rather than just hearsay.
Lastly while I welcome genuine discussion and reasoned argument, I do not intend to respond to any further ill-informed comment or remarks on this subject.
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A myth? Still in denial. :bang
http://setsail.com/class-b-ais-filtering-the-myth-is-real/
Also look at the Operator's Manual for the Furuno FAR2807 series ship's radar. On the front cover it clearly says "Complies with IMO MSC.192(79)" Read the AIS instructions in section 4.
In 4.3 it clearly tells you how to remove Class B targets from the display. Note also that you can remove targets below a certain length or below a certain speed - both of which could also be used to exclude leisure vessels.
Then in 4.10.1 it tells you how to turn off the lost target alarm for Class B vessels.
And in 4.12.3 it tells you how to turn off the CPA/TCPA collision alarm for Class B vessels.
Now, as you're in denial, I'm sure you'll claim that these are all mistakes, or that the manual doesn't mean what it says, or that the radar isn't actually fitted to ships, or some other wild claim. However, I believe what it says, as would most sensible people. You'll find the ship's radar manual at http://www.furunousa.com/ProductDocuments/FAR21x7%2028x7%20Operator's%20Manual%20P%20%204-8-11.pdf
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Seems like I've finally convinced Salty that my claims weren't "myth" and "scaremongering"! :)
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WOW, what a thread! From the original question posed I can only tell you what we do:
NASA AIS receiver, separate aerial, which will double as emergency VHF antenna, and input via serial/USB converter into laptop running windows, C-Map and Digiboat's "Software on Board "
All AIS data is available on the chart in real-time. Of all the extras we have aboard this the one goody that my wife would pay serious cash to replace were it to fail. It has been very comforting, especially at night, when you radio an approaching vessel with you distance and bearing to agree a safe passing protocol. Our calls to large ships have always been well received and the resulting avoidance taken impressive, even 25 knot Italian Cruise Liners!
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WOW, what a thread! From the original question posed I can only tell you what we do:
NASA AIS receiver, separate aerial, which will double as emergency VHF antenna, and input via serial/USB converter into laptop running windows, C-Map and Digiboat's "Software on Board "
All AIS data is available on the chart in real-time. Of all the extras we have aboard this the one goody that my wife would pay serious cash to replace were it to fail. It has been very comforting, especially at night, when you radio an approaching vessel with you distance and bearing to agree a safe passing protocol. Our calls to large ships have always been well received and the resulting avoidance taken impressive, even 25 knot Italian Cruise Liners!
Most of this thread is about AIS transponders, not AIS receivers. Nobody disputes the value of having an AIS receiver, especially if the VHF is interfaced with it so you can instantly make DSC calls to vessels. However, many people labour under the misapprehension that a Class B transponders will guarantee they're seen by ships. It won't.
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I recently sailed around Cabo Finisterre in fog and we could see lots of fishing boats on both AIS and radar (some only one one or the other). It was notable that when going in straight lines the fishing boats displayed AIS,but they would slow down and start to turn and then 'disappear' presumably they would find fish and not want others to see their concentrating on one area. Unfortunately some of them were wooden or GRP and were very poor radar targets. Not what you need in fog.