Uricanejack
Well-Known Member
The
I don’t mean to pick on you.
What you are describing has been said by many posters on this forum in slightly different ways.
I don’t disagree with the suggestion AIS and Radar are complimentary and used together make colision avoidance easier.
The situations you describe would give me cause for concern. Very close CPA with a Tanker. I presume you were the stand on vessel. You called the Tanker using the info from the AIS ton identify the Tanker. So far So Good.
By your own words the Radar info was a concern. In this case you made contact and made an passing agreement apparently in compliance with the coll regs.
This eased your mind. Again so far so good.
The Tanker on the other hand, not so good.
I doubt you were talking to the Master. More likley a junior mate. Took almost no perceptible action. A very minor course tweak. In the end both vessels have made assumptions based on scanty information from AIS and VHF.
The Tanker in particular should have known better. The alteration should have been large enough to be perceived by a visual observation and particularly if visabilty was poor by Radar.
2 degrees is not a good enough alteration. It’s a tiny little course tweak by a poor operator. In direct violation of the recommendation for action for a give way vessel. Which should be early substantive and keep clear.
I would certainly have been concerned by the Tankers lack of action. Even with the VHF communication. Without the passing arrangement I would have been very concerned.
I wonder if a lot of ships are ussing these tools to reduce safety margins rather than improve them. I wouldn’t trust the judgement of those ships who engage in such practice. Yet I recognize it appears to be a common practice.
My point is don’t let AIS lull you into a false sense of security. Accepting what would not be acceptable without AIS. Particularly in fog.
I would also suggest VHF communication to arrange passing should be used with caution. Don’t make arrangements on working channels use the VTS channel if one is available. Why, so other vessel’s are aware of what you are doing. Also because it recorded. There will be a record of the arrangement.
Even when you know which ship you are talking to. The actual communication can be confused leading to misunderstanding.
I sail in an area with VTS most ships have local pilots or are local mariners. Traffic can be quite heavy though not to the extent of the English Channel. Narrow channels and blind corners are a common feature. TSS schemes exist for the Jaun de Fuchs, the Straights. Approaches to Vancouver and Seattle.
The local Ferries are notorious for making private arrangements on thier own radio channel so they often do very strange things.
Even so most of them follow predictable routes. The very large number of small and large pleasure vessels is I find a bigger concern. Fishing vessels are concern but thier numbers have declined dramatically.
Well I’d never recommend exactly the opposite. Ie radar and no AIS. You can get an AIS receiver for under £100 and it is better at SHIP avoidance than radar in many respects
Not only does it clearly show CPA (this is not that easy on radar MARPA isn’t great on small boats and you have to actively intervene) but it shows heading, ROT and SOG. It also gives the vessel name.
I’ll give you a real example. Being overtaken by a tanker., CPA 80ft TCPA about 10 minutes. I called the tanker by name and told the master of my intention to stand on. He thanked me and turned to starboard by 2 degrees. I could see he had turned immediately even though the CPA dances around a bit it takes a while to trust the change. . All a radar would have done is give me brown trousers.
Also when monitoring CPA by MARPA or AIS it is (obviously) only a good estimate if both vessels maintain course and speed. Often masters nudge up by a degree or two to avoid a smal vessel traversing the channel. You can see that move before you trust the change in CPA. This avoids him altering course, you altering course because he’s big and so on. You have an obligation to stand on remember. AIS can help make that judgement BETTER than radar.
Of course radar can do loads AIS can’t. Squalls don’t transmit an AIS signal for example, nor as you quite rightly pointed out, do all vessels or rocks. But radars are expensive.
So why would I never recommend the opposite as you suggest.? If you can afford radar then have both, in boat terms the AIS cost is trivial.. Overlaid they make for a powerful contribution to decision making.
I don’t mean to pick on you.
What you are describing has been said by many posters on this forum in slightly different ways.
I don’t disagree with the suggestion AIS and Radar are complimentary and used together make colision avoidance easier.
The situations you describe would give me cause for concern. Very close CPA with a Tanker. I presume you were the stand on vessel. You called the Tanker using the info from the AIS ton identify the Tanker. So far So Good.
By your own words the Radar info was a concern. In this case you made contact and made an passing agreement apparently in compliance with the coll regs.
This eased your mind. Again so far so good.
The Tanker on the other hand, not so good.
I doubt you were talking to the Master. More likley a junior mate. Took almost no perceptible action. A very minor course tweak. In the end both vessels have made assumptions based on scanty information from AIS and VHF.
The Tanker in particular should have known better. The alteration should have been large enough to be perceived by a visual observation and particularly if visabilty was poor by Radar.
2 degrees is not a good enough alteration. It’s a tiny little course tweak by a poor operator. In direct violation of the recommendation for action for a give way vessel. Which should be early substantive and keep clear.
I would certainly have been concerned by the Tankers lack of action. Even with the VHF communication. Without the passing arrangement I would have been very concerned.
I wonder if a lot of ships are ussing these tools to reduce safety margins rather than improve them. I wouldn’t trust the judgement of those ships who engage in such practice. Yet I recognize it appears to be a common practice.
My point is don’t let AIS lull you into a false sense of security. Accepting what would not be acceptable without AIS. Particularly in fog.
I would also suggest VHF communication to arrange passing should be used with caution. Don’t make arrangements on working channels use the VTS channel if one is available. Why, so other vessel’s are aware of what you are doing. Also because it recorded. There will be a record of the arrangement.
Even when you know which ship you are talking to. The actual communication can be confused leading to misunderstanding.
I sail in an area with VTS most ships have local pilots or are local mariners. Traffic can be quite heavy though not to the extent of the English Channel. Narrow channels and blind corners are a common feature. TSS schemes exist for the Jaun de Fuchs, the Straights. Approaches to Vancouver and Seattle.
The local Ferries are notorious for making private arrangements on thier own radio channel so they often do very strange things.
Even so most of them follow predictable routes. The very large number of small and large pleasure vessels is I find a bigger concern. Fishing vessels are concern but thier numbers have declined dramatically.
Last edited: