Radar Reflectors -- observations and musings

[deblen]

Originally Posted by Lodesman

I agree that AIS is a great tool - but it does have its own limitations. I wouldn't count on it being safer than radar.

Based on your comments, I assume your location is Vancouver, BC - you should be aware of Rule 40 in the Canadian Rules, that requires small non-metallic vessels to have a radar reflector. An octahedral reflector in the "catch rain" orientation gives good (not great) performance - it's an inexpensive added layer of safety, and meets the legal requirements.

Masts don't make very good reflectors, particularly when underway and heeled over - poor angle of incidence. Frequently, radar picks up the engine or other chunks of metal.

Yes! What about Rule 40-Canada ? Under 65'(20M) must carry radar reflector....
And-Rule 41-Must NOT use a transponder.....
https://laws-lois.justice.gc.ca/eng/.../FullText.html
Cheers/Len

[Don C L]

My curiosity is piqued:


Rule 41
Transponders
(a)
No vessel, except a vessel in distress, shall use a transponder that can transmit radar responder signals or radar beacon signals in the 3- or 10-centimetre marine radar bands.
(b)
Notwithstanding paragraph (a), an exploration or exploitation vessel may use such a transponder if authorized to do so under this Rule and the transponder is used in a manner that does not compromise the safety of navigation.
(c)
The Minister shall authorize the use of a transponder if it will be used in a manner that will not interfere with or degrade the use of radar in navigation, having regard to factors such as
(i) the proximity of other transponders and the distinctiveness of their signals,

(ii) the frequency, range and power of the transponder, and

(iii) the marine radar band to be used.



So just what kind of "transponder" are they referring to exactly?

[CaptTom]

Originally Posted by Kettlewell

...In my experience, small commercial fishing boats are rarely paying attention when on the fish, though they do often respond when either on their way to or from fishing. Just don't expect them to notice you or make any maneuver to avoid you when fishing.

It's different around here. The moment they leave port, they set the autopilot and go below. You won't raise them until they get to the fishing grounds, and they won't alter course for anyone.

Maybe not all of them, but I've seen it way too often for it to be a coincidence. They're not going to sink if they collide with a small recreational boat. The onus is on those of us in the more fragile vessel to keep a sharp lookout.

[Jammer]

I believe that changes in radar technology over the last 20-30 years have resulted, in practice, in sailboats being more likely to be detected, and detected farther away, than used to be the case.

Earlier radars (1980s) did not have effective automatic gain controls. I believe they were typically operated either in the automatic mode (which was ineffective) or operated in the manual mode with insufficient sensitivity (which was also ineffective). That made it easy to miss weaker targets.

Modern radars have automatic gain controls and automatic sea state detection that actually works with minimal fussing by the operator. I routinely pick up kayaks on radar in flat water. I routinely pick up sailboats. It is hard for me to believe that other vessels will not see my boat on radar, particularly in the light to moderate sea conditions that accompany fog and that prevail in high-traffic areas (harbors/channels/inlets).

Radar reflectors were heavily promoted after a carefully analyzed and widely publicized accident at night where a freighter collided with a sailboat, about 25 years ago. I believe that some of the conclusions of the report were misguided (there was a failure of watchkeeping on both boats and they were both close enough to whatever point they were going around that they had limited time to see and react). There is a growing body of evidence to suggest that radar reflectors, in practice, as installed, help less than is generally believed, especially smaller ones that have reasonable windage and are unlikely to foul the sails and rigging. And I think any benefit that did exist has been rendered moot by the changes in technology and in how radar is used.

[LakeSuperior]

Turning things around, consider that no one looks out for you...like you! The point is I really don't care if other yachts, freighters, fishing tugs, etc. can see me. I just want make sure I can detect them.

The danger with AIS is it can lull you into a sense of false security where you are assuming that everyone is broadcasting and therefor, you are assuming that you see 100% of the threats. We know that is just not the case.

With radar I know I have 100% probability of detection especially if the range is short. The more powerful the radar, the higher the detection probability and the longer the detection ranges. In general, I can see everyone near me.

In summary, when my hide in the game I don't want to depend on the competence of random strangers if I can help it. I want to look out for myself.

[hjohnson]

Originally Posted by Lodesman

I agree that AIS is a great tool - but it does have its own limitations. I wouldn't count on it being safer than radar.

Based on your comments, I assume your location is Vancouver, BC - you should be aware of Rule 40 in the Canadian Rules, that requires small non-metallic vessels to have a radar reflector. An octahedral reflector in the "catch rain" orientation gives good (not great) performance - it's an inexpensive added layer of safety, and meets the legal requirements.

Masts don't make very good reflectors, particularly when underway and heeled over - poor angle of incidence. Frequently, radar picks up the engine or other chunks of metal.

Technically, we’re probably not in compliance with rule 40 (our radar reflector lives folded up in the bottom of our sail locker) but I’m not sure how much it matters. On a couple of occasions we’ve been on the radio with Victoria Traffic for various reasons, and they’ve had no trouble picking us up on radar.

But also, My day job is as a field service Engineer working on deep sea navigation systems. I work a lot with radars, ECDIS, and related systems, on both merchant and military vessels. The reality is that modern X-Band radars are remarkably good at picking up small craft. More than a few times I’ve tested things by tracking “around the can” races. I really have no qualms about them seeing the boat. Heck, in harbour, I’ve been able to track and spot kayaks and SUPs.

Earlier this year, I crossed the Atlantic on a deep sea (trying to track down a bug that only happened at sea) and the radar had no trouble tracking the couple of yachts we encountered/passed. Looking at them visually (we were playing with an Enhanced Optics/Infrared camera system) I didn’t see a reflector.

Anyhow, from my own personal experience, AIS is again far more valuable. This past Tuesday was a good example. I was sailing home from Porlier Pass to Vancouver, and we came into a crossing situation with a tug and gravel barge around the western tip of Point Grey. Tug was simply able to call us by name, and asked us for more room as he was constrained by draught. We let him know that we’d tack, let him slide by, then resume course.

[Lodesman]

Originally Posted by hjohnson

Technically, we’re probably not in compliance with rule 40 (our radar reflector lives folded up in the bottom of our sail locker) but I’m not sure how much it matters.

It doesn't matter until the CCG or VPD marine unit do a spot check and give you a ticket. Then you might kick yourself for leaving it in the sail locker.

It's kinda like when you see a cyclist ride by, with their helmet hanging from their arm by the straps. If you got it, how much effort is it, to use it?

I'm fully aware, that in perfect conditions you can tracks seagulls sitting on the surface of the water; I've done it lots. And most of the time you can pick up small boats. Most but not all. Put in some precip and a sea-state, and it becomes that much more difficult to discern the paint of a small boat.

Early in my navy career, we were cruising up the SoG, night-time in typical Wet coast mist drizzle. We approached a vessel, which due to its lighting blended into the blurry background light of Vancouver. We were aware it was out there from VHF traffic, and eventually picked it up visually, but we never managed to get a paint on radar, even though it passed within 3 miles of us. This is with 3 separate military radar sets - nav, surface search and air search. The OOW and myself as 2nd both had a go at manually tuning the nav radar, and ops team presumably tuned the surf and it remained invisible on radar. It was a cruise ship.

So I've never taken it for granted that you will be seen on anyone's radar; you don't even know if it's working, let alone if anyone's bothered to tune it or look at it. Much the same with AIS - useful tool for identifying potential risks of collision and putting a name on it - but I've seen enough wonky data, or vessels that fail to show, to not trust it for anti-collision.

[dlj]

Originally Posted by Srpulpo

I agree, most big ships should and do use AIS and they are the ones to watch out for including commercial fishing boats. you see each other better then just a dot on the screen. radar is becoming what SSB has become.

Key word is should. I have been rather surprised at how some of the big freighters do not run AIS.

Depending upon where, a lot of fishing boats do not use AIS. I just sailed up the coast of Nova Scotia and Newfoundland and found many of the fishing boats here so use AiS, but certainly not all.

Until close to 100% of all boats in the world use AIS, RADAR will remain very useful for spotting boats. Additionally, RADAR will still be very useful in areas with fog or other low visibility.

Running with both is highly desirable for long distance cruising, in my opinion.

dj

[hjohnson]

Originally Posted by dlj

Key word is should. I have been rather surprised at how some of the big freighters do not run AIS.

Under current SOLAS conventions, AIS is mandatory for all ships over 300 gross tonnage, and/or carrying more than 12 passengers. Even the RCN operates AIS at this point.

About the only commercial vessels I see that don’t operate transponders are the False Creek Ferries and Aquabus, and maybe the smaller water taxis.

[CaptTom]

Originally Posted by LakeSuperior

...I really don't care if other yachts, freighters, fishing tugs, etc. can see me. I just want make sure I can detect them.

The danger with AIS is it can lull you into a sense of false security where you are assuming that everyone is broadcasting...

Relying on any one technology is foolish. I want access to all the available information for my own decision-making. I don't rely on others to do the right thing. But I do everything in my power to give them the opportunity to do the right thing.

Like have my radio on. You'd be amazed how many only turn it on when they want to talk to someone else. You can hail them all day and get no response.

Like make my course corrections early and substantial, so the other vessel knows what I'm doing.

Like use my nav lights and fog horn when necessary.

Too many people don't do these things. They think they know better than everyone else. If you ask me, this is what leads to a false sense of security. I put dismissing AIS technology in this category.

My AIS transceiver is on whenever I'm underway. It's made encounters with other vessels, especially commercial vessels, much more pleasant and productive. I suspect it's also avoided many situations where another vessel would have to call me, or I'd have to call them, to figure out what we're each doing.

At the helm, I want every source of data I can get; every advantage. Underway, any sense of security would be false.

[deblen]

Originally Posted by CaptTom

Relying on any one technology is foolish. I want access to all the available information for my own decision-making. I don't rely on others to do the right thing. But I do everything in my power to give them the opportunity to do the right thing.

Like have my radio on. You'd be amazed how many only turn it on when they want to talk to someone else. You can hail them all day and get no response.

Like make my course corrections early and substantial, so the other vessel knows what I'm doing.

Like use my nav lights and fog horn when necessary.

Too many people don't do these things. They think they know better than everyone else. If you ask me, this is what leads to a false sense of security. I put dismissing AIS technology in this category.

My AIS transceiver is on whenever I'm underway. It's made encounters with other vessels, especially commercial vessels, much more pleasant and productive. I suspect it's also avoided many situations where another vessel would have to call me, or I'd have to call them, to figure out what we're each doing.

At the helm, I want every source of data I can get; every advantage. Underway, any sense of security would be false.

You are correctly following Rule 7.
Some other posters may not be
Trusting other vessels to do what they "should" do,may be risky.

[dlj]

Originally Posted by hjohnson

Under current SOLAS conventions, AIS is mandatory for all ships over 300 gross tonnage, and/or carrying more than 12 passengers. Even the RCN operates AIS at this point.

About the only commercial vessels I see that don’t operate transponders are the False Creek Ferries and Aquabus, and maybe the smaller water taxis.

Question: who must comply with SOLAS? How is it enforced? It's also my understanding fishing boats are exempt.

My statement comes from direct observation.

dj

[El Pinguino]

Back to the OP.
This is a shot of a mid 1990's bog standard commercial magnetron radar taken in about 2000.
No swell - afternoon sea breeze, Saturday afternoon, display is 'north up'
Departing Melbourne, Australia and have just rounded 'the Breakwater'. Range from 'own ship' to bottom right 5 miles or so.'Own Ship' is near top of screen at top end of the heavy green heading marker.
Apart from the stationary pairs running north south in centre screen which are channel markers for the Port Melbourne Channel you are looking at assorted small fishing boats - not commercial - typically sub 20 foot trailable GRP or 'Tinnies' - and sundry small yachts.

The mob bottom right is a race out of Sandringham YC which - having used the Fawkner Beacon as a rounding mark - pricks - were on their way back to the club for 'drinkies'. Doubt many/any had radar reflectors.

Did I mention how good 'target tails' are?

Manual clutter control.

Typical slack arsed watch keepers were always turning it up way to high and not only getting rid of all the clutter but anything else within a 5 mile range. A few of them are probably now in command --sigh.

I have 'target tails' on my 25 yo old Anritsu. Its good.

[Dockhead]

]

Originally Posted by LakeSuperior

Turning things around, consider that no one looks out for you...like you! The point is I really don't care if other yachts, freighters, fishing tugs, etc. can see me. I just want make sure I can detect them.

The danger with AIS is it can lull you into a sense of false security where you are assuming that everyone is broadcasting and therefor, you are assuming that you see 100% of the threats. We know that is just not the case.

With radar I know I have 100% probability of detection especially if the range is short. The more powerful the radar, the higher the detection probability and the longer the detection ranges. In general, I can see everyone near me.

In summary, when my hide in the game I don't want to depend on the competence of random strangers if I can help it. I want to look out for myself.

I wouldn't dismiss the importance of others seeing you, by all possible means including proper nav lights, and AIS.

But otherwise I agree with you. AIS - which is only helpful if the vessel or object is broadcasting - is no substitute for radar - which does not depend on the other guy.

[CaptTom]

What's all this talk about substitutes?

Use every source of data you've got. The Polynesians sailed the Pacific using (among many other things) the direction of swells reflected off islands.

You should never "substitute" anything. Nor should you dismiss any source of data simply because it's not perfect.