Has AIS throttled radar fits ?

[iLens]

Do you have hard evidence of this?
In UK waters I would like to think that a ship on passage with AIS Tx off would be taken to task if observed.

Sailing round GB this year I encountered ships at anchor with AIS off - no problem in good vis but a problem in fog. Having said that I only used the radar once in anger and even then it wasn't all that much help.

 

[prv]

Basically, virtual AtoN are markers or signposts to highlight hazards, channel markers, areas to avoid etc.
They are a progressive part of the paperless bridge, a drive to reduce cost for shipowners and authorities maintaining lights and buoyage.

But what's the point of the radio segment of the system? Why not just have those markers directly in the ECDIS data? That already contains information about non-physical things like TSSes, VTS reporting points, anchorage numbers, and so on - why transmit some of it by VHF radio and some of it by email and FTP?

Pete

 

[macd]

On the other hand small yacht radar these days is so much better than it was say 10 years ago. The latest models are lighter, cheaper, higher resolution, less power hungry and integrate well with modern electronics (MFDs)

All of those would make it a much more practical proposition for most small boat sailors than it was 10 years ago - so I would imagine radar sales are actually holding up or even increasing.

+1 to all that, to which I'd add that I've yet to encounter a thunderstorm equipped with AIS.

There's nothing essential to any of this kit, but we have both AIS and "broadband" radar. The acuity of the latter would (and certainly did, in my case) stagger anyone familiar only with the old technology. Instant-on, very low drain (1.5A when transmitting, next-to-nowt in standby), zero sea clutter, and can spot even plastic swimming marks 50 metres away. Brilliant, when needed. And, as suggested above, there's nothing better for dodging nasty weather at night.

 

[Chris Edwards]

I dont know for sure, but embedding time critical stuff in encs like a recent wreck or missing buoy will take time to get into the field through the chart update system and some mariners update better than others depending on the chart used and whether they are professional big ship, leisure sailors etc. Virtual AtoN can be put up (and taken down quickly) and all AIS users see them equally (or that is the theoretical intention).

Headlands and buoys will alarm on an ECDIS if the ECDIS is used properly, but not everybody sets it up correctly and many vector chart users dont utilise the alarm functionality for shallows and obstructions. Making these virtual gets around this and they should flash up as something to be aware of on the chart overlay. It might be that these are just really easy to make once you have the shore infrastructure - no extra cost so why not post them up ?

VTS centres come up on AIS too and Ive offered wondered why. Maybe its so you can visually assess the range for VHF comms with VTS - I really dont know.

But what's the point of the radio segment of the system? Why not just have those markers directly in the ECDIS data? That already contains information about non-physical things like TSSes, VTS reporting points, anchorage numbers, and so on - why transmit some of it by VHF radio and some of it by email and FTP?

Pete

 

[GHA]

Do you have hard evidence of this?
In UK waters I would like to think that a ship on passage with AIS Tx off would be taken to task if observed.

Very very rarely come across a ship not transmitting, very occasionally - from memory one down near Dakar & an occasional warship though probably more slipped from memory. Seen many more ships disappear on the radar into heavy rain clutter.

Nothings perfect, radar & AIS are very different animals though doesn't stop peeps on web forums comparing them

With AIS receive so cheap it's hard to come up with an argument not to have at least a receiver onboard, then ponder radar as a separate deal.

 

[lw395]

I know it's a joke, but think seriously for a minute - there'd be literally no point in doing this. All AIS does is say "I'm at latitude Y and longitude X", and that information is already printed on the chart. An AIS signal about a charted object is adding nothing at all.

Pete

It's putting that charted object into a CPA calculator.
It's a tool to ensure the object is avoided and left to the correct side.
If several vessels are moving, it's a reference point whch can aid traffic control.
Having AIS beacons on actual charted objects is a bridge towards virtual charted objects which exist only on AIS.

 

[[163233]]

Having finally had a decent look at a radar set - most people who have radar seem to have a broken set - the output is pretty hard to follow. I think you need to use it more than once or twice a year to really understand the thing. Some people are understating the difficulty of operating the set effectively when you have something else to do as well. It's much harder to follow than AIS output.

 

[lw395]

Having finally had a decent look at a radar set - most people who have radar seem to have a broken set - the output is pretty hard to follow. I think you need to use it more than once or twice a year to really understand the thing. Some people are understating the difficulty of operating the set effectively when you have something else to do as well. It's much harder to follow than AIS output.

I agree.
I suspect if your chart plotter and radar are trying to tell you different things, you will tend to believe the plotter. It's easy to convince yourself the radar is showing what you expect to see.
Using radar at close quarters singlehanded is very demanding.

 

[biscuit]

I have been caught in dense fog a few times. Early on in boats without radar or AIS, and been very anxious (around busy areas like Peterhead- Rattray- Fraserburgh for example). Scottish fishing boats either don't have AIS , or more likely rarely turn them on.
I now have both radar and an AIS reciever, which add a great deal to ones feeling of security at night and in fog.
I am thinking of uprating to an AIS transponder/ transciever, but am rather put off by the cost of the thing, that is around £400-£600. Considering that it is simply pulsing the same signal every few minutes, it is very hard to see why it should cost so much more than, say, a really sophisticated GMDSS VHF set (at half the price).
As usual, the argument is that you can't put a price on safety, but there is always a longer list of things to buy for the boat than there is money to pay for them.

 

[westhinder]

Do you have hard evidence of this?
In UK waters I would like to think that a ship on passage with AIS Tx off would be taken to task if observed.

The aircraft carrier that steamed across our track in the Bay of Biscay last summer definitely was not transmitting AIS. Neither were the other NATO warships on exercise that broadcast warning about firing live ammunition that same day. At that time visibility was perfect, so no problem. A few hours later during the night we ran into a massive fogbank with visibility down to 20-30 metres. I would have been a lot more worried knowing that there were warships around had it not been for my radar.
AIS is great, I’m a huge fan, but it does not replace radar.
By the way, I would not trust watch officers on big ships to pick me up on AIS. I have asked it a few times when meeting ships on the open sea, and the answer was always: hang on a moment, I’ll check. Which means they are not monitoring AIS all the time. They always immediately said they had me on radar though.
My next step will be to fit an electronic radar reflector.

 

[johnalison]

I have never found radar to be particularly difficult to interpret even though I have never taken a course in its operation. I know that I may not be getting full use out of it but basically, if there is a blob on the screen there is something there and if there isn't there isn't. if the screen is hard to understand, then changing the scale or the gain will usually clarify things. in twenty years of radar ownership its use has been critical to our passage on several occasions.

In one typical case we waited for quiet weather to do an overnight North Sea crossing, with the result that there was a forecast of possible poor visibility at some point. Without radar we would not have set off. In the event, visibility closed to <1/4 mile at dusk but with radar we were able to continue at cruising speed motoring around 6.5kn, With radar set mostly to 6 miles range the screen remained almost entirely clear, with the odd ship showing up easily for several hours before visibility cleared. What could have been worrying turned out to be a pleasant passage which even my wife enjoyed, once she learned to trust the box.

 

[Giblets]

Once conned a mate's yacht down the west and around the south coasts of Guernsey to St Peter Port in poor viz using radar. Before the days of chart plotters and GPS I hasten to add. Was very pleased to find that the radar trace matched the land profile on the chart beautifully. The Decca was next to bloody useless owing to the amount of water droplets in the air.

 

[Ladybirdgaffcutter]

The RYA offer a 1-day radar course, essential in my opinion. It just gives a hint of how much there is to learn..
If you do it at a school which trains commercial mariners, eg Gravesend, Warsash, they will have a bridge sim room which is great fun, (and so realistic you start grabbing for handholds and bracing yourself, despite being in bricks and mortar!)

Question: why do any yachtsmen still fit trad X-band radar, even with computerised MARPA, when FM radar looks to be so much more suitable?
( Apart from FM not seeing Racons etc)
Is there much price difference these days?

 

[Chris Edwards]

FMCW radars are good at very close range but not so good at longer ranges and they are prone to interference.
Pulse correlation radars are supposed to be better but its hard to get objective opinions. Everybody defends what theyve bought.

The RYA offer a 1-day radar course, essential in my opinion. It just gives a hint of how much there is to learn..
If you do it at a school which trains commercial mariners, eg Gravesend, Warsash, they will have a bridge sim room which is great fun, (and so realistic you start grabbing for handholds and bracing yourself, despite being in bricks and mortar!)

Question: why do any yachtsmen still fit trad X-band radar, even with computerised MARPA, when FM radar looks to be so much more suitable?
( Apart from FM not seeing Racons etc)
Is there much price difference these days?

 

[LadyInBed]

FMCW radars are good at very close range but not so good at longer ranges and they are prone to interference.
Pulse correlation radars are supposed to be better but its hard to get objective opinions. Everybody defends what theyve bought.

Your post makes me realise that I am woefully behind the curve with modern radar, as I don't known what you're talking about! I must do some reading
I'm fine with my 18yo JRC (which still works well), but I guess a replacement will be required in the not too dim distant future.

 

[Neeves]

Broadband IS very good at close range, I can see my dinghy hanging off the transom, see our bowsprit and pick up mooring buoys, not far away. I tested Simrad's 2G Broadband and it is more than adequate at long range, I was picking up ships at 42nm, but it is pretty useless at picking up low lying land at even 12nm, you can see land but it is not on radar. Not picking up land should not matter as you would normally (always?) have a chart plotter (which would show land). Though racing yacht hitting reefs show the flaw in this argument. In the past when we had our Raymarine radar, the Simrad unit replaced the Raymarine, the inability to use broadband radar as a navigation tool, at longer distances, was a surprise but not critical.

One, lazy, use of radar (and broadband is good) is as a tool to choose an anchorage point - you can locate yourself at whatever distance you want with some accuracy from intimidating shoreline and other yachts (something you cannot do with AIS nor a chart plotter). I'd also have more confidence in distances on radar than on a chart plotter - especially where many of our charts in some parts of Oz are based on surveys that may have been made too many decades ago.

 

[Chris Edwards]

It doesnt help when makers use expressions like broadband, 3G, 4G etc.
AFAIK these have nothing to do with the technology employed and is just marketing spiel to differentiate generations of kit.

I believe there are three technologies:

Conventional magnetron
FMCW
Pulse Correlation Doppler

Some companies use the last two on the same radar to get the benefit of both. FMCW should be better at very close range and pulse correlation better at longer ranges. As they use very low power to keep the power consumption down, they wont be able to see smaller targets at the longer ranges and I suspect that the magnetron has the edge on range detection although that older technology does suffer from clutter in rain or high seas.
Magnetron will also trigger a SART at range where the newer technologies either dont or only do at short range e.g. 1nm.

The solid state stuff has the benefit of no warm up time so you can switch it on and off quickly to save power. Also it can operate simultaneously at different ranges hence the split screen offerings.

Personally, I find the products on the market confusing - Im sure this is done deliberately to make comparisons more difficult.

When it comes to anti collision and the detection of targets in bad visibility, I just want a simple radar without the clutter of overlays - AIS is useful to correlate radar and AIS targets but charting is sometimes too much on a small screen.

Most radars with radomes will never be that good because the size of the antenna limits beamwidth and therefore the ability to discriminate between adjacent targets. This is why makers use open rotating scanners for many demos and reviews.

 

[maby]

That does mean you'd be navigating off a single source of position, though, albeit a normally accurate and reliable one.

Pete

We fitted radar after a very close night time encounter with a large and ugly mooring buoy in the Solent that was not marked on the less than one year old Navionics charts.

 

[maby]

Broadband IS very good at close range, I can see my dinghy hanging off the transom, see our bowsprit and pick up mooring buoys, not far away. I tested Simrad's 2G Broadband and it is more than adequate at long range, I was picking up ships at 42nm, but it is pretty useless at picking up low lying land at even 12nm, you can see land but it is not on radar. Not picking up land should not matter as you would normally (always?) have a chart plotter (which would show land). Though racing yacht hitting reefs show the flaw in this argument. In the past when we had our Raymarine radar, the Simrad unit replaced the Raymarine, the inability to use broadband radar as a navigation tool, at longer distances, was a surprise but not critical.

One, lazy, use of radar (and broadband is good) is as a tool to choose an anchorage point - you can locate yourself at whatever distance you want with some accuracy from intimidating shoreline and other yachts (something you cannot do with AIS nor a chart plotter). I'd also have more confidence in distances on radar than on a chart plotter - especially where many of our charts in some parts of Oz are based on surveys that may have been made too many decades ago.

We had the latest Raymarine broadband radar on our previous boat and it was amazing - the resolution and close-in performance was so good that you could park the boat in a finger berth without taking your eyes from the radar screen. The new boat is fitted with the latest Garmin and it is not a patch on the Raymarine.

 

[wully1]

Although with today's MFDs you'd have your radar overlaid on your chart at the helm...

...on your iPad in it’s waterproof case that you can take below when you make a brew etc.