AIS vs radar

[Airassmith]

Just got back from bringing our new (used) yacht from the Netherlands to her new home in Finland. We had two unpelasant experiences in sailing in thick fog for several hours close to or in areas used by shipping in the open seas passages and I have vowed to a) get a better radar reflector and b) fit either AIS or radar so I know what is going on around me. Any thoughts on radar vs AIS ?
Dave

 

[tcm]

Nopt the same things really - radar (supposedly) shows everything, AIs only shows those vessels (big ships) fitted with the gear. If you were only gonna have one, have radar.

You (later, if funds allow) get an AIS receiver box thingy and it can integrate with radar or chartplotter, possibly using the Not Much Explanation Available (NMEA) connection.

 

[roly_voya]

Some of the things AIS dosn't show that radar does

Fishing boats
Small ferries
Other yachts
Bouys & nav aids
Rocks, land etc
Any useful navigation information

Choice seams quite clear

 

[whiteoaks7]

AIS is only fitted to ships of 300 tons and over and also not to warships. 299 tons will make a hole in you. Also AIS will not help you navigate.

One piece of advice though - do the radar course, radar is not intuitive and there have been many 'radar assisted collisions'.

 

[CPD]

Radar first, AIS second. No question in my mind.

 

[Talulah]

I'm afraid I'm of the opposite view. If money is not an issue buy both but having got both I find the AIS far more useful. Each to their own though.

 

[pvb]

[ QUOTE ]
.... possibly using the Not Much Explanation Available (NMEA) connection.

[/ QUOTE ] /forums/images/graemlins/smile.gif

 

[pvb]

Radar...

[ QUOTE ]
...and b) fit either AIS or radar so I know what is going on around me.

[/ QUOTE ]Only radar can show you what's actually going on around you.

 

[fireball]

Re: Radar...

Cheap Radar Set ~£7-800 (I think the JRC can be purchased for about this)
Cheap AIS display ~£220 (NASA Display)

Cheap may not be the best solution for you though.
We've gone down the AIS Engine route - into AIS Capable chart plotter - total installation (inc CP & Map) ~ £600
Radar would be OK (I wouldn't get the £750 version though) , but expensive for the very few times I'd actually need it, so better off doing my best to avoid situations where I'd need it.

As has been said - AIS doesn't show you the whole picture - missing out any vessel that hasn't got AIS transmitter installed. So not ideal if you're regularly going to nav in low vis conditions.

 

[achwilan]

These devices address different (with some overlap) problems:
Radar allows you so get a somewhat distorted image of your whole environment (other ships, shore, buoys, ...), so it can be used for navigational purposes too. But identification may be difficult.
AIS only allows you to see and identify the ships emitting the required signal.
That's all ... So IMHO radar first.
Quite the same difference between military radars (the true ones) and most civilian airports radars (just improved transponders: can't see a passive target): the underlying working assumptions are quite different.

 

[bendyone]

Proper radar everytime

 

[jonjo]

You are going to get opposing views in answer to your question based on some of the following factors:

* Where the poster sails and what perceived threats have evolved from experiences in that sea area.

* Level of experience as a yacht skipper.

* Whether the poster has actually used AIS for real.

[ QUOTE ]
Where the poster sails and what perceived threats have evolved from experiences of that area.

[/ QUOTE ]Someone who sails locally in the Channel Islands or along the North Brittany coast will be more concerned with fog or small craft and so will naturally favour radar whereas the bloke who sails from the Solent to Cherbourg twice a year will worry about merchant ship collision situations in clear visibility.
[ QUOTE ]
Level of experience as a yacht skipper.

[/ QUOTE ]
An intersecting course with a merchant vessel is far less of an issue for someone who has been sailing cross channel 6 times a year for the past 25 years than compared with a new skipper. The experienced skipper can use his eyes and thinks he can do AIS CPA type computations in his head but he cannot control what pops out of the fog at 400m, this experienced guy places a far higher priority on radar.
[ QUOTE ]
Whether the poster has actually used AIS for real.

[/ QUOTE ]
Some people simply don’t get AIS technically nor do they appreciate the definitive assessment of collision situations that can be realized from an AIS display with very low input from the crew.

What surprises me is that the pro radar brigade ignore the evidence from the 2 most investigated small boat collisions in the Channel in recent years. In the case of the Wahkuna, the presence of fully featured leisure radar set distracted the crew and seemed to have led them into a collision in thick fog. In the case of the Ouzo, the official report speculated that in good visibility the crew did not know how to interpret the course change of the PoB which eventually ran them down.

In both the cases above, AIS would have been more useful than radar.

 

[fireball]

Exactly - choose your instruments for your conditions .... those of us who rarely venture out of home waters are unlikely to need either AIS or Radar.

Don't forget - you need to practice interpreting the displays - I believe AIS is easier, but both AIS and Radar displays will need some practice

 

[Colvic Watson]

Completely agree. We have the JRC £750 set on our boat and beacuse it's not in the cockpit it is so rarely used, that although we were taught how to use it by an RN navigator, we've now forgotten. It's definately NOT intuitive! AIS is pretty intuitive because it's like a plotter screen. On all our 6 cross channel trips I wished we'd had AIS. Our maximum journey is usually 8/10 hours, if your sailing is in darkness, fog prone areas, and if you have a crew, go for the radar as well. I could not safely steer, handle the sails and monitor/interpret the radar with any practical accuracy singlehanded. The alternative is an integrated radar and plotter with MARPA and gyro compass. But if we could afford that, we'd have bought a different boat.

 

[jstr]

We had a similar bad experience in the Channel shipping lanes at Easter. We took everyone's advice, and we ended up buying Radar AND AIS - (The Raymarine C80 as display) and I went on the radar course. As stated here they do different jobs. To be sure of what's around you, the radar is the best, the AIS scores with its rate of turn and identifies the big boys to you. To do the best you can in thick fog, you need both - especially in the Channel IMO

 

[Robin2]

IMHO the essential difference is that AIS does the work for you - i.e. it figures out the possibility of a collision and warns you. Radar does nothing unless you select a target (assuming you know what a target is, out of all the other strange shapes on screen) and get it to track that target.

Radar clearly takes both learning and experience on several clear days to relate what is on screen to the real world around you. How likely is it that you have a crew member with that training and experience? I don't reckon it is easy for the helmsman to attend to also be the radar operator, even if the radar is conveniently placed.

AIS can "see" around headlands, which radar cannot do. And chart plotters do a better job of showing where you are than a radar image.

Yes it would be nice if smaller "dangerous" boats had AIS - e.g. fishing boats. But the sea is a big place, the vast majority of boats are pleasure craft and away from obvious points of concentration (shipping lanes, ports etc) the likelihood of an accidental collision is small even if neither boat is keeping a lookout.

The Wahuna and Ouzo were horrible accidents, but also serve to show how rare this sort of thing is.

The most likely collision is with another pleasure craft - and I doubt it would be practical to follow them all on Radar or with AIS (even if they all had transponders). The acceptable margins of clearance are far below what can be managed by a computer.

 

[flaming]

never sailed with AIS.

However these days I hesitate going cross channel without Radar.
Ours is mounted right in front of the wheel, with a repeater at the chart table.
This does two things, firstly the on watch crew check the radar way more often as it's right there, rather than having to go below. (and the off watch crew appreciate the fewer disturbances!) And having one below means the on watch crew are more likely to call the skipper to "just have a quick look at this one" as they know he can make an initial assesment without getting out of his sleeping bag!

 

[chuzzlewit]

I too recently crossed the Channel shipping lanes in 10 hours of unexpected fog. AIS , Raymarine C80 and radar really saved our bacon. AIS is easier to interpret than radar/MARPA as it stays steady even if your course wobbles. The C80's ability to superimpose radar reflections on the chart would have been a blessing if we had met anything not transmitting AIS.

 

[achwilan]

The most likely collision is with another pleasure craft - and I doubt it would be practical to follow them all on Radar or with AIS (even if they all had transponders).

[/ QUOTE ]
I disagree. Modern leisure radars exhibit good capabilities especially at short range. And fog thickness is often in inverse ratio to windspeed... so less clutter... and efficient tracking...

 

[pappaecho]

AIS transponders are fitted to all warships, but they do not show identifying names or course