AIS vs radar

[MarkJohnson12345]

Agree,

No choice. Radar is active. AIS is re-active.

AIS wont be of any use to navigate ie reflections from bouys, headlands and MOB's doing 100's ok knots.

AIS really is a toy for small boats.

IMHO

MJ

 

[goldchip]

I have my JRC running most of the time, whatever the viz. It has taken a while, but I now feel confident about the settings i need to use for various sea states.
Despite what it said on the box, the max range it will reliably see a 20' ish boat in a F4-5 ish sea is limited to 2 miles. In bigger seas the same returns are still there, but become intermittent. In the same conditions, large commercial vessels are clearly visible at 6 miles.
During a recent trial, hoisting an octahedral reflector on a 25' sail cruiser didn't make any difference.
Bigger boats just return bigger targets!
It will see everthing at half a mile ( pot markers, gulls etc) if the sea is almost smooth and the boat is upright.

It soon became obvious to me that the greater the range the radar is set on, the more gain you need. So any targets close up just get lost.
Maybe the commercial ships are looking long range, perhaps thats why the Pride of Bilbao did't see the Ouzo?

 

[achwilan]

Quite right. A well tuned radar is a most efficient short range navigation tool. Lots of people trust their GPS a bit too much IMO.
You know flying pot markers, don't you? Some time ago I was creeping out of Aber Benoit with a thick mist, and after that slaloming between some pot markers (you see them first on the screen, and then on the water) when I saw 3 spots beginning to glide away steadily... were 3 gulls!... LOL

 

[DaveS]

Just to clarify, are you saying that warships broadcast their position (but little else) on AIS? Always? If this is the case then it would seem that the major perceived big boat exception is covered (to at least some extent).

 

[MichaelGarratt]

We normally sail in shallow waters and so our main risk of collision with with other small craft and fishing vessels. We try not to sail in poor visibility and so the risks are handled by keeping a good visual watch. Crossing the North Sea however, we perceive the risk to be potential collision with large, faster moving, AIS carrying vessels. Given that radar and AIS perform different tasks I went (in the first instance) for AIS. The unit is easy to use and displays the names of vessels. If we are getting close we can simply contact them by radio.

 

[Robin2]

I'm interested in your view. I have only minimal experience of radar - but its from that position that I must make a decision to buy it, or not.

Would you feel confident sailing through a yacht racing fleet in fog (leave aside the ethics of doing so) just using radar? My guess is that there would be so many targets that it would be difficult to impossible to figure out which represent the biggest risk of collision.

If you would only use the radar to make a decision to avoid the entire fleet then it would be, in my view, a limited value. There are probably other cheaper ways to avoid that sort of risk.

A chart plotter enables me to avoid bumping into land and other fixed objects - and it is at least as reliable as radar.

I am not denying that radar can be useful. I am questioning whether it is the best use of a limited risk reduction budget.