But I've had AIS for years! It has sat down at the nav station. I fully understand what does, how it does it and why the system was introduced.Now you have an AIS you just need to figure out what it does and how it can be useful, sounds like you've splashed out on a handy timer but are still randomly trying to figure out when the egg is boiled in your head .....
Doesn't sound like it from your posts, why have such useful info to hand but rely on your own perception which is orders of magnitude less accurate.
My feelings exactly, ever since I got my first 'NASA AIS Radar', which must have been about 20 years ago now? I had one of the first.The point of my question was to set the parameters for a trigonometry problem. You were saying it’s simple enough to check for constant bearing with a stanchion to determine risk of collision when crossing traffic. How simple making that “do I need to do something?” call is depends on how late you’re comfortable leaving it and what your safe passing distance is and I was going to illustrate that with an example of how much the bearing changes, or rather doesn’t, at the tcpa I’d like to know if I have problem. But if your parameters are different there’s not much point me wading through that trig
Bottom line: I used to think most vessels were on a roughly constant bearing until they were much closer than I was comfortable with. Some maths made me realise how little the bearing of a vessel that’s going to cross comfortably ahead can be changing when it’s 20 minutes away. No way I could possibly judge by eye their 2 or even 5 degree course tweak to avoid me. AIS not only gives me better info far further ahead so that I can plan dealing with multiple crossing vessels much further in advance, practice at cross referencing what I can see with what AIS tells me has vastly improved my ability to visually judge ranges and chance of collision.
Don’t take my word for the “how much does the bearing change at what tcpa” thing...run some numbers (even if you have to spend some time working out how to do an inverse tangent with the Mac OS calculator
Because it *isn’t* a game of chicken I want better information sooner, which is why I like AIS to supplement my eyes and hand bearing compass.
Of course I know Route 5 and Rule 10. And be prepared to stand up in court an defend your decision (and more challengingly this forum).
Is that because they aren't?
More that almost every yacht has wind instruments these days, and those are a similar cost to AIS transponder, probably more expensive in fact. It's not very often we see people mansplaining how they can tell the wind speed and direction with a moist finger, yet for some reason everyone feels compelled to explain that they have eyes when AIS comes into discussion.
Usual stuff, isn't it. Vital when racing. Generally very useful otherwise. But lots of people manage perfectly well without.More that almost every yacht has wind instruments these days, and those are a similar cost to AIS transponder, probably more expensive in fact. It's not very often we see people mansplaining how they can tell the wind speed and direction with a moist finger, yet for some reason everyone feels compelled to explain that they have eyes when AIS comes into discussion.
And no, of course they aren't
By my reckoning, that's one in 76 posts, or a little over 1%, which is definitely seldom in my book. ?It is seldom mentioned ..... although it was in my Post #46.
Richard
Yep, I agreed it was seldom .... but if anyone was going to have the foresight to do it ... etc.
A way to practice is to combine using the compass and AIS together. Like learning radar on a clear day. Racing sailors often have a fine tuned sense of bearing change coz of all the practice they get. It certainly gave me a good awareness of it. So I feel comfortable because of heaps of practice. But the short cut is to know that a vessels bow wave cuts the horizon if you are sat in your average cockpit a bit under three miles. Speed estimation is more difficult but ships often do around 15 knots, some slower, some faster. So that's yer three miles in twelve minutes so plenty of time for hand compass practice in those quite wide parameters. A starting point.Here's our source of misunderstanding I think. I for one wasn't suggesting using AIS to minimise CPA or change what I regard as a safe passing distance. I'd be hard pressed to do that anyway because the oow of give-way commercial shipping probably has standing orders to pass you at a certain distance.
What I to know in a channel crossing scenario is "Is that vessel going to pass me at a distance of more than my comfort threshold (which for many people will be somewhere between half a mile and a mile) or in the absence of other course changes, might I have to take action?" AIS answers that question for me much sooner than the naked eye, leading to a far more relaxed and enjoyable sailing. But then I acknowledge just generally worry too much
What? People on ignore on the boating forums?
I'm proud to be the first.