Sonar in demo 1.02

[DivingWind]

I tryed demo 1.02 ,mission with KILO.
Someone explane the phenomenon of contacts appearing an reappearing after 3-5 seconds and that happens through out the mission!
Is that normal behaviour?
Who else tryed demo 1.02,share your experience.

[Amizaur]

Noticed that too. I guess there is some random factor put in sonar model now. But question is, what should be time base for such change ?
Any sonarman here, is something like that (singal changing between strong/weak/no signal at all every second or two) existi9ng in real life ?
Or maybe there are changes but much slower ?

I also noticed that it's little difficult for me to after marking a contact in BB see it's data in DEMON station. You have to wait for moment when signal is strong and THEN switch to demon, if you do this in a moment when signal disappears, there will be nothing in DEMON...
Anyone else experienced this ? Would suggest it as something to fix (not very important but always...). And how to fix it. Would increasing time scale (the fluctuations would be slower, changing every few seconds, not every second) be OK ?

[Molon Labe]

Originally Posted by DivingWind

I tryed demo 1.02 ,mission with KILO.
Someone explane the phenomenon of contacts appearing an reappearing after 3-5 seconds and that happens through out the mission!
Is that normal behaviour?
Who else tryed demo 1.02,share your experience.

I thought it was the ship's propeller coming out of the water because of the waves, then re-entering...

[SeaQueen]

Originally Posted by Amizaur

Noticed that too. I guess there is some random factor put in sonar model now. But question is, what should be time base for such change ?

I haven't played it yet but if it's what it sounds like then your guess is as good as anyone's. :-) It does happen in real life. This is actually a very smart way to model sonar. When one does it, the usual answer is, "gee... that looks about right."

If you want to get REALLY technical, I think they've done something sort of like what's called the "lambda-sigma" process. The idea is that one's signal excess (the brightness of the lines you see on your waterfall display) is composed of the sum of two terms: a deterministic component and a stochastic component. The deterministic component is usually pretty nailed down. It comes from engineering data. The stochastic component is squishy no matter what you do because it depends on oceanographic processes.

[DivingWind]

Originally Posted by Molon Labe

I thought it was the ship's propeller coming out of the water because of the waves, then re-entering...

It happens to all ships in the KILO demo mission and MH-60 demo mission! (in helo mission sea is smooth as mirror)

[Amizaur]

Originally Posted by SeaQueen

pretty nailed down. It comes from engineering data. The stochastic component is squishy no matter what you do because it depends on oceanographic processes.

But how fast those changes are ? Change every second from strong to weak or no signal at all ? Or did you mean "every time you calculate it" ?

[DivingWind]

This phenomenon also occurs with MH-60,contact appears and then reappears on passive sonar display.

[Fish]

I replaced the sub east to 1000 feet of water, now the signal is steady, so has to do with water depth.
Bottom bounce perhaps?

[DivingWind]

:hmm: interesting... will track freight ship to deeper waters in demo, I whant to see how depth will change behaviour of sonar.

[DivingWind]

If this is a bottom bounce so it doesnt work on torpedos.Torpedos produce steady spike whatever the depth is...

[SeaQueen]

Originally Posted by Amizaur

But how fast those changes are ? Change every second from strong to weak or no signal at all ? Or did you mean "every time you calculate it" ?

I'm not sure what you mean. The signal excess you get changes from time to time as a result of the stochastic term. Nobody knows how often that stochastic component should change. It's the result of oceanographic processes, but that's about all that's known. So, from the perspective of modeling, no matter what you do it's kind of squishy.