Two TA = No bearing ambiguity

[Kazuaki Shimazaki II]

I personally wonder at times whether we should just eliminate that bearing ambiguity. With the frigate, the signal will resolve with a tiny, weeny turn and the false signal won't bother you again. With the subs, you might somehow resolve the false contact and squelch it, but the auto crew just plots it again in my experience.

I'm sure the disadvantage can be reduced by upping sensitivity as one sees fit (I've already proceeded to try that privately so Russian sonars progress from -8 to -10).

And there is no point in pretending the Akula is as good as the Seawolf in either silencing or sonar.

Something else one can try is change the torps of those ASW missile dropped torps from Circle to Snake. Overall, it is a more useful setting. Imagine when Seawolf shoots you, and you send off ASW missiles down the bearing line in 5nm increments, all of which start homing...

To forestall stupidities like deploying the missiles every nautical mile with a 14 SS-N-27 launch, try this. Put the new -27 torp on the Stallion (it is just a torp carrier, changing the torp carried shouldn't be outside the realm of possibility), and change that one's homing logic to Snake. Leave the SS-N-27 as is. That gives people a real reason to use it (right now, its slow torpedo and the limited utility of 100km class ASW ranges makes it not too attractive).

Another option, give them the Resolve Bearing thing, but on the -16, and drop sensitivity by two points, justified by:
1) They need contact on both arrays to do this.
2) They probably need more than a minimal signal on the weakest array to do the resolve automatically.

This turns the -16 into a Bearing Resolving sensor, and more people will deploy it.

[Wim Libaers]

Originally Posted by Deathblow

Bah, deep water conflicts are a thing of the past. When is the last time a "my giant fleet versus your giant fleet" conflict was ever plausible... about 15 years ago. Littorals is where its at. Then again, the littoral modeling in DW is *sigh* . Can't even figure out how to get the AI subs not to bottom out. .

Or the ships to stay in the sea...

[SeaQueen]

Originally Posted by Deathblow

For my own role-play purposes... Sometimes I delete the bearing ambiguity for the LA subs TA and then stream both the starboard and port arrays at the same time to simulate the twin-line system.... . Does wonders for the "clarity" of the taticaly picture.

The twin line thing is not for an SSN. It's for the SURTASS ships. I suspect it's because of the separation issue I just talked about. SURTASS ships are fascinating creatures. I'm always surprised the kiddies don't play with them more, considering how important they are to ASW strategy, but I guess it's another case of them not necessarily being "glamorous" hence, under-used in wargames made by hobbiests.

[SeaQueen]

Originally Posted by LuftWolf

So, the issue of twin-TA utlization is more an issue of computing power than physics for US subs currently... so the ambiguity stays for US subs. Nice try though.

Actually, as far as I've been able to tell, it's exactly the opposite. Computing power is probably not the big problem here. The thing is, the SURTASS ships are bigger, hence they are able to keep the twin line arrays sufficiently separated that the phase differences between corrolated signals are sufficient that one can exploit the effect.

[LuftWolf]

Wouldn't any offset do?

So two TA's streamed to different lengths wouldn't produce the same effect or a similar effect to two TA's streamed with some distance between them for their whole length?

[Kazuaki Shimazaki II]

Originally Posted by LuftWolf

So two TA's streamed to different lengths wouldn't produce the same effect or a similar effect to two TA's streamed with some distance between them for their whole length?

It won't. That's just roughly equivalent to a towed array with a longer set of hydrophones than normal. Bearing accuracy might go up if they are integrated correctly, but there will still be two solutions for the same time-differences.

As for offset, we are talking maybe 10 lousy meters (width of sub), and unlike the fixed bow arrays, the relative positions of the two are not precisely defined (they float around in the water).

[Bill Nichols]

I found this interesting little tidbit on a site about the Navy's ARCI sonar improvement program:


"Specific software improvements included passive ranging, spatial vernier processing, full spectrum processing, dual towed array concurrent processing, low frequency active interference rejection, passive broadband, passive narrowband and passive detection and tracking processing, track management, on-board training, and port/starboard ambiguity resolution."

http://www.defenseindustrydaily.com/...ated/index.php

[Henson]

Originally Posted by Bill Nichols

I found this interesting little tidbit on a site about the Navy's ARCI sonar improvement program:


"Specific software improvements included passive ranging, spatial vernier processing, full spectrum processing, dual towed array concurrent processing, low frequency active interference rejection, passive broadband, passive narrowband and passive detection and tracking processing, track management, on-board training, and port/starboard ambiguity resolution."

http://www.defenseindustrydaily.com/...ated/index.php

Yeah, with ARCI it'snow possible to run TB-16/23 and TB-29 thinline processing concurrently. It may or may not be used for resolving ambiguity, though I will say that the old-fashioned method has always worked just fine.

One gripe of mine in the game has always been the TA screens on subs. Our towed array broadband looks almost exactly what DW put in place for the FFG. This dual-sided nonsense is annoying, and clutters the screen in high contact density scenarios.

[Deathblow]

Originally Posted by Bill Nichols

I found this interesting little tidbit on a site about the Navy's ARCI sonar improvement program:

"Specific software improvements included passive ranging, spatial vernier processing, full spectrum processing, dual towed array concurrent processing, low frequency active interference rejection, passive broadband, passive narrowband and passive detection and tracking processing, track management, on-board training, and port/starboard ambiguity resolution."

http://www.defenseindustrydaily.com/...ated/index.php

Ah ha! So subs are toting dual towed arrays, or at least planning too. :hmm: Thanks Bill.

Originally Posted by SeaQueen

Actually, as far as I've been able to tell, it's exactly the opposite. Computing power is probably not the big problem here. The thing is, the SURTASS ships are bigger, hence they are able to keep the twin line arrays sufficiently separated that the phase differences between corrolated signals are sufficient that one can exploit the effect

.

Yeah those ships are pretty wide too, about 30meters in beam
http://www.fas.org/irp/program/collect/t19_bow.jpg
http://www.fas.org/irp/program/collect/surtass.htm
However, seeing what Bill just found seems like the projects has already been brought to subs, or at least soon will be. Intuitively, the wider the seperation, the better the resolution of the system, but the theory seems to still hold. Just cructhing some rough estimates...

...The speed of sound waves in water is roughly 1500m/s
With a distance of 10meters being the two arrays, the time delay between the two arrays intercepting the same signal should be on the order of a few hundredth to a few thousandths of a second. So if the signal processing is able to determine a 1/100th sec to 1/1000th sec time lag, in theory it shoud be able to delineate between the true and false contact vector with consistency, (perhaps not in turns as well). As far as range estimates, no idea here, as you said, range estimates are probably a bit trickier, and my recollection of advanced geometry and signal processing is too elementary/old.

So............ down with bearing ambiguity!!!

[SeaQueen]

Originally Posted by Deathblow

[
However, seeing what Bill just found seems like the projects has already been brought to subs, or at least soon will be. Intuitively, the wider the seperation, the better the resolution of the system, but the theory seems to still hold. Just cructhing some rough estimates...

Someone also pointed out that it's not clear whether this will be used for bearing ambiguity resolution or not. It might be, however, that improved processing might make phase differences that were previously not measurable measurable. It's hard to say, though.

.As far as range estimates, no idea here, as you said, range estimates are probably a bit trickier, and my recollection of advanced geometry and signal processing is too elementary/old.

It's called a hyperbolic fix. With two arrays you can't nail it down to a single point, but you can narrow it down to a range of possible points, from which you might be able to use other things to pick one.

[MaHuJa]

Running with two towed arrays out would provide you with a potential problem: towed arrays getting tangled in each other. That is not simulated in DW.

Further, you'd need to have the two TAs exactly as far out, and I think preferrably the same depth. (Oops, there went the ability to choose what sort of TA you need, fast or sensitive...)

What Kazushima (:hmm: gotta look that up, I suspect it will translate) said (non-fixed offsets) doesn't apply all that much for bearing resolution, until they swirl too close, into each other, or even switch sides, but when they do... If you stream them far, so as to let them get deep, and far from ownship noise, etc, etc, the swirling around will be greater.

Potentially even switching sides; That's a type of bearing resolution I would not want.


The only way I could see this get done is to give the TAs a small "tail" with two hydrophones and a "ballast" to make sure it doesn't roll, or four hydrophones and a direction sensor, and place them on the end of the TA. The idea is that the exact separation length shouldn't matter, as long as you can determine which side the sound came from. Essentially, this is to transform the TA from a one-dimensional to a two-dimensional sensor.

[SeaQueen]

Originally Posted by MaHuJa

Running with two towed arrays out would provide you with a potential problem: towed arrays getting tangled in each other. That is not simulated in DW.

This just increases the need for substantial separation between the two arrays.

Further, you'd need to have the two TAs exactly as far out, and I think preferrably the same depth. (Oops, there went the ability to choose what sort of TA you need, fast or sensitive...)

Why do you say that?