Two TA = No bearing ambiguity

[Deathblow]

OkeeDokee....Hypothetically....

If any ship were to deploy two towed arrays at the same time (as in the dual towed array systems being developed by some navies), then hypothetically both towed arrays together would be able to detemine "true bearing" to the contact without having to undergo ship course changes. The signals detected on the TA would just be time compared (to see which TA is seeing the signal a fraction of a second before the other, that TA is toward the real contact and not the mirror).

That being accepted as true.... shouldn't submarines be able to deploy both their TA to eliminate bearing ambiguity?

I have a theory that some subs do this already....... related to a theory that I have that the SW and VA actually have more than 2 TA (perhaps 3 - 4, and that is the reason it has 2 seperate TA fins instead of streaming the TA from the aft control surfaces like previous designs).

Therefore... I vote all US subs TA have their "mirrored contact" stats removed. :yep: :)

[TLAM Strike]

:huh:

With two TAs you would have two ambiguous bearings and two true bearings. :nope:

EDIT: As for testing the time a sound is recived by the TA that might (stress might) work with a contact off its beam but not with a contact fore or aft of it. And it might not work with a contact thats abeam unless it makes a trasient noise.

[GunnersMate]

And you'd have the task of syncronizing both TA's

[SeaQueen]

OkeeDokee....Hypothetically....
That being accepted as true.... shouldn't submarines be able to deploy both their TA to eliminate bearing ambiguity?

You're actually right on. In fact, by measuring the phase differences between corollated signals you could also determine the range. There's also some tricks to it, though.

In order for that phase difference to be measurable, you need to have the two towed arrays sufficiently separated. It's not clear to me that streaming a pair of towed arrays behind an SSN would result in sufficient separation. I suspect some other systems might use the technique. Also, signals become distorted as they travel through the water, so corrolating signals is not necessarily an easy thing to do.

They actually used to do a similar thing to what you're talking about with LOFAR sonobuoys, and use that to determine bearing and range with an omnidirectional sonobuoy. Unfortunately, the model doesn't really take that into account.

[Deathblow]

EDIT: As for testing the time a sound is recived by the TA that might (stress might) work with a contact off its beam but not with a contact fore or aft of it. And it might not work with a contact thats abeam unless it makes a trasient noise.

Not neccessarilty. The signal will be continously time shifted with or without a transient. As the sound is continuously intercepted, the signal/sound waves should have a predictable latency real-time, imho. Though how accurately it could be determined I don't know.

http://www.lockheedmartin.com/wms/findPage.do?dsp=fec&ci=17302&rsbci=0&fti=112&ti=0&sc=400
The SURTASS TL-29A twin-line system is an underwater passive acoustic sensor with a pair of arrays towed side-by-side from a ship. The TL-29A delivers unsurpassed capabilities, such as its ability to be towed in very shallow water environments in the littoral zones, to provide significant directional noise rejection, to resolve bearing ambiguities without turning, and to allow the ship to tow at higher speeds

http://www.fas.org/irp/program/collect/99-06_t-agos_upgrades.htm
The twin-line array, which was developed by a joint government-industry team comprised of the John Hopkins University Applied Physics Laboratory, Chesapeake Sciences, and the Navy’s Array Technical Support Center, Little Creek, Va. employs COTS telemetry architecture and consists of two short parallel acoustic arrays separated by several meters. The array provides for left-right ambiguity resolution, back lobe rejection, and the flexibility to tow in shallow water

So this capability already exist and is probably already deployed in some regards... only question is whether the distance seperating two TA on a submarine is sufficient enought to do the job... :hmm:

Down with bearing ambiguity!! :yep: :) .... at least for US subs

[Deathblow]

In order for that phase difference to be measurable, you need to have the two towed arrays sufficiently separated. It's not clear to me that streaming a pair of towed arrays behind an SSN would result in sufficient separation. I suspect some other systems might use the technique. Also, signals become distorted as they travel through the water, so corrolating signals is not necessarily an easy thing to do.

That is what I was thinking as well. It would probably take a whole lot of processing power to crunch through all the signal distortion, and provide an accurate deduction. Perhaps the COTS programs in the works are addressing the need.... I also wonder if the TAs themselves being a source of drag noise "muddying up" each other signals. But it seems since the systems are already in deployment that they have overcome most of the glaring obstacles.

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. :yep:

Does anyone agree with me that the SW and/or VA probably has more than 2 TA or at least the capability to fit more than 2 TA. 2 thru the designated TA fins at stern, and maybe another couple thru the aft dive fins like the old LAs. Seems only logical, whey else would the designers decide to bite that extra drag/noise penalty in creating two more seperate aft planes.... (of course it could be to the reason of "upgradeablility" where the 2 extra pylons are somehow more easily/cheaply serviced or upgraded than TA that run thru the dive planes..... just speculation)

[LuftWolf]

I don't think the 688/688i carry enough processing power to perform the necessary calculations... considering the SW was built without utiziling COTS from scratch (the TB-29 currently on the 21/22 are of the legacy variety as far as I can tell), I'd say it's the same for the 21/22 (JC probably has more significant COTS implementation so may already be utilizing the TB-29A, the COTS variety of TB-29).

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. ;) :-j

[Deathblow]

I don't think the 688/688i carry enough processing power to perform the necessary calculations... considering the SW was built without utiziling COTS from scratch (the TB-29 currently on the 21/22 are of the legacy variety as far as I can tell), I'd say it's the same for the 21/22 (JC probably has more significant COTS implementation so may already be utilizing the TB-29A, the COTS variety of TB-29).

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. ;) :-j

COTS can handle it! :yep: The programs needed to continously update the old 688i software has been in place since 1997. The 688 software systems have been undergoing continuous upgrades for the last 9 years. The SW was designed with open-enough architecture to be amendable to rapid software/systems upgrades.

http://www.fas.org/man/dod-101/sys/ship/ssn-688.htm
A-RCI is a four phased transformation of existing sonar systems (AN/BSY-1, AN/BQQ-5, or AN/BQQ-6) to a more capable and flexible COTS/OSA-based system. It also will provide the submarine force with a common sonar system. The process is designed to minimize the impact of fire-control and sonar system upgrades on a ship's operational schedule, and will be accomplished without the need for major shipyard availabilities. Phase I, which commenced in November 1997, will enhance towed-array processing. Phase II will provide additional towed- and hull-array software upgrades. Phase III will upgrade the spherical array, and Phase IV will upgrade the high-frequency sonar system on SSN 688I-class submarines. Each phase will install improved processing and control and display workstations. The current installation plan completes all SSNs through Phase III by FY03.

Processing power not a prob. :) Bearing ambguity.... going down! :yep:

[LuftWolf]

Yes, but SCS has modelled the non-COTS version of Western platforms. :)

I can't change that without altering the interface heavily and making the western platforms so VASTLY superior to the russian units that it wouldn't be worth playing much... my guess is with full COTS implimentation, the US acoustic superiority over the Russians is probably at least as great as during the height of the Cold War pre-Sierra class.

But again, I'm wildly speculating...

[Deathblow]

I'm not trying to be argumentative...oh wait, yes I am :-j :lol:

The currest LW&A is using a TA system that wasn't in place until 2002, and the Mk54 that wasn't slated to be deployed until 2003, both post-COTS (1997), so a 2005 launched twin-line array system isn't that much of a strecth....and besides.... those UI look pretty COTS to me, especially the SW.

Come on, you know you want to try it.... :yep: ... just click off the "mirrored" contact in the DWEditor. Come'on... everyone's doing it, you'll like it, don't you want be to cool, like the cool kids.

Go West!! :)

[LuftWolf]

Nope, no more help for Western platforms in DW as far as I'm concerned.

Not until the Russians start actually making competitive subs... so never. :lol:

There should be some reason to actually play the game, rather than just decide who wins in the game lobby (although five out of six players taking SW's in dives is no fun as it is...).

[Deathblow]

Fine. :shifty: Pooh. Not trying to imbalance the game, just a great sonar system is a great sonar system... and resolving bearing ambiguity is one of the more boring parts of the game IMHO, I'm glad to be rid of it (on my personal modded version).
Not until the Russians start actually making competitive subs... so never.
*awaits Kapitan's wrath of spam*

Well they do have the Kilo and now Lada, quiet as silent death, which is what has made these major sensor improvements necessary in the first place (for nukes that is). When in the littorals, and coupled with a AIP, the nukes are at some pretty big disadvantages.... SSK no longer as dependent on disiels and speed not been the issue in the littorals, super sensors are the only thing keeping the nukes "above water. :hmm: "

... hm... I guess what would *really* make it "even" is if SSKs began being modeled ingame with AIP...:hmm:. Whole different ball game then.:yep: *sigh* but once again we are at the "but the engine doesn't allow that* problem as always, deja vu.

[LuftWolf]

The littorals are of course a different issue... not particularly well modelled in DW. But as it is, in bad sonar conditions in DW things are pretty well balanced depending on how the mission is set up.

In any case, I was thinking specifically about deep water situations, where the Akula is at disadvantage all considered against SW and is close to 688i in the game and is actually at a considerable disadvantage to both 688i and 21 in real life now.

Diesel subs and shallow water are a whole different issue. :P

[Wim Libaers]

To eliminate the ambiguous bearing, I think you'd need sufficient lateral separation, which is probably hard for subs. Range determination would be easier with two TA's streamed to different lengths, and that's probably a more significant advantage as it's harder to be sure about that. Bearing only requires one turn.

[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. :yep: Then again, the littoral modeling in DW is *sigh* :nope: . Can't even figure out how to get the AI subs not to bottom out. :88) .

Although "simulation" and "balance" are sometime mutually exclusive, if the Akula needed some "boosting" it could alwasy be given the Squall Advanced version, something that I was arguing for a while back, which is toted to have a burst, then slow and search mode.

[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]

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. :yep: Then again, the littoral modeling in DW is *sigh* :nope: . Can't even figure out how to get the AI subs not to bottom out. :88) .


Or the ships to stay in the sea...

[SeaQueen]

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. :yep:


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]

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. ;) :-j

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]

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/2006/03/usa-upgrades-submarine-fleet-acoustics-under-arci-program-updated/index.php

[Henson]

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/2006/03/usa-upgrades-submarine-fleet-acoustics-under-arci-program-updated/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]

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/2006/03/usa-upgrades-submarine-fleet-acoustics-under-arci-program-updated/index.php
Ah ha! So subs are toting dual towed arrays, or at least planning too. :hmm: Thanks Bill. :smug:

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!!! :D :yep: :up:

[SeaQueen]

[
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]

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?