How is the convergence zone modeled in DW?

[Castout]

There's convergence zone modeled in DW as I noted in the mission editor.

So in theory it would be possible to get indirect contact through the convergence zone right? How far down? 1st convergence zone only? 2nd? Third?

It's a simple question please don't answer with an unnecessarily overcomplicated answers. In other words...keep it simple.

[Molon Labe]

It's just an area about 1-1.5nm wide at 30nm intervals where transmission loss is sharply reduced. For sure it goes out to three, I wouldn't rule out a 4th if you can get a loud enough source. Depth doesn't seem to matter at all.

[Castout]

Wow so it's possible to get a contact at 90nm. Though the window is pretty short so it's not possible to track a target at convergence zone. Is this correct?. Thanks.

Got a couple questions. Simple doesn't necessarily mean brief. Just do not go into that doctoral paper discussion. . My head just jams whenever I see a mathematical formula. Beautiful women too. Built that way it seems. LOL

Is indirect detection possible below thermal layer/deep depth in convergence zone?
Is direct detection range better when cruising below thermal layer for detecting a below thermal contact(same layer) compared with cruising above thermal and detecting a contact above thermal(same layer)?

Btw what is a surface duct. How is it different from convergence zone in terms of detection especially indirect detection.

You see I hardly know anything about the sonar environment. So help this poor fellow will you. never too late to learn something.
My questions are both for the game and in RL.
Many many thanks before.

[Molon Labe]

Originally Posted by Castout

Wow so it's possible to get a contact at 90nm. Though the window is pretty short so it's not possible to track a target at convergence zone. Is this correct?. Thanks.

It's actually somewhat easy to track a target in a CZ if you can make a reasonable guess about his course, since you automatically know the range. It's just a matter of getting on his course and matching his speed to hold him in the CZ.

Got a couple questions. Simple doesn't necessarily mean brief. Just do not go into that doctoral paper discussion. . My head just jams whenever I see a mathematical formula. Beautiful women too. Built that way it seems. LOL

Is indirect detection possible below thermal layer/deep depth in convergence zone?
Is direct detection range better when cruising below thermal layer for detecting a below thermal contact(same layer) compared with cruising above thermal and detecting a contact above thermal(same layer)?

I've never seen a cross-layer CZ contact and I don't expect to. That's not to say it's impossible; I don't know enough about the "rules" of the acoustics model to know that. But, the transmission loss across the layer at 30nm is already very, very high so even if it was within the "rules" to get the CZ bonus across the layer, I doubt it would be enough to result in a contact.

In a CV SSP, there is only a slight difference between direct detection ranges above and below the layer. IIRC, ranges are a bit longer below the layer; but, I made that observation before the studies were done by others showing a correlations between depth and detection range, and there is enough of a margin of error there to cast doubt on my observations.

Btw what is a surface duct. How is it different from convergence zone in terms of detection especially indirect detection.

In DW:

A SD SSP has a positive gradient above the layer (the surface duct) and a negative gradient below. You'll get long detection ranges above and short detection ranges below.

A CZ SSP has a surface duct above the layer and a sound channel below, in addition to having convergence zones modeled every 30nm. Detection ranges are long both in the duct and in the sound channel.

As for real life, DW is fairly close in the surface duct environment; a surface duct really is a zone of positive gradient above the layer where the sound bends away from the layer and refracts along the surface.

A real life CZ has very little resemblance to a DW CZ or DW CZ SSP. CZ's don't necessarily form at 30nm intervals and don't occur at all depths simultaneously, but at specific bands in 3-dimensional space (usually--or perhaps always?--near the surface). The SSP also isn't possible without a hell of a lot of excess depth, but a shallow bottom does not prevent the SSP from forming in DW.

[Castout]

Wow thank you for your explanation bear with me as I have to confirm some of the answer to make sure I don't get it wrong.

Originally Posted by Molon Labe

I've never seen a cross-layer CZ contact and I don't expect to. That's not to say it's impossible; I don't know enough about the "rules" of the acoustics model to know that. But, the transmission loss across the layer at 30nm is already very, very high so even if it was within the "rules" to get the CZ bonus across the layer, I doubt it would be enough to result in a contact.

So I take it that convergence zone contact across layer is actually not really possible but convergence zone contact on the same layer both below and above thermal layer is possible i.e convergence zone contact can happen below thermal layer.

Originally Posted by Molon Labe

A real life CZ has very little resemblance to a DW CZ or DW CZ SSP. CZ's don't necessarily form at 30nm intervals and don't occur at all depths simultaneously, but at specific bands in 3-dimensional space (usually--or perhaps always?--near the surface). The SSP also isn't possible without a hell of a lot of excess depth, but a shallow bottom does not prevent the SSP from forming in DW.

Now I'm a bit confused so convergence contact in RL can only happen near the surface? while in DW convergence zone contact can happen below thermal layer?

[Dr.Sid]

Check this thread:
http://www.subsim.com/radioroom/showthread.php?t=117814

I'm not sure if I tested it but I think you wont get CZ contact from under the layer. It should be possible and zones of focused sound should go deep. But it's quite complicated, and what more it depends on frequency a lot.

As for DW, I simply suggest you try it. My guess is they won't go under the layer.

[Dr.Sid]

Here is picture of general convergence zones situation from my SoundPropagation simulator (http://roger.questions.cz/other/SoPro.1.9.zip).
You can see that CZ goes deep, but not straight down. Note that this image is not much correct since it stops simulating the rays as they leave the rectangle and with convergence zones situation they would bend back and get 'into the picture' again.
Also this is raytracer, it applies only for high frequencies, so let's say it's applicable for active sonar.

While DW still can surprise with it's sound propagation model, it's much much simpler then this.

[Molon Labe]

Originally Posted by Castout

Wow thank you for your explanation bear with me as I have to confirm some of the answer to make sure I don't get it wrong.

So I take it that convergence zone contact across layer is actually not really possible but convergence zone contact on the same layer both below and above thermal layer is possible i.e convergence zone contact can happen below thermal layer.

Well, if Sid is going to dispute it, I'll say that it's possible that I'm wrong. But I don't think I am. To the best of my recollection, I've observed CZ contacts on both sides of the layer.

Now I'm a bit confused so convergence contact in RL can only happen near the surface? while in DW convergence zone contact can happen below thermal layer?

Well, I'm confused myself, hence the question mark. I know that propagation models will show sound paths converging in and around a sound channel; what I'm not sure about is whether these are called convergence zones or if they have another name. I've never seen them identified as such on anything I've read on the subject.

[Castout]

Thanks man I'll be sure to download your sound simulation.

We got books on submarine but I don't recall any of my books talk about the sonar environment. Doh.

[Castout]

So that is how surface duct sound propagation looks like.

I don't really understand it wholly but I think I get some idea .
Would be great if your program were to come with docs or manual explaining stuffs especially explaining the results gotten from the available profiles.

Do you happen to have written such docs? Would be great if you are willing to share them or at least some of them.

The scales they are per pixel? Would be great if they were labeled. Nice job. You're writing a thesis on sound propagation?

[Dr.Sid]

Well I might wright page or two tonight. I know it calls for some docs.

Every scale is per pixel, or it is mentioned in mini-help for actual parameter (or it should be). Also mouse can be used for reading results, it shows distance, depth, actual transmission loss and difference against simple spherical spreading.

This simulation has little actual sonar know-how. It's ray-bending based on propagation speed changes. This applies to sonar too, so if you enter correct values, you'll get more or less correct prediction for sonar, but it would be used for light propagation on atmosphere for example or anything similar.

As for books, this one is good, on the other hand the only I have:
http://www.amazon.com/Principles-Und.../dp/0932146627

MolonLabe: I'm not sure at all. Only only played with CZ for a while and I never actually used them in mission.

[Castout]

Originally Posted by Dr.Sid

Well I might wright page or two tonight. I know it calls for some docs.

Every scale is per pixel, or it is mentioned in mini-help for actual parameter (or it should be). Also mouse can be used for reading results, it shows distance, depth, actual transmission loss and difference against simple spherical spreading.

Haha that book is heavy stuff .

Thanks I'll be waiting for some sort of docs.

Oh yea my mouse shows the data. I just realized that doh.

From playing the program do all submerged submarines could be detected right on the surface top area directly above their location?

Because it seems no matter what the SSP is the sound always travels upright without any hindrance.

So no matter how deep the sub is the surface location somewhere right above it always leaves a tell tale of the sub noise? is this correct?

[Dr.Sid]

Yes that is correct. The more vertical the ray is, the less it is affected by bending. Vertical rays goes always straight.
This is even used with active sonar .. the ping is directed toward the bottom rather then directly at the target. Bottom bounce can get better results because the beam is less horizontal and less affected by SSP.
http://www.tpub.com/content/aerograp.../14010_181.htm

[Dr.Sid]

I've posted first version of the documentation here. I would appreciate if someone could proofread this and suggest better formulation where needed, or suggest unclear or missing parts.

http://subsim.questions.cz/sopro/doc/sopro.html

[Castout]

Though I haven't read it thoroughly may I suggest that for each SSP profile you include a 3 analysis set when the source is at near surface, medium depth and deep depth,

So could and would you please give some sort of analysis when the source is near the surface(0-30m), medium depth like 200-250m, and deep depth like 450-550m for each of the profile included.

Imo that would be a gem to read .

for lay man analyzing the simulation result himself may not be that straightforward so this 3 set analysis for each profile would make a fine reference for any of us to make better and more accurate sense of those beautiful wavy results.