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