No preset for 'in the layer' - should I be spending less time there?

[ColonelMolerat]

When I'm moving my submarines in areas that could be risky, I tend to set waypoints alternating between 'just above the layer', 'just below the layer', and a manually-set depth of 'in the layer'.

(I was under the impression that being in the layer would help reduce the chance of being detected by sensors coming from either above or below).

However, there is no preset for 'in the layer' - is this because, in actual fact, it's not so useful to be spending quite so much time there? Or was it just not included?

(Also, not quite on the same topic, but when setting depth, the slider doesn't show up on waypoints, only on the sub itself. Might this be changed?)

(One last thing - I thought to ask here first so I wasn't posting loads - the manual mentions subs can lie 'belly-up' at the bottom of the sea to reduce sonar echo. Is that modeled in the game? (Should I be taking advantage of it?)

[SeaQueen]

"In the layer" has no physical meaning. Unfortunately, the idea that "the layer" has thickness rests on a fundamental misunderstanding of the oceanography driving the speed of sound. It's one of the things, frankly, that Command gets wrong.

When people talk about "the layer" what do they really mean?

In underwater acoustics, "the layer" or "the thermal layer" refers to "the isothermal layer," or sometimes the "mixed layer" The isothermal layer is a layer of water which extends from the surface to some depth. It is created by the wind stirring up waves, which causes the water to stir up. The mixing can persist long after the original event which caused it so there's not necessarily a correlation between the layer depth and sea state. The "stirring" of the ocean's surface causes the upper portion of it to be of fairly uniform temperature as a function of depth. Since the water is mixed, the only thing driving the speed of sound is the pressure, so if you plotted the speed of sound (c), and a function of depth (z) you'd see a gently increasing speed of sound as a function of depth.

After a certain depth, the water temperature starts to drop and begins to dominate the speed of sound. The result is that the speed of sound begins to drop at the lower limit of the isothermal mixed layer. That drives the speed of sound down. The result is a discontinuity in the speed of sound as a function of depth at the lower boundary of the isothermal mixed layer. Sometimes that discontinuity is referred to as the "sonic layer" because discontinuities in the speed of sound cause sound waves to be reflected off of it. That is the phenomenon responsible for surface ducts and shadow zones.

[ThornEel]

Does it mean that "just above over the layer" should be replaced by something like "at the bottom of the layer" or "just above the layer limit"? How could it show that the (sonic) layer is an interface with no thickness?

[SeaQueen]

No, "just above the layer" is fine. It just means, "in the surface duct." It's a good place to be if you want to keep yourself opposite an opponent who might be just on the other side of the sonic layer and trail your towed array below it, in order to hopefully get a sniff of them. It's a bad place to be if you want to evade surface ships with hull mounted sonars.

ORIGINAL: ThornEel

Does it mean that "just above over the layer" should be replaced by something like "at the bottom of the layer" or "just above the layer limit"? How could it show that the (sonic) layer is an interface with no thickness?

[ColonelMolerat]

Thanks for your help!