Seeing the SSP in action?
 

I have understood in principle for a few years now how thermals affect sonar. However, I never saw anything concrete upon which to measure it in SC/DW.

Today, I was going through the Akula training mission for SC by Eric Fox. He pointed out that you could graphically signal strength in DEMON by number of lines and the thickness. I never knew this. Sure enough as you change depth across layers, the right most line simply dissappears. This is the first and only time I have seen and easy graphic representation of the SSP in action.

Is this common knowledge and everyone knows this already? For me, it just came as a revelation!!!

Thank you, Eric Fox.

Well DW had very very weak effects until version 1.03 came out. Than it chenged to this: http://www.subsim.com/radioroom/showthread.php?t=117814
In short - under the layer the signal is somewhat weaker, and under the layer at some range there is a shadow zone where you can't be heard (or pinged) at all. This is for surface to submerged and vice versa.
I didn't measure fully submerged vs. submerged yet.

I can't tell about SC .. and I have never seen such effects on DEMON .. but I simply wasn't looking for them.

I have been changing depths in SC today. It seems most noticeable with a weak contact on DEMON. So, for the ones I have been looking at sphere seems to illustrate this pretty well. Remember that sphere in stock SC seemed to provide detection out 10,000yds. This was greatly toned down in SCX such that sphere was very limited to only close contacts leaving TA as your only real tool for ASW work. In stock SC, getting a master contact between TA and sphere was pretty easy and then your solutions were much more accurate with triangulating. (In stock, even without a track on the waterfall or NB lines in sphere, once you had a TA bearing, you could often attempt to designate in BB to pick the contact up on a sphere.)

Anyway, I have seen two moderate rightmost DEMON lines drop off DEMON going from 100' down to 1550' in the 688I. Before they drop off, rather than get very thin they begin to break up into bursts of signal and then quiet. Eric implies in his tutorial that this behavior is analogous to how detectable your sub will be from the other platform.

Just the other day, I was experimenting with depth below the layer and detection ranges with a surface duct. I had contacts spread out from 1nm up to 18nm. I made a graph of it in excel, and I will post a screenshot of it when I can.

Does anyone know of a good place that will host the image?

The Towed Array Sonar on the FFG will display SNR values for particular tracks. As long as the Noise Level remains constant, the SNR is directly proportional to received signal power.

If I am not mistaken, there is a similar feature onboard the Seawolfs.

SNR in DW does not change with noise level, at least not when you change speed (thus increase your own waterflow noise). However I did not test it with different sea states.

Edit: it does not change even with different sea states. Noise however affects detection range. SNR in DW (FFG) is simply signal strength, not signal to noise ratio.

Sounds very interesting.
How did you make that?

Imageshack http://imageshack.us/ is a good place to upload a screenshot.

I had 18 Nimitz spread out evenly along 180 degrees to my front, since I was using the sphere array for this experiment. They were successively spaced in intervals of 1nm starting at 1nm from ownship. All speeds were at 15kts. I simply changed depth under the layer until I was able to hear a contact, then find the exact depth at which contact was gained. I recorded 3 trials, each with a different layer depth. The graph below also has trendlines included. I would assume that layer depth in this experiment would also equal contact's altitude above the layer (I havent tested with submarines yet).

http://img228.imageshack.us/my.php?image=layergk9.jpg

The shadow zone would be to the right of the curve, and the detection zone to the left.

Was the SSP for that data Surface Duct or Convergenze Zone?

Surface duct.

Nice one :up: Would be good to add even more shallow layers with CZ SSP. And to test if there is any difference in shadow zone shape with CZ SSP.

Sorry for refloating this post. I come from this one http://www.subsim.com/radioroom/showthread.php?t=131383 but I think this is a better place to talk about what I've made.

I've been making tests with this:
- O.H. Perry in ENCOM at 10 knots closing to an Akula2 (me) running at 5 knots.
- Seastate 2
- Surface duct, very deep water
- April, mid Atlantic (30N), clear weather
- LwAmi mod v3.08
- SONAR autocrew
- Created a trigger that tells me when I'm detected by the Perry.

These are my first results:

when I'm at 500m deep, I detected the Perry very far (more than 14nm if I remember well) and I was detected at 5 nm.

When just up or bellow the layer I was detected at 8,5 miles and I still not detected the Perry.

At 50 meters I detect the Perry at more than 10 miles (don't remember exactly) an was detected at 8 miles.

At PD I detect the Perry at 14 nm and was detected at 7,5

So I'm comfused :doh:

- seems that you're right about ownship's detection capability and shadow zones. But I allways thought that if you're in a shadow zone and you can't detect a ship, the ship can't detect you... but my tests doesn't support this... :shifty:
- Some players, like Dr.Sid, have stated that approaching just bellow the layer is a very good tactic, even better than doing it deep... but again my tests says that going deeper is better.

I have to test this with suonobuoys under and above the layer, but seems that against a surface ship in deep waters is better going as deep as you can...

My next tests will be with excel open...

EDIT: OK, I've made a new test with conditions changed a bit:
- Instead of my sub being the one detected by the Perry, I set up a line of 12 Akula2 AI subs at 5 knots a different depths and triggers that tell me when a sub is detected by the Perry.
Conclusion: you're right and I was wrong.

The detection depth is more or less the same above the layer (8 miles), but just below the layer it decreases highly to 3.6 miles and, as we go deeper, the range increases again to 7.8 miles at 500 meters.

I will make another test tomorrow, this time also with the subs detection range and will post some screens.
But seems you're right, being just above the layer is a great chance for the sub.

If you are using sonar autocrew, you cannot say with any confidence that you were in the shadow zone but were counterdetected anyway. In all likelihood, you were NOT in the shadow zone and you both could have detected each other.

There are no 'good tactics' in the abstract. Tactics are goal-dependent. If holding a track is more important that avoiding counterdetection, then deeper is better. If avoiding counterdetection is more important than holding a track, than shallower is better.

...a much better method of testing. :up:

Also think about towed arrays. You may be in the shadow zone, whily your TA not and vice versa. Also the FFG can use TA (in LWAMI i think it does) and it can get under layer.