Seeing the SSP in action?

MarkShot · 11-11-07, 04:36 PM

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.

Dr.Sid · 11-11-07, 05:06 PM

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.

MarkShot · 11-11-07, 05:51 PM

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.

Sonoboy · 11-12-07, 01:07 AM

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?

FERdeBOER · 11-12-07, 07:40 AM

Quote:

Originally Posted by Sonoboy

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?

Sounds very interesting.
How did you make that?

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

Sonoboy · 11-12-07, 08:05 PM

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.

Cyklop · 11-12-07, 05:54 AM

Quote:

Originally Posted by MarkShot

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.

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.

Dr.Sid · 11-12-07, 06:48 AM

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.

11-11-07, 04:36 PM	#1
MarkShot Ace of the Deep Join Date: Jul 2002 Posts: 1,134 Downloads: 93 Uploads: 0	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. __________________ War games, not wars! --- Only a small few profit from war (that should not stand)!

11-11-07, 05:51 PM	#3
MarkShot Ace of the Deep Join Date: Jul 2002 Posts: 1,134 Downloads: 93 Uploads: 0	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. __________________ War games, not wars! --- Only a small few profit from war (that should not stand)!

11-12-07, 01:07 AM	#4
Sonoboy Planesman Join Date: Aug 2005 Location: United States, CA Posts: 195 Downloads: 9 Uploads: 0	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? Last edited by Sonoboy; 11-12-07 at 01:39 AM.

11-12-07, 08:05 PM	#6
Sonoboy Planesman Join Date: Aug 2005 Location: United States, CA Posts: 195 Downloads: 9 Uploads: 0	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. Last edited by Sonoboy; 11-12-07 at 08:17 PM.

11-11-07, 05:06 PM	#2
Dr.Sid The Old Man Join Date: May 2005 Location: Czech Republic Posts: 1,458 Downloads: 6 Uploads: 0	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.

11-12-07, 06:48 AM	#8
Dr.Sid The Old Man Join Date: May 2005 Location: Czech Republic Posts: 1,458 Downloads: 6 Uploads: 0	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.