![]() |
SUBSIM: The Web's #1 resource for all submarine & naval simulations since 1997 |
|
![]() |
#1 |
Nub
![]() Join Date: Jul 2014
Posts: 4
Downloads: 62
Uploads: 0
|
![]()
Looking for advice on creating a test mission to see the differences of player 688i detection ranges for various things. My question is what water depth and environmental conditions are needed when creating this mission to get the best performance out of the 688i sonar. The manual does not go into detail about the various uses of bottom bounce, surface duct, and convergence zone. It doesn't say the right depths and conditions that are needed for each of these to occur. I would also like to know how I can setup a trigger for being counter detected. So I know exactly at what range the AI can detect me.
|
![]() |
![]() |
![]() |
#2 |
Gefallen Engel U-666
|
![]()
§amael!
![]()
__________________
"Only two things are infinite; The Universe and human squirrelyness?!! |
![]() |
![]() |
![]() |
#3 | |
XO
![]() Join Date: Jul 2009
Location: Preston, Lancs, UK
Posts: 418
Downloads: 137
Uploads: 0
|
![]() Quote:
![]() I can't answer your questions, but assuming someone can, I'll be watching this thread with interest. I suspect there isn't going to be the definitive answer that you want though. There are a lot of variables and they interact in ways that aren't always easy to predict. I mean the game is supposed to model real sonar performance, and the submariners on here seem to think it does a good job. As I understand it real-world sonar is anything but an exact science. Wish I knew more about this than I do, but As I say, I'll be watching the replies with interest.
__________________
Forget death - I'll take dishonour! [SIGPIC][/SIGPIC] TMO 2.5 1.5 Optical Targeting Correction 031312 for TMO 2.5 1.5 OTC Realistic Scopes for TMO TheDarkWraith_DC_Water_Disturbance_v2_0_SH4 Improved Stock environment v3_TMO&RFB TMO_Alt_engine-sounds TMO_Alternate_JS_Radar_performance TMO17_19_different_smoke |
|
![]() |
![]() |
![]() |
#4 |
Chief of the Boat
|
![]()
Welcome to SubSim §amael
![]() |
![]() |
![]() |
![]() |
#5 |
Commander
![]() Join Date: Jun 2004
Location: Switzerland
Posts: 469
Downloads: 2
Uploads: 0
|
![]()
not much to add to Invinovomitus post, too many variables involved and approximation must be met. Here it is well described http://fas.org/man/dod-101/navy/docs...P/snr_prop.htm
if i wanted to test maximum detection range i'd be looking for a rocky bottom and 200-700m depth, but there's probably a better way
__________________
If you are going through hell... keep going (Winston Churchill) |
![]() |
![]() |
![]() |
#6 |
Captain
![]() Join Date: Aug 2011
Location: Nuclear submarine under the North Pole
Posts: 481
Downloads: 1
Uploads: 0
|
![]()
There's really no simple answer here. Whether or not you can get a detect depends on the environment, the source frequency, the sonar operator's skill, and the array used and its processing.
For example, you could get a convergence zone detection at any number of multiples of 65 KYD, however you wouldn't be able to pick up the same contact in between the CZs, so would one consider this the "true" max detect range? Basically, you can expect a detection if the signal-to-noise ratio is above some threshold of detection, regardless of the range. Although range figures into the SNR, there are a large number of other variables, the most important one being the sound speed profile. DW's propagation modeling is extremely simplistic, so I wouldn't put too much faith in it. It doesn't take into account sediment types for bottom bounce, and doesn't do multipath, so there isn't much point in looking at the different paths where you might get detection. The CZs and surface ducts that DW models are basically hardcoded effects for gameplay and don't really have any bearing on accuracy from a physics standpoint. However, since you asked, here are the situations where you'd see the various paths: CZ: You need *really* deep water for this (> 12,000 feet or so) with a slightly downward-refracting sound speed profile near the surface. Remember that sound curves away from higher sound speeds, so at the surface you'd need a higher sound speed, and at deeper depths you'd also need a higher sound speed. This causes the sound to first bend downwards towards the ocean bottom, and, if the gradient is gentle enough and the water deep enough, the sound will eventually curve back towards the surface. This leads to "rings" of good sound propagation around the source. Generally these rings tend to form roughly every 65 KYD, but depending on the water chemistry this can change. For example, in the Mediterranean Sea, the higher salinity causes CZs to form at multiples of 35 KYD or so. BB: Bottom bounce basically just needs a strongly reflecting bottom and a sound speed profile that is isovelocity (same speed throughout) or slightly downward-refracting. Depending on the depth of the water, this leaves a good propagation "ring" around the source similar to a CZ, however the depth of the water and the incident angle of the sound path control how far out the ring occurs. If you then get a bounce off the surface, you can sometimes get another bottom bounce, leading to another weaker "ring" further out. SD: Surface duct is probably one of the most complex effects in the ocean. To get it you generally need a "notch" in your sound speed profile where the sound speed is the lowest at some depth (where your profile looks something like a < sign). This causes sound to bend down, then back up, then back down, trapping it for long ranges. Like CZs, surface ducts can carry sound extremely far, but unlike CZs they allow detection across the whole range instead of just a focused boundary. They also create a shadow zone, below which a listener on the surface cannot detect what's below the sound speed notch (formally called the layer depth), and which a listener below the layer can't hear what's above it (though propagation tends to favor listeners below the layer like a one-way mirror). Surface ducts, though, have a strong frequency component, and tend to trap higher frequencies better than lower ones. In fact, whether or not a frequency can even get trapped in a surface duct depends on its wavelength, with longer wavelengths (those longer than the depth of the duct) "leaking" out of the duct into the water below. This tends to put a limit on how far out a surface duct can propagate, as the seawater itself absorbs higher frequencies, so you shouldn't expect a surface duct detection at the same ranges you'd see a CZ detect. One exception to this is the half-channel duct, which is like a surface duct that goes almost completely to the bottom in shallow water. In this somewhat rare environment, detections out to many hundreds of KYD would not be unheard of. Keep in mind, although I've given you some ranges here, that doesn't mean you're guaranteed a detect; it just means that at these ranges the propagation loss is at its lowest, and so you have the best chance of picking something up. |
![]() |
![]() |
![]() |
#7 | |
XO
![]() Join Date: Jul 2009
Location: Preston, Lancs, UK
Posts: 418
Downloads: 137
Uploads: 0
|
![]()
Thanks for this - I think you may have advanced my understanding by an order of magnitude
![]() Quote:
__________________
Forget death - I'll take dishonour! [SIGPIC][/SIGPIC] TMO 2.5 1.5 Optical Targeting Correction 031312 for TMO 2.5 1.5 OTC Realistic Scopes for TMO TheDarkWraith_DC_Water_Disturbance_v2_0_SH4 Improved Stock environment v3_TMO&RFB TMO_Alt_engine-sounds TMO_Alternate_JS_Radar_performance TMO17_19_different_smoke |
|
![]() |
![]() |
![]() |
Thread Tools | |
Display Modes | |
|
|