JTS Wolfpack - Passive Sonar

[parmenio]

I don't normally do this, but here are the updated files for Wolfpack... as has been mentioned, these are only the exe files - no updated PDT files as of this time. Go ahead and play around and see what you think:

https://s3.amazonaws.com/JohnTillerSoftw...ck_101.zip

Thanks!  Look forward to seeing how it performs.
Presume the files are extracted into the Wolfpack directory, i.e., not into sub-dir

First test - no change!  Scenario: Convoy - OB-4  Passive indicated but no indication/reports.  Min speed.  Periscope depth.  First contact active sonar - bright green.

May I draw your attention to my post further up...

By default, you will see no change as it relies on updating the game PDTs via the Parameter Data Editor to provide new Passive Sonar ranges. For backwards compatibility, opening an older PDT whether in the game, scenario editor or parameter data editor sets the Passive Sonar Range the same as the Active. When saving the PDT in the Parameter Data Editor it ups the version as well as saving the new data values to whatever you set them to.

A full patch release will involve supplying customers with updated PDT files tuned appropriately by the Scenario Designers. As it is, I suspect you will have game exes only. So you will need to open up the updated Parameter Data Editor and change the Passive Sonar values (which are currently the same as the Active ones) for the PDT files in the game. Example screenshot attached...

(Suggest you back them up first )

[Lethal]

Hello Parmenio,

Apologies for my oversight!

Thanks for your assistance, I will let you know if I find anything.

Cheers,

L

[parmenio]

Hello Parmenio,

Apologies for my oversight!

Thanks for your assistance, I will let you know if I find anything.

Cheers,

L

No worries....

[Lethal]

Hello Parmenio,

Apologies for my oversight!

Thanks for your assistance, I will let you know if I find anything.

Cheers,

L

No worries....

Where does one start when contemplating these numbers?

I think the period 1939-black May 1943 is of most interest.  And restricting the discussion to active/passive sonar and visual sensors of the combatants and the data presented in the JTS Naval Campaigns Manuals.

Background
By 1940 active sonar (ASDIC) could detect a submarine at about 2200yds (2000m) and was viewed as an attacking device.  Obviously, this is irrelevant when the U-boat is on the surface.  This was the method used to defeat underwater detection devices and surface attack was a feature of early U-Boat operations.

So passive sonar was very important for both sides early in the war.  A U-boat using GHG could detect a convoy up to 50nm, but could it determine a bearing?

The Game 
But, back to the game and the U-Boat in particular.  It appears to me the game is designed to have a U-Boat just out of visual range of the target, whether single ship or convoy.  It could be submerged or on the surface. 

Visibility and Sighting, p. 19 NC User Manual
Maximum visibility determined by scenario, can be variable.

Submarine Visibility and Detection, Standard Rules, p.39 NCUM
A submarine on the surface can only be detected at 1/2 the normal radar range of another ship.

Submerged Submarine at periscope depth, p. 40:
a.  periscope visibility range is half of ship visibility,
b.  the periscope can be detected at the Periscope Visibility Parameter Data value.

Enhanced Submarine Rules, p. 43
Night
At night, the maximum spotting distance to detect a submarine on the surface is halved.

Sea State
The maximum spotting distance to detect a submarine is reduced by the fraction – sea state/max sea state.
Example:  Calm water, surfaced submarine = nominal visibility.  Each increase in sea state (1-12) spotting distance is reduced by 8%.

Testing, Scenario #39_0916 Convoy OB-4, 1939

Misc Values:
Horizon: 30000yds
Periscope and Torpedo Visibility: 1000yds
Submarine Visibility: 0.8
Sea State?  From comments, presume 1

39-40.pdt Values
Side A: Allies  Side B: Axis

Sonar Guesstimates!
If the horizon is 30000yds (+-25nm) then it is reasonable to suggest that passive sonar is greater than that, say 40000yds (+-33nm).

Hope these ideas are useful for you.  Obviously, the numbers need playtesting to determine practicality.  The image below is from the scenario with the values suggested.  Why have two escorts not been detected? - stopped, slow speed?  need to check.  How is escort passive detection compromised by proximity of convoy?

Allied Max Sonar Speed - 20.  Presume kts?  (everything else in imperial)  If so, suggest too fast and is this graded in game, ie lower speed better detection?  Surface Ship Sonar Speed Modification, p.46 

http://www.users.on.net/~jennnie/JTS/ConvoyOB4.jpg

[Gary McClellan]

As it stands, I was planning on starting with 30,000 as the initial test for Passive Range for when the patch goes official (which won't be for a time yet).

Otherwise, I will note that surface ships currently don't have passive sonar capability. It's a database issue, and one that will be looked at in the update, but that level of database change is not something that we can really release on the fly, trust me.

One thing I'd have to look at in detail before anything else is the ability of a surface ship to pick out a sub in the midst of the ambient noise, especially if it's a convoy guard. That many merchies are going to make life difficult for the poor guy on the duty :)

[Lethal]

Hi Gary,

I have used passive sonar with surface ASW ships. Invoke Inhibit Active and the dk gn line will appear. Good tactic to have one ship active and the other inactive. If you watch the active closely you can see the sub fire decoys to confuse the signal.

When selecting the range for active sonar you will need to consider the Sonar Speed Limitation, p. 46. I am presuming the maximum range set is for a target that is stationary. The maximum Sonar Range Modifier will then shorten the range according to speed of the target and source vessel.

Interesting point re convoy noise and passive performance. The Passive Range Modifier takes into account ship size and speed. There is no mention of performance in a multi-ship environment.

A question I have here is how far can a sub detect active sonar? The user manual says twice detection range, so 4400 yds. At the moment it can detect active at default passive sonar range. Hopefully, you have better data than I can get access to to answer these questions.

Pleased you are maintaining an ongoing interest in the title. The active/passive sonar performance and visual detection really are at the heart of this game. Good luck with your research and testing.

[Gary McClellan]

One thing I would like to make clear to everyone is this. I've said it, but just to make sure we're all clear.

The next patch won't be out for awhile. (Unless we find a must-fix game breaking bug) When will it be out? That depends on a few things, but if you go back and look at Rich's Start of the Year update email, you'll get something of a hint. :)

[rahamy]

Variety of other things going on right now, so I'll circle back to this when I can and contact you via email - will only do so when we have altered PDT files to share.