Sh3.exe and Asdic in shallow waters

[Stiebler]

@Fish-in-the-water:
Many thanks indeed for such comprehensive and encouraging feedback on the shallow-water asdic mod.

@LGN1:
I agree with you that shallow waters provided erratic protection against asdic detection. Hitman also made the same point earlier.

However, my answer in #43 above still stands, concerning use of random number changes, and repeated below for others who may not have seen it:

What exactly would the random number mean? For example, if the code says that there is a 20% (or an 80%) chance of changing the Minimum Surface value, what does it mean? That there is a 20 (80)% chance that the U-boat is next to a rock rather than next to soft mud?

In fact the presumption is already made in my code that, at shallower depths, you are more likely to be moving next to something that confuses asdic (a rock, a wreck, a shallow tidal flow). So, in my opinion, the changes in Minimum Surface reflect *the average* of these random changes already.

As stated previously, it would be very easy to introduce a random change if a strong enough case can be made. I should like to see more experiences from other players with the current system before making new changes. U-boats operated in shallow waters with the confident belief that shallow waters would protect them. They were ordered to make use of local shallow effects, such as fast running underwater streams or tides to aid their protection. They could not have had such confidence if their asdic protection suddenly disappeared, randomly and unpredictably.

Perhaps I can quote from one of my own books, the report of Nollmann (U 1199) when he returned to base after a patrol off the north-east coast of Scotland. The report was later transmitted by BdU to all U-boats at sea on 5 December 1944:
'Experiental 193 [Boat has operated 30 days in AN01.]
"Shallow water is best protection against search gear. Boat was not intercepted, and we felt completely safe on the bottom. Schnorchel completely tested, 50 days submerged without surfacing. I have a feeling of complete superiority with the schnorchel... " '

Stiebler.

[LGN1]

Hi Stiebler,

thanks for your reply. What I had in mind is to have a probability that, e.g., every two days the shallow depth effect is switched on or off randomly so that the player never really knows whether he's safe or not.

From what I've read many commanders considered shallow waters dangerous and tried to stay away from it. I don't remember who it was, but I think there is a quite impressive report from a sub commander in 1940 who was depth-charged in shallow water and reported that the destroyers always knew where he was (IIRC, Der Teddy Bar always quoted this report in connection with early-war ASDIC performance) Having this report in mind, I find it strange if shallow water is less dangerous in SH3 than deep water.

On the other hand, the submarine commander's handbook (http://www.hnsa.org/doc/uboat/index.htm) mentions shallow water, too (57.) It says that shallow water can be indeed quite safe. However, it seems that this depends heavily on the area where you are. The question is whether the commanders back then knew where and when it was safe

I guess as long as it's not possible to have the effect dependent on the area, one has to choose either to a) neglect the effect (stock SH3) or b) have the effect everywhere (your mod). Both choices are not really realistic.

Regards, LGN1

[Fish In The Water]

@LGN1:

First up, thank you for taking a balanced look (with sources from both sides of the issue).

In regard to your 'strange' feeling that shallow water should be less dangerous than deep in SH3, I would like to mention the following. Firstly, it seems to me, it would primarily be safer in terms of a greater degree of sonar 'scattering' which is bound to occur due to the increased proximity of the bottom.

Secondly, it seems in reality to be just as dangerous if not more so due to the limited room for manoeuver. Throughout my tests, if I failed to maintain a low surface exposure (even for a moment), I was quickly detected and just as imperiled (if not more so than if I had been in deep water).

Furthermore, the 'scattering' I spoke of occurs from both the surface and the bottom as well as from small objects in the water. All three of these factors seem analogous to all regions so I have a hard time understanding how a random aspect would improve realism in this instance.

[LGN1]

Der Teddy Bar about NYGM Tonnage War 2:

"... Shallow waters were a very dangerous place for the u-boats, yes there were sound detection difficulties, but compared to deep water, shallow waters were very dangerous.

With the AI now more actively using the ADSIC shallow waters are now very dangerous. It is not impossible to survive 1 maybe 2 escorts with skill and some luck when in shallow waters of 50 metres or less, but more often than not, you will find that it will end tragically..."

The full post is here:

http://www.subsim.com/radioroom/show...03&postcount=1

Regards, LGN1

[Fish In The Water]

He goes on to say:

"With ADSIC the key to minimising your chances of detection will be minimising your profile, stern on or bow on is key."

This seems to fit quite nicely with the 'MinSurface' variable approach which (as has been pointed out previously) appears to be completely lacking in other super mods.

As for the two passages you cited, I really don't see an issue with either of them as I've already stated my belief that shallow waters are more dangerous than deep primarily due to the lack of available depth.

He's already acknowledged the sound difficulties, and at the risk of repeating myself, in my tests I found it quite challenging to try and maintain a profile that was low enough to avoid being successfully pinged again.

If the player remains committed he can manoeuver for a period of time without detection, but eventually (usually within a few minutes), the DD's search ark becomes such that you are unable to turn quickly enough to avoid sufficient exposure.

At this point depth charges are soon in the water once again and the time available for a 'flank knuckle break' is limited due to the shallowness of the water. If that's not dangerous then kindly explain to me what is.

[Stiebler]

As Fish-in-the-Water says, your freedom of manoeuve is limited at shallow depth. U-boat commanders always demanded of the designers that the boats should be able to dive deeper, because a deep boat had more time in which to turn as the depthcharges sank slowly.

Shallow waters are certainly more dangerous for a U-boat than deep waters, *after* the U-boat has been once located. But it is harder to locate the U-boat initially.

The quotation from DTB refers, I believe, to the well known incident reported by Topp, when his IIA boat was located at shallow depth in 1940 to the north-west of Britain, and was hunted for many hours while stationary on the sea-bed. By chance, his U-boat had settled into a small deep channel on the sea-bed, so that the the boat was protected by the high banks on both sides. Because the boat was stationary (to conserve power), and also in a position where it could be detected by asdic, the attacks were very precise.

I cannot think of another example like this, until 1945, when asdic was more refined, and the Squid depthcharge device was fired automatically with settings from the asdic.

Stiebler.

[LGN1]

Thanks for your replies, Fish In The Water and Stiebler!

With my previous post I just wanted to point out that it was a big improvement when the NYGM team improved the ASDIC capabilities and therefore, IMHO, it would be bad to go back (to the 'Glingon Cloaking Device' as DTB has called it).

However, from Fish In The Water's reply and tests I conclude that Stiebler's new mod does not revert the situation, i.e., ASDIC still works quite well even in shallow water. So, everything is fine

Just one more question:

@Stiebler: Do you know how DTB could influence the amount of ASDIC usage by the escorts? Did he just increase the detection probability by ASDIC so that the escorts get more contacts with ASDIC and therefore, will use it more? It's my understanding that all units can only use one sensor at a time and switch quickly between the sensors until they have a contact with one sensor. The units will then use this sensor until contact is lost

Regards, LGN1

[Stiebler]

@LGN1:
Re Increase of asdic influence:
It was Observer who made the changes, but DTB certainly knew what had been done - unlike myself, who never thought it necessary to ask at the time, although I performed a lot of the testing.

It's my understanding that all units can only use one sensor at a time and switch quickly between the sensors until they have a contact with one sensor. The units will then use this sensor until contact is lost.

This may indeed be true, I regret that I do not know.

Inspection and comparison of the AI_Sensors.dat file with stock SH3 shows that most or all parameters for each of the several asdics have been altered in NYGM. Also some of the parameters in sim.cfg. One particularly important change was to provide a 'dead area' (no detection) for asdic behind the warship's stern, in order to mimick the propeller noise behind the escort. Also, another dead area was provided when the escort was within 100-200 metres of the warship (ie, loss of asdic as the warship began its attack run). Neither of these last two changes were available in stock SH3.

Stiebler.

[Fish In The Water]

Originally Posted by Stiebler

One particularly important change was to provide a 'dead area' (no detection) for asdic behind the warship's stern, in order to mimick the propeller noise behind the escort.

Any idea how this was implemented? The only thing that comes to mind is possibly adjusting the 'detection cone' via the Min and MaxBearing variables. Or is there some other approach that's more effective?

Also, another dead area was provided when the escort was within 100-200 metres of the warship (ie, loss of asdic as the warship began its attack run). Neither of these last two changes were available in stock SH3.

I take it this can be achieved by setting MinRange to say 100 meters to mimic the real life loss of contact just prior to depth charging. Again this is just a semi educated guess , so if I'm way off base here I'd appreciate a little course correction.

[andqui]

If I'm using GWX, could I just use the NYGM parameters for ASDIC for more realism, or would that have unintended side effects?

[Fish In The Water]

Originally Posted by andqui

If I'm using GWX, could I just use the NYGM parameters for ASDIC for more realism, or would that have unintended side effects?

That's basically what I did and it worked out quite well. The main factor is to make sure the values in the AI_Sensors.dat file and the SIM.cfg file are 'on the same page'. If they work together (i.e. align properly) then you shouldn't experience any nasty side effects.

[Stiebler]

@Fish-in-the-Water:

Dead Area behind the propellers.
Sorry, I don't know how this was implemented.

Dead area as warship approaches sub.
As you say, this is achieved by changing MinRange to 300m (I thought 100-200m from memory, earlier, but it is 300m).

Stiebler.

[Fish In The Water]

Originally Posted by Stiebler

Dead area as warship approaches sub.
As you say, this is achieved by changing MinRange to 300m (I thought 100-200m from memory, earlier, but it is 300m).

Very good, that helps. Thank you!

[Leitender]

@Stiebler:

Sir,

at first i would like to thank you very much for sharing your thoughts and your whole work with the community. Personally i follow every discussion with you und every post from you because i know you are somenone who loves that game and which posts are really worth to be read.

Also with this thread. As i want to implement h.sie´s v.16B and your new addon, i wonder if you (or anyone else) made some experience with your chosen MS-values in the meanwhile. I ask because longer ago, i made a test with this value: My boat stood in a perpendicular course to a destroyer (can´t remember distance) and although i showed my broadside, ASDIC didn´t recognize me at a MS=100², which in result meant a total dysfunction, at least in this trial. I then reduced MS to 75 and at last to 50m² and the result was i was recognized when in perpendicular position, but when i showed the DD my narrow side (bearing +-30deg) ASDIC lost contact. Confident about this result, I used from then on MS=50m².

Now i like to use your addon. But since you wrote about a "unique" value for MS which you have used to identify whether this MS-parameter works or not, i wonder if your mod is linked to this explicite value or if it also works e.g. with my favourite 50m². In general this mod is a great idea an i would really miss it within my game if it wasn´t usable with my settings.

So i would really be glad to gather some words about this from a great modder.

Yours sincerly

Leitender

[Stiebler]

@Leitender:

Thanks for your interest. I have provided the answer to your query here in this thread (Stiebler3A_addons):
http://www.subsim.com/radioroom/showthread.php?t=193301

Stiebler.