Asdic "only"

[LGN1]

Hi John,


I made a small test by limiting the hydrophone sensor depth to values > -30m, then dove to -50m and approached an escort. As I expected the escort detected me with ASDIC without any previous hydrophone detection.


I'm pretty convinced that the escorts use both sensors all the time. Just because one does not hear the pinging, one should not conclude that the escorts don't use ASDIC.


The problem with removing the hydrophone is that it gives you an unrealistic advantage because in this case you can escape ASDIC much easier by running full-speed ahead without any risk. Therefore I think you need both sensors: hydrophone to keep you from running high rpms and ASDIC to keep you from becoming 'invisible' by 'Schleichfahrt'.


Best, LGN1


PS: The real problem is that in SH3 the hydrophone also provides your depth to the escort. Since this was not possible in real-life, escorts had to use ASDIC for hunting. However, it's my understanding that they also listened all the time to prevent the u-boat from running away at high speeds.

[John Pancoast]

Originally Posted by LGN1

Hi John,


I made a small test by limiting the hydrophone sensor depth to values > -30m, then dove to -50m and approached an escort. As I expected the escort detected me with ASDIC without any previous hydrophone detection.


I'm pretty convinced that the escorts use both sensors all the time. Just because one does not hear the pinging, one should not conclude that the escorts don't use ASDIC.


The problem with removing the hydrophone is that it gives you an unrealistic advantage because in this case you can escape ASDIC much easier by running full-speed ahead without any risk. Therefore I think you need both sensors: hydrophone to keep you from running high rpms and ASDIC to keep you from becoming 'invisible' by 'Schleichfahrt'.


Best, LGN1

Thanks LGN1, great info. as usual. I noticed that running at high rpm escape example you mention.
I recall Ducimus stating that the AI could only use one sensor (in terms of hydrophones/asdic) at a time.
However, his work was long before yours and much could have been learned in the meantime. Also, what is your take on whether the .exe file contains these functions too ?
I.e, it is possible to delete the sim.cfg file (and the other three "ai files" for that matter) and the game still runs but the escorts detection ability is super powered implying that the files purpose is to modify such.

[LGN1]

Hi John,

I know Ducimus' statements quite well, but I don't know how he came to the conclusions. In one post he mentions that the "AI" always chooses the sensor with the highest probability of detecting you and that it can switch very quickly between the sensors. In this case I'm wondering what's the problem if it can only use one sensor, but knows which is the best to use and switch to it in a fraction of a second (and both sensors provide exactly the same information to the escort).

I have no definite answer on your question concerning the exe, but some general remarks. I regard it always as 'dangerous' to remove expected(?) input. You just don't know what you might break without noticing. Therefore I always prefer to keep the 'structure', but adjust the sensor's parameters. For instance limit the range of the hydrophone to 1m, its depth to -1m and 'deactivate' it (practically remove it from the game) in this way. To make a sensor more sensitive I would increase either the sensitivity parameter (a quite sensitive parameter) or decrease the detection time (less sensitive; basically scales the detection probability in a linear way).

Best, LGN1


PS: Or LinkName=NULL for the sensor in the *.sns file.

[Randomizer]

I have read that one of HMS Courageous' escorting destroyers detected U-29 by hydrophone but misidentified the contact as the other escort. A few minutes later, three torpedo hits confirmed the presence of a U-Boat. Granted, this was 1939, when the War was new but the hydrophone operators would likely have been pre-war, long service professionals and presumably well trained.

-C

[John Pancoast]

Originally Posted by Randomizer

I have read that one of HMS Courageous' escorting destroyers detected U-29 by hydrophone but misidentified the contact as the other escort. A few minutes later, three torpedo hits confirmed the presence of a U-Boat. Granted, this was 1939, when the War was new but the hydrophone operators would likely have been pre-war, long service professionals and presumably well trained.

-C

Any mention of asdic beforehand or at all ? I seem to recall Macintyre of "U=Boat Killer" fame was there but would have to look to be sure.
He's one who said they never used hydrophones.

[John Pancoast]

Originally Posted by LGN1

Hi John,

I know Ducimus' statements quite well, but I don't know how he came to the conclusions. In one post he mentions that the "AI" always chooses the sensor with the highest probability of detecting you and that it can switch very quickly between the sensors. In this case I'm wondering what's the problem if it can only use one sensor, but knows which is the best to use and switch to it in a fraction of a second (and both sensors provide exactly the same information to the escort).

I have no definite answer on your question concerning the exe, but some general remarks. I regard it always as 'dangerous' to remove expected(?) input. You just don't know what you might break without noticing. Therefore I always prefer to keep the 'structure', but adjust the sensor's parameters. For instance limit the range of the hydrophone to 1m, its depth to -1m and 'deactivate' it (practically remove it from the game) in this way. To make a sensor more sensitive I would increase either the sensitivity parameter (a quite sensitive parameter) or decrease the detection time (less sensitive; basically scales the detection probability in a linear way).

Best, LGN1


PS: Or LinkName=NULL for the sensor in the *.sns file.

Appreciate your thoughts. I agree with you on changing parameters, etc. I used the Linkname=NULL for these tests. I know I'm going over a lot of old ground covered by a lot of very bright folks but its fun to tinker anyway, plus I'm the kind of stubborn idiot who if told the sun rises in the east has to see for myself.

One other thought; regarding your test of setting the hydrophone to > -30m do you recall if you were using SH3 Commander with that ?
If so I'm wondering if Hemisent's thermal layers may have changed your hydrophone editing ? Though there's only a 10% chance of that happening.

[Mister_M]

Originally Posted by LGN1

I know Ducimus' statements quite well, but I don't know how he came to the conclusions. In one post he mentions that the "AI" always chooses the sensor with the highest probability of detecting you and that it can switch very quickly between the sensors. In this case I'm wondering what's the problem if it can only use one sensor, but knows which is the best to use and switch to it in a fraction of a second (and both sensors provide exactly the same information to the escort).

Exactly. And you should add that the AI will not only know your exact position (including depth) but also your exact speed and course...

[John Pancoast]

Originally Posted by Mister_M

Exactly. And you should add that the AI will not only know your exact position (including depth) but also your exact speed and course...

For knowing so much it sure is dumb as bricks.

[Randomizer]

Any mention of asdic beforehand or at all ? I seem to recall Macintyre of "U=Boat Killer" fame was there but would have to look to be sure.
He's one who said they never used hydrophones.

Looking at some of the primary sources I suspect that active and passive searches were the norm.

Here US Fleet Anti-Submarine Instructions differentiates between search patterns and active-sonar search patterns (Echo Searches) so presumably passive listening with hydrophones were an option if conditions were suitable.

Buried in this tome is warnings about interference between escorts depending on the frequency of the active sonar (ASDIC) but not too much specific data. I suspect that these issues would have been addressed at the Operator/ASW Officer level and so not part of the Big Picture covered by this document. I had not considered this but it makes sense that coordination and control would be required to keep escorts from jamming each other.

Here Arctic Convoy Instructions there is a throw away entry regarding horrible acoustic conditions in the Arctic using ASDIC and the context suggests active rather than passive detection means. I think that it was Milner, in his book about U-Boats Against Canada, commented on the inability of ASDIC to find U-Boats in the Gulf of St Lawrence for a variety of reasons including fresh-water eddies bottom conditions and irregular thermal zones.

Food for thought though as these days active sensors can bring all sorts of nasty countermeasures but in WW2 it seems that the rules were "Ping all you want".

-C

[Mister_M]

Originally Posted by Randomizer

Here Arctic Convoy Instructions there is a throw away entry regarding horrible acoustic conditions in the Arctic using ASDIC and the context suggests active rather than passive detection means.

Quoting :

"Article 9014

Asdic Conditions

Owing to temperature layers, asdic conditions in these northern waters have often found to be very bad, and experienced escort groups which have had success in the Atlantic have frequently reported this fact when escorting North Russian convoys. Cases have often occurred of a U-Boat torpedoing a ship and completely escaping detection both before and after the attack.

Experience has also shown that echoes can often be obtained from surface craft while a submerged u-Boat remains undetected."

[John Pancoast]

Originally Posted by Randomizer

Looking at some of the primary sources I suspect that active and passive searches were the norm.

Here US Fleet Anti-Submarine Instructions differentiates between search patterns and active-sonar search patterns (Echo Searches) so presumably passive listening with hydrophones were an option if conditions were suitable.

Buried in this tome is warnings about interference between escorts depending on the frequency of the active sonar (ASDIC) but not too much specific data. I suspect that these issues would have been addressed at the Operator/ASW Officer level and so not part of the Big Picture covered by this document. I had not considered this but it makes sense that coordination and control would be required to keep escorts from jamming each other.

Here Arctic Convoy Instructions there is a throw away entry regarding horrible acoustic conditions in the Arctic using ASDIC and the context suggests active rather than passive detection means. I think that it was Milner, in his book about U-Boats Against Canada, commented on the inability of ASDIC to find U-Boats in the Gulf of St Lawrence for a variety of reasons including fresh-water eddies bottom conditions and irregular thermal zones.

Food for thought though as these days active sensors can bring all sorts of nasty countermeasures but in WW2 it seems that the rules were "Ping all you want".

-C

Yes everything I've found states that asdic was constantly banging away 24/7 with fixed search patterns. I.e., x degrees arc port/starboard of the bowline with x degrees between each movement of the device.

[Fifi]

Originally Posted by LGN1

. To make a sensor more sensitive I would increase either the sensitivity parameter (a quite sensitive parameter) or decrease the detection time (less sensitive; basically scales the detection probability in a linear way).
.

So in Sim.Cfg, giving a higher value for sonar sensitivity will decrease the detection time...and giving a lower value will increase the detection time?
Or is it the inverse?
A bit lost this time Need other coffee cup!

[Mister_M]

Originally Posted by Fifi

So in Sim.Cfg, giving a higher value for sonar sensitivity will decrease the detection time...and giving a lower value will increase the detection time?
Or is it the inverse?
A bit lost this time Need other coffee cup!

There is also a sensitivity factor for each device in AI_Sensors.dat (in the Library)... And if this parameter = 1, the device doesn't work anymore, even if the definition given in S3D is : "Sensitivity = At (Sensitivity * MaxRange) distance, we have a double detection time", which doesn't make sense in case of =1 (in this case, according to S3D's definition, the device still should be able to work, and with the same detection time, whatever the distance is (between 0 and max range)...).

Moreover, S3D says : "If 0, then the value from sim.cfg is taken". So if Sensitivity is not =0, then the sensitivity factor of Sim.cfg would just not be taken into account ?...

[John Pancoast]

Originally Posted by Mister_M

There is also a sensitivity factor for each device in AI_Sensors.dat (in the Library)... And if this parameter = 1, the device doesn't work anymore, even if the definition given in S3D is : "Sensitivity = At (Sensitivity * MaxRange) distance, we have a double detection time", which doesn't make sense in case of =1 (in this case, according to S3D's definition, the device still should be able to work, and with the same detection time, whatever the distance is (between 0 and max range)...).

Moreover, S3D says : "If 0, then the value from sim.cfg is taken". So if Sensitivity is not =0, then the sensitivity factor of Sim.cfg would just not be taken into account ?...

That's part of the problem with the SH3 ai imo. There are numerous such examples of duplication of effects, overlap, etc.
Such a structure is a recipe for problems. Sometimes the KISS principle is the best way to go.

[Mister_M]

Originally Posted by John Pancoast

Sometimes the KISS principle is the best way to go.

What's that ?