Static Search Vs. Dynamic Search

[Armistead]

I get the concept and Wahoo certainly did it to a degree. I am in fact reading "Wahoo" again for probably the 10th time. One thing our game lacks is historical realism that would make submerged static hunting viable since we play against AI.

Near Japan Morton did more submerged static hunting, but would place himself in shipping lanes and choke points. When he sunk ships, he usually quickly moved to another location 50-100nm's away and attacked again hoping the enemy would think two subs were in the area and split their ASW effort. Near Japan if you were spotted it usually prompted a ASW response, so one stayed dived more during the day. Many of the island chains also had land radar which would pick you up.

The other factor missing in game is ocean currents.

I added a lot of China coast traffic in 44 and 45 that basically hugs the coast and travels between the small islands and reefs, in and out of ports, not to mention many patrol boats, fishermen, minefields, shoreguns, coastal lights, air patrols, etc.. In such shallow water it's a dangerous game. I go in at night and attack and slip back to the deeper edge during the day and static hunt where I can still pick them up on sonar. It's fun playing, but hard and mistakes or risk can easily get you killed.

[magic452]

Originally Posted by TorpX

Here is a slightly different example to further illustrate the concept:

Suppose you are astride a N-S sealane and want to "search" it. I will assume, as before, freighters traveling 9 kts. and a 10 nm detection radius. (This is good for SH 4, since nothing is rendered beyond 10 nm anyway.) If you sit still you will detect 100% of ships in a 20 nm "slice" (10 nm East and 10 West). If you want to move E-W across the sealane (in effect yo-yoing back and forth), how far can you go East or West, without letting ships "slip through"? If you are cruising at 10 kts., you can go 11.1 nm on either side, and still make sure nothing gets by in the center. Why do I say 11.1 nm? Because in the time it takes you to go 11.1 nm East and 11.1 nm West (back where you started), an enemy ship could move through the 20 nm deep band you are searching. Going any farther would allow some ships to slip past. Following this plan, you will detect 100% of ships within this 22.2 nm zone, and some of the ships within a 10 nm 'fringe' zone on either side. If you wanted to cruise at 15 kts., the figures would be 33.3 nm with a 10 nm 'fringe'.

A couple of points here.

First a sea lane is not a narrow straight line even in the heavily traveled choke points. Markassar Strait is about 50 nm. wide. Luzon three times that.
Shipping lanes are no doubt about the same. You can sit in the center and still leave more than enough room for convoys to sail right by. Why give up the higher percentage for contacts just to save some fuel that is for the most part not an issue.

Second ships and convoys don't run straight courses they zig zag and can very easily sail right past you. Again a dynamic search will increase your chances of making contact and I would think the increase would be greater than what your figures suggest. The zig zags put them in your contact zone longer than a straight course would. The course changes reduce their overall progress on their base course. I do your yo-yo across the lane almost exactly as you describe but I'm also moving North or South. I described this in my second post.
Again your giving away contacts to save fuel you most probably won't need.

Third Radar. 20 nm. range Your search area doubles and enabling you to cover most of area of a choke point if you're moving.

If I'm in a dead area I'm going to patrol in a way that searches the greatest area in the shortest amount of time. Your not going to find much no matter which method you use.
Your mission is to interdict shipping not stay on station for 60 days. They have other boats to replace you in that area.

I'm wanting to RTB knowing I gave myself the best opportunity to have success.

And when I get there I'm going to say "I one of the top guns and don't send me to the Marshals again." I'm sure they will listen.

But I do see what you are saying and your points are well taken, I can see several places that a static search might be the best tactic especially early in the war where fuel is a little bit bigger concern. Armistead has pointed out a couple as well.

Magic

[TorpX]

Originally Posted by Armistead

I get the concept and Wahoo certainly did it to a degree. I am in fact reading "Wahoo" again for probably the 10th time. One thing our game lacks is historical realism that would make submerged static hunting viable since we play against AI.

It might work better than it should. In SH4 your view doesn't improve when your higher. Did you ever play SHCE? You could actually see farther when you raised the scope higher (or surfaced).

The other factor missing in game is ocean currents.

True. Another thing is the sea state. I remember O'Kane describing how in rough seas, there was "green water coming over the bow", causing them to waste fuel. I think this is a big part of the reason fuel is less of an issue in this game. Something else that was modeled much better in SHCE.

In such shallow water it's a dangerous game. I go in at night and attack and slip back to the deeper edge during the day and static hunt where I can still pick them up on sonar.

I agree. I've come to the conclusion that operating in shallow/coastal areas is fundametally different than deep water ops. O'Kane used the term 'horizontal evasion'; if you cannot use vertical evasion, all you got left is horizontal evasion.

I just finished OPERATION DRUMBEAT recently. U-boat ace Hartigen would roam around wreaking havoc at night, then go back out to deeper water before daylight, submerge and just lay there resting until the next night. It was a shooting gallery; no trouble finding enough targets there.

[TorpX]

Pardon for the double post.

Originally Posted by magic452

A couple of points here.

First a sea lane is not a narrow straight line even in the heavily traveled choke points. Markassar Strait is about 50 nm. wide. Luzon three times that.
Shipping lanes are no doubt about the same. You can sit in the center and still leave more than enough room for convoys to sail right by. Why give up the higher percentage for contacts just to save some fuel that is for the most part not an issue.

The math I used does not require a particularly wide or narrow sea lane. You can use different figures with these calculations and get substantially the same results. Fuel not being as much an issue is due to shortcomings in the game. In RL rough weather would slow you down much more. Even as it is when I am playing an S-class, fuel is indeed an issue. If I cruised continously in an S-class, it would be a short and unhappy patrol.

Second ships and convoys don't run straight courses they zig zag and can very easily sail right past you. Again a dynamic search will increase your chances of making contact and I would think the increase would be greater than what your figures suggest. The zig zags put them in your contact zone longer than a straight course would. The course changes reduce their overall progress on their base course. I do your yo-yo across the lane almost exactly as you describe but I'm also moving North or South. I described this in my second post.

I'll grant you targets zigging will give you more of a chance to detect them, but this doesn't fundamentally alter the math.

Again your giving away contacts to save fuel you most probably won't need.

I would say you are giving away contacts by wasting fuel and terminating the patrol prematurely.

Third Radar. 20 nm. range Your search area doubles and enabling you to cover most of area of a choke point if you're moving.

I'm not disputing the usefulness of radar (or sonar or anything else). Anything that doubles your detection range will double your chances, likewise anything that halves your detection range will halve your chances. This is true whether you are moving or not. Radar really has nothing to do with it. If you want to compare a radar equipted boat to one without radar, the radar boat will obviously win.

In any case, if you have a 20 nm radar, you can cover most of the area of a choke point even if your not moving.

If I'm in a dead area I'm going to patrol in a way that searches the greatest area in the shortest amount of time. Your not going to find much no matter which method you use.

OK, lets say you arrive at your patrol area on monday. No matter how quickly or intensely you search search your box. You will have to do it again tuesday, and wednesday and thursday....... However quickly you search, you cannot pull the targets to your location. If the area has an average of 2 ships transiting each week, it will take weeks to obtain a good number of contacts. And it is unlikely you would find them all. Realistically, most areas would not give you a contact every day, but by continuously cruising you would be burning a lot of extra fuel each and every day.

Your mission is to interdict shipping not stay on station for 60 days. They have other boats to replace you in that area.

I'm wanting to RTB knowing I gave myself the best opportunity to have success.

And when I get there I'm going to say "I one of the top guns and don't send me to the Marshals again." I'm sure they will listen.

But I do see what you are saying and your points are well taken, I can see several places that a static search might be the best tactic especially early in the war where fuel is a little bit bigger concern. Armistead has pointed out a couple as well.

Magic
[/INDENT]

Look, I can see your just a bit skeptical. I am not trying to convince you to do it my way, but the math is the math.

The bottom line is a moving search is not as big a help as you like to think. When you are moving to the east, targets can slip by to the west, when you move to the west, targets might slip by to the east. If you go farther to the east to "cover more ground", a target could go past in the center or the west. You cannot be in two places at once, nor can you hasten or delay their arrival.

[gi_dan2987]

So what is the MOST optimal search method, please let me know, because right now I'm driving around in the Marshalls about ready to head to the area between Rabaul and Truk. I've only Sunk Nibu Maru in the Marshalls, and that was because I picked up a hydrophone contact while surfaced.

[Rockin Robbins]

Originally Posted by TorpX

Pardon for the double post.

Look, I can see your just a bit skeptical. I am not trying to convince you to do it my way, but the math is the math.

The bottom line is a moving search is not as big a help as you like to think. When you are moving to the east, targets can slip by to the west, when you move to the west, targets might slip by to the east. If you go farther to the east to "cover more ground", a target could go past in the center or the west. You cannot be in two places at once, nor can you hasten or delay their arrival.

You're confusing yourself by uncalculable random effects. If you are standing still they can miss you in any direction. If you are moving the same is true. You can't count the ones you miss. That's the defect in your method of calculation.

It is much better to think of searching in the same way Eugene Fluckey of the Barb did. He spent a lot of time explaining the situation, so I'm going to condense it.

The fact is, we don't know the disposition of the enemy on the ocean. If you are static in the middle of the horde, you're going to be successful. If you're static in a vacuum, you're coming back with a goose egg.

So you say, if you get a goose egg in 24 house, move! That's fine. Murphy's Law says you just moved from the next hot spot.

The only thing we can say for sure is that in any moment in time, the enemy is distributed in an unknown array over the surface of the ocean.

According to Fluckey, and I agree, the odds of finding a target approach unity when the distance between your sub and a target is within sensor range. So your job is to get within sensor range of as many targets as possible in a 24 hour period.

The corollary of that statement is that the number of targets you encounter is directly proportional to the number of square miles of ocean surface you search each day.

Let's do the math! You're static with a visual search radius of about 5 miles and a sonar search range of 20 miles on a good day. So you're searching a circle 20 miles in radius. The area you've searched is 3.14*20^2 square miles or 1,256 square miles.

Let's move out! We'll assume a 20 mile range for our radar and we're moving on the surface for 24 hours at our best fuel economy speed of 9 knots. Now your searched area approximates a rectangle 40 miles wide and 216 miles long. That's 8,640 square miles.

Since the enemy is moving and the effect of that movement is random we can safely ignore any effects on our results. Our movement will bring as many targets in range as it will leave beyond range. Therefore the comparison in the number of targets we develop can be expressed as the ratio between the two numbers of square miles searched.

So you are 8640/1256 times more likely to develop a target when moving. That is 6.88 times more likely. Another valid way to interpret the data is that a patrol during which you are actively searching at 9 knots, you will develop 6.88 times more targets in the same number of days as you would be searching statically.

But that is not the entire story. There are monstrous advantages to searching on the surface as opposed to searching submerged. Of most importance is the value of fully charged batteries. They can save your life, you know!

[gi_dan2987]

Therefore I choose to surface patrol

[TorpX]

Originally Posted by Rockin Robbins

You're confusing yourself by uncalculable random effects. If you are standing still they can miss you in any direction. If you are moving the same is true. You can't count the ones you miss. That's the defect in your method of calculation.

Not true.

It is much better to think of searching in the same way Eugene Fluckey of the Barb did. He spent a lot of time explaining the situation, so I'm going to condense it.

Fluckey did a lot of unorthodox things. As I recall part of his efforts involved probing/ raiding coastal anchorages where enemy ships were hiding out during the night. Is this what you are refering to? Looking for anchored ships or raiding coastal locations is not quite the same as searching for ships moving thru an area.

The fact is, we don't know the disposition of the enemy on the ocean. If you are static in the middle of the horde, you're going to be successful. If you're static in a vacuum, you're coming back with a goose egg.

How does this invalidate anything I said?

So you say, if you get a goose egg in 24 house, move! That's fine. Murphy's Law says you just moved from the next hot spot.

The only thing we can say for sure is that in any moment in time, the enemy is distributed in an unknown array over the surface of the ocean.

According to Fluckey, and I agree, the odds of finding a target approach unity when the distance between your sub and a target is within sensor range. So your job is to get within sensor range of as many targets as possible in a 24 hour period.



The corollary of that statement is that the number of targets you encounter is directly proportional to the number of square miles of ocean surface you search each day.

This is only true if you are searching for things that are not moving. While you are searching one end of your area, targets can move through the other and you'll never know it. Moving from one part of an area is not the same as being in both places at once.

Let's do the math! You're static with a visual search radius of about 5 miles and a sonar search range of 20 miles on a good day. So you're searching a circle 20 miles in radius. The area you've searched is 3.14*20^2 square miles or 1,256 square miles.


Let's move out! We'll assume a 20 mile range for our radar and we're moving on the surface for 24 hours at our best fuel economy speed of 9 knots. Now your searched area approximates a rectangle 40 miles wide and 216 miles long. That's 8,640 square miles.

Again, the square area is not what is important. If you were trying to find sea shells on a strip of beach, this would work ok. You could search an area, cross it off your list and move on to the next section. However, if the "sea shells" have the ability to move out from the water to the beach, and back into the water again, you will not be able to find nearly as many. They would be moving about in sections that you had "cleared". Your search efforts are only effective if there is a target nearby at the moment you are there. If the target moves thru either before or after you go by, you won't find it. Based on your analysis, it doesn't matter how fast enemy targets move, or if they move at all! An enemy cruiser moving at 30 kts could be found as easily as a drifting barge. You should see this is obviously not the case.

Since the enemy is moving and the effect of that movement is random we can safely ignore any effects on our results.

This is patently absurd if you think about it for two seconds.

Our movement will bring as many targets in range as it will leave beyond range. Therefore the comparison in the number of targets we develop can be expressed as the ratio between the two numbers of square miles searched.

If the first statement were true, it suggests there would be no difference.

So you are 8640/1256 times more likely to develop a target when moving. That is 6.88 times more likely. Another valid way to interpret the data is that a patrol during which you are actively searching at 9 knots, you will develop 6.88 times more targets in the same number of days as you would be searching statically.

OK, if this was really true, then you would get 2*6.88 times the number of targets in two days and 7*6.88 the number in a week. Do you really think just by moving at 9 kts this will get you 48 targets for every one I get in a single week? At this rate you could sink nearly 200 times as many targets in a month. Nice try, but your math does not hold up. Assuming that the number of contacts found will be proportional to the sq. area is a gross oversimplification.

But that is not the entire story. There are monstrous advantages to searching on the surface as opposed to searching submerged. Of most importance is the value of fully charged batteries. They can save your life, you know!

I never suggested submerged searching was better than surfaced searching. In fact the opposite is implied. Anything which increases your detection range (visual or otherwise), will improve your number of contacts by the same proportion. People seem to be reading things into this that I didn't write and don't intend. I never said it was better to drop anchor and remain motionless as if in a coma, or hide on the bottom of the ocean. Please, if you want to criticise what I've written, at least read it a little more carefully.

Ughh, too much typing. I'll try to find the relevent page in O'Kane's book.

[Stealhead]

I am not sure how the surfaced vs. submerged argument got into this.


@gi_dan2987 I would generally use a more active searching method while in open waters such as you find yourself and to use a more static approach if you find yourself in a choke point really though you should try every tactic find what works best for you.Sometimes also you can just have a dry patrol.

The sonar man being able to make passive contacts while on the surface is a game bug you could not do this in a real WWII sub so it is sort of a cheat(ever notice that spinning device of the deck of your sub that is the passive sonar head)

To me it depends if you use an active search but try to cover too large an area or use to high a speed I can agree that you are actually reducing the odds of making contact.

[magic452]

I'm not doubting your math, it's the tacit I'm questioning.

1 to 1.49 Your objective is to interdict enemy shipping in the Marshalls.
A 10 kn. search will give you more contacts in a given period if time.
Weather you get 12 contacts or 2 or 3 isn't all that important. If they aren't there they aren't there. What is important is to interdict as many as you can in the most efficient way possible and in the shortest time.

According to the math that is a 10 kn. search. There will be another boat along to replace yours. The objective is to cut off supplies to the Marshalls not stay on patrol longer. If I come home with torpedoes in the tubes but have 6 kills in three weeks patrolling I have done my job. Someone else comes homes with the same results but stayed 4 and a half weeks, not so good, at least one ship that I sank the other guy didn't and the Marshalls got resupplied. My patrol wasn't cut short costing contacts but the most efficient way to conduct business. My short patrol will be followed up by another boat to continue the operation and he will get the ship I didn't get in the next week and a half.

There are places where a static patrol is good, Tawi Tawi is one. Others have been mentioned.

I wouldn't be so quick to dismiss the zig zag thing. The contacts are now moving through the area at a reduced speed overall and I would think that would increase to ratio in favor of a dynamic search?


@ gi_dan If I'm in the Marshalls, I'd do my time and head to Truk or Rabaul as soon as I could.

Magic

[magic452]

Originally Posted by Stealhead

I am not sure how the surfaced vs. submerged argument got into this.


@gi_dan2987 I would generally use a more active searching method while in open waters such as you find yourself and to use a more static approach if you find yourself in a choke point really though you should try every tactic find what works best for you.Sometimes also you can just have a dry patrol.

The sonar man being able to make passive contacts while on the surface is a game bug you could not do this in a real WWII sub so it is sort of a cheat(ever notice that spinning device of the deck of your sub that is the passive sonar head)

To me it depends if you use an active search but try to cover too large an area or use to high a speed I can agree that you are actually reducing the odds of making contact.

Stealhead please correct me if I'm wrong but at least Gato and above had some surface sonar capability as the sonar heads were mounted on the keel. As I understand it the game bug is that it works too good, above 10 kn. If I'm wrong I will have to change some of the way I play.


Magic

[Stealhead]

I am fairly certain it is even mentioned in "Thunder Below" and some others that it was not possible to use passive sonar(hydrophones) on the surface for the obvious reason that the head is on top of the hull and therefore not in the water.Now a ping using the active sonar was possible of course these are on the keel more or less so they are always in the water they could be retracted in real life as well.

The rotating device near the bow is the JT head and the man operating this actually sat in fore torpedo room later in the conning tower.The previous design was JP which I believe was located somewhere inside the upper hull I am not sure because my reference "US Submarines Though 1945" does not go into much detail about the older WCA/WDA sets nor the JT but goes into much better detail on the later war gear.But it seems that the passive part of sonar systems always where located on top of the hull and the active on the bottom(later war some times two on bottom one on top for active) excluding the S-boats where it was all on the deck.Later in the war they also had WFA which could also detect mines with great accuracy and was also much more accurate against ships but this is not included in the game.

In other words if you want to play more realistically then you cant use the passive sonar on the surface and in an S-boat you cant use any sonar at all fully surfaced.In a fleetboat you can use active sonar on the surface though it was done commonly I am pretty sure I recall its use being mentioned in "Thunder Below" and "Wahoo" of course it wold be used with great care and very briefly something the game does not really simulate is how the density of water effected the active and passive sonar of the submarine sometimes very strongly in a negative manner.(reducing range and accuracy) What helps you hide from the IJN also hinders your sonar or it should.

look at this a little about the JT.You like math?Click on the Sonar home page at the bottom ans start from the first page of the manual you'll see tons of it.
http://www.hnsa.org/doc/sonar/chap13.htm

[Sailor Steve]

I've always had a problem with sonar, even active sonar, working on the surface. The problem I have is that if sonar works for a surfaced submarine then it should also work for a surface ship against other surface ships. I served on a destroyer and I don't recall ever hearing of anything like that. Of course I wasn't a sonarman, so maybe they just didn't tell me about it. If there is information that they used it and it worked, then they did use it and it worked.

I'm just sayin'.

[Bilge_Rat]

The issue with sonar not working on the surface is not where the heads are located, but basically a problem of ambient noise and the limitations of the SH engine.

To simplify the issue, to be able to hear sounds which are far away, you must not be close to a source of noise which is loud enough to cover far away noises. For example, if you are standing next to a noisy engine, then that is all you will hear. If you turn off the engine, you will be able to hear fainter noises which are farther away. The noise of the engine nearby masks fainter noises which are farther away.

The same in a sub, if you are travelling at 2 knots 100 feet deep using electric motors, you generate relatively little noise and are able to hear sounds from farther away. If you are travelling at 10 knots on the surface using Diesel engines, you generate a lot more noise. In addition, you also have the turbulence caused by the ship moving at the surface which will also render the heads less effective. The noise is the reason why U-Boats running their diesels on Snorkel were unable to hear anything on sonar even though they were underwater.

In theory, a motionless sub could use its sonar on the surface, but then we run into the limitations of the SH engine. In SH, Sonar is an on/off switch: when ships are within a certain range you hear them, when they are outside you don't. In SH 3/4, this range is not affected by speed, although in SH5, speed will degrade the effectiveness of Sonar. So modding the Sonar so you cannot use it on the surface is a practical solution to place the player in a similar situation to a WW2 sub skipper.

[Stealhead]

That sir makes absolutely no sense if the passive sonar head is above the water then there is no way on this earth that it is gong to be able to hear anything the same would apply to the S-boats all of the sound gear is on the deck so if you are on the surface and you can see the gear in the air then it can not possibly be in the water to enable it to hear anything the location of the gear 100% has an effect if said gear is on the deck on the surface and not in the water.In fact a sub on the surface trying to use sound gear which is above water will hear nothing.

I agree that there are limitations in the SH4 simulation but it makes perfect sense for a piece of sound gear not actually being submerged in the water not to be able to hear what might be in the water so the SH4 sound man is evidently Kent Clark and has super hearing.You seem to be confusing various things causing interference in a situation where the sound gear actually is in the water.I am talking about sound gear actually not being in the water and with US Navy subs the passive gear was above the water while the sub was on the surface but the active gear exluding the S-boats was below the water while surfaced.So active sonar while surfaced yes passive sonar no though I doubt the active sonar would be very accurate in such a setting.


EDIT: ok I found this in the very extensive US Navy Sonar manual from HNSA the manual Bilge Rat posted is also from HNSA but is from a different manual from US Navy Sonar pg.241;

"Submarine listening equipment is designed to receive and reproduce underwater sounds-both sonic and ultrasonic-for the purpose of identifying the sounds and locating their sources. Sonic sounds (below 15,000 cycles per second) are made by propellers, engines, rudder motors, pumps, gear wheels, and many other devices. Ultrasonic sounds originate mostly from high-speed propellers. The bearings of the sources of sounds usually can be determined, so that targets can be located without the use of echo-ranging gear."


"Model JP Listening Equipment

DESCRIPTION
Models JP-1, JP-2, and JP-3 equipments are used on submerged submarines to obtain bearings on other vessels by directional detection of underwater

sounds. They can be used also to listen for own ship's noise. Models JP-2 and JP-3 differ from JP-1 in the amplifier circuits. Models JP-2 and JP-3 are alike except for the method of mounting the hydrophone."

Which basically means that if you are only using the keel mounted ultrasonic heads you will not hear slower props in the sonic range as well or at all so you will hear something with a fast screw like a DD but not a slower screw or perhaps not as far or clearly.So in other words we are both wrong and both right though to get the full sonar picture the sub would need to be submerged.