Fast 90, where am I going wrong.

[knight76]

I seem to be having trouble getting the fast 90 attack to work out. I used to attack with the Dick O'Kane 90 degree attack setting AOB to 75 and shooting along periscope bearing - or + 15 degrees from 0 or 180. This was in silent hunter IV.

This worked out well but meant you were fixed alot of the time on attacking along a set bearing, the fast 90 attack, in the U-boat gives you the option to look around and fire at will, grab a range and shoot.

I'm not sure where I am going wrong though, I am missing from ranges as close as 500m which is practically point blank.

Here is a run down of my attack procedure.

1) I get the sonar contact and run a course to jump well in front of them then setup on the 90 degree angle, this is done from their rough plotting of the sound contact at first.

2) Next up, I sit on the surface awaiting visual contact at which point I mark his position on my map. Then depending, I either measure his speed at that point, followed by a dive to periscope depth, or I go immediately to periscope depth and get the speed when he is a bit closer.

3) Method for getting speed is to measure time interval for 3 minutes plotting positions on map. 3 minutes due to the game being in metric.

4) As I have now plotted his course more accurately I re-plot his track and re-align to the new 90 degree angle.

5) I await his arrival at bearing 15 or 345 and shoot.

Now, here is some pictures of my attack setup which will show you my dials, map screen etc.

Pic 1: Shows my map picture of my step, im on the 90, just waiting now. I have set his speed, and re-plotted his track etc.
http://i6.photobucket.com/albums/y242/knight76/Misc%20Stuff/sh3%20attack1_zpsardgobrj.jpg

Pic 2: Target has arrived in my strike zone and is a bit wider than my plotted track, this would throw out my 90 degree setup maybe 1 degree I think. Also, I have moved in to improve my odds and am now sitting about 600m from the targets plotted course line.
http://i6.photobucket.com/albums/y242/knight76/Misc%20Stuff/sh3%20attack2_zpsrf0xgrnf.jpg

Pic 3: These are all my settings, I am not looking directly at 0 degrees in my periscope here, but when I am, the gyro thingy is pointed at 0, and the AOB is at 90 degree to the direction the target is traveling, in this example, target is traveling right to left in front of me. You can also see my torpedo settings, these are just to set the torps to run shallow with impact detonators and that is it. It is early war. Speed was measured at 8 knots. Torp tubes have been opened also so this is not contributing to the situation. Toprs launch immediately.
http://i6.photobucket.com/albums/y242/knight76/Misc%20Stuff/sh3%20attack3_zpsje7vpkp7.jpg

Now, even though I am sitting at 600m from the targets track where it intersects my perpendicular track, in this case I set range to 700 as I found previously when I had set it to exactly as measured by the ruler, I had missed and thought the range may have been off. I manually took the range with the statimeter thing (ID target, measure mast height in periscope) once and it measured longer than the ruler. That shot missed aft so I thought my range via ruler may have been too short.

So that pretty much sums up my fast 90 technique, but I tend to miss most shots with it and I have no idea why. On my current patrol I have sunk 6 ships, all but 1 of them were via deck guns which I can get away with early war. But I would really enjoy hitting with a few more torps.

In the example above, I did hit with one but it was a dud, the second missed just barely aft.

I'd appreciate some corrective advice if I am doing something wrong or can improve my setup technique.

[scott_c2911]

Torpedo solution SOP.
Close to within 2000m of plotted target track and position yourself 90' to the track.
Identify ship accurately as soon as possible.
Slow to 0-1kts.
At target bearing 45' or 315' relative (AOB should be 45' port or starboard also) do an initial range measurement. Forget ruler on the map.
Use the stock method for gaining speed data. (Lock target and time the target for 30s using notepad stopwatch icon)
THIS ONLY GIVES AN ACCURATE SPEED READING IF YOU ARE AT 1KT OR LESS.
Forget 3.15 method although some folks have success with it.
Click on the tick on the notepad twice. One to accept the data and again to plug in solution. Remain locked on to target.
Set up torpedo depth using ship id book. The draft data is important here. If using magnetic pistols set it 1m below keel. If using impact pistols set up at mid draft.
At 10' or 350' relative open outer doors. When the sound has stopped fire your torpedo. To aim at particular points I unlock just before firing and aim directly at a given spot.

I have just started using manual targetting and I have had a 90% success rate so far using above procedure. Good luck.

PS Use T1 torpedoes and forget the T2s. They are shocking. If theres a warship around, dive deep and change course immediately after firing.

[Zosimus]

The problem might be with the 3 minute measure. The right time is 3:14.4 so if you have enough time, you should watch the vessel for 6:28.8 and multiply by 5 to get the speed.

[knight76]

See I thought the 3:15s timing was for imperial measurement and metric was 3 minute even?

scott_c2911 - Having read the forum I have seen comments stating the stopwatch gives inacurate speed measurements and the 3 minute style timer is more accurate.

I'll give the stopwatch a go, when clicking the tick twice, does this just enter speed data, or range and AOB data also?

If I was meant to be timing for 3:15s that may give the target another knot, so may explain why my torps tend to hit later than aimed, or just miss aft.

[Zosimus]

1 knot = 0.514444 meters per second.

Therefore in 3 minutes (180 seconds) @ 1 knot, a ship will have covered approximately 92.6 meters. In 190 seconds @1 knot, a ship will have covered 97.74 meters. At 195 seconds, a ship will have covered 100.3 meters.

Therefore, the rule of 3:15 (more precisely 3.14.4) is the amount of time that a ship traveling at 1 knot will need to cover 100 meters.

If you are timing for only 3 minutes, then you are getting 92.6 percent of the ship's speed. Therefore a ship traveling at, let's say, 7 knots, will show up as closer to 6.5 in your reckoning.

[Kip336]

It's been a while since I did manual solutions, but the fast 90 is a good way to learn! Soon once you get more comfortable with the process you'll start attacking with other AOBs.

I agree with Zosimus, use the 3,15 timer for better speed estimates.
another thing that helped me was to make a 90degree turn and to keep taking measurements, while also manually drawing bearing lines on the map.

The 90 degree Turn causes the bearing lines to shift, BUT, as the target keeps the same speed and course, there will be one line where the bearing lines are all equidistant from each other.
If this isn't the case, you know your calculations are off.

If I don't forget, I'll post a picture this afternoon after work

[knight76]

Thanks for the tips guys. I am very meticulous in my setups so I can't imagine there would be an issue with the 90 degree setup etc.

I think the problem is going to be the 3 minute timing. I even setup a spreadsheet to enter the data to try to convert distance traveled in 3 minutes to knots, but the game does not give increments only increasing distance in 100m lots. So it's not as accurate.

Can ships in game go 7.5 knots etc or are they always 7 or 8 knots?

I'll give the 3:15 timer a go tonight and see how that works out.

[Kip336]

Only on long distances (1000m + ) should half a knot start to matter.

3:15 is quite easy.
Take a location fix, 3;15 later another one. The distance between both fixes divided by 100 is speed in knots.

1200m travelled in 3:15, speed 12 knots
700m travelled speed 7 knots etc.

If the ship travels 650m, you can set the torpedo to 6,5knots with the dial.

[Pisces]

Just to make sure, did you mix T1 and T2 torpedoes in those tubes? If so then it may be due to a game bug. It doesn't update the torpedo speed calculation when you switch between T1 and T2 tubes. So the torpedo goes to the wrong gyro angle. If you do have both T1 and T2 in the tubes make sure you reset the right speed and re-aim before you shoot.

Other than that it might have been made worse by the 3m vs 3m15s confussion. If you want better resolution in the speed then take multiples of 3m15s: 6m30 and divide by 2, 9m45s and divide by 3, 13m and divide by 4. The latter gets you down to a quarter knot preciscion, which is what the user interface allows you to set visually anyway. You can't see it much more precise.

Target speed isn't always constant though. If it is wrestling with the waves then it temporarily slows down, which might just make it dodge the bullet. Remember that the 3m15s rule is an average speed.

Ships can go at any fractional speed that the campaign designer desires to enter in the editor. (the ship's max speed permitting ofcourse) So it's just a question how lazy he was. Don't count on whole numbered knots if you want to shoot accurate. Nature and physics doesn't count that way either in the real world.

[scott_c2911]

I start from the top of the notepad and work down. Id is first, then range, then AOB. Without that data speed is hard to determine using the in game controls without using 3:15 method. I noticed that the gyro angle didnt change when clicking the tick once after timing the target and gaining speed data. I realised that I was just accepting the speed and not the solution. I clicked the tick again and the gyro angle was altered. This is a bit controversial but I consider the 3:15 method cheating but then Im being hypocritical as I play with map contacts on too, which is also cheating a bit. I can plot perfect intercepts exactly 90' to the targets track. At the end of the day its whatever you feel comfortable with and you enjoy. Theres no fun in sitting there for ages searching for contacts and finally missing it all together. The important thing is that the built in method for gathering speed data doesnt work unless you are practically stationary where the 3:15 method still works at flank speed. I can understand why its so popular but I have missed everytime I tried it.

[knight76]

No not mixing torpedoes just using the standard loadout.

I've been on my next patrol now just arrived on station, on the way had good weather so the 4 merchants I attacked were with deck guns. Still early war so they aren't armed yet.

At the moment I am lying in wait ahead of a convoy with a destroyer way out front and one way in the rear but none flanking the convoy. This will be a longer distance shot so I guess we will see if I score any hits :D

[Kip336]

Take out the rear DD, hide and take out the front. You'll have ample time to set up torpedo attacks and use a deck gun on the convoy from a few hundred meter :p

[Zosimus]

I start from the top of the notepad and work down. Id is first, then range, then AOB. Without that data speed is hard to determine using the in game controls without using 3:15 method. I noticed that the gyro angle didnt change when clicking the tick once after timing the target and gaining speed data. I realised that I was just accepting the speed and not the solution. I clicked the tick again and the gyro angle was altered. This is a bit controversial but I consider the 3:15 method cheating but then Im being hypocritical as I play with map contacts on too, which is also cheating a bit. I can plot perfect intercepts exactly 90' to the targets track. At the end of the day its whatever you feel comfortable with and you enjoy. Theres no fun in sitting there for ages searching for contacts and finally missing it all together. The important thing is that the built in method for gathering speed data doesnt work unless you are practically stationary where the 3:15 method still works at flank speed. I can understand why its so popular but I have missed everytime I tried it.

I have no idea why you, or anyone else, would think that the 3:14.4 method is cheating. I also don't understand why people say it's 3:15. Doesn't 3:14.4 round down to 3:14? Not that it really matters.

You should easily be able to use the three-bearing method to get the target's exact course, and if you get a fourth bearing, you'll know his exact range, too. From there it's simple to plot his speed by measuring two points 6:29 apart. Multiply the distance in kilometers by 5 to get the speed. For example, if the ship has covered 1.4 km then you'll know his speed is 7 knots.

Personally I have found the two-bearing method to be good enough. Even from a hydrophone, the two-bearing method gives a course and range that's close enough for government work. Range, generally speaking, has a negligible effect on torpedo solutions. It's only important for setting the spread angle on salvos.

[Pisces]

... I also don't understand why people say it's 3:15. Doesn't 3:14.4 round down to 3:14? Not that it really matters.The 15 seconds is easy to see on the clock and add multiples in your head. It's easier to handle quarters of a minute than mentaly adding .23333 every time. That 1 second in 195 seconds total that it is off is insignificant.

You should easily be able to use the three-bearing method to get the target's exact course, ....And I don't understand why you say "exact" here. As the 3 bearing method is far from exact as a practical method. To get an exact course you need to know the precise bearings (at least 1 fractional decimal), otherwise it results in a range of courses tens of degrees wide. It tested this with my 3-bearing AOB slideruler (http://www.subsim.com/radioroom/showthread.php?t=147719), only using bearings rounded to the degree as the crew reports them. This depends much on how long the time intervals were. Longer time intervals results in more degrees between the bearings and makes the result more granular. Also the problem in is you are using intersections of lines that are almost parallel, and that can result in wildly varying course and range results. Doesn't matter if you use the formula, or do it graphically. If you rely on the map plotting the exact thin line bearing then this could be somewhat of a cheat, similarly to using the target icon markers when plotting, as it seems to be fairly precise. In reality hydrophone set could not give that level of precision.

Personally I have found the two-bearing method to be good enough. Even from a hydrophone, the two-bearing method gives a course and range that's close enough for government work. Range, generally speaking, has a negligible effect on torpedo solutions. It's only important for setting the spread angle on salvos.To my knowledge, there is no 2-bearing method that can give that level of information (course and range). Course needs at least 3 bearings. Otherwise you are assuming things that might not be true. Please explain how it works. Unless you mean 2 bearings with range measurements like the SH4 TDC does, or as on a maneuvering board is done. But that does not apply to SH3.

[Zosimus]

First of all, I refer you to https://en.wikipedia.org/wiki/Sinking_of_the_RMS_Lusitania#American_court_procee dings wherein we read:

"Captain Turner gave evidence in England and now gave a more spirited defence of his actions. He argued that up until the time of the sinking he had no reason to think that zig-zagging in a fast ship would help. Indeed, that he had since commanded another ship which was sunk while zig-zagging. His position was supported by evidence from other captains, who said that prior to the sinking of the Lusitania no merchant ships zig-zagged. Turner had argued that maintaining a steady course for 30 minutes was necessary to take a four-point bearing and precisely confirm the ship's position, but on this point he received less support, with other captains arguing a two-point bearing could have been taken in five minutes and would have been sufficiently accurate."

A two-bearing method is not as precise as a three- or four-bearing method. It is, however, good enough to get a u-boat into a solid firing position where last-minute updates and visual inspection can permit the final adjustments necessary to get the job done.

With nothing more than a hydrophone, a ship's approximate bearing and range can be known. This range is not that accurate, but I generally put a 200 meter circle around the ship's location to represent that the ship is "around there somewhere." This circle can show up differently on different zooms and will not be exactly on the ship depending on the zoom you use. Accordingly, it's necessary to use the right zoom and this is more an art than a science. Some practice will be required.

Some 5-10 minutes later a line can be drawn from the ship's old position (the center of the circle) through the ship's new position. Your sub can move during the procedure. The longer you permit between the two measurements, the more accurate the result will be. For example, you may find that the ship seems to be moving at 60º (ENE) or thereabouts. This is usually accurate give or take 2-3º either way.

When you are within 5000 meters of the ship, you can detect the ship using the periscope (weather permitting). Your TC will drop to 1 (depending on your settings). Pre-radar I just move forward at 2 knots with the scope up at TC 64 and I know the ship is 5,000 meters away when it gets spotted. From there I can draw the ship's course through its location (shown by map contacts) and go scope down for 6:29. In real life this probably would not have been necessary because I could have just ordered my hydrophone operator to count the propeller rotations and tell me the speed. I believe there's some sort of a mod that permits one to do so manually. Still, I have found 6:29 to be "good enough" as it gives me accuracy to within 0.5 knots. Ship's speeds will vary anyway depending on the weather – it's not uncommon to see ships vary between slow/medium depending on wave strength. That will tell you that it's 7.5 knots right off the bat.

After going scope up, if the ship seems to be on the line you drew, then the course is accurate. Alternatively, you can adjust it 1º either way and set up your firing solution. I generally fire a two-torpedo salvo and both hit about 70 percent of the time. Even if you're slightly off, one should still hit and that might be enough or you may have to follow up later with the deck gun. Even if both hit, sometimes one turns without exploding. These things happen.

[TorpX]

"... Turner had argued that maintaining a steady course for 30 minutes was necessary to take a four-point bearing and precisely confirm the ship's position, but on this point he received less support, with other captains arguing a two-point bearing could have been taken in five minutes and would have been sufficiently accurate."




I don't mean to argue for using or not using whatever hydrophone method, but you are taking the above statement out of context.

The ship's captain is interested in navigating. He knows his previous positions, speed and his present course; he really only needs limited supplementary info for safe navigation. Intercepting an unknown target on the basis of sound bearings alone is a much harder task, as you would not know it's course, speed, range, or really, if it is zigging or not.

[Zosimus]

I don't mean to argue for using or not using whatever hydrophone method, but you are taking the above statement out of context.

The ship's captain is interested in navigating. He knows his previous positions, speed and his present course; he really only needs limited supplementary info for safe navigation. Intercepting an unknown target on the basis of sound bearings alone is a much harder task, as you would not know it's course, speed, range, or really, if it is zigging or not.




The RMS Lusitania was was torpedoed and sunk by a German U-boat on 7 May 1915. This event caused the deaths of 1,198 passengers and crew. The quotation above was made by the captain to explain why he was not at fault for the sinking of his vessel.

So no, the captain is not only interested in navigating. He is interested in not getting torpedoed.

[Pisces]

Still, this does not sound like any proof or explanation of a solid method based on 2 bearings alone. Perhaps it is considered 'expert opinion' in that court case, but it doesn't show how it is done in practice. So that leaves nothing to verify it.

I guess you could do with just 2 bearings if you rely on the fading length of the line on the map, but that is nearing on cheating reality. With only a single ended line in a specific direction you cannot judge distance. So you can't plot 2 such indefinate lines and get a course from that. At best you can tell it has a course to either side if the bearing drifts to left or right.

[Zosimus]

Still, this does not sound like any proof or explanation of a solid method based on 2 bearings alone. Perhaps it is considered 'expert opinion' in that court case, but it doesn't show how it is done in practice. So that leaves nothing to verify it.

I guess you could do with just 2 bearings if you rely on the fading length of the line on the map, but that is nearing on cheating reality. With only a single ended line in a specific direction you cannot judge distance. So you can't plot 2 such indefinate lines and get a course from that. At best you can tell it has a course to either side if the bearing drifts to left or right.

First of all, I think that you are woefully ignorant of just how good the GHGs were. I think you should start by reading http://www.cdvandt.org/GHG1996.pdf to get some perspective. The distance between the GHG receivers was around 4.25x the distance between our ears, so as to take into account the different speed at which sound travels in water as opposed to in the air. Someone wearing these headphones could, therefore, point to the source of the sound as easily as you can point in the direction of a nearby barking dog.

Second, we know that GHGs came with a resistor that was used to decrease the level of sound. It came with hundreds of settings, but even assuming that it only came with 40, and assuming that a GHG can hear a lone vessel out to 20 km, that means that each setting shows 500 meters of range distance. Therefore the very idea that I should run around pretending that my GHG cannot tell me the approximate range of the boat is idiotic.

Furthermore, the very idea that using the capabilities that my u-boat comes with in the game, and most likely had in real life is "cheating" is insulting in the extreme. I do, therefore, request that you retract the statement.

[scott_c2911]

I feel I must reply to the last post due to the fact I believe I have also used the word "cheating" in this discussion. The reason I have used that phrase is due to the fact I have map contacts on and I found it a little too easy to determine speed by drawing a mark at t=0 and t=3:14.4 or to the layman 3:15. If you dont use map contacts then hats off to you with your 2, 3 and 4 bearing methods as I have no idea what your talking about. I have tried with no map contacts on and I hadnt got a clue. I freely admit ww2 sub drivers didnt have a super accurate spy satellite to help them but I am still learning how to do it with the aid of the map as it is. This post was about helping someone hit a target and I was trying to keep it as simple as possible for the op. I knew when I wrote that part of the post it might stir up a few anger issues however I felt it was outweighed by the fact I had called myself a hypocrit and went on to say that its not how you play but whether you enjoy playing that counts. I enjoy timing the target the stock way and I have had more success doing it so I tried to pass that advice on to the op. Im sorry if any offense has been caused.

[TorpX]

The RMS Lusitania was was torpedoed and sunk by a German U-boat on 7 May 1915. This event caused the deaths of 1,198 passengers and crew. The quotation above was made by the captain to explain why he was not at fault for the sinking of his vessel.

So no, the captain is not only interested in navigating. He is interested in not getting torpedoed.

You can zig till your heart's content without taking any bearings whatsoever. He needed the bearings for navigation purposes. The point being that the two situations are not remotely comparable. The skipper of the Lusitania has much more information before he takes the first bearing, than any U-boat skipper would have of a potential target.

[Zosimus]

You can zig till your heart's content without taking any bearings whatsoever. He needed the bearings for navigation purposes. The point being that the two situations are not remotely comparable. The skipper of the Lusitania has much more information before he takes the first bearing, than any U-boat skipper would have of a potential target.


So you're arguing with me by agreeing with me? This makes no sense.

Obviously I have skipped a few steps in the explanation. Steps that I thought were obvious. Apparently, however, you aren't up to speed. Let me try explaining again in a simpler way that may be more appropriate to your knowledge base.

You see, there exists this thing called an ocean. It's filled with water. Goods produced on one side of the ocean often need to be used on the other side of the ocean. The method of moving the goods from one side to the other normally involves things called ships.

Ships are big metal containers with motors. The ships float because they are airtight and water does not get into them. However, during wars, another type of ship, called a submarine, often tries to pierce these ships so that they no longer float. When the ships stop floating, it's called "sinking."

The method of sinking ships normally involves something called a torpedo. A torpedo is a narrow tube filled with explosives and a motor. When launched from a submarine, a torpedo will (hopefully) intersect with the ship and then explode. If successful, this torpedo will cause the ship to fill with water and sink.

Now from the point of view of the skipper of the submarine, the problem is getting the torpedo to intersect the ship – not where it is now, but where it will be in the future when the torpedo arrives. In order to do so, the skipper will need to gather some information about the ship's speed, direction, and how often these things change.

Now the ship in question, known as RMS Lusitania, was torpedoed and sunk. With that fact in mind, we must realize that Kapitänleutnant Walther Schwieger apparently managed to solve the complex geometrical problem that faced him well enough to intersect the Lusitania with a torpedo thus causing her to sink.

Now the Captain of the Lusitania, one Mr. William Thomas Turner, was asked to explain why he didn't do a better job of ensuring that his ship didn't get sunk. Captain Turner claimed that it taken 30 minutes or more for the u-boat to acquire the exact heading of the ship using the four-bearing method. Thus, according to the Captain, it wasn't his fault that his ship got sunk.

Other captains, however, disagreed and pointed out that there is a simple two-bearing method that would have worked well enough under the circumstances and that doesn't take 30 minutes. It only takes 5-10 minutes.

So you see, TorpX, the subject at hand is not how a captain can zigzag a ship. It is not about what bearings a captain needs or doesn't need to zigzag a ship. Nor is it about what bearings the captain of the Lusitania might want or need to make. We are concerned entirely about the problem from the point of view of U-20, the German-made submarine that torpedoed the Lusitania.

If you still don't understand, maybe you can sit with your mommy and she can explain any big words that you don't get.

[Pisces]

With that kind of response I have no intention to continue this discussion. Zosimus, why do you feel threatened so much? There is no need to take this so personal.

[TorpX]

......
If you still don't understand, maybe you can sit with your mommy and she can explain any big words that you don't get.

Being snotty doesn't make you smarter, or even appear smarter. You might want to think a little more before you post.

[Zosimus]

With that kind of response I have no intention to continue this discussion. Zosimus, why do you feel threatened so much? There is no need to take this so personal.

Good! Because, other than calling me a cheater, you contributed nothing to the thread.

[Zosimus]

Being snotty doesn't make you smarter, or even appear smarter. You might want to think a little more before you post.




No, before YOU post, you might want to actually understand what the person you are responding to is trying to indicate. Otherwise you end up with threads like the above.

For example, if someone writes: "My dog died when he was 24. He was old, sick, blind, deaf, and could barely move around. We finally took him to the vet and had him put down." then an appropriate response doesn't start by saying that your vet lived to 86 years old.

Why not? Because the age of the vet has nothing to do with the subject at hand. Even if you could prove to everyone's satisfaction that no vet had ever died under the age of 24 in the history of the universe, it still wouldn't have anything to do with the topic at hand.

It's the same thing here. The bearings taken by a ship's captain (regardless whether he is zigzagging) have nothing, zero, zip, zilch, nada, rien, to do with the problem of a u-boat captain hitting an enemy vessel with a torpedo and nothing to do with whether this problem can be solved by using a two-bearing, three-bearing, or four-bearing method.

In case that's not clear, let me restate it. I don't care ... not even in the smallest, part of my mind ... how many bearings a captain needs or doesn't need to zigzag effectively. I am concerned with the problem of the u-boat effectively calculating an intercept solution that's close enough for a two-torpedo salvo to hit with at least one fish.

[Sailor Steve]

Let me make something clear as well. Discussions are great. Disagreements are fine. Arguments are valuable. Dismissive language and insults are not.

Please keep it civil.

[Pisces]

Good! Because, other than calling me a cheater, you contributed nothing to the thread.I never personally called you a cheater. I did however say that the way the game displays the hydrophone bearings on the map, both in direction and length is cheating reality. This is of course not in anyway "bad" because SH3 is a game, and by definition it does that. SH3 is not a real simulator. And even simulators cut corners sometimes. So there is no need to feel threatened or consider your self attack as being a "cheater". If you want to play with the tools that the game gives you then that is OK and fine. I'm just saying in reality is wasn't so easy and reliable. Which I will explain next why I think that, based on the document you linked to. I have read it! In fact, I think I was the first one* that introduced it the SH3 forum to it by linking to this writer's site:

http://www.subsim.com/radioroom/showthread.php?t=130404

*: Ok, I forgot it was linked in the GWX 1.03 manual.

Why is the precise direction of the plotted bearing line 'cheating' reality?

Well if you read that document then you'll find that the bearing preciscion was very dependant on the frequency of the sound. Only with the higher frequencies (above 3 khz) could you get bearing precision narrower than 1 degree. Lower frequencies (in the order of 500Hz) give a much 'fuzzier' bearing, making the actual bearing somewhere in a range of up to 8 degrees. Which would make it a lot harder to find the center of the sound, just like listening to the sound manually at the station. And as higher frequencies decay in strength much sooner than lower frequencies these bearings would not have been as accurate at long range as the game portrays. Page 15 of the document you linked:
The British carefully investigated the capabilities of the GHG (Elac) apparatus in the captured U-570, in May 1942.
On successive selections of the high pass filters it was found that on the 6 kHz high pass-filter (utilizing the sonic spectrum between 6 kHz - 7 kHz), the bearing proved to have an accuracy of # 1°, for 3 kHz (utilizing the spectrum between 3 kHz - 7 kHz) the accuracy was . 1.5°, and for
1 kHz (utilizing the spectrum between 1 kHz - 7 kHz) the accuracy was . 4°, at 500 Hz, thus bypassing the high pass filters, the accuracy was decreased to. 8°.
Average merchant ships, cruising at 12-13 knots, produced a maximum sonic spectrum at 100 Hz and only 10% at 4 kHz. For destroyers cruising at 15 knots, the maximum sonic spectrum was at . 200 Hz, but still supplying 30% of its harmonic spectrum between, 4 kHz and 8 kHz.
Thus the proportion of sonic signal level left at the higher harmonics, had to be compensated for by increasing the amplification gain.
The question remains then how much this amplifier could enhance the higher frequencies without distorting the signal or flood it in self generated noise making it useless at longer ranges. This is hard to verify so long after the war, without first hand experience of the operators written down. (one of the conclusions of the writer)

Range determination based on hydrophone

The other place where I used the word cheating was in relation to the length of the hydrophone bearing line on the map in the game. Which as we know has the faint end of the line exactly ending at the source of the noise detected. Your eyesight, screen settings and antialias settings of your videocard determine if you get the right pixel spot on.
You state that the GHG or hydrophone had a resistor with which the signal strength could be reduced to determine the range of the source. You suggest that this variable resistor could be adjusted to get an absolute value on the range. Or at least get steps of 500m if it had 40 intermediate steps covering an expected max range of 20 km. However, I read that section about the resistor differently:
Page 3 of the PDF document:
All systems were subject to interference by the noise generated by electrical generators and other rotating devices, inside the submarine. The first step taken by the Germans to reduce this noise used a variable resistor parallel to the earphone circuit, a crude but quite common method used, in those days, to quantify the strength of a wireless signal. A special potentiometer was fitted with a 270 degree scale and was calibrated in ohms. The parallel resistance had to be reduced until the sound, in the headphone(s), had vanished. The signal strength was, for instance, considered as being 150 ohms. The value of the parallel resistance could indicate the increase or decrease of the sonic signal strength and allowed an approximate distance estimation, as well.
To reduce the man made noise picked up by the hydrophones, 1050 Hz band pass filters were inserted between the microphones and the earphones circuits.
The next step was to increase the system sensitivity, by adapting the valve amplifier used for the wireless station. Ships could now be observed up to 20 - 25 nautical miles, but greater attention had to be given to the reduction of man-made noise, from inside the submarine so as not to negate the improvements.

"could indicate the increase or decrease of the sonic signal strength"
- I read that as it could indicate a relative change in signal strength, and hopefully by relationship, distance.
What this means is that this resistor control could indicate if the sound source got stronger or weaker than to what it was calibrated. It does not say to which range it was calibrated. Which would require a known distance under the same conditions, which is something you don't have when you haven't located the target yet. In fact the writer mentions it is calibrated to a ohms value, not actual distance. And indicates that this can work upto 20-25 nautical miles, depending on the conditions. So, with background noises changing daily, or maybe even hourly due to the weather and internal conditions, this cannot be considered an indication of absolute range. It's only relative, and at best an indication of how much percentage wise the distance closed or opened up. That's why I feel the line length of the hydrophone bearing is not supposed to indicate the exact position. There is not enough variability in it to match the real world.

So, if you want to play the game as it is given then you should not feel offended by me using the word cheating. Especially as I wasn't personally addressing you. I'm just saying it lacks quite a bit in terms of realism, which understandably the game does not provide on all accounts.

Play as you like.

[Pisces]

Anyway, I still don't know how that 2-bearing method works.

[knight76]

Nup, I've read my first post a few times and just can't for the life of me find where I asked about realism in the game!

My issue was that using the Fast 90 attack that something was going awry and causing my tubes filled with explosives to not make the rendezvous with the intented water tight hull.

Anyway, on with the show.

I ended up having a great time attacking that convoy. I lay in wait sitting at 90 degrees with the lead destroyer already well past my position. Unfortunately whilst at Silent Running I hit a wrong button and made a little too much noise for short moment but this was enough to attract the attention of the lead destroyer.

With it running directly at me firing at my periscope, I sent a torpedo down it's throat and managed to sink it. Immediately set depth for 180m and crawled out of there. But did not escape the attention of the rear destroyer which proceeded to repeatedly depth charge me, though none were close enough to do any damage.

Eventually as the convoy sailed away, the DD decided he should probably catch back up to the convoy since he is the only DD on guard duty now. I decided to pop up and try to entice the DD back, even surfacing and firing my deck gun in his vicinity, but I could not goad him back to allow my to fire another torpedo down his throat like the first one.

Each time I would have him turned around and on his way back, he would return to the convoy just as fast.

I gave up and overtook the convoy to lay in wait again.This time sinking the rear DD as it maintained it's rear position. I did notice however, a distinct warship shape section in the middle of the convoy, but could not get a good look at it as it was obscured by other merchant ships.

Again, I overtook the convoy though laying ahead of their course no ships arrived. I was lucky enough to find them again 100km to the east of their previous track. They must have decided to take a lone evasive maneuver to avoid me as when I found them, they were headed back towards their original track. with the convoy now with no DD escort I lay in wait a third time. This time, I positioned myself ahead of the convoy in it's direct path and targeted a southampton class cruiser, I'm not sure why the cruiser didn't get in on the depth charge fun after I sunk the first DD but I'm thankful it didn't. It went to the bottom with 1 torpedo under the screws.

Whilst laying in wait for the convoy this third time, I noticed two red warship lines on my attack map, instead of just the one I was expecting. This second red line turned out to be an S type sub.

This set off a series of engagements with the sub both from long distance shelling and short range flak gun fire. You see I got a little annoyed that after sending 20 shells from my deck gun in to it's sides, it refused to sink, though it's shots hitting me cause all sorts of drama and flooding.

I sank to periscope depth and moved to a position just behind it, surfaced and engage the sub at close quarters with the aim of blowing it's deck gun out of commission. Which when given a good angle on it, I did just that. For the cost of two of my sailors lives who were manning the deck gun with me.

After this I left the S type alone and stayed out of range of it's flak gun which seemed able to cause flooding by itself.

From there it was a turkey shoot with a good number of merchant ships finding the ocean floor either through torpedo or deck gun attack.

[Hambone307]

Well Knight, this was an interesting derailment of a thread related to needing help with an attack tactic. I had tried to use the 90 degree method the other day after seeing your initial question and had probably a 40% hit ratio. For some reason I kept shooting behind the merchants, and couldn't figure out the issue. :-?

[Kip336]

Knight I'd almost go as far as saying that the S class I'd bugged. I ran Into one, many 8.8cm and flak later it did not sink. It was in the harbor so I shot off his deck and flack guns and proceeded to take my time at sinking her with below the Waterline hits.

[knight76]

Hambone307 - I think my issue was probably with my timing the ships for speed. I was using 3 minute flat, so that would have thrown the speed out a little, and I generally don't get my ship lined up perfectly on the 90 degree line, the target tends to be a little off my plotted track by the time it gets to the intended shoot bearing.

This probably combines to mean my torps trail the target slightly. On larger ships I still score hits, just further back than I aimed, on smaller ships, I may miss just aft.

I haven't had a great deal of time to practice the attack as each lone merchant I find is not armed and I sink them with deck guns.

I have found though, that shooting from 500m rather than 1000 cuts the error down a fair amount also.

Kip336, has to be bugged. I easily hit the S type with 20 shells total, mixed above and below the water line. I didn't notice any adverse effect at all.

Just stumbled on a slow/stationary ship in the water off the coast of england. I read the flag wrong thinking it was yugoslav but it turned out to be a neutral. Anyway, this ship was a depot ship, armed all over and in war paint, funny a neutral country ship, anchored off the coast of england, armed to the teeth and in war paint, I called bull**** and sent it to the bottom. Will take a renown hit though. It got me thinking though, I wonder if there are U-boat trap merchants in the game. I've never seen one.

[Zosimus]

I never personally called you a cheater. I did however say that the way the game displays the hydrophone bearings on the map, both in direction and length is cheating reality. This is of course not in anyway "bad" because SH3 is a game, and by definition it does that. SH3 is not a real simulator. And even simulators cut corners sometimes. So there is no need to feel threatened or consider your self attack as being a "cheater". If you want to play with the tools that the game gives you then that is OK and fine. I'm just saying in reality is wasn't so easy and reliable. Which I will explain next why I think that, based on the document you linked to. I have read it! In fact, I think I was the first one* that introduced it the SH3 forum to it by linking to this writer's site:

http://www.subsim.com/radioroom/showthread.php?t=130404

*: Ok, I forgot it was linked in the GWX 1.03 manual.

Why is the precise direction of the plotted bearing line 'cheating' reality?

Well if you read that document then you'll find that the bearing preciscion was very dependant on the frequency of the sound. Only with the higher frequencies (above 3 khz) could you get bearing precision narrower than 1 degree. Lower frequencies (in the order of 500Hz) give a much 'fuzzier' bearing, making the actual bearing somewhere in a range of up to 8 degrees. Which would make it a lot harder to find the center of the sound, just like listening to the sound manually at the station. And as higher frequencies decay in strength much sooner than lower frequencies these bearings would not have been as accurate at long range as the game portrays. Page 15 of the document you linked:

The question remains then how much this amplifier could enhance the higher frequencies without distorting the signal or flood it in self generated noise making it useless at longer ranges. This is hard to verify so long after the war, without first hand experience of the operators written down. (one of the conclusions of the writer)

Range determination based on hydrophone

The other place where I used the word cheating was in relation to the length of the hydrophone bearing line on the map in the game. Which as we know has the faint end of the line exactly ending at the source of the noise detected. Your eyesight, screen settings and antialias settings of your videocard determine if you get the right pixel spot on.
You state that the GHG or hydrophone had a resistor with which the signal strength could be reduced to determine the range of the source. You suggest that this variable resistor could be adjusted to get an absolute value on the range. Or at least get steps of 500m if it had 40 intermediate steps covering an expected max range of 20 km. However, I read that section about the resistor differently:
Page 3 of the PDF document:


"could indicate the increase or decrease of the sonic signal strength"
- I read that as it could indicate a relative change in signal strength, and hopefully by relationship, distance.
What this means is that this resistor control could indicate if the sound source got stronger or weaker than to what it was calibrated. It does not say to which range it was calibrated. Which would require a known distance under the same conditions, which is something you don't have when you haven't located the target yet. In fact the writer mentions it is calibrated to a ohms value, not actual distance. And indicates that this can work upto 20-25 nautical miles, depending on the conditions. So, with background noises changing daily, or maybe even hourly due to the weather and internal conditions, this cannot be considered an indication of absolute range. It's only relative, and at best an indication of how much percentage wise the distance closed or opened up. That's why I feel the line length of the hydrophone bearing is not supposed to indicate the exact position. There is not enough variability in it to match the real world.

So, if you want to play the game as it is given then you should not feel offended by me using the word cheating. Especially as I wasn't personally addressing you. I'm just saying it lacks quite a bit in terms of realism, which understandably the game does not provide on all accounts.

Play as you like.
Only to a limited extent would I agree with you.

Certainly SH3 is a game, and the game does not accurately model reality. A surfaced submarine, for example, traveling at 8 knots should still be able to detect a medium-sized target at 5,000 meters (see https://books.google.com.pe/books?id=OJLiSJ1w6IYC&pg=PA12&lpg=PA12&dq=ghg+calculating+distance+hydrophone&source=bl&ots=JptzufNARb&sig=kaTMnhV_smPUloSWs0iSSOy3kbs&hl=en&sa=X&ei=g9qaVcX3JIOnNpKZiaAN&ved=0CEcQ6AEwBA#v=onepage&q=ghg%20calculating%20distance%20hydrophone&f=false ). Personally, however, while traveling surfaced in the fog in SH3 the first notice I get of nearby vessels is when the destroyer shoots me twice before ramming into me at high speed.

Were you aware, for example, that by turning broadside to the ship the accuracy of the GHG was greatly increased? Turning broadside to the ships does not, as far as I know, improve the accuracy of the hydrophone in SH3.

Or perhaps you think that the GHG in SH3 gives one GPS-like location-finding ability. It does not. Play a bit with map contacts on, maneuver underwater until you close to within 5,000 meters of a ship. Zoom in as much as you like and put a big X on the location the GHG places the ship at. Then go scope up. Whoops!! The ship isn't where you thought it was.

The point is, however, that GHG shortcomings have a tendency to cancel out.

Imagine, for example, that your intrepid crew believes (falsely) that a ship that is 10,000 meters away is really 8,000 meters away and that the second bearing you take, when the ship is 8,000 meters away, falsely shows up as 6,400 meters off. I think if you break out your drawing tools that you will find that the course still ends up close to the real one.

Similarly if you hydrophone operator mistakenly believes that the signal is some 5º higher than it really is – i.e., that a ship that is really at bearing 30º falsely shows up as 35º – that when the second bearing is taken falsely showing the ship at 55º when in fact it's at 50º that the ship's heading still comes out close enough for government work.

You can move into position, get visual contact on the vessel (by periscope), adjust your firing solution, and hit it with a two-torpedo salvo more often than not.

[Zosimus]

The following is an extreme example of error using hydrophones.

http://i42.photobucket.com/albums/e350/Elias_Latour/SH3Img6-7-2015_16.2.2_535_zpsfrmozbt3.png (http://s42.photobucket.com/user/Elias_Latour/media/SH3Img6-7-2015_16.2.2_535_zpsfrmozbt3.png.html)

The top line, at 100º heading shows the true course of the ship we are hoping to track. The bottom line, which is shown by two marks 1.0 apart, shows our course. We assume that we are submerged, running silent, at 2 knots. We cover 1000 meters in 16 minutes 12 seconds. During the same time period, the target ship covers 3500 meters @ 7 knots.

The real range of the target is 18 km at the moment the first hydrophone contact is made. However, since we are exaggerating the error, we assume that our not-so-skilled hydrophone operator mistakenly places the ship at 9 km distance. In short, the ship is twice as far away as we think it is.

At the second point, the ship is 16 km away, but our hydrophone mistakenly gives us 8 km distance. Using these two bearings and ranges, a course is plotted. We calculate that the ship is heading 95º when in reality it is heading 100º

We surface and move full speed (heading 5º) to intercept the ship, moving at (we assume) 14 knots because of weather. As you can see, even with this extreme error in distance, we are still very close to getting it right. As soon as visual contact is obtained, we will be able to adjust our course and set up a firing solution.

[DownPeriscope]

Alternatively, as opposed to the 3:15 method, assuming you have GWX installed, you can use the nomograph on the right hand side in the navigation map for any time period you find convenient - though obviously the longer the time the more accurate it should be. Using the nomograph is really easy - just draw a line between the 'time' and 'distance' mark to get the speed in knots

You can also try the four bearing method. This is also useful when you don't have visual contact and are relying on hydrophones, esp. without map contacts on you won't be able to judge distance

Here is a pretty good explanation of the four bearing method:

http://ricojansen.nl/downloads/the_four_bearings_method_v2,%20Kuikueg.pdf

Note that it doesn't tell you exactly how to construct the paralell lines - I use a combination of compass and protractor for that (there should really be a T-square tool in this game :-)