Hi RR

i'm no subjockey, but i've read quite a bit on the matter - including modern techniques, and the problem is ultimately a mathematical one. I'm just one of Hitman's acolytes!

i'm also fully in favour of using historical techniques, and i even like to play using techniques that develop as the war continues

This approach is WW1 stuff and probably not even at first an American technique, and it works because triangles are triangles even under the water.

For this method requires an aob estimate used this way, or it requires a speed estimate to produce AOB.

[A couple of years ago i wrote a tutorial that described a complicated method based around this that does actually give range course and speed estimates, but it does require guesswork about the target speed. You can get it from my ff link if interested]

anyway your assumption that the first contact aob is 10 degrees is, in short, wrong - unless you are only talking about the case in your mission setup.

Or unless you approach on the surface and only submerge when you know you're ahead of the target with a small AOB - in which case you have a visual AOB estimate which as i said, is something this method requires

Secondly, at long range it produces the greatest error in speed estimate because it's harder to determine whether you are in fact on a collision course since it takes so much longer for the bearing to target to change

Thirdly with very small AOBs the speed estimate is most inaccurate because a wider range of speeds can give a "near solution" for the triangle. The larger the AOB the more accurate your estimate is, but of course the faster you have to travel to maintain the collision course

But you can reinforce your estimate with the hydrophone trackers speed estimate - in SH4 with RFB, "moderately fast screws" generally translates to a speed range of 9-10 knots.

You do know, right, that AOB and target course are esssentially the same thing, right? It's a simple conversion of one to the other that can be achieved in seconds with use of an ISWAS (already linked) or even the TDC.

Also using the point at which the hydrophone contact is first made as a range datum is risky, since the contact point varies with the quality of your equipment, speed and type of target and weather conditions. At least i think it does:-?

so other means are required to determine expected time of arrival. it's not impossible, but your method either isn't reliable, or if it is it's gaming the system, but in my experience in some circumstances i've failed to pick up targets within 2000m in some conditions

Anyway, read this: you'll find it interesting:

http://www.hnsa.org/doc/attackfinder/index.htm

it's in the same place as the fire control manual you already read.

But lastly the point that hyper-accuracy is not required, is absolutely true, andimportant to acknowledge

I would say in general that extremely long range shots, those over 3,000 yards, are foolhardy anyway, even with perfect data. My studies have shown that fully half of Mark 14 torpedoes, I don't remember which speed I used, died after 3,300 yards. In one experimental firing five of six died before 3,500 yards.

At the time I was trying to replicate somebody else's extremely impressive video of hits at 5,000 yards simultaneously on two or three targets. I just have been using slow speed (ya think?:88)) My experiments showed it was a parlor trick, sort of like making an elephant vanish in a parking lot. It depended for its success on what you did NOT know. First, it was a precisely set up mission and second, who knows how many times the video was shot before all the torpedoes both got out to that range and hit the two targets? This is not to say that the video wasn't impressive, it was magnificent! But it had no application to playing the game in making anybody a better sub skipper, just as sawing a beautiful assistant in half and putting her back together on stage can't help a surgeon develop his skills.

So extremely long range passive sonar techniques are really of little value except for satisfying curiosity. HOWEVER, if you are in a fog or severe rainstorm in a boat without radar THEN you have to use something. I'd go ahead and ping for range, twice. You can tell with your passive sonar if you are about to ping a warship unless you have tunnel vision like I did one time. Having that knowledge, pinging is of very little risk.

I'm still curious to violate my standard operating procedure of working only with in-game tools and work up some outside-the-game bearing rate plots and bearing difference plots to see if they could be of more use to me than they apparently were to the real WWII skippers, including Dick O'Kane and Eugene Fluckey.

That also raises a really interesting question. Is a technique useful because it COULD have been used during the war, or because it WAS? We're going to divide into two very sensible groups based on the question. I straddle the fence. After all, Dick O'Kane did not follow exact established procedure in his targeting and neither need we be so long as it was clearly possible and similar techniques were in actual practice. I'll live unambiguously in the gray area there!:haha:

All that sensible stuff being said, I love to stretch the envelope and see where that leads, so I'm very interested in greyrider's investigation and findings. I'll be one who downloads his mission and plays with it with an open mind.

I think you've misunderstood what the purpose of this approach is. It's not intended for long range shots, just for gathering speed data. My point is that unless you have visual AOB (and greyrider, as i can, can determine AOB visually, reliably and accurately) then you do not actually get a speed estimate with this method, unless you guess, and that guess turns out to be right.

There are ways of doing it. Simply put if you have made an ISWAS or Submarine Attack Course Finder (and i'm surprised you haven't, RR), you can get a range datum after you have established a collision course, by changing your speed for a short period.

You can obtain a second datum by doing it again later once you are nearer the target, or even using the point at which the target arrives in front of you as the second datum

here's the link to the tutorial i wrote nearly two years ago, although i have refined the method somewhat since then

http://www.subsim.com/radioroom/show...highlight=SACF

but nonetheless given a choice a couple of periscope observations makes a lot of difference, and more fun is to use the Submarine attack course finder the way it is intended.

As for using non-historical options - play the game how you want. obviously historical skippers were constantly trying to optimse their performance with better techniques and newer technology, and ultimately as time progresses they succeed, but in practice they had limitations that we don't necessarily have.

if you want you can use your boat's hydrophones like a modern sub will, since the bearing report by the sonarman is much more reliable than it was in ww2. You try getting a long range bearing by listening to the hydrophone yourself and detecting when it's changed by exactly 1 degree. It's not at all easy!

Just following greyrider's thread there on the long shots and being naturally pessimistic that long range is appropriate with passive sonar technique.

I have built CapnScurvy's Angle on the Bow and Speed Calculator, which is a kind of Is/Was. I even used it a couple of times before I formulated my present way of playing, which is in-game tools only and no pausing the game to fiddle with settings. Just my personal style, to play real-time only when in combat, with no time compression, no pauses while in contact. I think it helps with immersion and encourages lousy decision-making, just like reality did. Seems to work pretty well and I've been happy with it.:har:

Instead of the Is/Was, I've substituted the Vector Analysis method, which is quicker and can be done in-game. You ARE working in real time, with all the potential brain damage that tends to induce, then.

In the meantime, I'm waiting for greyrider's next post so I can duplicate what he does there. I get to go to work at 2am in a few minutes to work the Daytona 500 situation, so I probably won't get all that downloaded until this afternoon.

Joe, I am interested in your refined method for inclusion in the Sub Skippers' Bag of Tricks thread. Do you have a run-down on the new and refined improvements?

quickly joe, i just wanted to say that you are right and i am wrong about aob being small at long ranges, i made a mission putting a target at max hydrophone range,
just making two different target courses showed me that range has nothing to do with aob at LR.

i havent worked on the magic bullet since last post, im not bankrupt for ideas, if one thing wont work something else might, and who said we need to make the calculation at long range,
i didnt, i said it might work, until i made that mission to test aob at LR, it was still an idea that MIGHT work, but it didnt, and im grateful for your input.
it may be that a map plot is the only way at LR, but again who says it has to be done at long range, that was just a thought, now proved to be wrong.
but until i can sit down, with some time to work on this problem, or someone else does, theories will abound, but be unproved, nothing wrong with that.
im not bankrupt for ideas, i would still like to determine target speed using that formula, and there must be a way to do it with the hydrophones, ill work on it when i can, and i hope to come up with some answer,
but i know one thing, it wont be aob at LR.
thanks joe, after reading your post, you forced me to check that idea out, now i wont waste time with a bad idea.

rethinking my post earlier today, i may still be wrong about aob being small at LR. i may be right after all, but only on one target track at LR, and that would be at a 90° target track,
all other angles to track, and joe is absolutely right, but not on a 90.
i will be able to work on this tomorrow

then again it could be as high as 45°, the sum of the angles in a 90° triangle has to add up to 90°

Sir, mistakes are the portals of discovery. Persistence is better than brilliance.:up:

:hmmm: Maybe this will help: when a ship's sonar range is at a constant distance, its course is perpendicular to its bearing from your sub. Normally, the sonar man will call out "constant distance" for more than one bearing ... the mid-point would most often be the bearing you're looking for.

Hey greyrider

sorry if i'm sounding acerbic. I know you are a great one in the realm of sub ideas. I've read all your previous tutorials. Your work with turn count is legendary.

I still think the 90 degree bearing idea is a red herring. The inital aob (as all aob's) is simply a function of your course, target course and bearing to target. That's all it ever is.

Still you should read that document i linked: the submarine attack course finder, and devote a little time to building a replica Submarine attack course finder. you'll have a lot of fun. Captain krunch printed out some pdfs, you just paste them to cardstock, and press them overnight, then assemble. (Cap'n Scurvy's imitation is less than half of the real thing, i'm afraid. The periscope feature and the reverse side are very important for the fancy stuff)

@Munchausen

constant distance reports are not as accurate as you say, but still very helpful. In practice constant distance can be with an aob anywhere between 60 and 90. At 90 it tends to report moving away(and sometimes at 70 or 80)

thanks joe, you didnt sound anything but helpful to me, i appreciate your imput and welcome it anytime.

but i worked on it alittle last night, until about 1:42 in the morning, it was to late to post last nite, but i think i have something very interesting to show you and our fellow members tonight, when i will get a chance to post.

Cool!:yeah:

It's definitely a barn-sized area to work with. But my tests show "constant distance" averages about the same number of degrees either side of 90 AOB. For example:

http://img.photobucket.com/albums/v9...SH4/middle.jpg

In the above screenshot, the first time the sonar man called out a constant distance was on a bearing of 280. His final bearing before reporting that the target was going away was 339. That's about 60 degrees. Splitting the difference, I drew a 30-degree angle off the first bearing (as shown above) ... then drew a line perpendicular to it to determine the target's course.

The target's course measured 070. Actual course, according to the SH4 Mission Editor, was 70.0484 ... pretty close.

It would be nice if the "barn-sized" area was always a sixty-degree slice of pie ... then you could simply add thirty degrees to the first "constant distance" report to get the perpendicular.

well, i did some work on this problem, and im about to show you what i came up with, but i first want to explain or describe the idea, and then set some of the units paramenters for you
in this problem, to orientate ourselves to the same sheet of music. im going to try to use the sh4 editor, with fraps as the picture taker, then ill switch to real game pictures when needed.


i have been trying to see if the hydrophones would be any use to us with the formula

ss x sin LA / sin AOB

ss = submarine speed
LA = angle from the bow of the submarine to the bearing of the target
AOB = target AOB.

according to the TFCM, the relations between the variables in the formula will determine target speed.

i would just like to say at this time that if you have the target as a visual sighting, this formula will determine target speed for you. visual sighting is the easiest way to use it and get good results
from its application.

i can also see its good use in radar, along with map plotting. but were not using radar or visual sightings to use the formula, we are going to try using the hydrophones.

target speed by hydrophones! by sound? your nuts goomba, you cant get speed from passive sonar, go home!

well maybe, it depends on if we can setup a relationship between the targets AOB, lead angle, and submarine speed so that we could know the AOB, on the unseen target, from the moment of first contact,
and following thu to the completion of the torpedo firing, and target destruction.

we need to devise a way to do it that would have some of the data needed for the solution, either known or approximated, and some
of that data has to come from the target itself that we know nothing about, but its propellers are heard in the hydrophones, and most of the time at long range.

if we could do that, then we would have a constant that we could work with.

this is where im going to make my start to solve this problem, determining target speed by hydrophone using the formula in the TFCM.

this i believe will work extremely well with the point and shoot technique, and maybe the dick o'kane and cromwell methods, with some adaptations.

ok, lets get to it.

i made a mission, a t-3 tanker and balao submarine, this is a perfect setup, and might not come as close as real game play, but i still believe it works, using the point and shoot technique of
getting the target on an eighty degree offset.

this i did with the mission i made, the target is bearing at 280°, and has just entered the hydrophone listening range of 18.9nm away, 0r 35.012km or 38276 yards away. the submarine is pointing north, the
target is heading east. because the hydrophone range is known, the targets range is known when the sonar operator
first picks up the sound of its propellers, in real life, this would only be a few seconds between the time it enters,and the SO picks it up, i hope.

H range probably depends on sea states, but in the game we dont have to worry about sea states
and real life subs could go deeper to get away from surface noise to compensate.

so the targets bearing two eight zero, range 18.9 nm from the submarine, closing, which means its course is in a potential 90° target track. when the target is on an eighty degree offset from the submarine, on a 90 track,
the targets AOB, is going to be 11°.

now we have our constant, if we can keep the targets AOB at 11° constant, we will have a 90° target tract relative to submarine, and we should be able to collide with the target, we dont want to collide the sub with the
target, we want the torpedoes to collide, so at some point, when the target becomes visual, we will slow or stop to shoot beyond torpedo arming distance when the time is right.

knowing now that we have the target on a 90° tract, using the formula: RANGE X SIN AOB, we can determine target course for 90°, and determine how far away the targets course is and
how much distance we need to go to close on it.

in this problem, RxsinAOB, 18.9nm x sin 11° will give us range to target course of 3.6nm. this is not necessary, but nice to know, getting the lead angle of eighty degrees on a closing target and keeping it there garantees
visual sighting, eventually.

so now, in order to keep the targets AOB at 11°, the submarine speed in this problem will have to be 2.35 knots, which will make the targets speed 12 knots,
if a 4 knot submarine speed was needed, then the targets speed would be 20 knots.
as you can see, whatever submarine speed is needed to keep a closing target at the 11° aob with lead angle of 80°, determines your target speed.
http://img6.imageshack.us/img6/2301/...9021oa2.th.jpg

Hi greyrider

ok you are using max hydrophone range to give you an exact bearing, range and time fix. This of course is the missing piece of information to make it all come together

I think with slow ships, hydrophones are not that reliable, and also i do not think that historical hydrophones had such a fixed cut-off point. In the right conditions you can hear very long distance sounds, but equally sometimes only short sounds.

I'm not sure they were so reliable that you could ever consider them to provide a bearing and range in one go.

the other thing is, you still seem to be assuming you know target course, and target course IS aob after a quick conversion, which means again you require an aob solution for speed

however one possibility is once on a collision course, solve the target speed for different aobs. then once you are at a range where a visual sighting is easy, up scope, check aob, then look up the correct speed for it from the list you already made.