TARGET SPEED, searching for the magic bullet

[greyrider]

i think i have found it, im working on it, may take a week and, it may take longer, but i made a mission to test
this formula from the torpedo fire control manual, using the procedure explained by the FCM, using just the hydrophones to determine target speed. it works like a charm,
i just need to test it alittle more at extreme hydrophone range, 18.9 nm. i wont post again, until i have it down pat, but as soon as i do, i will present it to you, in a post, and in a mission.


formula is:


SS x(sin LA) / (sin AB)
where
ss = sub speed
la = lead angle
ab = angle on bow

[Rockin Robbins]

Are you defining lead angle as the bearing to target expressed in number of degrees from the bow, as in the German bearing system?

If so, you're onto something with some playing around. All by itself, it means nothing. BUT if you put yourself on a collision course with the target, that is the bearing to target doesn't change over time, THEN his speed is a known proportion of yours based on the Angle on the Bow. (unless his AoB is zero or 180, in which case the target speed is undefined)

I don't have my drawing software right here at work, but I could work it up and shoot you the diagram for you to troubleshoot the rest of the way if you'd like. You're onto something really useful here.:yeah:

[DarkFish]

...
using just the hydrophones to determine target speed
...

SS x(sin LA) / (sin AB)
where
ss = sub speed
la = lead angle
ab = angle on bowIsn't it a bit hard to determine the AOB with only your hydrophones :hmmm:
I don't know what kind of hydrophones you've got but mine only give the bearing

Ah well maybe its just an American superweapon for a change, the japs have got UFOs and such, so it'd only be fair if the US have got superpowered hydrophones:rotfl:

[Rockin Robbins]

Uh DarkFish, it isn't nice to make fun of others. Especially when the ignorance is yours. Greyrider is on solid ground here.

I shall draw a mental picture and see if you can get up to speed here. With your sonar, you determine a bearing to the target. A simple ping will give you a range. Range plus bearing equals position. Plot the position. Three minutes later, ping again. Range plus bearing equals position number two. Connecting the two positions and extending in the direction of travel gives the target track. With the protractor, clicking ahead of the target position on the track, clicking again on the target position and a third time in the middle of your sub position, you can read the AoB right off the nav map. By inspection with the compass rose on the end of the ruler with help on you can read the target's course. The number of hundred yards between the two positions is the target speed in knots. No superweapons, UFOs, or cute puppies were harmed in this procedure.

Note that the target speed is not necessary to derive the course or AoB. Greyrider is working out another way to determine the speed without plotting two positions 3 minutes apart. I can see this being useful for a visual target where you could use his Mark 1 Eyeball method of measuring AoB. Greyrider is brainstorming here on the message board, and the number one rule of brainstorming is that wacky ideas are encouraged and enthusiastically followed up to see where they lead. We whack people who make fun of ideas over the head with a belaying pin.
http://i196.photobucket.com/albums/aa293/RockinRobbins13/smileys/one_bat.gif

[AVGWarhawk]

Yes, RR, that is how you can get the track of the vessel and formulate the AOB relatively accurately :up:

[DarkFish]

With your sonar, you determine a bearing to the target. A simple ping will give you a range.Yeah i can see your point
My previous post indeed sounds a bit diminishing, it wasn't meant that way.
If anyone feels hurt I'm sorry for it.
I just thought Greyrider meant using passive sonar only (hydrophones is passive sonar only, isn't it, or am I completely wrong here:-?)
Using passive sonar only it'd be completely impossible to determine AOB.
But now that I understand what he is meaning I can definately see the use of this formula, it'd be a very accurate and easy way of determining the targets speed.
So keep up the brainstorming and don't mind about people like me joking about UFOs:up:

[Rockin Robbins]

I just smell progress here. Even if an idea turns out to be positively lousy, often it leads to productive directions. Just ask Ducimus. Oh, you can't.

[Armistead]

I just found this...I just asked the basic same question in another thread. I've been trying to figure out how to track aob and speed with sonar.

I would ping, mark bearing and range on the map. I don't know if the 3 minute rule applies or not, but ping again at 3 minutes, mark on the map range and distance.
My speed is zero and don't see how it can be done if your sub is moving.

I just didn't know if this rule worked to determine speed. Now I see it's easily possible to get AOB.

Course the problem is TF...ping, and it's a new ball game. If you get this figured out, someone please sticky it.

[sckallst]

You can do it if you are moving, but you need to do some vector addition. Most easily accomplished if you are moving at a constant speed along a straight line.

[Pisces]

With your sonar, you determine a bearing to the target. A simple ping will give you a range.Yeah i can see your point
My previous post indeed sounds a bit diminishing, it wasn't meant that way.
If anyone feels hurt I'm sorry for it.
I just thought Greyrider meant using passive sonar only (hydrophones is passive sonar only, isn't it, or am I completely wrong here:-?)
Using passive sonar only it'd be completely impossible to determine AOB.
But now that I understand what he is meaning I can definately see the use of this formula, it'd be a very accurate and easy way of determining the targets speed.
So keep up the brainstorming and don't mind about people like me joking about UFOs:up:It's NOT impossible to determine AOB with passive hydrophone listening. It maybe not a quick thing to do. And being stationary simplifies alot (just like sckallst mentioned) But certainly possible. Look to the following thread:

http://www.subsim.com/radioroom/showthread.php?t=110619
(further down the thread are links to a video)


Or if you want to take a shortcut for such a drawing with a handheld tool:

http://www.subsim.com/radioroom/showpost.php?p=1038860&postcount=14

(or this one, works the same, but linear as opposed to the circular above:
http://www.subsim.com/radioroom/showpost.php?p=875260&postcount=10)

[greyrider]

i havent worked on it for two days, been busy. but i mean passive sonar, its always passive sonar with me, with pinging, you might as well surface, call a cab, and tell them where to pick you up.
when i first heard of the early war theory of the us navy, i was very intrigued , i believed it was possible, and there had to be some substance to it,
otherwise it would not have been brought up.
my mission has always been to prove the us navy was right, i just dont think they had enough time to develope the concept, i have had years of sh playing to develope it, and i think i have done that in alot of ways.

guys it does work. i made the mission , and i did get the target speed , but i did reverse engineering, i already new the course of the target, and i had measured aob from the editor with my GTA 5-2 12 COORDINATE SCALE AND PROTRACTOR,
that i still have from the u s army.
i just wanted to test the formula, it works, i have that mission, i could upload it for you if you want to try it
i believe i placed the target 9. something nm away from the sub.
it only take seconds to get target speed using this formula, once you have the bearing constant, which is alittle difficult, because of the speed telegraph of the sub.
but i did it, and i know it can be done, and the TFCM says it can be done, so who am i to doubt them.
i have not tried from max hydrophone range yet, but my theory it using this formula with the point and shoot method, because of the 80 degree offset thing, once the target is there and constantly there, speed is no problem with this formula.
this is the best thing about sh i think, always trying out new concepts, this is what i love about the game the most., the war is over for me, i made it to 8/16/45, i wont start another career, for the rest of the time, im going to emmerse myself in the TFCM,
and bring to you if i can, what i can get from it .
rock, go for it, make the diagram, ill try to get the mission out, the one from long range as soon as i can, but i will add the mission that i first tried it on, it will be on filefront in about 5 minutes, if you want to add what you observe, by all means, do it.
ill call the mission formula test
also rock, you nailed it, the lead angle is from the bow of the sub, to the bearing of the target, good job buddy!

i had some problems uploading to filefront, but its up there now, you can use any one of three files, that say formula in it, as of yet, it wont let me delete any two at the moment, and there all the same, so you can use any of them

[Rockin Robbins]

There were many plotting tools that the US Navy had in WWII that we do not have available to us: bearing rate plot, bearing difference plot, stadimeter plot, slide rules up the wazoo, etc. Technically, with the bearing rate plot and bearing difference plot it was possible to compute relative course, but not range from passive sonar or visual information. However I have not found a single incidence where this was ever done during the war.

For those interested, the relevant parts of the Submarine Torpedo Fire Control Manual:

561. BEARING RATE PLOT

As was explained under the duties of the Navigational Plotter we usually plot true bearing and ranges to determine the target's true course. If this is done on a maneuvering board we get target relative course and speed.

Now if we substitute for actual range a relative or abstract range we will get the direction of the relative movement line of the target (or relative target course). It can be proved mathematically that:

r = square root (K / (db/dt))

It is obvious that it would not be practicable to

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CONFIDENTIAL SLM 1
actually compute the various values of relative range during an approach. We can, however, assume a convenient value for K which is a constant and construct on a large maneuvering board a graph on which we can plot values of rate of change of bearing (db/dt) against true target bearing. Plate IX is a picture of such a plotting sheet in which K = 200

Plate X is a set of data which has been recorded by the Sonar Plot Recorder. The numbered lines are the actual sonar bearing of the target at 30 second intervals. The data which are plotted by the sonar plotter are the differences between bearings one minute apart and the mid-bearing from the recorder sheets For example, the first db/dt is 2 1/4 degrees plotted at true bearing 330 1/2 degrees. The mid-bearing from the recorder sheet say not be the exact mathematical mean of the two bearings but it is close enough for practical application. These values represent the rate of change of bearing db/dt, for a dt of one minute and the average true target bearing during the period for which the rate has been computed. These values are shown plotted on Plate IX and indicate that the relative course of the target is 120 degrees T. Since Plate IX is also a maneuvering board we may lay out the own course and speed vector of 000 degrees T, 3 knots, and transfer the relative course line to the end of the vector and for a target speed of 15 knots obtain a true course for the target of 110 degrees T.

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CONFIDENTIAL SLM 1
This method of obtaining the target's course is obviously laborious and subject to sonar errors and arithmetical errors of the plot recorder. In obtaining the target course by this method there are several points which should be remembered:

a. Even though each change of course by the target will produce a new relative motion line they will not be connected in such a manner as to produce a plotted track of the target.

b. Since the errors in the present JT sonar can be as much as plus or minus 1 to 2 degrees the value of db/dt which are plotted will vary considerably and the best that can be expected is a relative motion line obtained by "fairing" in the plotted points.

c. The inherent errors of the sonar system render it impracticable to plot values of db/dt of less than 2 degrees/mm.

d. Although a dt of one minute is used in the example smaller values may be used to obtain more plotted points without changing the graph itself or the answer desired. Experienced plotters will ordinarily use a value of dt = 30 seconds. This value of dt, however, cannot be changed during a problem.

e. The method will not work if continuous bearings are not available. Bearings obtained at intermittent intervals are of no practical value.

f. One erroneous bearing will cause two plotted points to be in error.

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CONFIDENTIAL SLM 1

g. When the target changes course an immediate change will occur in the rate of change of bearing (db/dt) and tile the change of course is in progress it will change at a varying rate which will continue until the target is steadied on its new course.

562. BEARING DIFFERENCE PLOT:

The Bearing Rate Plot as has been shown plots a varying amount of bearing change occurring over a fixed time interval. The Bearing Difference Plot plots a specified amount of bearing change occurring over a varying time interval. In the Bearing Difference Plot as in the Bearing Rate Plot the result obtained is the relative course of the target. (a) Plate XI is a Bearing Difference plotting sheet using a scale factor of twenty. The mathematical proof of this method is long and involved and will not be discussed. The formula used in the construction of a bearing difference plotting sheet is Tan B = X Tan A in which B is the angle between the Y axis and any radial line; A is the bearing difference angle and X is the scale factor. In Plate XI the tangent of angle B = 20 X tan 0.5 degrees or

Tan B = 20 X .0087
Tan B = .174
B = 99 degrees

In like manner radial lines representing each 1/4 degree of bearing difference are laid out up to 5 degrees.

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CONFIDENTIAL SLM 1
Beyond this varying difference angles are used as desired. The time scale used has no effect upon the solution obtained. A scale which will facilitate accurate plotting should be selected. It can be seen that increasing the scale factor will decrease the value of the minimum value of bearing difference which can be plotted for a given size of plotting sheet. When the rate of change of bearing of the target is large it will be found that a plotting sheet made up for a scale factor of ten or fifteen will give better results. Plate XII is a plotting sheet made up using a scale factor of ten.

The procedure for using this plot is as follows:

1. Start the stop watch on any even degree of bearing.

2. Label the Y axis as the reciprocal of this bearing.

3. Note the stop watch time and plot a point each time the bearing changes 1/4, 1/2, 3/4, etc., from that which obtained when the watch s started.

4. When enough points have been plotted to establish a line, measure the slope of this line. In Plate XI this is done by transferring the line to the origin and reading value of the slope on the vertical or horizontal scales around the maneuvering board plot. In Plate XII it is done by placing an overlay scale on the line as shown and reading the value directly.

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CONFIDENTIAL SLM 1

5. Apply this slope to the value of the Y axis determined in step 2. If the true bearing is increasing the slope is negative. If the true bearing is decreasing the slope is positive.

6. This is then the true direction of the target relative motion.

7. On the mooring board combine this value with own course and speed and known or estimated target speed to determine true target course. Each time the target changes course it is necessary to repeat again steps one through six.

(b) Plate XIII is a set of data plotted on Plate XI and labeled one (1). In this example the true bearing of the target was 000 degree T increasing. The "Y" axis is then 180 degrees T and the slope is 8 degrees. This gives a value of 172 degrees for the true direction of relative target course. This is then plotted on the maneuvering board to give a true target course of 171 degrees T. Note that the target changed course at 6 minutes and that points plotted at 06-15 and 06-17 indicate a definite change in the slope of the line. All changes of target course will be indicated in this manner.

(c) Plate XIV is another set of data in which there is a much larger rate of change of target bearing. This is shown plotted on Plate XI and labeled two (2). Note that a slope has been determined in 1 minute and 42 seconds. In the example the initial true bearing of the target was 010 degrees T increasing.

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CONFIDENTIAL SLM 1
The "Y" axis is then 190 degrees T and the slope is 50 degrees. This gives a value of 140 degrees T for the true direction of relative target course. This data is then plotted on the maneuvering board to give a true target course of 132 degrees T.

It can be readily seen that it is inconvenient to plot in the lower left hand corner of the plotting sheet. This can be prevented by using a plotting sheet made with a smaller scale factor. A second method is to double the time scale. The line labeled three (3) in figure XI shows the data of line two (2) plotted with the time scale doubled. Note, and this is important, that changing the time scale does not change the slope of the line.

It is sometimes desirable to plot bearing differences against equal increments of time instead of the method used in step 3 of the procedure. This does not vary the result and allows more points to be plotted with very low bearing rates.

(d) comparison of the Bearing Rate Plot and the Bearing Difference Plot as shown in the examples brings out the following points which should be noted in selecting the method to be used.

1. The greatest advantage of the Bearing Difference Plot over the Bearing Rate Plot is that bearing inaccuracies inherent with the sonar equipment are absorbed resulting in smaller and smaller percentage errors as the plot progresses.

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CONFIDENTIAL SLM 1
The Bearing Rate Plot uses bearing rates computed between one minute observations. The effect of the error of the sonar equipment for any given bearing rate will remain the same. In the Bearing Difference Plot this is not the case as the plotted values are always taken from a reference bearing. As the problem progresses the bearing difference becomes larger and larger and the percentage error becomes smaller and smaller.

Due to the inherent errors of our present sonar equipment the Bearing Rate Plot is not usable with a bearing rate less than 2 degrees/minute, The Bearing Difference Plot may be used at rates less than 1 degrees/minute.

As our sonar equipment is improved both plots will of course become more effective.

2. In the Bearing Rate Plot no data are available before an elapsed time of 1 minute. In the second example of the Bearing Difference Plot twenty-eight (28) points were plotted and a solution obtained in an elapse time of 1 minute, 30 seconds.

3. In the Bearing Rate Plot one bad bearing affects two plotted points. In the Bearing Difference Plot a bad bearing affects only one point.

4. In the Bearing Rate Plot a recorder and complicated arithmetic computations are required to obtain data. These are of course subject to error. In the Bearing Difference Plot no recorder is required and the data

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CONFIDENTIAL SLM 1
is obtained directly from the sonar bearing repeaters by observation.

5. In the Bearing Difference Plot where the angle on the bow of the target becomes larger than 30 degrees the slope of the line becomes very critical and a slight error in picking off the slope will introduce a fairly large course error. However, as the angle on the bow increases the target course becomes less and less critical in the fire control solution as the optimum torpedo track is approached.
Have at it and have fun!

[joegrundman]

RR and Greyrider are talking about two different things. Even if both are from the same manual.

RR is describing early forms of TMA based on rate of bearing change. in essence this is the same as the method of TMA described by Aaron Blood in his MoBo and by mittelwaechter with his method.

This method that RR is talking about predates ekelund ranging and whatnot and will only provide relative course (note not true course, unless you are staionary), not speed or range.

Greyrider's formula that seems to work is nothing other than the necessary result of basic trigonometry. This formula has by other names been very well known in this community for years already. it is simply that knowing your own speed as one leg of the triangle, the bearing to target and the aob of target, the target speed makes the other leg.

Hell you can even do it without a constant bearing with one of these, but then you do need at some point in the process a range.

http://www.subsim.com/radioroom/showthread.php?t=106923&highlight=iswas

[Rockin Robbins]

@joegrundman: I'm not convinced you're right, joe, because how do you know the AoB if....:hmmm: But IF you did know it you're right, it's a basic trig function. Good to have a real modern sub jockey as a backup.

I'm sure now that greyrider is looking for something he can actually use without knowing anything that he couldn't find out using the passive sonar. Relative course is the info he needs because that translates directly to AoB, just like target track can translate into AoB.

I'm not convinced that the mathematical gymnastics will make it a practical tool for SH4 players, but I"m just like greyrider, always looking for another angle, but unlike you, without the advantage of direct knowledge of modern techniques. Maybe we can cobble up some PDF WWII authentic bearing rate plots and bearing difference plots. A spreadsheet could perform the math song and dance without stepping on its shoelaces. It's just a very interesting problem that's caught my imagination.

[greyrider]

the reason why i think this could work so well at very long range is because at long range the aob is going to be very small, less than 10°, and that would be the best time to make the calculation, and once the speed of the target is known, or approximated, matching up bearings to target at
the speed you calculated should bring you very close to the targets relative course, over time. but speed is more important than course here, because even if your playing auto tdc, once target direction has been established, its very easy to drive your sub into a 90 target track angle.

in the formula test mission thats now up on my filefront page, if you try it, use a target aob of 20° in the formula, i think i kept the target bearing constant at bearing 291°, and own ship speed of 5 knots,
the target speed in the formula test mission is 12 knots, lead angle was upper 60's, cant quite remember because i took subsequent readings also, as the aob got deeper.
in my estimation, the hydrophone max range in sh4 is 18.9nm. even in the formula test mission, at 9nm, the target aob was only 20°, or near 20°, so i would be looking for a very small aob at long range, it could even be less than 10° at that range.

anyway
target speed is the mission is 12 knots
sub speed was 5 knots, when the bearing of the target changed, i increased or decreased speed to keep the bearing constant, i took other readings as the aob increased, to test my estimation of aob by hydrophones.
lead angle is from the bow of the sub to the bearing of the target.
what skill needs to be developed is estimating aob by sound, target diection is easy, but finding a number for aob might and is alittle harder but not impossible, even if target speed is off by a knot or 2, estimating the time of arrival
at your calculated speed into your visual ao, would tell you if your speed calculation is accurate or not, if target arrives too early( earlier than your estimation), its going alittle faster than your calculated speed, the reverse if its arrives later than you thought it would
theres always ways around things, we just need to always be flexible in our thinking, and make adjustments if we have to.

if i learned anything from sh about sub warfare, its that precision is not mandatory,
just being close is good enough, in most of the data we need except for speed, that has to be pretty close to precise.

[joegrundman]

@joegrundman: I'm not convinced you're right, joe, because how do you know the AoB if....:hmmm: But IF you did know it you're right, it's a basic trig function. Good to have a real modern sub jockey as a backup.

I'm sure now that greyrider is looking for something he can actually use without knowing anything that he couldn't find out using the passive sonar. Relative course is the info he needs because that translates directly to AoB, just like target track can translate into AoB.

I'm not convinced that the mathematical gymnastics will make it a practical tool for SH4 players, but I"m just like greyrider, always looking for another angle, but unlike you, without the advantage of direct knowledge of modern techniques. Maybe we can cobble up some PDF WWII authentic bearing rate plots and bearing difference plots. A spreadsheet could perform the math song and dance without stepping on its shoelaces. It's just a very interesting problem that's caught my imagination.

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

[joegrundman]

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.

the reason why i think this could work so well at very long range is because at long range the aob is going to be very small, less than 10°, and that would be the best time to make the calculation, and once the speed of the target is known, or approximated, matching up bearings to target at
the speed you calculated should bring you very close to the targets relative course, over time. but speed is more important than course here, because even if your playing auto tdc, once target direction has been established, its very easy to drive your sub into a 90 target track angle.
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.

what skill needs to be developed is estimating aob by sound, target diection is easy, but finding a number for aob might and is alittle harder but not impossible,
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

[Rockin Robbins]

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.

[joegrundman]

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/showthread.php?t=115366&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!

[Rockin Robbins]

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?

[greyrider]

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.

[greyrider]

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°

[Rockin Robbins]

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

[Munchausen]

: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.

[joegrundman]

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)

[greyrider]

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.

[Rockin Robbins]

Cool!:yeah:

[Munchausen]

@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)

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/v97/pjcham/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.

[greyrider]

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/sh4missioneditor2009021oa2.th.jpg (http://img6.imageshack.us/my.php?image=sh4missioneditor2009021oa2.jpg)

[joegrundman]

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.

[greyrider]

joe, your right again in what you say, i havent finished checking out this theory as yet, but im to tired right now to think, or even offer rebuttels, even if i had one.
but i just feel that if you keep the mathematical relations related, we should have no problem.
i mentioned hydrophone range only to make the target as far away as i could, but the range was not a factor in the speed estimation, just in the placement of the target r to sub.
it factored in the range times sin aob formula, but was not needed, i just put that there for the heck of it.
historically, you are probably right about hydrophones not being reliable at lr, some input from a real sound man might be worth its weight in gold here, but where would they be?
altho, american hydrophones, with the magic eye as it was called, was probably very accurate, i know QB was for shorter ranges, and jp for longer, whether weather
and rough seas degraded them seems likely, but i havent read much to say one way or another.
anyway im going to sleep now, tomorrow ill work some more on this, what i havent done yet is run this mission to completion, everything i did so far has been with a calculator.
i know the rock is probably busy with mobo, checking this out, and he always bring value to any discussion when he checks things out with that program, so im looking forward to what he has to say.
the one problem i have when i make these missions is that i know all the factors involved, i wish that someone could make a mission, and send it to me, so i know nothing, so that i can work it out by playing it,
i think i would give my left you know to go down to the lionfish 50 miles away and work the hydrophones on it, if they still work, and they would let me, i would love to sit and talk with someone who did in ww2

[Pisces]

That lead formula can certainly be used to aim torpedos based on bearings only. I'm not sure it is very reliable, but that also depends on your amount of patience and 'triggerhappy-ness'.

As Joegrundman said, you must turn to maintain the target on a contant bearing. Typical intercept-course trial and error fiddling with the rudder based on hydrophone feedback. Then once stable (long enough to prove it is realy constant), the trick is to assume the target has an AOB of 90 degrees (sin AOB=1) while it is on that constant bearing, no matter what his real AOB and speed is. From this 90 AOB follows a certain (target)speed which is less than the true target speed as it it the component perpendicular to the bearing. The rest of his speed is aimed along the bearing line and is cancelled out. That perpendicular speed is all you need for leading. (well, sort of :nope: , remember gyro parallax, read further down)

The following picture illustrates it:

http://ricojansen.nl/image/intercept_angles2.JPG

So:

perpendicular speed= sb_speed*sin(lead_angle)/sin AOB

which is actually =sb_speed*sin(lead_angle) , since sin(90)=1

This 'perpendicular' speed is the same for you, trying to keep up with the target, as it is for a torpedo, that tries to merge with it.

If you can enter that speed and AOB 90 (referenced to that particular bearing) in the TDC you have allmost everything done. You only need a range to account for gyroangle parallax. Or you can turn towards the target (quickly, so not to invallidate the constant bearing) just before shooting to make the gyro angle 0.

But the inaccuracy will be in how long you give it time to prove the bearing drift is really zero. And given that bearings are reported per degree. A slow drift might take tens of minutes to show with long range targets. Drift means there is a difference between your perpendicular speed and his perpendicular speed. Because of this difference the torpedo lead will be off and so can be passing in front of the bow, or behind the stern. Depending on range, since distant targets are small angular-wise. The nearer the better chance of a hit.

[Pisces]

One caveat: A target that in reality is moving away will 'appear' to have the same perpendicular speed. The only way you can distinguish is the sonar opperator telling you it has a changed range qualification, or if the sound becomes weaker in the earphones.

[greyrider]

i was thinking about what i wrote here, and i may have been off one degree with my target AOB measurement. im thinking that the constant should be 10°, and not 11°,
as i said , i measured the target aob using a gta 5-2-12 coordinate scale and protractor, its clear plastic, and has a piece of thread in the center of it that extends beyong its
edges, and used to bearings, azimuths, in mils and degrees. well to get the thread to stay you have to tie one end in a knot, and so when using it to plot on maps, you have to place
the center of the protractor over your sub, sometimes the knot is alittle to big, and the editor doesnt help at long ranges, i did the best i could to be as accurate as possible, but i think it should be
10°.
when i made the mission, i set the targets course for 90°, so if you follow the aob trainers advice, 280-180=100.
because the targets aob is starboard, you subtract aob from the difference of 280-180.
if thats the case, then subtracting 11° from 100°, would give the target course 89°, but i set it for 90°.
so belay that on 11°, the aob for the target constant should be 10°

[greyrider]

One caveat: A target that in reality is moving away will 'appear' to have the same perpendicular speed. The only way you can distinguish is the sonar opperator telling you it has a changed range qualification, or if the sound becomes weaker in the earphones.


or, you could tell by trying to keep a bearing constant that just wont stay constant:salute:

pisces, il havent got time now to think about your post rite now, but i will certainly sit down with it soon, thanks

[Pisces]

One caveat: A target that in reality is moving away will 'appear' to have the same perpendicular speed. The only way you can distinguish is the sonar opperator telling you it has a changed range qualification, or if the sound becomes weaker in the earphones.


or, you could tell by trying to keep a bearing constant that just wont stay constant:salute:

pisces, il havent got time now to think about your post rite now, but i will certainly sit down with it soon, thanksNope, targets moving away (AOB >90) can also be made to be at a constant bearing. AOB X appears just the same as AOB (180-X) if you depend on bearings alone. (remember: sin(53)=sin(127) ) Infact the target would appear to be at a constant bearing more easily as the range increases, which slows the drift down as time progresses. The perpendicular speed isn't smaller or bigger, or changes in an unstable way (which is what "wont stay constant" implies), it's just divided by an ever increasing range to result in a slower angular rate.

EDIT: if you cannot get a constant bearing at all, then either you are too slow (his perpendicular speed is bigger than your top-speed), or you have not turned your speed to it's best use which is really when the target is on 90 or 270 degrees bearing. But a target moving away is then out of the question.

If those two aren't the case, the only reason left is you have a traitor on board telling the target what you are doing.

[greyrider]

yes, your right, im wrong, sometimes i dont know what im thinking, but the key word in all this was closing. targets like you mentioned and targets going away are another ball game, you either persue, or leave alone,
thats a command decision. i really appreciate you and everyone who supported this thread with thier own knowledge.
believe me, after i posted this, i was sweating bullets, thinking that someone would find a flaw in this, but no one has posted saying anything like," grey, nice try, but it just wont work"
thats what i have been waiting for, someone to prove the theory wrong.
i have alot on my mind at the moment, im not employed now, my former boss is a little greedy piece of crap, and i stuffed it to him, nobody practices economic terrorism on me, and i decided i will not work for anybody again.
so now i have to find a way to bring in an income.
i have always loved greyhound racing, and im pretty good at it, or at least i was, i havent really applied myself to it in quite a while, but ill be damned if im going to be blackmailed by some freaking employer,
my favorite track is gulf greyhound park in texas, i have an account with paydog, and i can bet, "invest" by simucast, im going to be spending alot of time looking over racing programs, because i need to make a living and pay my mortgage and other bills,
including property taxes that i just hate.
i know one thing, my former boss regrets what he did, and asked another technician i worked with to talk to me about coming back, i refused. if i can make my living thru racing, then the checkmate is complete, and i can laugh.
one thing im not going to allow, im not going to be defeated, so ill have to concentrate mostly on this, ill post things here about the game when i can, because thats always pleasure.
all i can say to you guys is thanks for your support in this thread, at least none of you guys have called me a bonehead here.

[Pisces]

yes, your right, im wrong, sometimes i dont know what im thinking, but the key word in all this was closing. targets like you mentioned and targets going away are another ball game, you either persue, or leave alone,
thats a command decision. i really appreciate you and everyone who supported this thread with thier own knowledge.No worries, me too, more often than I'd like to admit. Sounds like you had enough on your mind to allow yourselve to make a bit of an error.

While I would be the first to advocate a profession you actually enjoy doing, common sense tels me something that involves race-betting might not be a smart thing to do. But maybe I misunderstood what you actually have in mind. Anyway, it would be going off-topic. Best wishes for whatever you do.

[joegrundman]

I think, greyrider, nice try. it works almost as you envisaged, but not exactly. Nonetheless, i think this is a valid, important, historical and effective technique for getting speed that you have hit upon, and works particularly well when you have the skill of visual aob recognition - which you do. In fact the two techniques are matched for each other.

So all you have to do is set up a constant bearing collision course, and once the target is in visual range, take one aob and range estimate and then you have all the information you need with a single periscope view using the formula you have(best at medium range *)

This seems to me a very authentic way of doing it without hundreds of periscope views. Just one is enough - with the aob and range you can work out the course you need to maneuver for attack position and then just need one more scope view before firing

the whole thing can be done in this technique with just two scope views - which is i think you can agree - a very satisfactorily authentic attack style.

I suppose once you've done this you could make a new trainer demonstrating an entire attack this way and attach it to your aob trainer thread

* if you use follow contact only, you don't get a range approximation, but if you regularly hit report nearest sonar contact, once if it's between around 4000 and 2000m it is reported as medium range (i don't know the exact ranges)

Finally, i hear that the best way to make a living in the gambling business is to be on the selling side, rather than the buying side. You could get involved in dog training or race organising for example.

[joegrundman]

Here's a step-by-step example

So you have a long range sonar contact

Phase 1: set up collision course

Step 1. point your submarine at the contact
Step 2. Observe if target is going to pass your port or starboard(ie the bearing to target moves from 000 to 359, or if bearing to target moves to 001)
Step 3. if target will pass to port, turn about 80 degrees port. If target will pass to starboard, turn about 80 degrees starboard
Step 4. Adjust speed so that over a 5 minute period the bearing to target doesn't change, and are thus on a collision course

Phase 2: get the data

let's say after 30 minutes of staying on this collision course at 3 knots the report sonar contact says that range is now medium. The bearing to target has not changed in all this time

Step 1. Up scope ID target, note aob and range, down scope
Step 2. Use the formula (or an iswas if you have one) Let's say the bearing(lead angle) is 90 and the AOB is 30 and the range is 5000 m.

The formula:

ts=ss x (sin LA / sin AOB )

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


ts = subs speed(3knots) x sin lead angle(sine 90 = 1)/ sin AOB(sin30 = 0.5)
ts = 3 x (1/.5) = 3 x 2 = 6 knots.

Step 3: plan attack course. Having worked out range and aob you can use the map tools to draw the target course (or an iswas or sacf if you made one) and range and work out the angle you want to be on for an optimal shot and at what range you want to be when you fire.

Step 4. adopt new course

step 5. when target reported to be approaching the firing point, up scope, recheck aob and bearing/range, and fire the fish

[greyrider]

well, joe, i was the author of the point and shoot technique, the method that doesnt need to know target course, range, or aob, all it needs to do is get a closing target on an 80 degree offset,
what the TFCM calls lead angle, and a speed estimation, which i always did by scope in sh4.

i knew nothing of this formula when i made it. i wasnt satisfied with getting target speed by ship length with the scope, and turn counts in sh4 are practically useless.

so i tried this formula. the way i set this mission up to test it was what would happen after you turn
the submarine to get the lead angle on the target, (80° offset) on a closing target.
even tho i have not run this mission, i already know the end result, the target will be destroyed, because it is the point and shoot technique,
with just a different way to get a targets speed, without putting your scope up, that was my objective, and it is done,

no one can prove this not to work, because this was the way i have always gone about sinking ships,
its just another way of getting target speed.

for me, it needs no more external analysis to work, but i wont stop anyone from putting thier own ideas up, and trying out something different, to each thier own, but ill tell ya, military people are just ordinary folk,
with ordinary intelligence, the best ideas and the best tactics are the ones that are kept simple.

i have done alot of work on alot of different things, i have exploited almost, well everything we have for sensors, in keeping with the inspiration i got from the u-boat commanders handbook.

the actual history of the point and shoot technigue goes back to sh2, when i commanded that great wolfpack seetufel, with jim and yvonne hill, peter wolf, and myself. it was in sh2 that we learned how to fire underwater at 26 meters, and get hits
against first fleet, the bearing speed charts were made while seetufel was still in existance, we never practiced it tho, but it was invented by then, i just carried over that work on my own after sh2.

those where good days playing against people like iron reaper, microdot, oneger, sword, kalloth, von spike, stdev and others. i have fond memories of all those people, it was also the cause of the first great flame war in the wpl,
and that was a real shame, because it broke up seetufel, and some of the key members of the first fleet.

i guess what im trying to say is that of all the things and tactics i worked on, the formula presented in this thread has been the most exciting thing for me that i did since learning to shoot underwater with seetufel.

im not playing the career in sh4 any more, im waiting for sh5 now, and i wish so much for a destroyer command 2, because i would love to work on destroyer tactics. everyone in seetufel had destroyer command too.

and one of the reasons why i share all the tactics i make here is because seetufel was called cheaters, which was not true, and if all my work is examined by the members here, everyone can plainly see that no cheating takes place,

i did that to vindicate seetufel, because seetufel did what any military organisation does, we were silent about our tactics until it had reached the breaking point, then we told the members in the wpl what we were doing,
it didnt do any good by then, bad blood had taken hold.

for me, im done here in this thread, when i can, ill look again at the TFCM, if i think theres more we can gain from it, ill work on it. of all the things i work on, this thread is what im most proud of, and the funny thing about it is i dont know where it came from.

again thanks joe, and all the members who contributed.