Calculating position, real course and speed only by hydrophones!

[Mittelwaechter]

Interested in plotting a contact-course, position and speed only using hydrophones? Read on!


U 42 is hunting for single merchants in the Western Approaches. It's 2300 hours, the sea is calm. The sky is cloudy and two hours ago a light fog came up.
The Kaleun has ordered all engines stop at periscope-depth, Heinz is listening at the hydrophone for contacts.

"Contact! Freighter, inbound. Bearing 60°."

Konrad - our WO - activates the stopwatch and orders Heinz to report the bearings exactly all 8 minutes. Konrad notes the contact on the map. He draws a line of 20 km length from our position - bearing 60° to our bow.
Additionally he grabs a green pencil and draws a perfect circle (he's a genius!) on a free area of the map and marks the center with M. He draws the horizontal diameter and marks the ends with P1 and P2. The contact is reported on the starboard side, therefore he marks the right point P1. The line P1-M shall represent the distance the contact will travel in 8 minutes, the line M-P2 shall represent the distance for the following 8 minutes. Logically the length of both lines is equal as long as we assume the contact is moving with constant speed on a straight course.

8 minutes have passed, Heinz reports: "Contact now at 50°."

Again Konrad starts the stopwatch and notes the bearing on the map - a line of 20 km length - 50° to our bow. He notes the angle of the bearinglines - 10° - and names it A1.
He calculates: (180° - 2A1) : 2 = 80°. He grabs a blue pencil and the protractor to construct an isosceles triangle under the P1-M baseline - both angles read 80° - the sides meet in Point C1. The angle at C1 reads 20° (2A1).
Konrad - a golden colour pencil in his hand - draws a circle using C1 as center and the line C1-M as radius.

"Contact at 34°."

Our WO orders "Full speed, Heading 270" and reactivates the stopwatch. He notes the new bearingline carefully on the map. The new angle reads 16° - marked as A2.
To complete his auxiliary drawing he calculates again: (180° - 2A2) : 2 = 74°.
Using the blue pencil he constructs the second triangle similar to the first procedure, but now under the M-P2 baseline. Both baseangles read 74° - the sides meet under an angle of 32° (2A2) - the point is marked as C2 and used as center for a circleline - golden coloured - which meets M.

The two golden circles show two points of intersection - one is already marked M - Konrad names the other one U using the black pencil.
"U" represents the position of an U-Boot that locates a moving contact under the bearingangles A1 (10°) and A2 (16°).

Konrad draws the angle U-P1-P2 in red - it reads exact 33°.

He transfers this angle to the first bearingline representing the first contactreport at 60°. The new arm reads the quite exact courseDIRECTION of the freighter.
Fat chance the freighter doesn't move along this line but on a parallel courseline.

The intersectionpoints of the transfered courseline with the three bearinglines cut the courseline into two equal parts. They represent the distance our freighter moved in 8 minutes.
Konrad extends the courseline by 50% ("s") to mark the theoretical fourth bearing Heinz would have reported after 8 minutes without changing the position of the U-Boot.
He draws the bearingline to meet the new end of the courseline.

Seven minutes have passed since Heinz's last bearingreport. Our WO orders all engines stop to enable Heinz a proper report after 8 minutes.

"Contact! Freighter at ..."

Konrad notes the new bearing on the map. The line meets the theoretical fourth bearing in the freighters current position.

All necessary information to start an optimal attack is collected: position, course and speed (well you have to do some calculations on your own!) of the contact.

"Kessler! Wake up our Kaleun! We've got a job to do."


To confuse you even more - this shows Konrads auxiliary drawing. The colours are used in the correct chonological order. Well therefore it's in german.:D
http://img468.imageshack.us/img468/3479/beispiel1016sy2.th.jpg (http://img468.imageshack.us/my.php?image=beispiel1016sy2.jpg)

And here Konrads NavMap notes.
http://img102.imageshack.us/img102/7330/navmapwoenglishoi3.th.jpg (http://img102.imageshack.us/my.php?image=navmapwoenglishoi3.jpg)

Good Hunting, Gentlemen.

[GreyOctober]

Wow Mittelwaechter very nice narrative and very informative. But i somehow find your method too complicated. What i usually do is once i locate a contact by hydro i allow myself a minute or so to figure out the general direction of the contact my moving the hydro angle 2-3 deg left and right of the target. Once i figure this out, i make a mental note on the amplitude of the sound and start the stopwatch. I then move the hydro angle ahead of the target by several degrees and wait for the contact to intersect it. Once it does so, i stop the stopwatch, listen for the sound amplitude and note the bearing change. This will give me a rough estimate of the contacts speed and bearing and i can move to intercept.

Cheers!
Grey

[raduz]

you guys can find all this and even much more here:

http://www.subsim.com/radioroom/showthread.php?t=107303&highlight=hydrophone+hunting

[Mittelwaechter]

Complicated but capable to sink contacts without even viewing them. :cool:
You may position your U-Boot at the right place and do some manual TDC settings to hit the contact in heavy fog or with periscopes destroyed.

You get correct speed, AOB and distance whenever you want.

[P_Funk]

I felt good when I figured out AoB way back.

This makes me want to cry.:cry:

[Sailor Steve]

Complicated but capable to sink contacts without even viewing them. :cool:
You may position your U-Boot at the right place and do some manual TDC settings to hit the contact in heavy fog or with periscopes destroyed.

You get correct speed, AOB and distance whenever you want.
Pretty good, since no one ever did that successfully in real life. Once again the game cheats.

[Mittelwaechter]

Well "the game" allways cheats as long as you know your exact own position on the NavMap.

Have fun with it - or simply don't do it.

[Canovaro]

Looks interesting, will study it closer later.

[Mooncatt]

does look really good, however if i tried it it would probably look like a dot-to-dot and resemble mickey mouse:doh: and miss completly

[Canovaro]

does look really good, however if i tried it it would probably look like a dot-to-dot and resemble mickey mouse:doh: and miss completly

:rotfl:

[Vandecker]

Thanks mate, just figured out how this method works, It's taken 3 hours thinking about it and trying to copy out the map as you draw it felt like I was :damn: for a long time. But I did it:D and am now off to try it for real. Thank for this I've been having real problems plotting courses by visuals, now all I need to figure out is a rough range and I can plot an intercept:D.

Again thanks

edit: hold on a moment:o! what the hell do you move the U-boat for:damn:?? it dosen't apear to be neccesarry to calculate the course:huh:??

edit edit: OH NICE:cool:! The theorietical fourth bearing from your original position intercepts the actual contact bearing at your new position giving you the course and distance of the merchant from your U-boat rather than a parallel one. Brilliant:lol:.



Edit your narrative slightly, give step by step diagrams, and get the moderators to sticky this thread, this is fantastic!

[jmr]

Edit your narrative slightly, give step by step diagrams, and get the moderators to sticky this thread, this is fantastic!

This would help a lot at least for me. No roleplaying, just a straight up "how to" along with having having Konrad's auxilary drawing in English.

[Dantenoc]

This would help a lot at least for me. No roleplaying, just a straight up "how to" along with having having Konrad's auxilary drawing in English.

Yes please :yep:

[High Voltage]

This Kaleun has to go lie down as his head has been pounding ever since he read the above post...

[Vandecker]

It works!!:lol: only problem with this method is if the bearings are too small it requires a full page to work it out... or a very very small initial circle

[Hitman]

It's a good meathod even if it takes advantage of certain historical unaccurancies in the game. Anyway, those who are familiars with modern subs simulators like 688i, Sub Command or Dangerous Waters will sure learn this method very fast. It is essentially what a modern sub/frigate does all the time.:up:

[Mittelwaechter]

:hmm: Ok gents, I'm working on your request, but it'll take some time.

@Vandecker
You're right, sometimes Konrads auxillary drawing covers a big part of the map.
Did you realize you can prepare the circle + the protractors whenever you want?


Someone sank a freighter already without visuals?
It's thrilling to follow the torpedo bubbles (F12) until the freighter appears out of the fog.

[raduz]

:hmm: Someone sank a freighter already without visuals?
It's thrilling to follow the torpedo bubbles (F12) until the freighter appears out of the fog.

as I already told before, I edited an exhaustive hydrophone tutorial describing blind shooting, too (but not only). check here:

http://www.subsim.com/radioroom/showthread.php?t=107303

[Mittelwaechter]

Stand at ease, gentlemen.

As a special service for you a live ~17 minutes tutorial how to hunt down a contact only using hydrophones.

You should have read the story starting this thread.

Link: http://files.filefront.com//;7207059;/ U42HydroHunt

The file is a Bink.exe (player included), ~ 123 MB, 512 x 384, 20 fps, hints and comments added, no cuts, no audio but in color ;)

Don't expect to get a biscaya sightseeing-tour.
It's 08/01/1940 - midnight, heavy clouds and rain, heavy fog - U42 stays submerged at 18 meters all the time.

Dismissed!

[XanderF]

It's a good meathod even if it takes advantage of certain historical unaccurancies in the game. Anyway, those who are familiars with modern subs simulators like 688i, Sub Command or Dangerous Waters will sure learn this method very fast. It is essentially what a modern sub/frigate does all the time.:up:

Yeah, I was going to say...it's pretty much a straight TMA solution, although without the computer to help you 'line up the dots'.

It is EXACTLY how you calculate weapon solutions in the modern sims.

[jmr]

What can I use to fast forward/rewind/pause this Bink video?

edit: Ok I downloaded the RadVideo Tools and converted it into a Microsoft Windows Media compatiable file which makes it bigger but I can fast forward etc.

[Raus]

If I hear a contact on hydrophone, and it's something I wish to attack, I go to periscope depth.

This confuses me. :oops:

[Hondo314]

Stand at ease, gentlemen.

As a special service for you a live ~17 minutes tutorial how to hunt down a contact only using hydrophones.

You should have read the story starting this thread.

Link: http://files.filefront.com//;7207059;/ U42HydroHunt

The file is a Bink.exe (player included), ~ 123 MB, 512 x 384, 20 fps, hints and comments added, no cuts, no audio but in color ;)

Don't expect to get a biscaya sightseeing-tour.
It's 08/01/1940 - midnight, heavy clouds and rain, heavy fog - U42 stays submerged at 18 meters all the time.

Dismissed!

Thank you for the effort, but the link is dead now. Any chance of a repost?

[jmr]

I have the video but since I didn't make it I'm not sure if it would be appropriate for me to host it without the author's permission.

Besides that it was recorded in the Bink format which doesn't allow you to pause, fast forward, or rewind which is a HUGE pain in the ass because it's about 20 minutes long and it has a lot of instructions you need to follow.

I converted it the video to make it compatible with Windows Media player so you can pause, rewind, fast forward, so you can duplicate the procedure side by side with the video which makes learning the technique a helluva a lot easier. Unfortunately by converting the video to WMV format the the file size ballooned up to 335 MB.

[Canovaro]

I have the video but since I didn't make it I'm not sure if it would be appropriate for me to host it without the author's permission.

Besides that it was recorded in the Bink format which doesn't allow you to pause, fast forward, or rewind which is a HUGE pain in the ass because it's about 20 minutes long and it has a lot of instructions you need to follow.

I converted it the video to make it compatible with Windows Media player so you can pause, rewind, fast forward, so you can duplicate the procedure side by side with the video which makes learning the technique a helluva a lot easier. Unfortunately by converting the video to WMV format the the file size ballooned up to 335 MB.

Have you PM'ed the author?
I'm interested in this video. ;)

[Nuoz]

Complicated but capable to sink contacts without even viewing them. :cool:
You may position your U-Boot at the right place and do some manual TDC settings to hit the contact in heavy fog or with periscopes destroyed.

You get correct speed, AOB and distance whenever you want. Pretty good, since no one ever did that successfully in real life. Once again the game cheats.

That's probably because they had to identify the ship they were hitting to save torpedos, hitting them in the most adequate spot amd avoid a friendly hit.

[joegrundman]

This geometrical based technique is great and it really works well within certain parameters. I didn't find it so hard to understand, and it was brilliantly written. I also don't see how it can be cheating, unless the hydrophones just weren't that accurate. But in fact the technique doesn't require especially great hydrophone accuracy. I guess that it was tricky to be sure of your own absloute motion, but again, extreme accuracy isn't needed there.

In fact i think towards the end of the war, sonar based target motion analysis was being used, wasn't it?

Anyway, I've used it to sink a target blind, but i used a longitudinal spread to do so. It's accuracy under favourable conditions is marvellous, although given the chance i prefer to make visual contact before shooting.

For me, there are two kinds of situation where the conditions are not favourable. Firstly when the intial AOB is very small, the changes in bearing at the beginning are too small to be helpful, and then as the target nears the changes are too large to be able to make the third "bearing prediction line" with great accuracy.

Secondly, when the initial AOB is large, or the target is moving fast, the 16 minutes wait time means that you cannot intercept targets which may be reachable using other techniques (unless you are prepared to run on the surface without sonar contacts at all)

Still, this technique has definitely entered my box of tricks, and I love those big circles everywhere!

[jmr]

Have you PM'ed the author?
I'm interested in this video. ;)

I just PM'd him now but it looks like he doesn't frequent these boards all that often.




In fact i think towards the end of the war, sonar based target motion analysis was being used, wasn't it?

Yeah I believe so as well. In fact when I'm done with my VII career I'd like to start a new one with a XXI and use this technique almost exclusively. Although like you said I still like to use the periscope to get a visual ID of what I'm targeting and to refine my firing solution.


For me, there are two kinds of situation where the conditions are not favourable. Firstly when the intial AOB is very small, the changes in bearing at the beginning are too small to be helpful, and then as the target nears the changes are too large to be able to make the third "bearing prediction line" with great accuracy.

Secondly, when the initial AOB is large, or the target is moving fast, the 16 minutes wait time means that you cannot intercept targets which may be reachable using other techniques (unless you are prepared to run on the surface without sonar contacts at all)

Aye I've found this out as well when I began learning and using this technique.

[Louis Wu]

Copied soundtrainer.mis to the singlemissions/english directory and also to a singlemissions/english/SOUNDS directory. It shows up under Single Missions, SH3 1.4b, as SOUND. Clicking on Start does nothing. What is the correct way to install Sound Trainer?

[VolvicCH]

First post in the thread might as well have been written in sanskrit......but then again i was never very good at math :) Oh well, i still manage to get pretty decent tonnage :)




Have a nice day :)

[Shelton]

this is excellent stuff - the problem I have is determining course!! and thanks for that other link as well!! excellent!! :up:

[Pisces]

I asked Mittelwaechter privately to re-upload his video explaining this method. He managed to find the file on an old harddrive. He was lucky to find it again. He thought it was lost due to a systemcrash.

The movie plays by itself, No WMP or other player required. It's an .exe containing the video. It's actually an FRAPS AVI compressed into an .exe by software from Radgame tools (http://www.radgametools.com/)

It plays automatically in 512/384 resolution but you can stretch that by adding " /H1024 /W768" at the end of the filename in a shortcut. It has no sound but the text explains it perfectly. Also, really good quality compared to fuzzy Youtube. But then again. It's a big file: 123 MB

[EDIT: Old rapidshare link died out. I've uploaded it to my Filefront page: MittelWaechter video (http://files.filefront.com/U42HydroHuntrar/;13649593;/fileinfo.html)

[Fincuan]

I hope you don't mind, but I uploaded the instructional video to Vimeo:
http://www.vimeo.com/3064633

The quality is what it is after a couple of conversion steps, but it's still ok. Youtube would be slightly better, but the video is way too long to post there in one piece. Vimeo also allows you to download the original(lower right corner). If someone still has the original .avi give me a shout, since I could re-encode from that and get a massively improved quality compared to what it is now :yeah:

[Weiss Pinguin]

What exactly is an .mkv file and what do I need to play it? :hmmm:

[Fincuan]

It's a multimedia containter, just like .avi, .wmv or a bunch of other containers, but more versatile. See here: http://en.wikipedia.org/wiki/Matroska. Here's a guide for .mkv playback: http://www.afterdawn.com/guides/archive/how_to_play_mkv.cfm

Of the free media players I'm familiar with at least Media Player Classic HC (http://sourceforge.net/project/showfiles.php?group_id=170561) and VLC Media player (http://www.videolan.org/vlc/) play it out of the box, no additional stuff needed. They both also contain the necessary codecs(H.264 and AAC) for the video and audio in that film. These are really the easiest options, since you won't have to install anything else.

Then again if you can't be bothered with all that just watch the streaming version :yeah:

[surf_ten]

Hey Thanks Fincuan, it's great that this video is now up on a public video site. I had Mittlewaechter video on my laptop but an updated verison of Norton AV removed it as a virus. I had great success using Mittlewaecther's method and point anyone interested in using passive sonar to his original thread. The video demonstrates exactly how to use his method. My thanks to Pisces also was maintaining a link to his original bink video. I downloaded it last night.

[Mittelwaechter]

Here is a rapidshare link to the original file:

http://rapidshare.de/files/44679804/U42HydroHunt.exe.html

It's an EXE because a WMV file would have been a ~320 MB file and I tried to keep it as small as possible. I used the Bink Video Codec from RAD Game Tools - a free game development standard - to compress the file to ~123 MB. Check your different games files and you'll certainly find more BIK movie files (i.e. Intros) from RAD Game. I added the BinkPlayer to ensure everybody can play the tutorial - and therefore it's an EXE.

You can pause the clip with space bar and exit with ESC, but there is no FWD or BWD. If you want to decode it back to a WMV file, download the RAD Game Tools and simply convert it back. It will blow up to ~320MB again, but you can handle it as usual. I didn't record any audio.The filesize - you know...

I don't know why the new Norton Anti Virus Software detected a virus,but I don't know either, what happened to the file since my first upload some time ago. :D

Well, here we have again the original file without any virus!

MD5 checksum: 51FD9E1859D2B18410BC919F106BFA3B

What's that? -> http://www.diamondcs.com.au/freeutilities/md5.php
(free, small, no installation required and extremly useful)


Enjoy!

[Pisces]

I don't know why the new Norton Anti Virus Software detected a virus,but I don't know either, what happened to the file since my first upload some time ago. :D

Well, here we have again the original file without any virus!

MD5 checksum: 51FD9E1859D2B18410BC919F106BFA3B

What's that? -> http://www.diamondcs.com.au/freeutilities/md5.php
(free, small, no installation required and extremly useful)


Enjoy!Who knows. Might have been a "false positive" warning.

I think I used the Radgame tools to change the default viewing settings to stretch fullscreen. That means the file was saved differently so Mittelwaechter's MD5 checksum won't match for the file I uploaded. I'm sorry for this added uncertainty of it's integrity but I didn't expect at the time I would reupload it. I checked it again just now with AVG virus database 270.10.17/1934. Nothing wrong with it.

[Mittelwaechter]

Hi Pisces,

your idea to modify the resolution settings of the EXE player is formidable. The size of the file should stay the same, but the clip would be shown in lager format. Some people did indeed complain about the small screen.

I'll try to compile the original EXE again, to make it switch your screensettings to some "recognisable" size.

[Fincuan]

I would recommend distributing it as a normal video file and not an .exe, since a) it can only be played with the RAD player and b) the player isn't very good.

[Mittelwaechter]

Well, there is a significant difference in up- and downloading of a 123 MB file and a 320 MB file. The RAD Game Tools is a 1.25 MB download and you can extract the regular video file anytime you want.

Let's say it's like to be zipped. You can use it as it is or you have to use a program to "unzip" the file. It's on you to decide what to do.
Rest assured, both of my original files are free of any malware.

Here is the original 123 MB file - but now the included player switches your screensetting to show the clip. For those who 'couln't see anything', it's a little bit bigger now!

http://rapidshare.de/files/44734341/U42HydroHuntBIG.exe.html

MD5 815F02F65BB837EE7CDEC6BBD3279E41

Have fun!

[Fincuan]

The thing is, each conversion step eats quality unless lossless codecs(which Bink isn't as far as I know) are used.
Like this:
The original FRAPS .avi is very good quality, but also very big. You edit the video and enocode it to .wmv -> the size gets a lot smaller, but you lose some quality.
Then you "Bink it" with RAD game tools -> the size again gets smaller, and again you lose quality.

Then you want it back to .wmv -> You unpack it with RAD game tools. Size gets bigger but the quality lost in previous step cannot be returned.


Nice job with the tutorial btw :yeah:

[Mittelwaechter]

Of course you are right Fincuan. And here is a gift for you.

I did an AVI for you - it's only 56 MB now - using the RAD Game Tool to extract the clip from the EXE and encode it again with MPEG4V2. So let's not talk about quality, but you have an AVI to zoom, fullscreen, FWD, jump or do whatever you want to.

:D

http://rapidshare.de/files/44743198/U42HydroHunt.avi.html

MD5 D1661D8749333AB5C523440638FA3374

[Fincuan]

Lol thanks, I'll take a look :up:

I'm afraid I already did the same thing though, check the Vimeo vid a few posts back. It's an .mkv with H.264 video.

[Pisces]

I would recommend distributing it as a normal video file and not an .exe, since a) it can only be played with the RAD player and b) the player isn't very good.a) That is not correct. The exe works by itself. You do not need to download the tool to play it. Only to change settings if you want like I did then. I just mentioned the makers of the Bink/Smacker software to allow people to make up for them selves if this weird .exe really is a movie and not something nasty in disguise.

b) I don't know what you were seeing on your screen as you were watching that vimeo link you provided but I thought the file I uploaded had alot more sharper lines displayed (you know the faint grey drawn lines as you release the drawing tools). My screen is only 1024x768. I think that vimeo site or whatever made it's quality worse. But that's just my two cents. :up:

[Fincuan]

a) That is not correct.

b) I don't know what you were seeing on your screen as you were watching that vimeo link you provided but I thought the file I uploaded had alot more sharper lines displayed


a) I know I don't have to download any tools, of course the .exe plays itself. Unfortunately the player is crap, and in order to play it in any other player one needs to convert it with the tools.

b) The quality is worse because I had to first convert it to an .avi, which I then encoded with x264 so that Vimeo would accept it. Vimeo also does it's own things, so that's three steps where quality gets a bit worse each step.

[Kubryk]

Hi,

this tutorial is what I was looking for. It's simple and well explained. Thanks!


But...
I tried this method 3 times and... I must be doing something incorrectly.

First try:
When my sonarman shouted contact I ordered engine stop. Only when in dead stop (I checked on the map) I took 1st bearing, started stopwatch, after 8 minutes another, after 8 minutes 3rd. Then I started engines again, after 8 minutes since last bearing I took bearing nr 4. Here I paused. I did all calculations required. Angles on triangles p1-m-c1 and m-p2-c2 were close to 90 degrees, so my circles were big.

As you can see on screenshots, I was able to calculate contact's position. I ploted an intercept course. I was really amazed that my guy is shouting 'long range', from my map it looked like the ship is less than 3km from me. After checking with periscope and hydro I surfaced and chased contact with all my speed. He was additional 7km away. It's course was more or less the same as I calculated by hydro-method.
http://img207.imageshack.us/img207/9329/miss01.th.jpg
screenshot nr 1 (http://img207.imageshack.us/my.php?image=miss01.jpg)


http://img259.imageshack.us/img259/5593/miss02.th.jpg
screenshot nr 2 (http://img259.imageshack.us/my.php?image=miss02.jpg)


Now I see that I could make mistake - I misplaced P1 with P2. Contact was on my left side, so P1 should be on left side of the helping circle, and I can see I used right end of a diameter as P1. My bad. I'm pretty sure that in other cases I was right though and this mistake is an exception :)

Second try:
After some time I heared another contact. I sailed towards it, so eventually my crew reported bearing. Again, only when I was in dead stop I started the Mittelwaechter's procedure.

Again, I heard 'long range', so I instantly knew the ship wasn't where it was suppose to be :)

This time however I tried to estimate. I assumed contact's course-direction is valid, so in order to find him I have to calculate distance between me and contact. I knew it was a merchant. I calculated distance it would travel in 8 and 24 minutes, and using angle calculated with Mittelwaechter's method (29 degrees in this example) I put circles on my map.

This may be confusing, so here's a screenshot:

http://img218.imageshack.us/img218/9674/miss03.th.jpg
screenshot nr 3 (http://img218.imageshack.us/my.php?image=miss03.jpg)

I assumed - if the contact's speed is constant he would travel x km. I calculated distance for (AFAIR) 5, 6, 7 and 8 knots. I was drawing circles over the protracted angle, aligning circle arrowhead with protractor, so later all I had to do was to put circle over the bearings.

Than I took another bearing, it was 313, 47 degrees to my port.

http://img21.imageshack.us/img21/3075/miss04.th.jpg
screenshot nr 4 (http://img21.imageshack.us/my.php?image=miss04.jpg)

This bearing line crossed my 4.4 cirlce. Accidentally, it the same spot it crossed the 4th (virtual) bearing to contact I would made if I wouldn't leave my first position.

Anywho, I was already going on perpendicular course. Now funny thing happened. For 14 minutes (game time) bearing to contact was 313 degrees. I was going 8 knots. When my speed changed to 7 (I don't why, I still had juice in batteries) bearing started to change. By this accident I knew two things: contact was doing 8 knots and I really was perpen... our courses would form 90 degrees angle :)

(maybe if my speed wouldn't drop I would be part of a sea collission? :) )

http://img524.imageshack.us/img524/2203/miss06d.th.jpg
screenshot nr 5 (http://img524.imageshack.us/my.php?image=miss06d.jpg)

When I saw contact, I plotted it course etc. Turned out it was different than I calculated with hudro and I (my course hasn't change) was no longer perpendicular towards it. The difference between hydro and real course of the contact was ca. 10 degrees.

I sunk the merchant, but was starting to think I cannot use hydro to locate contact with precision. Or - I have badluck and in stock SH3 my merchants are zig-zaging.

http://img412.imageshack.us/img412/571/miss07.th.jpg
screenshot nr 6 (http://img412.imageshack.us/my.php?image=miss07.jpg)


3. This gave me a lot to think about. BdU gave me spotted contact on my map. I knew its course (+- 2 degrees). I tried to use hydro-method for the third time.


Again, from my calculations I learned that contact should be very close to me
. I didn't bother to mark that place on my map.

Those two small circles you can see on screenshot represents contact position marked by periscope observation. Note that real course of the contact was true to BdU report and was ca. 10 degrees off than my hydro calculations. BdU was right, not me.

http://img149.imageshack.us/img149/6087/miss08.th.jpg
screenshot nr 7 (http://img149.imageshack.us/my.php?image=miss08.jpg)


http://img141.imageshack.us/img141/2281/miss09.th.jpg
screenshot nr 8 (http://img141.imageshack.us/my.php?image=miss09.jpg)

Now to questions: what can be wrong? I'm 100% positive there's nothing wrong with my bearing. I can put things like that on my map. There's nothing wrong with my helping circle (except for example 1). I often pause the game to draw everything as perfect as possible. So?

I noticed one thing - the biggest challenge for me is to draw a 'virtual' bearing, one I would have made if I didn't start engines after initial 3 bearings. My problem is I'm having hard time judging distance. When I use angle calculated from helping circle (giving me course-direction) distance between 1-2 and 2-3 bearing are different. Eg. it's 2km in first 8 minutes, but 1,8km in the second. So how can I put that 'virual' bearing correctly? In your example Mittelwaechter you seem to use circle with radius = distance between 2nd and 3rd bearing. But in your picture this is the same as between 1st and 2nd.

:damn:

Can anyone help me?

Sorry for suprisingly long post :)
Kubryk

PS
I don't know how to put clickable thumbnails hence the link under every picture.

[Mittelwaechter]

Hi Kubryk,

nice to see you are working on this, you are doing a good job there! :up:

Whenever the angle between first and second bearing is small, add a few minutes and ask for the second bearing again to reduce error probability.

The bearing of the hydrophone operator is a cone. In 20 km distance the bearing covers a width of ~ 350 meters (2r pi /360)
The SH3 map tools are not designed to do these 'hydrohunt' calculations.
Try to center the bearingline in the 350 meter cone.

The best way to calculate the virtual bearing is by dividing the complete distance travelled on coursedirection and add the average.

After third bearing estimate the virtual bearing and try to achieve a big angle for the fourth bearing. You may want to surface and go flank for some minutes. Start immediately and do the calculations while sailing.
Try to come to a full stop before asking for the fourth bearing.
Make sure to follow your U-boats coursepath and try to work the fourth bearing exactly.

I have no idea what's going on, but checking your screenshots the initial contact would have been in ~ 5 km distance - according to your fourth bearing and the resulting real courseline. Your hydro operator is not that bad.

There is allways a difference between the real courseline and the calculated courseline, due to the map tools limitations - but it is small enough to still get a proper target solution. Even the distance is irrelevant as long as you head perpendicular to the courseline.

Try to 'correct' the weapons officers perfect settings and change the AOB for +/-10° - you'll still score a hit. Change the distance - Pythagoras will give you a smile.
The real source of error would be the contact speed. But if you want, you can calculate the speed from the complete travelled distance!
(timestamp the initial contact report... :DL - or keep on restarting the stopwatch...)

The more you close in to your contact, the more error tolerant your setup.
Well, this all requires an exact 'cross bearing' to get your real contact position.

Have fun!


Edit: your conclusion about same speed is correct (your 8 knots story), but the assumption of a perpendicular course is not consequently correct.

[Contact]

Of course you are right Fincuan. And here is a gift for you.

I did an AVI for you - it's only 56 MB now - using the RAD Game Tool to extract the clip from the EXE and encode it again with MPEG4V2. So let's not talk about quality, but you have an AVI to zoom, fullscreen, FWD, jump or do whatever you want to.

:D

http://rapidshare.de/files/44743198/U42HydroHunt.avi.html

MD5 D1661D8749333AB5C523440638FA3374


Hello,

The link seems to be expired, could you please re-upload it ?
Thanks in advance :)

[Pisces]

Contact: I have reuploaded the exe-version I have (stretches to fullscreen) to my Filefront page:

http://files.filefront.com/U42HydroHuntrar/;13649593;/fileinfo.html

[Mittelwaechter]

Thanks Pisces :up: - would you mind to host the AVI file too?

Here is a link to the 56 MB AVI - you can pause, zoom and jump with VLC or WMP or whatever player you prefer.

http://f.imagehost.org/download/0424/U42HydroHunt

MD5 D1661D8749333AB5C523440638FA3374


:salute:

[Pisces]

Kubryk, I think you did the drawing perfect. The things you did 'wrong' (imho) was too short time intervals, and moving perpendicular to the target course. And perhaps you were too slow (submerged perhaps?). Note that it isn't really wrong, but it made the results less accurate than it could have been.

If you take more time between bearings the AOB calculation/drawing becomes more accurate. Do you remember how big the bearing differences were? Judging from your pictures I think they were about 5 degrees between 1st and 2nd, and 7 between 2nd and 3rd (or 12 between 1st and 3rd bearings), for the 29 degree AOB situation. Correct? Well, 2 degrees more than the first 5 is a bit crude, considering bearings are measured in 1 degree. Using a bit of magic I profecise ;) (http://files.filefront.com/3BearingAOBfinderpdf/;13179092;/fileinfo.html) that if you had waited until the first bearing difference becomes 19 degrees, the 2nd difference (between bearing 2 and 3) becomes about 41 degrees. At the 3rd bearing the contact would have shown about 90 degrees AOB, and have the closest distance to your listening position. From 1st to 3rd bearing would have roughly taken 45 minutes. But that is a different kind of magic ;) :

time_1st_to_90AOB= 2*short_time_interval/(1- tan(AOB1)/tan(AOB3)

What I am trying to say here is patience is a virtue that pays well in accurate AOB and contact course. Perform some magic yourself, and see what variation in AOB you get for small deviations (0.5 degrees) in your bearings.

2nd point: You moved perpendicular to the contact's courseline. That does make you get closer to the courseline as quick as possible. But is that what you need? You really want to know where the 'virtual 4th' crosses the 'real 4th' line. For that to be accurate you need the biggest angle as possible between them. That means you need to start your move perpendicular to the 3rd bearing. With the 'magic suggestion' above that would also be parallel to the contact course.

See in this picture (showing a pure intercept) how the bearingline would start to turn when your speed is completely perpendicular and greater, than his perpendicular speed component.

http://members.home.nl/rico.v.jansen/intercept_angles2.JPG

The quickest change of bearing is when you move in the direction where he came from (speeds on opposite side of bearing). But that could get him out of hydrophone range, and you need to catch up to it again later. If you move in the direction he is going (speeds on same side of bearing), and if you are as fast as possible (surface if you can), the bearing turns slower but still makes the 'virtual and real 4th' cross. Since the target is the one that decreases the range (remember you have no component along the bearing) the bearing-change will speed up over time.

Other than that, well done on your work.

[UberTorpedo]

Kubryk

(Not to hijack a thread but..) You might like to try Pisces' "3-Bearing AoB finder" as a supplemental tool. It's really slick. :up:

http://files.filefront.com/3BearingAOBfinderpdf/;13179092;/fileinfo.html

[Pisces]

Kubryk

(Not to hijack a thread but..) You might like to try Pisces' "3-Bearing AoB finder" as a supplemental tool. It's really slick. :up:

http://files.filefront.com/3BearingAOBfinderpdf/;13179092;/fileinfo.htmlHush please... You uncovered my magic. ;)

But to return the praise. :salute:
Kubryk, if you like to try another way of drawing AOB based on 3 bearings, have a good look at the image in UberTorpedo's signature. This (http://files.filefront.com/bearingsonly+TMApdf/;13598315;/fileinfo.html) shows how it is done. (and where it is from)

[Kubryk]

Thanks for your reply! I noticed that small angle difference between bearings is somewhat inconvenient, still I'm worried that target would escape. It happened once, I took two bearings but third one I had to do manually, sonarman no longer could hear him. I will try to make that distance bigger though.

I try to accomplish two things thanks to your tutorial - it would be nice to know target's course just by hearing, and I would really like to sink at least one ship while submerged and without periscope. Must be a great feeling :)

I didn't know that bearing is a cone 350m wide, thanks for that info. I always try to center things, must be something wrong with my brain :) (I don't use this rule in photography, thank God :) )

I did all my calculations sumberged. I will surface after 3rd bearing and go flank, we'll see if it's going to help. Thanks for the tip!


There is allways a difference between the real courseline and the calculated courseline, due to the map tools limitations - but it is small enough to still get a proper target solution. Even the distance is irrelevant as long as you head perpendicular to the courseline.
I've been meaning to ask about this, I read that sort of statement a lot on subsim. How is it possible that distance doesn't really matter as long as you have speed and AOB correct? I don't get it, it's against my intuition :)


Try to 'correct' the weapons officers perfect settings and change the AOB for +/-10° - you'll still score a hit. Change the distance - Pythagoras will give you a smile.
I only use weapons officer to see how long till loading a tube, I'm my own weapons officer for calculating firing solutions :)


your conclusion about same speed is correct (your 8 knots story), but the assumption of a perpendicular course is not consequently correct.
I don't have a ruler on me so I will ask - same speed means same bearing ALWAYS? No matter how courses are related to each other?

It's true with parallel and perpendicular for sure, hm... maybe it's true always... no. It can't be.

[Kubryk]

Pisces and UberTorpedo,

thanks for your help. I downloaded both PDF's, I have to look at them in the morning when my body is clear from alcohol poisoning :)

Right now I'm not exactly sure I understand everything in post nr 52 (http://www.subsim.com/radioroom/showpost.php?p=1089860&postcount=52) in this thread. But I will give it a try tomorrow.

Thanks guys!

[Contact]

This video is strongly lacking comments.:nope: Or is it suppose to be for deaf people ? :DL

Anyway better than nothing. Thanks.

[Pisces]

This video is strongly lacking comments.:nope: Or is it suppose to be for deaf people ? :DL

Anyway better than nothing. Thanks.There is indeed no audio, which feels weird when you watch it. But the text in the video, and the resolution, makes everything clear enough.

[Pisces]

Thanks for your reply! I noticed that small angle difference between bearings is somewhat inconvenient, still I'm worried that target would escape. It happened once, I took two bearings but third one I had to do manually, sonarman no longer could hear him. I will try to make that distance bigger though.The hydro-man only starts calling out within 20km or so (or was it 25km?). But you can hear upto 34km. That range is 70% bigger, and almost 3 times the area of 20km range. At the bearing where the contact has an AOB of 90 degrees it only halve-way through your hydrophone range. So there is usually plenty of time before you really loose it. Unless it happends to be very near the extreme end of the range. Oh well, can't have everything.

Listening yourselve for the soundbeam-sides where the sounds die out is tricky. You do loose a bit of bearing accuracy that way. But listening for maximum volume at the middle bearing is VERY tricky. Then bigger bearing differences are a must.

Use the smaller bearing difference drawing to estimate how much time there is before it is near 90 degree AOB, or it leaves hydrophone range (if you don't mind catching up to it later). Remember, speed of contact is constant, so any distance it has moved along the course is proportional to time between bearings. Then use halve of the time available as the new interval (but be conservative as it is very crude). Or use the old 3rd bearing as the new 2nd bearing if that 1st new interval has allready past, and double the interval before taking the new 3rd bearing. The 3rd bearing doesn't have to end up at 90 degree AOB. It just a way to not fall behind.

But you must be suffering from information overload now. I'll let you digest it first. And alcohol doesn't help. :()1:

[Mittelwaechter]

Well, Herr Kaleun, your Navigator Konrad Schlumberger has been asigned to command his own U-Boot.
But during the last shoreleave Heinz Voigt - your hydrophone operator - visited the new hydrophone operator seminar at the U-Boot school in Kiel.

He came back with some great skills to support you in hunting contacts only with hydrophne.
He is able to calculate most of the tricky stuff to get the real courseline of an inbound contact under those conditions where the initial angles between the first three bearings are small. It indicates the contact is sailing along a course coming close to your position.

Heinz will give you constant reports of the bearings, including the information whether the contact is closing in or whether it sails in constant distance.
At the bearing this information changes, the AOB of the incoming contact is 60° (!).

Additionally Heinz reports proper distance statements and tells you if the contact is far away or at medium distance.

Whatever occurs first - note its bearing on the map. Draw a circle to represent the medium distance around your U-Boot.

(please someone provides the information what distance is medium in GWX - I changed my settings in Contact.cfg and didn't back up! I guess it was 8000 meters, but I'm not sure.)

At the time you have both informations, copy the courseline of the 60° AOB to the "medium distance" bearing at the point it intersects the medium circle.

You may want to change your position if the 60° AOB information comes first, of course heading perpendicular to the "courseline", to ensure the contact will cross your medium distance circle.

Well, the rest should be easy...

:salute:

[Pisces]

....
(please someone provides the information what distance is medium in GWX - I changed my settings in Contact.cfg and didn't back up! I guess it was 8000 meters, but I'm not sure.)...
Correct. S/M/L=1km/8km/16km. (for GWX 2.1, but must be the same for 3 aswel)