plotting course passive sonar only

[PurpleCity]

I've been unable to find a tutorial that describes the process to determine the course of sound contacts (without using sonar).

I have the bearing, I just need to calc range (without active sonar)

Is there some mathematical trick, such as plotting bearing lines at a set time intervals?
Or is this just a guess?

[Fincuan]

It's not easy at first, but entirely doable with the help of aaronblood's excellent program called Mobo.

Get Mobo here: http://www.subsim.com/radioroom/forumdisplay.php?f=225
It would be wise to start by reading some of the basic tutorials and learning the program a bit.

Once you've got a good grip of the basics proceed on doing what you originally wanted to do: http://207.44.214.111/subsim.com/rad...d.php?p=602444

Good luck

[joegrundman]

it's possible to do, and there are tutorials on how to do it, including one written by me a couple of years ago, but it's not really historical. Purely passive sonar only solutions i think only really came into being in the cold war era, when turn-count technology was much more sophisticated and one was able to identify the exact boat by it's sound signature

A more historical method that does a lot of the work for you, but not all of it, is upon getting a hydrophone contact, up your speed a bit and point your boat directly at the target.

Now observe whether the target is swinging to pass your port or starboard. That is, if the bearing to target goes from 000 to 357, then it will pass to your port on your current heading. If the bearing goes from 000 to 003, it will pass your starboard on your current heading.

If the target will pass your port, turn 80degrees port; if the target will pass your starboard, turn 80 degrees starboard

try to find a speed that means the bearing to target remains constant.

you are now on a collision course with the target, and will eventually find it

[RSColonel_131st]

Basically yes, you plot the bearing lines at set time intervals (they will likely fan out, especially if you are stopped), and then you will either need two range/bearing combos or a good speed estimate. You want to find the target course that crosses your bearing lines at appropriate speed (i.e. 500 yards between two bearing lines taken at three minutes means 5 knots, if you know the target makes 9 knots, then you need 900 yards between the lines, which then results in a course and range).

[XLjedi]

Originally Posted by RSColonel_131st

Basically yes, you plot the bearing lines at set time intervals (they will likely fan out, especially if you are stopped), and then you will either need two range/bearing combos or a good speed estimate. You want to find the target course that crosses your bearing lines at appropriate speed (i.e. 500 yards between two bearing lines taken at three minutes means 5 knots, if you know the target makes 9 knots, then you need 900 yards between the lines, which then results in a course and range).

Just remember... If you're not stopped, you're not plotting true motion either.

If you want to take bearings and keep moving, the relative motion plot/solution has to be converted (with vector addition) to true motion.

You can also predict future bearings to target and then triangulate on the exact target position. Knowing the position you can solve for distance, knowing the distance you can solve for speed. So you don't absolutely need to ping the distance, or try to get range, or a speed guesstimate. It is possible to do it all by analyzing the bearing motion from 50m below.

Now keep in mind, while doing all this there's a good chance your target will be out of firing range by the time you've solved for course, speed, location. At this point you surface a good 8000m away and do a surface run end-around. It's not that easy to keep track of all this without a good attack course plotter to help you manage the data (perhaps like a tracking team would?). But, I s'pose it could be kept track of on the in-game map and with a paper-pencil moboard. You'd probably need to make yourself some sawtooth speed rulers to help with a paper-pencil solution.

Obviously, I prefer to use MoBo.

[RSColonel_131st]

Originally Posted by aaronblood

Just remember... If you're not stopped, you're not plotting true motion either.

If you want to take bearings and keep moving, the relative motion plot/solution has to be converted (with vector addition) to true motion.

Easier to just draw the bearing lines on the map always starting from your sub, and try to solve it that way.

[XLjedi]

Originally Posted by RSColonel_131st

Easier to just draw the bearing lines on the map always starting from your sub, and try to solve it that way.

Yeah... assuming you're stationary. If you try to apply the same concept to a maneuvering board solution (ownship at center, even when moving), it results in a RM plot that needs to be converted to TM. It's not particularly difficult... just a fact.

...be easier in the game if you maybe had a sawtooth speed ruler gadget to use. I know modders can add gadgets to the game, don't know if they can add rotatable ones though. I s'pose it's easy enough to just hold up a paper one to the screen. You ever tried that?

[Soundman]

Originally Posted by joegrundman

it's possible to do, and there are tutorials on how to do it, including one written by me a couple of years ago, but it's not really historical. Purely passive sonar only solutions i think only really came into being in the cold war era, when turn-count technology was much more sophisticated and one was able to identify the exact boat by it's sound signature

A more historical method that does a lot of the work for you, but not all of it, is upon getting a hydrophone contact, up your speed a bit and point your boat directly at the target.

Now observe whether the target is swinging to pass your port or starboard. That is, if the bearing to target goes from 000 to 357, then it will pass to your port on your current heading. If the bearing goes from 000 to 003, it will pass your starboard on your current heading.

If the target will pass your port, turn 80degrees port; if the target will pass your starboard, turn 80 degrees starboard

try to find a speed that means the bearing to target remains constant.

you are now on a collision course with the target, and will eventually find it

I like that, it's very clever. It's very logical and simple to understand, yet most people would not think of using this technique.

[PurpleCity]

Originally Posted by joegrundman

If the target will pass your port, turn 80degrees port; if the target will pass your starboard, turn 80 degrees starboard

Just curious, why 80 degrees?

[joegrundman]

80 degrees is mathematically most likely to intercept against the widest possible range of target courses and speeds. If you find it's easy to maintain your collision course you can narrow the angle to speed up the intercept without using up your batteries.

[greyrider]

you can derive course, speed, and target position from bearings only, radar or sound bearings, it doesnt matter. below is a link to the maneuver board manual,
i beliieve its on page 56 of the manual , you will find a chapter headed, "COURSE, SPEED, AND POSITION DERIVED FROM BEARINGS ONLY".
that chapter will teach you how to obtain the target data you asked for from bearings only.
now, i did this once, using sh3 and sh4, i had it all worked out, and i was going to present that as a tutorial on the forums here, unfortuately, i had to do a few system recoveries, and lost all data.
i would do it again, but its really intensive, and im getting very lazy, and dont wanna do it again. the key to it all is bearing changes, and that more than anything else determines
COURSE, SPEED, AND POSITION
you need a parallel ruler, which sh4 does not have, but you can use the nav tools and make one, maybe later ill send up some pics of the sh map, showing how to use and make a parallel ruler.
if you try the chaper on "COURSE, SPEED, AND POSITION DERIVED FROM BEARINGS ONLY" from the manual, you will find that its time consuming, i dont know about you, but i know i have no time for something like that to work
out.
so something else was made that hunts and kills targets with ease, and whats great about it is you dont have to map plot. its called the point and shoot technique, and there is a thread somewhere here called
the "point and shoot" thread, locate that on subsim forums, learn it, and you see how easy it is to track and kill ships using sonar, radar, and or visual sensors.
it is also my belief that world war 2 submarine skippers, on both sides of the atlantic, used this method, i know captain eli t reich used this method to take out bb kongo in 1945.
not only is this technique lethal as hell, if you learn this technique well, you leave the PERISCOPE and TDC dependent on these forums behind. now you bring all your long range sensors to bear, you can attack and kill ships that you
have no visual sighing on. dont let others here tell you about the consequences of shooting at unidentified targets, you might here that argument, but just remember, that didnt stop captain reich, it should not stop you either.
another thing about the point and shoot technigue, silent hunter has seen four versions sh1 to sh4, and every time a new version comes out, the tdc is always different, and you have to relearn the tdc, with every new version that comes out.
with the point and shoot technique under your belt, you will be a killer, from day one of a new version, because the p+s method never changes, because its not TDC and periscope dependent, its all based on trig.

good luck purple city
grey

http://www.nga.mil/portal/site/marit...c24fd73927a759