Hydrophone Hunting (tutorial)

[ERPP8]

You know Benno has a great skill called "Total revealing"

[gutted]

Originally Posted by ERPP8

You know Benno has a great skill called "Total revealing"

And you learn nothing from using it.....

[timmy41]

in step 4 you draw the 'NW line', but what if the contact is to the SE or NW? it will not work?

[Pisces]

Originally Posted by timmy41

in step 4 you draw the 'NW line', but what if the contact is to the SE or NW? it will not work?

Why wouldn't it? The bearings show where the target is (and was). In step 4 Alcibiades has just drawn a line in a random direction (well, from bearing 1 over to and across bearing 3). Look at step 5 to 8. Using the circle and line parallel to bearing 1 he corrected the NW line to the correct course. It doesn't matter where he comes from or it's actual course being totally different. The circle and parallel line will show if it is a wrong guess, and what the right course is.

[Alcibiades]

Originally Posted by Pisces

Why wouldn't it? The bearings show where the target is (and was). In step 4 Alcibiades has just drawn a line in a random direction (well, from bearing 1 over to and across bearing 3). Look at step 5 to 8. Using the circle and line parallel to bearing 1 he corrected the NW line to the correct course. It doesn't matter where he comes from or it's actual course being totally different. The circle and parallel line will show if it is a wrong guess, and what the right course is.

Yes.

The line in step 4 is just a random line (guess) to allow use of geometry to get the real heading.


Also, since you were sitting still and not moving from when you took bearing 1 until when you took bearing 3 - then you know that the target is moving towards the west. And you guess he's coming towards you.

If the target is E or N of you when you first pick him up, follow the same procedure, but just "guess" his route and assume he is 'slanting' towards you.



additional note: you can also tell he is coming towards you based on how much larger the angle is between bearing line 2 and 3. The larger that angle, the sharper angle the target is heading towards you. if the big angle is between lines 1 and 2 (and a small angle between bearing lines 2 and 3) then hes moving away!


Hope the PDF's help!

word of caution again: be careful if trying to use it against a convoy!!! if you record a different ship each time you listen (likely), then your estimates will be off. usually close enough to plot a rough intercept course, but that's probably about all

[timmy41]

aha, ok, so the line is just placed in the general direction.
There are a few tiny things that could use better clarification, simple tiny things like making the 'X's larger that signify the variable for kilometers. at step 14.4 I had to wonder for a second what the X was, until I zoomed in and saw the tiny x on the plot! The info is there, its just sometimes a bit hard to find, and maybe someone with bad eyes wouldnt even see it! Could either make the X's a bit larger, or explain on the bottom of step 14 that X is the distance the ship has traveled in the time interval one is using.
Overall, great guide!

edit:
for convoys, one could simply manually listen for the median of the convoy and base off that knowing a medium convoy is about 5k wide and 3k forward, and so on. Yes?

[Pisces]

Originally Posted by timmy41

edit:
for convoys, one could simply manually listen for the median of the convoy and base off that knowing a medium convoy is about 5k wide and 3k forward, and so on. Yes?

I guess so. But the sound level is probably not the same for small and larger ships. If it happens so that the convoy has rather silent ships mostly on one side then the peak sound-level of the whole convoy is slightly displaced to the louder ships. This would cause a slight deviation in the bearings. But listening to the sounds yourself is already quite crude. So you might not notice.

Basically, don't expect accurate readings from a convoy. But it is usually so big (wide) you'll run in to one of it's members anyway.

Advice: Do listen for the edges of the sound where it is faded out, and take the middle bearing! Trying to find the maximum sound-level is difficult to get accurately. It because of how our ears work. They can't detect small changes in a loud sound. But are better at detecting quiet sounds or no sound at all.

[Alcibiades]

Originally Posted by timmy41

aha, ok, so the line is just placed in the general direction.
There are a few tiny things that could use better clarification, simple tiny things like making the 'X's larger that signify the variable for kilometers. at step 14.4 I had to wonder for a second what the X was, until I zoomed in and saw the tiny x on the plot! The info is there, its just sometimes a bit hard to find, and maybe someone with bad eyes wouldnt even see it! Could either make the X's a bit larger, or explain on the bottom of step 14 that X is the distance the ship has traveled in the time interval one is using.
Overall, great guide!

Thanks for the feedback. It is appreciated. When creating it - it's tough to tell what it will "read" like to someone else. Or what parts could be explained better. Thanks.


But be careful - hydrophone hunting can be addicting!!