Hydrophone Distance Estimation

[ChrisPhoenix]

Thank you Fanders! That was exactly what i was looking for. I Can't wait to test that out.

[Fanders]

Relevant question!

My settings of the high and low pass filters was at the deaufult level:

High Pass - o khz (clockwise maximum)
Low Pass - 22 khz (counter clockwise maximum)

[stellaferox]

Originally Posted by Fanders

Hi everyone!

I just did some data collection with the hydrophone in tutorial mode (where you can se the other ships distance and bearing on the map).
I focused the hydrophone in the exact vector to the target, then I turned the gain knob to the point that the sound turned into distorsion. At that point I collected the distance of the target from the map.

I plotted the data in google sheets and found out that the relationship between the gain and the distance is linear.
Thats quite strange btw, because the sound preassure should decrease with the square of the distance.

One more thing that was a bit strange is that gain level of 2 seems to be the limit. There was no point lowering the gain below 2 -no matter how close i got to the target.

Anyway,

from the data colleced i managed to make a trendline/regression curve of the plot. In my website below you can download the pdf of the diagram i did and use if you want!

Of course this could be done with more precision, but i think its a good diagram to use for rough estimations!



www.gnomon.se

Hi Fanders,

Would you mind sharing the mathematical equation resulting in that line? From the graph I get something like Y = 5555.55 * X - 10833.33 (meter) right? Or in hm Y = 55.55 * X - 108.33

[Fanders]

Of course!

The linear equation for the trendline is:

y=5273x-9656

[Kermit the Frog]

Ok Here's what i have:

Tutorial,
we'll start out with a basic setup. High/low pass rotated to the right, gain at about 1-2.

We hear a contacts, but they're very "wide", it's almost impossible to give a precise bearing.

1. slowly raise "gain" level. At some point your contact rapidly becomes louder. Stop immediately.

2.
hight pass - will help us to isolate engine/screw sound
low pass - will help to isolate asdic source.

(i am not sure if it shall work like that but it's how it works right now).

3.
Rotate "High pass" a littlebit to the left - 2 points will do.

4. now check your contact how it "behaves" if you're rotating from side to side it shall sound like this "thumbthumbthumbthumb - HRKSZRKSZ - thumbthumbthumbthumb" you shall have an area where your contact sounds like very loud, broken radio.

5. Turn "high pass" more to the left and adjust "gain" accordingly: if you can't hear "broken radio" type of noise right in the middle, add some more "Gain" lvel and scan again. if "broken radio" is to wide - lower "gain" level.

6. Now you narrowed you contact to 2-3 deg. Bravo! You have precise bearing. ( in tutorial i reached precise bearing for "High pass " set about 12-14)

7. if your contact suddenly stops making "broken radio" type of noises it means that he's moving away, and you have just discovered it. Report to the commander! contact, bearing XX, moving Away. A "Gain" level will give you quite good info about how far is your contact, and if he's moving away, or getting closer.

Good luck!

[VonHoffman]

A method I use to center a contact is to look for where the "ends" of the sound are (where it fades out completely and I can no longer hear it). The contact is in the center.

When dealing with a convoy at distance, I use this method to discover which way the convoy is moving before I move to intercept. I head for the quiet end of the sound in the forward direction of the convoy, as it will take me some time to get there, putting me ahead of the convoy where I can wait...

The "width" of the sound tells me if they are getting closer or moving away. The wider the spread, the closer the convoy/ship.

I like the idea of using the training mode for learning the ranging with the hydrophone! I will give this a try later!