just a quesion.

[Krauter]

Hi all,

Just been wondering, one of my basic maneouvres is to dive deep under thermals when attacked and track a certain target via sonar readings so i can come up at a later time to strike, however sometiems when i come to PD i notice the target is 10-20 degrees off and maybe 500yrds away then what the original sound bearing was..

So here's the question: Does th depth your boat is at, affect your sonar readings, and if so , how?(accuracy, bearings, picking up only certain targets [say targets running hi revs and those running low wont be picked up?])

Answers would be greatly appreciated!

Krauter

[simonb1612]

As I understand it the thermal layer does cause some additional refraction of the sound waves.
Here is a link to an interesting powerpoint lecture on the principles of underwater sound. (I do not know what the status of copyright is on this lecture but it has been posted online without any restrictions given)

www.owlnet.rice.edu/~nava201/presentations/Lecture09.ppt (http://www.owlnet.rice.edu/~nava201/presentations/Lecture09.ppt)
:know:

[Krauter]

Thanks simon, so from what i gather from the power point is that themrals work both ways. To counter this i should move above the thermal layer to get my bearings go down, rinse and repeat till i have a solution?

[simonb1612]

You have got me on that one, I am sure that there are some folks here with real life experience that could help us both out on that. One thing you might be able to dicern is whether the ships are always ahead or behind the range estimate and to the left or right of the bearing. By altering your depth below the thermal layer (ie 20, 40 ft below and taking readings then surfacing after the same time interval you might be able to calculate the effect of the refraction on your readings and thus allow for them when setting up your attacks....:hmm:

[Powerthighs]

This may be a dumb question, but is the target moving between the time it takes to rise from deep to PD?

[Krauter]

There are no such things as dumb questions:nope: ..

I thought about that and tracked the target on the attack map as i go up.. with periscope up, target automatically goes to vis wen XO sights it.. most of the time its off.

Also, tried switching up and down between the thermals. WHAT A DIFFERENCE!..
I think thats what ill have to start doing from now on..

With Regards,

Krauter