How do you detect surface ship at long range?

[Dron22]

Originally Posted by Hinrich Schwab

The Kilo doesn't exactly have the best sonar package in the game. However, the ship should be detectable from a good way out. Also, 90 meters is definitely deep enough for a thermocline to interfere with sonar, if a thermal layer is present. Check the SSP station's XBT report to see where the thermal layer is. If you are below it, your passive detection drops dramatically.

What is the SSP station XBT report?
I can detect some of the ships from a long range if I use the narrow band sonar from a good range. However if I use the broadband sonar I cannot hear any of them even when they are less than 10nm from me. It was the same in missions where I played as an Akula Improved. I stay deep to avoid detection.

[Pisces]

Originally Posted by Dron22

What is the SSP station XBT report?
...

S(ound) S(peed) P(rofile) station (e)X(pendable) B(athy)T(hermograph) report.

Basically it is a temperature sensor that is floated up to the surface. When it reaches the surface it starts to measure the soundspeed as it dives to the bottom. This station (last button of the Sonar station) shows a table and graph of this sound speed change versus depth. A sharp bend in that graph is a location of a layer where soundrays get curved towards lower soundspeeds. But the layer may not be shown on it if the seabed at your current location isn't deep enough. The sensor simply wasn't able to measure it. Depending on the scenario settings there may not even be a layer, just a straight line as the curve.



Convergence zones are circular regions on the surface around the source where sound-rays get focussed after they are emitted deep into the ocean. As they reach further into the depth and penetrate increasing water-pressure they get curved back upwards to the surface. Once they reach the surface the sound can bounce downwards again to repeat the dive and make the 2nd or possible 3rd convergence zone. Assuming the sound was strong enough to be detectable at those ranges.

Subguru's download page (www.subguru.com) should have some documents that explain underwater accoustics a bit. Atleast enough to the extent that 688i Fast Attack, Subcommand and DW simulate it.

The following link may be too technical, but does show how sounds curve based on the shape of the sound speed curve:

http://www.fas.org/man/dod-101/navy/...P/snr_prop.htm