It is like WernerSobe wrote...
There is not a real sonar system modelled in SH III or SH IV.
We have a some kind of "device" wich is replacing the sonar system in most situations but not always.
If you are into the detection cone, into the max min, angles, ranges, depth, heights.... you will be detected, affected by attenations as thermal layers, background noise, waves etc... but you always will be detected.
It is what we have.
As Sailor Steve wrote, will be nice to have those improvements modelled...
Modern sonars have troubles to detect a target into the sea floor, most sure in that age....
