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Originally Posted by Dr.Sid
- ray splitting - this should be faster closer to the sound source and more accurate far from the sound source. Simply after some distance ray will be split in two with half energy, sure, ray amount must be kept reasonable, but like this I have much more control over it.
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I wouldn't worry so much about this.
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- surface scattering .. I already tried that, but it needs more rays so I guess the above technique will make it better. I'd also keep some scatter info along the ray. High frequencies suffers more from scattering and if I know how much each point was subject to scatter I can have even some frequency characteristics.
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In real life, this depends on sea state as well as frequency. There exists empiricle and theoretical curves for this.
There's other surface interactions like the Lloyd mirror effect that you don't capture, I've noticed. That becomes important when you get within a few miles because it can cause the signal to get strong or totally fade out in weird ways.
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- bottom .. should be similar to surface
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Sort of. To do the prediction correctly, you need bottom loss v. angle curves that depend on the bottom type (rock, sand, silt, etc.)
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- exact energy loss
- fit it to realistic parametres, so it gives believable results. I need realistic sound speeds, realistic surface and bottom characteristics.
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The speed of sound can be determined by one of several equations. The most modern and accurate is called the Chien and Millero equation. I think you can find it on the web. There also exist several older empiracle relationships, like the Wilson equation and the Mackenzie equation that give decent results as well, and are a lot easier to write down.
A lot of the stuff you're looking for can be found in
Principles of Underwater Sound by Urick. That's sort of the sonar engineer's bible and pays at least lip service to pretty much everything there is to know in sonar. It's actually really creepy how every time I thought I found something not in Urick, I usually end up realizing I just forgot something he wrote.