What sensors models are used?

[Krabb]

I'm interested what models are used to simulate various sensors. Particularly, the sonar - does it use sonar equation like in Harpoon or sonar ray tracing like in GCB2 or maybe something else? Does it consider weather effects, shadowing, deep channels, ambient noise of ocean traffic? Or radar - weather effects again, refraction, atmospheric inversion, ducting, maybe surface roughness, other effects?

I would be glad to see the equations used if possible. But any details would do.