auv-ee, thank you for your answers about the underwater propagation of sound waves & sonars.
Indeed the Thales sonar signal processing derived from the Barracuda program (the future French nuclear submarines) must be classified. The Emeraude is fitted with a massive dome antenna and what it takes for passive detection/goniometry, and I guess that the sonar data collected by the Emeraude can be related to a very accurate datum/position of the submarine (it relies on a very accurate navigation, given its primary mission/constraints). I don't think that the Emeraude went below -600m (max op. depth is also classified): it remained above the highest peaks of the seafloor.
The SHOM slideshow suggests that most of the montainous seafloor of the area of interest is rocky (muddy in its lowest parts/valleys, probably below -3500m) so I guess this offers a good texture for high reflections/backscattering coefficients near specular directions. The high res. bathymetry of the area shows that nearly 10 % of its slopes are found to be between 30° and 50-60° max (among them faults & scarps of several tens of meters).
About the sampling of the speed profile, isn't it nearly linear in the deep isothermal layer ? (or between the sub and the seabed, see the SHOM profiles).
mm43, don't you think that the area 1 should be entirely scanned at the end of this day or tomorrow ?
Jeff