[lindzey]

Using our sensor geometry, there's an ambiguity from where off to the side the energy was returned from. So, the solution would wind up being non-unique whatever you do.

There has been some fun work along the lines you describe that uses maps of the surface shape (generated from camera imagery or scanning laser data) to discriminate which apparently-subsurface echoes are most likely due to the surface topography. So far as I know, this hasn't been automated - it's more an aid to human interpretation (we have an army of undergrads that "picks" the most likely bed location).