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And MY whole point has been that those "other ways" are not nearly accurate enough to prevent the aborted dive we are discussing here. To re-iterate:

Your original comment: It sounds like very poor planning, given that the worlds oceans are pretty much mapped as to depth. Sheesh.

That was in response to the post that included:"In this case the vehicle's programmed to fly 30 metres over the floor of the ocean to get a good mapping of what's beneath." Charts put the depth at 4,200-4,400 metres, he said.

In other words, the operator correctly programmed the Bluefin-21 with the depth parameter on the official charts, but those depths are not generally charted from closely spaced soundings and that do not show much deeper or shallower areas (as I have repeatedly explained). This is quite possible in the very deep parts of the ocean.

So, since the Bluefin-21 is autonomous the only way to prevent it from diving too deep is to program an abort depth, since its course and depth are pre-programmed and not controlled in real time from the surface.

Once again, there is nothing in the post that suggests anything like very poor planning involved here.

Finally, if you still want to argue, read the full artcle which includes the section:
Mysterious and unmapped
It has not been mapped -- in fact most of the deep ocean has not been mapped," Charitha Pattiaratchi, an oceanographer at the University of Western Australia, said of the search area.
"It is very cold and dark with high pressures -- 450 times that at the surface."
Experts cannot even agree on the nature of the seascape, variously described as flat, rocky or coated in super-fine silt that could envelop and hide wreckage.