[djmcmath]

Modern submarines (almost) always use only passive sonar -- just listening. We avoid hitting the ground by driving based on the chart, mostly. If something isn't on the chart, or is charted inaccurately, we may very well hit it.

The southern hemisphere is particularly bad about underwater topography. We have relatively little data about many areas. While there are spots in the northern hemisphere accurately charted enough to ... well, to have all kinds of fun, the southern half isn't quite so sound. This sort of thing ought to be more common, except that the theory of "Big Ocean Little Submarine" usually works in our favor.

As to this particular seamount, there is a patch of "discolored water" visible on the satellite photos about 5km from where the SFO thought they were when they grounded. Of course, at the depth she was running, the ground that she ran into was probably well below satellite visibility. The investigation so far hasn't found any evidence that the ship should have or could have known about anything at that location.


Dan