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Lu, you wrote:
"Consider then the crudeness of our charting capabilities. Satellites can't
spot stuff below the water like they can above the water. Side scan sonar is
great -- if you've got the time and money to scan the ocean a few hundred
yards at a swath.  Bottom line:  we really don't know what's out there in
the great oceans."

This is very true. In this age of terabytre databases and mapping systems
like Google Earth, it's hard to remember that most of the Earth's surface is
beneath the oceans and nearly unknown. Some satellite technologies can be
used to create pseudo-maps of the ocean's bathymetry. For example,
satellites can accurately map small bumps and depressions in the mean
surface of the ocean that are caused by gravitational anomalies beneath the
sea. A seamount has its own gravitational field and piles up water above it
in a little hill. This type of data has been used to generate a few popular
databases which seem to map the ocean floor in considerable detail. One
version of this database is known as ETOPO2 (a successor to the low-accuracy
ETOPO5). The claim is that the ocean floor is mapped with a spatial
resolution of about 2 minutes of arc. Here's a description:
http://www.ngdc.noaa.gov/mgg/image/2minrelief.html.

Unfortunately, this system for generating bathymetic data is only valid on
average. Some seamounts can be detected this way, but many cannot. The basic
problem is that mountains can exist without the associated gravitational
anomaly. Seamounts slowly settle into hydrostatic equilibrium with the crust
beneath them and when that equilibrium is reached, the sea surface above no
longer shows the gravitationally-induced hills. As a result databases like
ETOPO2 cam reveal unknown seafloor features, but they can also miss a lot.
They also include spurious bathymetry, essentially random noise, on scales
of 5-100 kilometers. In addition, the satellite data is constrained by some
trackline bathymetry which leads to strange "stripes" of pits and bumps on
the ocean floor where the tracklines over-rule the satellite data.

Naturally, there are bound to be classified datasets which include better
resolution of features in some areas, but the problems above are rather
fundamental. There's no cheap way around them. Unless someone develops a
radically new technology for surveying the ocean floor, it will remain
largely unknown for many decades.

And:
"The San Francisco's captain received a career-ending reprimand because
another chart (not the one he was using) referred to the possibility of
seamounts in the region in which he was operating and the court of inquiry
found he was negligent for not using "all available navigational
information." "

It's also a question of prudence. The trick is recognizing that the chart
may not be complete in an area like that. In the end, the captain took the
fall because that's part of the captain's job. A sailor died. A nuclear
submarine suffered a hundred million dollars in damage. Then again, he and
his crew saved the boat from mortal injury... but the captain doesn't get
credit for that.

Can you imagine what that collision sounded like to the sonar operators
aboard other vessels in the area? They must have guessed the sub was lost.

 -FER



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