Tuesday, November 9, 2004
Matthew A. Russell has been an
archeologist with the National Park Service Submerged Resources
Center since 1993. He serves as Project Director for the USS
Arizona Preservation Project.
Back in the Water. . . Again.
USS Abraham Lincoln departs Pearl
Harbor. Photo by Brett Seymour, NPS.
yesterday in transition, that is, moving from one phase of the project
to the next, our ambitions for an early start were thwarted once again
by the US Navy. This morning USS Abraham Lincoln, which arrived
last in port last week, departed and the harbor was locked-down tight as
a drum until 0930. On a positive note, this give me the opportunity to
Fed Ex the SonTek wave/current meter back to the factory after
discovering yesterday it has some, shall we say, issues. Once we got
back to the Memorial and into the water on Arizona, we were in
for a second not-so-pleasant surprise: apparently due to the torrential
rain we had last week, visibility was worse than any of us have every
seen it. That, plus the absolute lack of wind, which means the leaking
oil doesn’t disperse, but instead pools on the surface of the water
above the ship, made for a less-than perfect series of dives.
A single image to incorporate into the
Photo by Brett Seymour, NPS.
Dave and Brett got to
try out their photo frame, and began the task of shooting images for the
photomosaic. The idea is to shoot many overlapping digital images, and
then stitch them together in Adobe Photoshop. Photomosaics have been
around for as long as underwater archeology, but the results are hit or
miss. To get a precisely accurate image takes enormous effort and
control, and often means constructing an elaborate gridwork or frame
underwater. This is extremely labor intensive, and can take more time
and effort than the final product warrants. On the other end of the
spectrum, one can swim over a site, shoot tons of overlapping images and
somebody skilled at Photoshop can create a stunning visual image – in
all likelihood, however, it won’t be extremely accurate and shouldn’t be
used as a substitute for an archeological map. This type of image can
still have great interpretive, educational and management value,
however. We’re striving for something in-between – a methodology that
is fairly quick, but gives us some controls. We’re not trying to
replace the hand-drawn map, we just want the stunning image to augment
it. To strike this balance, we’re going to experiment with several
different techniques. The first is to use 2 ft. 6 in. by 3 ft. 6 in.
PVC frame and leapfrog it while placing brightly painted weights at each
leg. Our photographer, Brett Seymour, then shoots a single image per
frame; later he’ll use Photoshop to remove lens-distortion and stitch
each image into an overall mosaic. From the photographer’s point of
view, this is like seeing a 608 ft. battleship one small, 2 ft. by 3
ft. rectangle at a time. For the viewer after the mosaic is complete,
hopefully it will be like floating over Arizona with all the
water miraculously removed.
Dave Conlin (left) and Matt Russell retrieve
an oil sample from our collection tent. Photo by Brett Seymour, NPS.
Our other task of the
day was to collect a series of water, oil, sediment and concretion
samples for Dr. Ralph Mitchell and Dr. Chris McNamara at Harvard
University. Ralph and Chris are creating experiments to determine how
microbial-induced corrosion (bugs that eat steel or whose metabolic
byproducts corrode steel) affects Arizona’s hull, particularly
its oil bunkers. We also started measuring the rate that oil is leaking
from the ship at various locations, which we’ve been doing periodically
as part of a long-term monitoring project. Jeff Woods, from the
Memorial dive team, and I set-up a custom-built oil collection device (OCD)
– made by our good friend Kim Johns at USIA, a drysuit manufacturer
(among many other things) – over an oil leak-point, then capture the oil
for a 24 hour period. We’ll shift the OCD around to a different site
each day, and at the end we’ll have a good idea how much oil is leaking
from Arizona each day. In the past its varied between 1-2 quarts
per day. We’ll see where it is now. . . .
SRC divers (l. to r.) Brett Seymour, Dave
Conlin and Matt Russell. Photo by Art Ireland, NPS.