2006
Nancy Foster Maritime Cruise
A
five day research cruise was conducted on the NOAA ship Nancy
Foster in June 2006 to locate and document the sanctuary's
maritime heritage resources. The project utilized several types
of undersea technologies to study and interpret the historic shipwrecks
that lie on sanctuary's sea floor. Project personnel used side
scan sonar, multibeam sonar, and a remotely operated vehicle (ROV)
to find new shipwrecks and further investigate previously located
shipwrecks.
The NOAA ship Nancy Foster was the platform for this project.
The vessel is equipped with all of the technology and capabilities
required to conduct multi-day maritime heritage research in the
sanctuary.
The
primary research tool for this project was the side scan sonar
which was used to locate potential maritime heritage resources.
Side scan sonar uses sound pulses emitted from transducers on
each side of the sonar towfish. The pulses are sent in a wide
angular pattern down to the bottom, and the echoes are received
back in fractions of a second. The pulses are then transmitted
back to a computer which allows the archaeologist to "see"
the bottom's features.
Utilizing
an Edgetech DF-1000 side scan sonar (left), the project's side
scan sonar survey located acoustic targets within a defined
survey area in the sanctuary. A side scan sonar image of the
F/V Josephine Marie (right) located in the shallower waters
on top of Stellwagen Bank.
While
the towed side scan sonar was only used during the day (to lessen
the risk of entanglement in fishing gear) the hull mounted multibeam
sonar was used mainly at night to maximize the amount of data
gathered during the cruise. Multibeam sonar provided a rapid means
of determining the nature of the sediments and objects on the
seafloor. The data was used to generate high resolution images
which contain information about the composition of the seabed.
Multibeam sonar is similar to side scan sonar in that it uses
sound pulses that reflect off the bottom. The difference is that
multibeam sonar sends sound pulses focused directly down from
the sensor. The end product of a multibeam survey is a bathometric
map which shows depth.
Hull-mounted
multibeam sonar (left) and towed side scan sonar (right) (Courtesy
of NOAA).
Multibeam
images of the coal schooners Frank A. Palmer and Louise
B. Crary (left) and the steamship Portland (left) (Courtesy
of NOAA).
The
final phase of the project was a ROV investigation of several
potential maritime heritage sites. Project archaeologists used
a Seabotix LBV150 to conduct a video survey to determine whether
certain side scan sonar targets were in fact shipwrecks. The ROV
gathered color video of the anomalies, which were used to characterize
the targets origin (ie. anthropogenic or geologic). The ROV successfully
interrogated several targets in the sanctuary and determined that
the targets were not maritime heritage resources.
Project
archaeologist Matthew Lawrence checks the ROV prior to its dive
in the sanctuary to investigate side scan sonar targets to determine
if they are maritime heritage resources.
Sanctuary
maritime archaeologists were joined by two graduate students from
East Carolina University's Program in Maritime Studies and Coastal
Zone Management Program. The project was also supported by the
National Undersea Research Center at the University of Connecticut.
Potential shipwreck sites located with side scan sonar will be
investigated in subsequent years through diving investigations,
remotely operated vehicles (ROV), or an autonomous underwater
vehicles (AUV).
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