EquipmEnt & cabling updatE 33
source pulse in the range of 1 to 6 kHz results in
increased depth of penetration.
Figs. 1 and 2 show data examples of the
improved DW-106 Subbottom Profiler compared to
the DW-216 Subbottom Profiler. Subbottom data in
the West Africa is drastically improved in resolution.
The Gulf of Mexico example shows nearly double the
penetration depth in some locations. An upgrade of
the subbottom profiler in C-Surveyor I is anticipated
for August 2009.
Digital camera
Earlier this year, C&C added a digital camera to
the C-Surveyor III payload (Figs. 4 and 5). The
ultra compact camera is capable of recording two-
megapixel, black and white photographs of the
seabed. The anticipated AUV altitude for camera
operation is 6.5 metres and field of view is 4 x 3 with
the longer view in the alongtrack direction. The low-
power camera takes a picture every 1.5 seconds with
a strobe light supplying illumination. This firing rate
allows approximately 25 per cent overlap between
pictures. Pipeline or wellhead inspections typically
performed with ROV are now possible with this
AUV. The primary advantage of using an AUV over
an ROV is the speed at which data images can be
Fig. 3. Comparison of standard 410 kHz and dynamically focused 230 kHz
collected (3.8 vs. 1.5 knots). The camera will allow
sonar imagery collected at a deepwater shipwreck site in the Gulf of Mexico.
pre-route survey inspections to ensure no debris
or obstacles were missed with the other acoustic
transducers are segmented providing high-frequency systems. Groundtruthing of sonar targets for deepwater
sonar imagery out to 200metres on each channel (Fig. 3). UXO investigations or archaeological assessments is
Significant effort was put into building a superior another application for the AUV camera. Usually a
subbottom profiler for C-Surveyor III. Edgetech was second mobilisation of an ROV is needed to investigate
contracted to design and build an AUV chirp subbottom sonar targets. Environmental concerns or studies, such
profiler with increased source output power, larger as chemosynthetic communities or deepwater corals, are
receiver array, reduced beamwidth and a lowered another application of the AUV camera. l
frequency content. The Edgetech DW-106 Subbottom
Profiler resulted from the effort. A single transducer for Enter 33 or ✔ at www.engineerlive.com/ihss
the source was replaced with a 2 x 2 transducer array.
The larger transducer array reduced beamwidth and Robert A ‘Tony’ George is with C & C Technologies Inc,
increased the dB output of the source. The receiver array Lafayette, LA, USA. www.cctechnol.com
sized was increased from two 19-in hydrophones to eight
32-in hydrophones. A lowered, frequency modulated
Fig. 5. AUV picture of a siphonophore taken in the Gulf
of Mexico. The most common type of siphonophore is
Fig. 4 AUV camera photograph of deepwater 16-inch the Portuguese man of war.
pipeline in the Gulf of Mexico. Bob Carney, LSU, personal communication.
www.engineerlive.com
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