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Fieldwork

Using the SeaBED AUV for Geologic and Benthic-Habitat Studies of the Sea Floor


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Digital photograph of the sea floor acquired by the SeaBED Autonomous Undersea Vehicle (AUV)
Viewing the sea floor: Digital photograph of the sea floor acquired by the SeaBED AUV. Mobile coarse sand with storm-generated ripples surrounds a small (about 3/4 m long) boulder encrusted with finger sponges, anemones, hydrozoa, and other epifauna. Small flounder lies on sand to left of boulder. Image shows an area of the sea floor measuring 1.95 by 1.55 m (3 m2).
Scientists from the U.S. Geological Survey (USGS), the National Oceanic and Atmospheric Administration (NOAA), and the Woods Hole Oceanographic Institution (WHOI) participated in a March cruise to the Stellwagen Bank National Marine Sanctuary off Boston, MA, to test an autonomous undersea vehicle (AUV) developed by Hanumant Singh and his colleagues at WHOI's Deep Submergence Laboratory.

The AUV is constructed of two horizontal bodies configured one above the other, connected by struts, and weighs approximately 400 lb in air. The SeaBED AUV is designed to precisely navigate survey tracks at altitudes as low as 2.5 m above the sea floor. Propellers oriented in different planes allow the AUV to maintain course and altitude while avoiding obstacles.

On launch, the vehicle propels itself vertically downward until its navigation system locks onto the seabed at 30-m altitude and it can begin its programmed survey. It can acquire digital color photographs, sidescan-sonar imagery, high-resolution swath topography, and current-meter data.

In its present configuration, the AUV can remain submerged for as long as 3 hours (to be increased to 8 hours in the near future) and can acquire 1,200 photographs per hour, with varying degrees of overlap as determined by vehicle speed (0.5-2 knots). Processing of the images provides stunning views of the sea floor.

The SeaBED AUV is preprogrammed to perform various functions during its dive. Vehicle speed, altitude, photograph timing, and use of camera and sidescan sonar all can be varied during a single deployment. For example, the AUV can acquire photographs (2.5-m altitude) along separate transects, or along overlapping transects to make a mosaic of the seabed, and it can perform a sidescan-sonar survey (10-m altitude). Maximum water depth for the AUV at present is 2,000 m.

Retrieval of the SeaBED Autonomous Undersea Vehicle
Recovery: Retrieval of the SeaBED AUV by the research vessel Oceanus in Stellwagen Bank National Marine Sanctuary. Electronics and flotation are in the upper body; digital camera, sidescan sonar, scanning fathometer, current meter, and batteries are in the lower body. Note placement of the twin propulsion units on the rear strut and the single, vertically oriented propulsion unit on top of the lower body.
The cruise to the Stellwagen Bank National Marine Sanctuary aboard WHOI's research vessel Oceanus was designed to test the AUV in an area that has been mapped by using multibeam swath-sonar imagery and extensive groundtruthing with video and photographic imagery and geologic and biologic sampling.

The vehicle successfully conducted several long (3 km) photographic surveys across various habitats and major topographic features; it also performed a tight grid survey of a boulder ridge to obtain a mosaic of the seabed. The lines of the grid survey were spaced 1.4 m apart to ensure adequate overlap of digital photographs.

In addition, the SeaBED AUV performed a survey of the sea floor in tandem with the REMUS AUV (deployed from a different ship), which surveyed the water column by using a CTD (conductivity-temperature-depth sensor) and a video plankton recorder.

The SeaBED AUV proved to be a valuable tool for acquiring sea-floor data for a range of purposes, from the making of detailed mosaics of specific features to conducting long photographic and sidescan-sonar transects for describing surficial geology and benthic habitats. Cruise participants included chief scientist Hanumant Singh (WHOI), Page Valentine and Soupy Alexander (USGS), James Lindholm (Stellwagen Bank National Marine Sanctuary), and Ryan Eustice, Oscar Pizzaro, Ali Can, and Ken Foote (WHOI).


Related Web Sites
Stellwagen Bank Studies
U.S. Geological Survey (USGS)
Stellwagen Bank National Marine Sanctuary
National Oceanic and Atmospheric Administration (NOAA)
Woods Hole Oceanographic Institution
non-profit research facility

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in this issue: Fieldwork cover story:
Autonomous Vehicle Studies the Sea Floor

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Research Ecologically Sensitive Islands in the Bering Sea

Outreach Track Florida's Manatees Via Web Site

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Meetings Saltwater Intrusion and Coastal Aquifers

Gas Hydrates CODATA

Natural Science and Better Health

Staff & Center News New Chief Scientist for Western Coastal and Marine Team

Mendenhall Fellows Lecture in Reston, VA

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Netherlands Scientist Visits Woods Hole

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Publications Manatee Hurricane Survival Paper

May Publications List


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