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Ocean Imaging Expedition – Log 1

Ocean Imaging Expedition – Log 1

The first survey

Nancy Barr

The first low-altitude survey of this expedition centered on an area surrounding an instrument node located about 30 kilometers offshore at a depth of 1,850 meters in Monterey Canyon.

Here’s how it works: Four systems record data as the ROV runs a preprogrammed path across a 100-meter-square section of the seafloor. The multibeam sonar system sends sound waves toward the bottom; the time it takes for the sound to bounce back indicates the depth. The lidar system is similar in terms of sending a signal to the seafloor and recording the time it takes to bounce back, but it uses laser light beams instead of sound. Two strobe lights fire to provide light for a stereo-image camera system that takes photos as the ROV flies just two and a half meters above the bottom. Finally, an inertial navigation system records the speed, orientation, and velocity of the vehicle—important information for helping to tie all the data together.

The sophisticated imaging, navigation, and mapping equipment are mounted in a tool sled under remotely operated vehicle Doc Ricketts. Photo by Dave Caress.

On a full-day’s ROV dive, these systems would bring back more than a terabyte of data, which researchers then piece together to create detailed seafloor images. Processing that much data continues late into the night, so images are not immediately available.

Scientist Charlie Paull, left, met with Chief ROV Pilot Knute Brekke on the ship before the cruise. Paull is looking forward to seeing what the data collected on this cruise will reveal about the changing shape of the seafloor. Photo by Dave Caress.

—Nancy Barr

About Ocean Imaging Expedition

In early March, MBARI's Ocean Imaging Group conducted low-altitude seafloor surveys aboard the R/V Western Flyer as part of the Coordinated Canyon Experiment.