Off-Topic: Imaging Ocean Sediment
The U.S. Geological Survey (USGS) is renowned worldwide for its studies on the environment. The organization aims to provide reliable scientific information to describe and understand the Earth.
One of its divisions, the USGS Coastal & Marine Geology Program (CMGP), focuses on research on the coastal and marine environment such as river and ocean sedimentation. The program has three field centers in the United States: Wood’s Hole, MA; St. Petersburg, FL; and Menlo Park/Santa Cruz, CA.
At the Menlo Park/Santa Cruz, CA, location, the organization is undertaking a sand grain study. An objective of the project is to capture close-up color images of sand grains in order to study their coarseness and how their size influences re-suspension of sediments by waves and currents. The team is looking to develop a theoretical model to predict how the seabed morphology off the Californian coastline might change over time and, in the longer term, study changes in ocean behavior.
The USGS has undertaken similar projects in the past; however, this is the first time that the organization has used a camera with Gigabit Ethernet technology.
System SetupThe Prosilica camera used in this system is the 5-megapixel GC2450C with Gigabit Ethernet output. The camera has a Sony ICX-625 charge-coupled device (CCD) image sensor and was selected by the CMGP team for its image quality, sensitivity, low noise, high resolution (2,448 by 2,050) and compact size (33 millimeters by 46 millimeters by 43 millimeters).
The GC2450C was set up inside a 30.5- by 9-centimeter stainless steel pressure housing with 5-millimeter thick acrylic windows fitted with a light ring to ensure even lighting around the main target area. The pressure housing itself was mounted on a custom-made tripod, which is raised and lowered into the ocean via a hydraulic system. The system is linked to a PC located off the Santa Cruz wharf via a 100-meter Cat-6 cable. The GC2450C was fitted with a macro-lens.
Technical ChallengesAfter being tested at the marine facility in Santa Cruz, where technicians worked on camera focusing, a crucial matter for this project as the team will be studying sand grain particles measuring approximately a few tenth of a millimeter, the system was moved to the ocean just off the coast of Santa Cruz, where it is lowered to the bottom of the ocean every hour or two, depending on conditions, to capture aerial view images of sand grains.
In the event of a storm the camera will be set to image more frequently to observe the higher activity. Other sensors will monitor other factors such as turbidity, solidity, concentration and grain size of particles and wave pressure to further study all the elements influencing sedimentation.