bayesian

Omnicam deployed at Birch Aquarium

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On Wednesday last week we deployed our new omnidirectional imaging system named OmniCam in the Birch Aquarium kelp tank. This deployment allowed us to test and set buoyancy in a salt water environment, check the operation of the instrument, and acquire video data on all six cameras of the environment in the kelp tank.

The OmniCam is a high resolution, high-speed imaging system designed to capture the ambient light field in the open ocean. It uses six scientific grade HD-CCD cameras, each supported by its own pico-ITX computer and solid state drive. This allows each camera to record data in parallel allowing for simultaneous acquisition of uncompressed HD video at up to 20 fps. Fisheye lenses are used on all six cameras to cover as wide a field of view as possible. The entire system is housed in a 44cm diameter glass sphere.

The system is now packaged and ready to take out to sea this week where it will be deployed as part of a multi-university program to study squid camouflage. Towards this effort, the OmniCam will record the light field in the squid’s natural habit. These data will then be played back to squid in a controlled laboratory setting.

 

“Enhanced extended range underwater imaging via structured illumination” published in Optics Express

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Dr. Jaffe’s work investigating the use of structured illumination for extended range underwater imaging systems (Enhanced extended range underwater imaging via structured illumination) appears in Vol. 18, Issue 12 of Optics Express this month.

iPhone goes to out sea: Testing the iPhone GPS receiver for locating and tracking autonomous underwater vehicles

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One of the key components of the Autonomous Underwater Explorers (AUEs) currently under development in our lab is a GPS receiver for locating, tracking, and recovering the AUEs after a deployment. Because the AUEs will be floating right at the surface of the water, there are problems acquiring satellites and getting reliable GPS fixes using conventional receivers.

On a recent cruise, we had the opportunity to test the GPS receiver of the iPhone 3G. The test consisted of putting together a small plastic housing for the iPhone that was weighted to ensure the iPhone was at the surface. Below is a photograph of the components of the housing:

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The housing consisted of a set of large washers for ballast, some padding to fill the empty space in a 1 L plastic jar, electrical tape to fix a line to the jar, and the iPhone. The iPhone was then powered on, and a GPS application was started to acquire and log GPS fixes. The parts were then assembled:

 

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We then deployed the iPhone off the stern of the ship, payed out about 200 feet of line, and then towed the package behind the ship for a few minutes. After recovering the package, downloading the GPS data and plotting using GPSVisualizer, we obtained a nice GPS track:

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Follow this link to explore the GPS track intertactively on EveryTrail.com

Note that this was recorded by the iPhone while it was partially underwater, bobbing up and down as it was towed behind a ship!

Many GPS receivers fail to work at all when used right at the surface of the ocean. Yet the iPhone not only worked, it worked well! There are several factors to this performance. Perhaps one of the most significant is that the iPhone uses the cellular network to acquire GPS almanacs and therefore can rapidly initialize and start computing GPS coordinates.  Of course without the cellular network, this performance would be reduced, but none the less, the iPhone does provide a solution for acquiring GPS fixes at the surface (perhaps even slightly under water) of the ocean!