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AUE GPS communication successfully tested at SIO Pier

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We made a big step forward in the past weeks with a successful test of the GPS system that is to be used on the Mini-AUEs. The system uses the Global Star Network to transmit the location of the vehicle to a remote server. This information can then notify researchers that the vehicle has returned to the surface and give its precise location to aid in recovery.

The Global Star network has significant advantages over other networks due to much lower cost (single transmission costs are on the order of $0.15) and its widespread use.  However, adapting the RF electronics to work while bobbing around at the ocean surface was a non-trival task. The positive results of this test make us optimistic that the Global Star system will provide a reliable solution to location and recovering these autonomous underwater explorers.

The figure below shows GPS fixes sent from the vehicle over the Global Star network. The upper left corner shows a view of the vehicle in the water.

For more information about the AUE project check out the Autonomous Underwater Explorer Page.

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Results from the Global Star test off SIO Pier

 

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!

 

AUEs in the news

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Today the Autonomous Underwater Explorer project was featured in an article in the Scripps News and also a press release from the National Science Foundation. From the press release:

In an effort to plug gaps in knowledge about key ocean processes, the National Science Foundation (NSF)’s division of ocean sciences has awarded nearly $1 million to scientists at the Scripps Institution of Oceanography in La Jolla, Calif. The Scripps marine scientists will develop a new breed of ocean-probing instruments. Jules Jaffe and Peter Franks will spearhead an effort to design and deploy autonomous underwater explorers, or AUEs. AUEs will trace the fine details of oceanographic processes vital to tiny marine inhabitants.

 

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