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The Next Big Thing
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Other new uses for ocean mapping are at once promising and perplexing. The possibity of mining the seabed, for example, raises challenging questions: Where does one country end and another begin? Who does the deep ocean belong to, if anyone? And multibeam sonar can also be used to calculate specific numbers of fish. "Our data is controversial because it can be easily misused—and people's livelihoods are at stake," says Mayer, who has done work for Canada's Department of Fisheries and Oceans. Rightly applied, emerging data about the oceans' fish stocks could be used to help promote conservation and renewable resources.

Mayer, who spends a good deal of time as a sort of ocean mapping detective, has also helped decipher earthquake faults off the coast of California and dump sites off the coast of Oahu—complete with indentations where chunks of concrete from the old Honolulu hospital had been deposited. He has worked with Mobil Oil to help map a pipeline route and with the World Wildlife Fund to produce maps of potential marine sanctuaries. Mayer was also called in to study some apparent fault lines in Lake Ontario. A nearby nuclear reactor had people nervous about the potential for disaster. The mapping revealed that what people thought were fault lines were actually trails of fly ash left behind by the steamers that made their way across the lake in the 19th century.

Sometimes these techniques result in unexpected discoveries. Such as the British Freedom. Over the course of four decades, Canadian hydrographers had developed a safety and navigation map for the waters off the coast of Halifax. But the single-beam sonar systems had missed the 400-foot vessel. Sunk by a German submarine in 1945, the ship went down in about 150 feet of water—right in the middle of a major shipping lane. Her masts reached high enough to be a hazard to navigation.

An ocean mapping image of the bottom of San Francisco Bay.

The bathymetric maps Mayer produces reflect their Greek roots: bathos, meaning deep, and metria, meaning the process of measuring. Like some fantastical multicolor dream, the maps depict a world of mysterious pink peaks and deep yellow gullies, expanses of cerulean blues, emerald greens and reds the color of poppies. "To anyone used to looking at little numbers and lines," says Mayer, "this really is a profound experience, to see the ocean floor for the first time in three dimensions." The results seem as much art as science. But the goal is far more than colorful pictures.

The big challenge right now in the field of ocean mapping is keeping up with the torrent of data. An acronym for "sound navigation and ranging," sonar emits pulses of sound and then reads the depth as the pulses bounce back off the bottom. Multibeam sonar sends out a fan of beams that can measure 60 depths simultaneously, and the incoming data is enough to fill a single CD-ROM in just one hour. How do you manage such a volume—and how do you transform it into something people can use?

Enter Colin Ware and his flying mouse. A computer scientist also from Canada's University of New Brunswick, Ware specializes in data visualization techniques; he will head UNH's new Data Visualization Center, which will work in conjunction with C-COM. During the past decade, he has collaborated with Mayer to develop Fledermaus, a "fly-through" software program that does just what its name suggests. Holding the "flying mouse" in midair in front of the screen, viewers can use simple hand gestures to navigate through amazing on-screen underwater worlds. "It's like a video game," says Ware. "Except it has a purpose."

Fledermaus allows people to see sonar readings in a way they can understand. "Flat, hand-contoured paper charts have literally 99 percent of the data missing," says Ware. "Now you can look at the sea floor from any angle, poke in here to check the depth, zoom over there to look at something else." Had it not been for Mayer, Fledermaus might have gone the way of so many other academic projects—a brilliant paper that sits on a shelf. "But Larry came along," says Ware, "and saw the potential to make this into a usable tool to understand data."

Just last summer, the U.S. Secretary of the Interior Bruce Babbitt was featured in front-page news photos "Fledermaus-ing" his way through Lake Tahoe. Famous for its exceptionally clear water, the 105,000-acre lake was dubbed by Mark Twain as "the fairest sight the whole earth affords." But clarity has been diminishing recently at a rate of one foot each year—and no one knows why. In 1968, a 10-inch white dinner plate could be seen from a depth of 105 feet. In 1997, it could only be seen at 70 feet.

Until last year, the only bathymetry of Lake Tahoe were maps made in 1923, inadequate for today's level of scientific study. Which is why the USGS launched cruise IS-98. To orchestrate the project, they worked with Mayer, who applied state-of-the-art ocean mapping technology to the problem. Mayer coordinated the appropriate sonar system, hired a survey company and then spent a week at command central, a condo on the shores of Lake Tahoe. "Larry's the fellow who really pulls everything together," says Ware. "These survey ships cost many thousands of dollars per day. So you need somebody with logistical skills and organizational abilities—a sort of military commander."

Out on the water, the 26-foot Inland Surveyor, with an EM1000 sonar system attached to its bow, spent each day carefully "mowing the grass," sending sonar images back to the computers as the vessel moved steadily back and forth across the lake. Manning the computers, Mayer and USGS colleague Jim Gardner studied the data as it came in, cleaning it up and removing disturbances. When they were finished, the bottom of Lake Tahoe had been recorded in a stunning gallery of three-dimensional digital photographs. Some of these images are posted on the Lake Tahoe Data Clearinghouse Web site http://blt.wr.usgs.gov/. With the information provided by these maps, scientists now have a better foundation from which to tackle the problem of diminishing water clarity.

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