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Mapping on a grand scale

LAFAYETTE, LA. — LAFAYETTE, La. - Tourists will tell you, and Kodak no doubt would confirm, that it's easy to take a snapshot of the Grand Canyon: Just point and shoot. Repeat as desired.

But a detailed image of the big ditch is another matter.

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Explorer John Wesley Powell and his men spent three months rowing the Colorado River in 1869 to provide the first sketches of the canyon. A century later, renowned cartographer Bradford Washburn required three years and a helicopter to complete his map for the July 1978 issue of National Geographic magazine.

But in April, swooping hundreds of feet below the canyon's rim in a laser-equipped chopper, a small team of surveyors from Louisiana took four hours to create a highly detailed digital map of five miles of the canyon's floor.

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"When you look at the images, you say, 'Holy smokes - this is how [survey] work is going to be done in the canyon in the future,'" said Mike Liszewski, information systems program manager for the Grand Canyon Monitoring and Research Center.

Having accurate data on environmental changes deep in the canyon is not only vital but also required by federal law to monitor the effect of the Glen Canyon Dam.

Alarmed by reports of ecological deterioration, Congress a decade ago passed the Grand Canyon Protection Act, which requires an annual report that includes precise monitoring of conditions created by the dam.

Built more than 40 years ago upstream from the Grand Canyon, the dam blocks the natural flow of water and sediment and is responsible for the loss of four species of native fish as well as the disappearance of sandbars and beaches.

To comply with congressional orders, the Grand Canyon Monitoring and Research Center, an office of the U.S. Geological Survey, sends teams of surveyors into the canyon on foot to get precise readings on its sandbars. But there are more than 450 sites - some highly inaccessible. So the surveyors, called rod men or "ground truth," reach fewer than 1 percent each year.

"It is accurate but expensive," Liszewski said. "And it is hard on the environment itself to have people tramping all over the place."

There is another hitch. About 100 sandbars are part of archaeological sites.

"That's an extremely large problem," said geologist Phil Davis of the U.S. Geologic Survey. "People don't like to have them disturbed."

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In 1998, the center staff tried using lasers to map those changes during a high-altitude flyover of 20 miles of the Colorado's riverbed. The quality of the data was poor.

Two years later, they tried again with different laser technology, this time flying the 277-mile section of the river that passes through the canyon.

But neither type of laser mapping provided the level of detail that scientists needed.

Last year, the center turned to John Chance Land Surveys, a company that made its reputation in the 1950s mapping the Gulf of Mexico for oil companies.

Chance takes on a lot of high-profile projects. It laid out 54 miles of underground tunnels and rings for the now-defunct Superconducting Super Collider. It flew the length of Amtrak's Northeast Corridor, from Washington to Boston, providing data to guide track upgrades for Amtrak's high-speed Acela trains. Early this year, it performed a similar aerial survey of New Jersey Transit's rail lines.

Intrigued, the Army Corps of Engineers paid $50,000 to see if Chance's technology could be adapted to canyon use. "It wasn't an easy job," acknowledged Blaine Thibodeaux, the company's project manager. "This is not something you just get up and do."

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Security and safety were issues. The National Park Service, which has strict permit standards for flying above the canyon, had to be convinced of the merit of below-the-rim flights in a nonrescue situation.

Finally, there were the logistics.

Chance uses a patented system called FLI-MAP, a combination of laser scanners and video recorders guided by global positioning satellites.

"Because the GPS operates by line of sight, we had to coordinate our flying time to when the satellites would be directly overhead," Thibodeaux said. "The canyon walls screen out everything in view. In some areas, there's a 45-degree blockage. It was extremely challenging. "

But not nearly as challenging as it was for Powell and his men in 1869, as the explorer's journal from that summer indicated: "We are three-quarters of a mile into the depths of the earth. ... We are but pygmies, running up and down the sand, or lost among the boulders. We have an unknown distance to run, an unknown river yet to explore. What falls there are, we know not; what rocks beset the channel, we know not; what walls rise over the river, we know not."

Thibodeaux and his survey team finally settled on a four-hour window that would enable them to fly two passes on two consecutive days. The helicopter moved at about 45 mph, the lasers scanning the terrain, sending out pulses at the speed of light and collecting 8,000 data points a second - one point for each square foot.

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"Every small step you take is equal to a point, so that's as dense as any readings we've ever gotten," USGS' Davis said.

The field work went off without a hitch. Chance took the next four months to analyze the data at its Lafayette facility, where technicians "married" the survey information to the video images to create a three-dimensional view of the beaches and sand bars.

When Davis finished his analysis for the government early this month, he found some problems with readings taken in or near vegetation that obscures the system's view. But overall the results are good, he said.

The question, at $10,000 a mile, is whether the government wants to spend the extra money to get a better and more extensive picture. But given intense public interest in the national icon - along with controversy and lawsuits surrounding efforts to preserve it - Liszewski and Davis say Chance's laser technology provides the best information with the least amount of human bias.

"It's not worth buying inferior data unless it satisfies your needs," Davis said. "The model makers need a high volume of information, accurate information, to be able to say there definitely was a change or not."

Added Liszewski: "The very best science is still to send in the rod men, but it's physically impossible to send enough people down there to do what John Chance can do in a few hours. And the bottom line is, the speed of light doesn't lie."


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