Airborne lasers sharpen mapping of streams, rivers 10-fold

February 23rd, 2009 - 11:45 am ICT by IANS  

Washington, Feb 23 (IANS) Lasers beamed from airplanes are greatly sharpening images of streams and rivers and interpreting how well water bodies can help maintain or expand fish stocks, according to a new study.
“It’s kind of like going from your backyard telescope to the Hubble telescope,” says Boston College Geologist Noah P. Snyder. “Restoring fish habitat is just one example. For the fisherman, backpacker, forester, land-use planner or developer - anyone who uses map data - this new technology is the next revolution in mapping.”

Airborne laser elevation (Lidar) surveys provide a 10-fold improvement in the precision with which topographical features are measured.

Lidar represents the latest technology to improve digital topographical maps - known as digital elevation models (DEM). Pulsing laser beams released by a Lidar device from a plane overhead bounce off of rocks, trees, soil, even water, and send signals back to the device, which makes topographical calculations based on the time it takes the laser signal to return at the speed of light.

Hundreds of beams produce a dynamic topographical picture, Snyder said. In the case of streams and rivers, the technology means that channel features such as water surface, bank edges, floodplains, even the slope of a stream, can be measured, he reports in the journal.

In addition, Lidar provides new types of data about the vegetation that covers a particular watershed, such as the height and density of the tree canopy, Snyder said.

“We can look at much finer scale features in streams using a remote mapping technique, as opposed to field work over the entire lengths of streams,” says Snyder, chairman of the steering committee of the National Centre for Airborne Laser Mapping.

“Digitally, we can now connect topographical features to habitat characteristics or the habitat that needs to be restored,” he said, according to a Boston release.

That means geologists and other earth scientists will be able to digitally search large swathes of Lidar-mapped territory for a particular feature of interest - like salmon habitat or particularly steep sections of streams - then narrow down likely candidates for field study.

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