Washington, Feb 12 : A new study has indicated that lasers beamed from planes overhead are adding greater clarity to mapping streams and rivers and interpreting how well these bodies of water can help maintain or expand fish stocks.

Restoring habitat for spawning species of fish, such as Atlantic salmon, starts with a geological inventory of suitable rivers and streams, and the watershed systems that support them.

But, the high-tech mapping tools available to geologists and hydrologists have had their limits.

Now, airborne laser elevation (or 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, or DEMs.

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.

According to Boston College Geologist Noah P. Snyder, hundreds of beams produce a dynamic topographical picture.

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.

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," said Snyder, chairman of the steering committee of the National Center for Airborne Laser Mapping.

"Digitally, we can now connect topographical features to habitat characteristics or the habitat that needs to be restored," he added.

That means geologists and other earth scientists will be able to digitally search large swaths 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.

"I don't think this will replace field investigations, but it will allow us to better focus our field investigations," said Snyder.

"Researchers, government agencies and private companies are increasingly using the technology to speed the creation of the next generation of maps," he added. (ANI)