Washington, May 31: Researchers are using a ranging and location system based on light instead of radio waves to monitor changes in geologic faults and ice sheets, speakers said on Wednesday at the American Geophysical Union spring meeting. The Light Detection and Range or LIDAR system provides highly detailed, three-dimensional surface maps from airborne or space-based platforms, said Jean-Bernard Minster, a geophysics professor at the Scripps Institution of Oceanography in La Jolla, Calif. One of the system`s great features is its ability to image land obscured from radar by foliage, he told an AGU news conference. "When you send the laser pulse to the ground, almost always a few photons make it between the leaves and come back. This is all that`s required," Minster said. "(Lidar) can detect those photons, the last ones coming back, and get a map of the ground without the trees."
Lidar`s unique ability allows researchers such as David Harding, with the National Aeronautics and Space Administration`s Goddard Space Flight Center in Greenbelt, Md., to examine fault lines in forested regions. Along Puget Sound in Washington state, Harding said, mapping the relative movements of both sides of the Seattle fault zone help to model the strain along fault lines in the region.

One drawback with current Lidar platforms is they cannot linger over an area long enough to provide a constant data stream, Harding said, so Nasa and other agencies are looking at unmanned, very-long-endurance planes or balloon-based platforms to allow round-the-clock monitoring of active geologic faults or volcanoes. Detecting inch-scale movements in such areas could provide advance notice of an earthquake or eruption, he said.

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When used in tandem with radar, the system can track changes in the thickness of glaciers, ice caps and sea ice, said Waleed Abdalati, manager of the Cryosphere Sciences Program at Nasa. Understanding the extent of such changes is important in monitoring global climate, he said.

Advances in Lidar technology also could put such systems on satellites in geosynchronous orbit, where they could monitor entire continents continuously. This could occur within about 10 years, Minster said.

Researchers also are looking at using several frequencies of light to gather information on chemical composition as Lidar maps an area. Bureau Report