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LiDAR strips landscapes down to their bare glory

LiDAR strips landscapes down to their bare glory
From Engadget - December 4, 2017

The image above depicts a LiDAR relative elevation model (REM), showing current and previous channels carved out by the Sauk River in Washington State's Skagit and Snohomish counties. In the regular satellite image below, however, only the active, vegetation-free channels are clearly visible -- a striking display of what the technique can reveal.

"REMs are extremely useful in discerning where river channels have migrated in the past by vividly displaying fluvial features such as meander scars, terraces, and oxbow lakes," explains Washington State geologist Daniel E. Coe in a PDF. "This type of information is very informative in channel migration and flood studies, as well as a host of other engineering and habitat assessments."

Carried on special aircraft, LiDAR produces visible-light laser beams. While much of it bounces off of trees and vegetation, enough make it through to the ground. By examining the raw data to see which beams travel the farthest, scientists can "edit out" trees, vegetation and man-made structures. That reveals hidden seismic faults, glacial landforms, landslides, lava flows and other features that are invisible on a regular satellite photo.

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