LIDAR Promises Improved Inventory-taking

Linda Benedict  |  6/27/2006 11:23:37 PM

This three-dimensional plot of LIDAR data depicts the canopy of a section of forest. Color gradations from blue to red show the differences in height from ground level.

LSU AgCenter scientists have been researching remote sensing work with airborne lasers to develop three-dimensional pictures to measure the stand and take inventory of a forest.

Called LIDAR, an acronym for Light Detection and Ranging, the process uses a scanning laser in an airplane and global positioning system (GPS) technology to measure the vegetation in a forest. The results are a three-dimensional depiction of the surface below.

“A laser scan ‘paints the surface’ in three dimensions,” said Thomas Dean, a researcher in the School of Renewable Natural Resources. “It creates a picture of the canopy of the forest – the number of trees and their heights.”

Like a flashlight beam, the rays of the laser are reflected back to the sending unit, and the increments of time it takes for the beams to return indicate distance. The information is used with a GPS to create what looks like a relief map. But instead of depicting the contours of the ground, the map represents the forest canopy.

Dean likens the LIDAR map to draping a virtual sheet over the forest to look at the top surface to count trees and measure their heights.

The first application of LIDAR in forestry was in the early 1990s, and the technology has been gaining interest since then.

Dean and Quang Cao, another researcher in the School of Renewable Natural Resources, have been using LIDAR to measure specific properties of the forest canopy, such as length of the green crown.

Dean said their and others’ research indicates LIDAR is feasible and accurate for both measuring trees and conducting a forest inventory. The scientists hope to refine the technology to improve the accuracy and speed of taking an inventory of a standing forest.

“It’s still too expensive for regular use,” Dean said. “People on the ground are cheaper, but technology always becomes less expensive with time.

(This article was published in the spring 2006 issue of Louisiana Agriculture.)
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