A New Application of Lidar Technology
Lidars send a short pulse of light energy from a laser at a target. The time it takes for each pulse to complete a roundtrip to and from the target is converted into a direct measure of the elevation of the target. VCL's Multi-Beam Laser Altimeter goes one step further by also recording the "waveform" of the returned signal. The unique shape of the waveform reveals wherein the space between the ground and the tree topsthe foliage, trunk, and branches are concentrated. VCL is the first multi-beam, waveform-recording lidar to fly in space.
The VCL lidar holds five lasers that each send 242 pulses per second at the Earth's surface. Each beam covers an area 75 feet across. By spacing the five beams a little over a mile apart, each VCL orbit will sample an area 5 miles across. The VCL science team is using the airborne Laser Vegetation Imaging Sensor (LVIS), built at NASA's Goddard Space Flight Center in Greenbelt, Md, to acquire VCL-like data that they will use to fine-tune their data analysis methods. LVIS uses one laser, but it maps 100 percent of an area more than a half mile wide at a single pass. A rotating mirror reflects each laser pulse out from the aircraft at a slightly different angle to hit a series of consecutive areas in a strip across the flight path. next: Applications to Forest Management Needs
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Vegetation Canopy Lidar |
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