2020-01-14
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Laser lidar
Laser-based lidar (light detection and ranging) has also proven to be an important tool for oceanographers. While satellite pictures of the ocean surface provide insight into overall ocean health and hyperspectral imaging provides more insight, lidar is able to penetrate beneath the surface and obtain more specific data, even in murky coastal waters. In addition, lidar is not limited to cloudless skies or daylight hours.
“One of the difficulties of passive satellite-based systems is that there is water-surface reflectance, water-column influence, water chemistry, and also the influence of the bottom”, said Chuck Bostater, director of the remote sensing lab at Florida Tech University (Melbourne, FL). “In shallow waters we want to know the quality of the water and remotely sense the water column without having the signal contaminated by the water column or the bottom”.
A typical lidar system comprises a laser transmitter, receiver telescope, photodetectors, and range-resolving detection electronics. In coastal lidar studies, a 532-nm laser is typically used because it is well absorbed by the constituents in the water and so penetrates deeper in turbid or dirty water (400 to 490 nm penetrates deepest in clear ocean water). The laser transmits a short pulse of light in a specific direction. The light interacts with molecules in the air, and the molecules send a small fraction of the light back to telescope, where it is measured by the photodetectors.
Abstract (Summary)
Laser lidar. “Laser Focus World”, 2003, v 46, №3, p45.
The text focuses on the use of laser-based lidar in oceanography.
The ability of lidar to penetrate into the ocean surface to obtain specific data in murky coastal waters is specially mentioned.
Particular attention is given to the advantage of laser-based lidars over passive satellite-based systems iN obtaining signals not being contaminated by the water column or the bottom.
A typical lidar system is described with emphasis on the way it works.
This information may be of interest to research teams engaged in studying shallow waters.
Task II. Read the texts and write summaries according to given one.
Text 1
