| Description |
ASCII XYZ point cloud data for a portion of the submerged environs of Saint Thomas, U.S. Virgin Islands, was produced from remotely sensed, geographically referenced elevation measurements collected on March 7, 8, 11, 12, 13, 14, 17, 18, and 24, 2014 by the U.S. Geological Survey, in collaboration with the National Oceanic and Atmospheric Administration (NOAA) Coral Reef Conservation Program. Elevation measurements were collected over the area using the second-generation Experimental Advanced Airborne Research Lidar (EAARL-B), a pulsed laser ranging system mounted onboard an aircraft to measure ground elevation, vegetation canopy, and coastal topography. The system uses high-frequency laser beams directed at the Earth's surface through an opening in the bottom of the aircraft's fuselage. The laser system records the time difference between emission of the laser beam and the reception of the reflected laser signal in the aircraft. The plane travels over the target area at approximately 55 meters per second at an elevation of approximately 300 meters, resulting in a laser swath of approximately 240 meters with an average point spacing of 0.5-1.6 meters. The nominal vertical elevation accuracy expressed as the root mean square error (RMSE) is 13.5 centimeters. A peak sampling rate of 15-30 kilohertz results in an extremely dense spatial elevation dataset. More than 100 kilometers of coastline can be surveyed easily within a 3- to 4-hour mission. When resultant elevation maps for an area are analyzed, they provide a useful tool to make management decisions regarding land development. [More]
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