Coastal Topography—Anegada, British Virgin Islands, 2014

A seamless (bare earth and submerged) topography Digital Elevation Model (DEM) mosaic for a portion of the submerged environs of Anegada, British Virgin Islands, was produced from remotely sensed, geographically referenced elevation measurements collected March 19-20, 2014 by the U.S. Geological Survey. 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 20 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.

本数据集为英属维尔京群岛阿内加达岛部分淹没周边区域制作的无缝（裸地与淹没区）地形数字高程模型（Digital Elevation Model, DEM）镶嵌图，数据源自美国地质调查局（U.S. Geological Survey）于2014年3月19日至20日采集的遥感地理参考高程测量数据。该区域的高程测量采用第二代实验型先进机载研究激光雷达（Experimental Advanced Airborne Research Lidar, EAARL-B）完成，这是一款搭载于航空器的脉冲激光测距系统，可用于测量地面高程、植被冠层与海岸地形。该系统通过航空器机身底部的开口将高频激光束投射至地球表面，激光系统会记录激光束发射与机载接收反射激光信号之间的时间差。航空器以约300米的飞行高度、约55米/秒的速度飞越目标区域，由此形成约240米宽的激光扫描带，平均点间距为0.5至1.6米。以均方根误差（Root Mean Square Error, RMSE）表征的标称垂直高程精度为20厘米。峰值采样率达15至30千赫，可生成密度极高的空间高程数据集。单次3至4小时的飞行任务即可轻松完成超过100公里海岸线的测绘工作。对某一区域生成的高程地图进行分析后，可作为土地开发相关管理决策的实用工具。