EAARL-B Submerged Topography—Saint Croix, U.S. Virgin Islands, 2014

A submerged topography digital elevation model (DEM) mosaic for a portion of the submerged environs of Saint Croix, U.S. Virgin Islands, was produced from remotely sensed, geographically referenced elevation measurements collected on March 11, 19, and 21, 2014 by the U.S. Geological Survey, in collaboration with the National Oceanic and Atmospheric Administration Coral Reef Conservation Program. Elevation measurements were collected over the area using the second-generation Experimental Advanced Airborne Research Lidar, 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.

本数据集为美属维尔京群岛圣克罗伊岛部分近岸淹没区域的水下地形数字高程模型（Digital Elevation Model, DEM）镶嵌数据集，由美国地质调查局（U.S. Geological Survey）联合美国国家海洋和大气管理局珊瑚礁保护计划（National Oceanic and Atmospheric Administration Coral Reef Conservation Program），基于2014年3月11日、19日及21日采集的遥感地理参考高程测量数据制作而成。
高程数据采集采用第二代实验型先进机载研究激光雷达（Lidar）系统，该系统为搭载于飞机的脉冲激光测距装置，可用于测量地面高程、植被冠层及海岸地形。系统通过飞机机身底部的开孔将高频激光束投射至地球表面，并记录激光束发射时刻与机载平台接收反射激光信号时刻之间的时间差。飞机以约55米/秒的速度、300米左右的作业高度飞越目标区域，可形成约240米宽的激光扫描幅带，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13.5厘米。该系统峰值采样率达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有效工具。