EAARL-B Topography-Big Thicket National Preserve: Big Sandy Creek Corridor Unit, Texas, 2014

A bare-earth topography Digital Elevation Model (DEM) mosaic for the Big Sandy Creek Corridor Unit of Big Thicket National Preserve in Texas was produced from remotely sensed, geographically referenced elevation measurements collected on January 19, 21, 22, 29, and 30, 2014 by the U.S. Geological Survey, in cooperation with the National Park Service - Gulf Coast Network. 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 density of 1.4 points per square meter. 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.美国地质调查局（U.S. Geological Survey）联合国家公园服务局墨西哥湾沿岸网络（National Park Service - Gulf Coast Network），于2014年1月19、21、22、29及30日采集了遥感地理参考高程测量数据，以此制作了德克萨斯州大厚地国家保护区大桑迪溪走廊单元的裸地地形数字高程模型（Digital Elevation Model, DEM）镶嵌图。本次区域高程测量采用了第二代实验先进机载研究激光雷达（Experimental Advanced Airborne Research Lidar, EAARL-B）——一款安装于机载平台的脉冲激光测距系统，可同步测量地面高程、植被冠层与海岸地形。该系统通过飞机机身底部的开口将高频激光束投射至地球表面，并记录激光发射与机载接收反射激光信号之间的时间差。作业飞机以约300米的飞行高度、约55米每秒的速度飞越目标区域，形成约240米宽的激光扫描条带，平均点密度达每平方米1.4个点。其峰值采样率为15-30千赫兹，可生成极高密度的空间高程数据集。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实用工具。