EAARL Coastal Topography--Assateague Island National Seashore, Maryland and Virginia, 2005: First Surface

A first-surface topography Digital Elevation Model (DEM) mosaic for the Assateague Island National Seashore was produced from remotely sensed, geographically referenced elevation measurements acquired cooperatively by the U.S. Geological Survey (USGS) and the National Park Service (NPS). Elevation measurements were collected over Assateague Island National Seashore using the first-generation National Aeronautics and Space Administration (NASA) Experimental Advanced Airborne Research Lidar (EAARL), 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 60 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 2-3 meters. The EAARL, developed originally by NASA at Wallops Flight Facility in Virginia, measures ground elevation with a vertical resolution of 3 centimeters. A sampling rate of 3 kilohertz or higher results in an extremely dense spatial elevation dataset. Over 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.阿萨蒂格岛国家海岸的首表面形貌数字高程模型（Digital Elevation Model，DEM）镶嵌图，由美国地质调查局（U.S. Geological Survey，USGS）与国家公园管理局（National Park Service，NPS）合作获取的遥感地理参考高程测量数据制作而成。本次高程测量依托首代美国国家航空航天局（National Aeronautics and Space Administration，NASA）实验型先进机载研究激光雷达（Experimental Advanced Airborne Research Lidar，EAARL）在阿萨蒂格岛国家海岸开展采集；该系统为搭载于航空器的脉冲激光测距装置，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，机载激光系统可记录激光束发射时刻与接收反射激光信号时刻之间的时间差。航空器以约300米的飞行高度、约60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2至3米。EAARL最初由美国国家航空航天局在弗吉尼亚州沃洛普斯飞行设施研发，其地面高程测量的垂直分辨率可达3厘米。当采样率达到3千赫兹及以上时，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，该数据可作为土地开发相关管理决策的实用工具。