EAARL Coastal Topography--Assateague Island National Seashore, Maryland and Virginia, 2010

A digital elevation model (DEM) of a portion of the Assateague Island National Seashore in Maryland and Virginia was produced from remotely sensed, geographically referenced elevation measurements collected cooperatively by the U.S. Geological Survey (USGS) and the National Park Service (NPS). Elevation measurements were collected over the area on March 19 and 24, 2010, using the 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 50 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 the National Aeronautics and Space Administration (NASA) at Wallops Flight Facility in Virginia, measures ground elevation with a vertical resolution of +/-15 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. For more information on Lidar science and the Experimental Advanced Airborne Research Lidar (EAARL) system and surveys, see http://ngom.usgs.gov/dsp/overview/index.php and http://ngom.usgs.gov/dsp/tech/eaarl/index.php .本数据集为美国马里兰州与弗吉尼亚州境内阿萨蒂格岛国家海岸部分区域的数字高程模型（Digital Elevation Model, DEM），其数据来源于美国地质调查局（U.S. Geological Survey, USGS）与国家公园管理局（National Park Service, NPS）联合采集的遥感地理参考高程测量数据。2010年3月19日与24日，研究人员使用实验先进机载研究激光雷达（Experimental Advanced Airborne Research Lidar, EAARL）对该区域开展高程测量工作；该系统为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。系统通过航空器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接收反射激光信号时刻之间的时间差。航空器以约50米/秒的速度、300米左右的飞行高度飞越目标区域，由此形成约240米宽的激光扫描条带，平均点间距为2-3米。EAARL最初由美国国家航空航天局（National Aeronautics and Space Administration, NASA）在弗吉尼亚州瓦勒普斯飞行设施研发，其地面高程测量的垂直分辨率为±15厘米。当采样率达到3千赫兹及以上时，可生成极为密集的空间高程数据集；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。 如需了解激光雷达（Light Detection and Ranging, Lidar）科学、实验先进机载研究激光雷达（EAARL）系统及相关测绘的更多信息，请访问：http://ngom.usgs.gov/dsp/overview/index.php 与 http://ngom.usgs.gov/dsp/tech/eaarl/index.php。