EAARL Coastal Topography--Cape Cod National Seashore, Massachusetts, 2002: First Surface

ASCII XYZ point cloud data were 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 Cape Cod 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.

ASCII XYZ点云数据由美国地质调查局（U.S. Geological Survey, USGS）与国家公园管理局（National Park Service, NPS）合作采集的遥感地理参考高程测量数据生成。本次高程数据采集覆盖科德角国家海岸，采用的是初代美国国家航空航天局（National Aeronautics and Space Administration, NASA）实验先进机载研究激光雷达（Experimental Advanced Airborne Research Lidar, EAARL）——该系统为安装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向地球表面发射高频激光束，机载激光系统会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60米/秒的飞行速度、约300米的飞行高度飞越目标区域，由此形成宽度约240米的激光扫描条带，平均点间距为2至3米。EAARL最初由美国国家航空航天局位于弗吉尼亚州的沃洛普斯飞行设施（Wallops Flight Facility）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（kHz）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。对某一区域生成的最终高程地图进行分析时，该数据集可作为土地开发相关管理决策的实用辅助工具。