EAARL Topography-Fire Island National Seaashore

A first return elevation map (also known as a Digital Elevation Model or DEM) of Fire Island National Seashore was produced from remotely-sensed, geographically-referenced elevation measurements in cooperation with the U.S. Geological Survey (USGS), National Air and Space Administration (NASA), and the National Park Service (NPS). Elevation measurements were collected over the area using the 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 50 meters per second at an elevation of approximately 300 m. The EAARL, developed by NASA at Wallops Flight Facility in Virginia, measures ground elevation with a vertical resolution of 15 centimeters. A sampling rate of 3 kHz or higher results in an extremely dense spatial elevation data set. Over 100 kilometers of coastline can be easily surveyed within a 3- to 4-hour mission time period. When subsequent 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 .

本数据集为美国火岛国家海岸（Fire Island National Seashore）的首次回波高程图（亦称为数字高程模型（Digital Elevation Model，DEM）），由美国地质调查局（U.S. Geological Survey，USGS）、美国国家航空航天局（National Air and Space Administration，NASA）以及美国国家公园管理局（National Park Service，NPS）合作，基于遥感地理参考高程测量数据生成。

研究团队采用美国国家航空航天局实验先进机载研究激光雷达（NASA Experimental Advanced Airborne Research Lidar，EAARL）采集该区域高程数据：该系统为搭载于航空器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。系统通过航空器机身底部的开口向地表发射高频激光束，记录激光束发射与机载接收反射激光信号之间的时间差。作业时，航空器以约50米/秒的速度飞越目标区域，飞行高度约300米。

由美国国家航空航天局弗吉尼亚州沃洛普斯飞行设施（Wallops Flight Facility）研发的EAARL，其地面高程测量垂直分辨率可达15厘米。当采样率达到3千赫兹（kHz）或更高时，可生成密度极高的空间高程数据集。单次任务时长3至4小时，即可完成超100公里海岸线的测绘作业。当对某一区域的后续高程图开展分析时，该数据集可作为土地开发管理决策的有效辅助工具。

如需了解更多激光雷达科学、实验先进机载研究激光雷达系统及相关测绘作业的信息，请访问http://ngom.usgs.gov/dsp/overview/index.php 与http://ngom.usgs.gov/dsp/tech/eaarl/index.php。