EAARL Coastal Topography--Eastern Florida, Post-Hurricane Frances, 2004: Bare Earth

A bare-earth digital elevation map (also known as a Digital Elevation Model, or DEM) of a portion of the eastern Florida coastline was produced from remotely sensed, geographically referenced elevation measurements cooperatively by the U.S. Geological Survey (USGS) and the National Aeronautics and Space Administration (NASA). 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 meters. 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 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 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 .

美国地质调查局（U.S. Geological Survey，简称USGS）与美国国家航空航天局（National Aeronautics and Space Administration，简称NASA）合作，基于遥感地理参考高程测量数据，制作了佛罗里达州东部海岸线部分区域的裸地数字高程图（亦称数字高程模型，Digital Elevation Model，简称DEM）。研究团队使用美国国家航空航天局的实验型先进机载研究激光雷达（Experimental Advanced Airborne Research Lidar，简称EAARL）在该区域采集高程数据，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孔，将高频激光束投射至地球表面，并记录激光束发射与机载接收反射激光信号之间的时间差。航空器以约300米的飞行高度、每秒约50米的速度飞越目标区域。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的EAARL，其地面高程测量的垂直分辨率可达±15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。对某一区域的后续高程图进行分析后，可作为土地开发相关管理决策的有效辅助工具。

如需了解更多关于激光雷达科学、实验型先进机载研究激光雷达（EAARL）系统及测绘作业的相关信息，请访问：http://ngom.usgs.gov/dsp/overview/index.php 与 http://ngom.usgs.gov/dsp/tech/eaarl/index.php。