EAARL Coastal Topography--Mississippi and Alabama Barrier Islands, Post-Hurricane Gustav, 2008

A digital elevation model (DEM) of a portion of the Mississippi and Alabama barrier islands, post-Hurricane Gustav (September 2008 hurricane), was produced from remotely sensed, geographically referenced elevation measurements cooperatively by the U.S. Geological Survey (USGS), the National Park Service (NPS), and the National Aeronautics and Space Administration (NASA). Elevation measurements were collected over the area 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 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 .

本数据集为2008年9月飓风古斯塔夫（Hurricane Gustav）过境后，美国密西西比州与阿拉巴马州部分障壁岛的数字高程模型（Digital Elevation Model，DEM），由美国地质调查局（U.S. Geological Survey，USGS）、国家公园管理局（National Park Service，NPS）与美国国家航空航天局（National Aeronautics and Space Administration，NASA）合作，基于遥感地理参考高程测量数据制作完成。

研究团队采用实验型先进机载研究激光雷达（Experimental Advanced Airborne Research Lidar，EAARL）采集该区域的高程数据：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，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，以此反演得到高程信息。

航空器以约300米的飞行高度、约50米每秒的航速飞越目标区域，可形成宽度约240米的激光扫描带，平均点间距为2至3米。EAARL最初由美国国家航空航天局弗吉尼亚州沃洛普斯飞行设施（Wallops Flight Facility）研发，其地面高程测量的垂直分辨率可达±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。当对区域后续高程地图进行分析时，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、实验型先进机载研究激光雷达系统及其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。