EAARL Topography-Vicksburg National Millitary Park 2008: Bare Earth

A bare earth elevation map (also known as a Digital Elevation Model, or DEM) of the Vicksburg National Military Park in Mississippi was produced from remotely sensed, geographically referenced elevation measurements cooperatively by the U.S. Geological Survey (USGS), National Park Service (NPS), and 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 easily surveyed within a 3- to 4-hour mission. When subsequent elevation maps for an area are analyzed, they provide resource managers with a useful tool 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, 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，生成了密西西比州维克斯堡国家军事公园的裸地高程地图（亦称为数字高程模型，Digital Elevation Model, DEM）。该团队使用美国国家航空航天局实验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——这是一款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。该系统通过飞机机身底部的开口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。作业飞机以约50米/秒的航速，在约300米的飞行高度飞越目标区域。由美国国家航空航天局位于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（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100公里海岸线的测绘作业。对某一区域的后续高程地图进行分析后，可为资源管理者提供关于土地开发的实用辅助工具。

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