EAARL Coastal Topography--Central Wetlands, Louisiana, 2010

A digital elevation model (DEM) of a portion of the Central Wetlands, Louisiana was produced from remotely sensed, geographically referenced elevation measurements by the U.S. Geological Survey (USGS). Elevation measurements were collected over the area on March 4 and 5, 2010, 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 the National Aeronautics and Space Administration (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 resultant elevation maps for an area are analyzed, they provide a useful tool to make management decisions regarding land development. The Central Wetlands data provided represent the last return pulses and were processed and filtered for bare-earth topography. The difference in water levels between data collections on March 4 and 5 resulted in elevation variations in the merged data.

美国地质调查局（U.S. Geological Survey，USGS）依托遥感地理参考高程测量数据，制作了路易斯安那州中部湿地部分区域的数字高程模型（digital elevation model，DEM）。2010年3月4日至5日，该机构使用实验性先进机载研究激光雷达（Experimental Advanced Airborne Research Lidar，EAARL）完成了该区域的高程数据采集——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向地球表面发射高频激光束，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。作业时，飞机以约50米/秒的速度在约300米高度飞越目标区域，可形成约240米宽的激光条带，平均点间距为2至3米。实验性先进机载研究激光雷达最初由美国国家航空航天局（National Aeronautics and Space Administration，NASA）在弗吉尼亚州沃洛普斯飞行设施研发，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公里海岸线的测绘工作。对生成的区域高程图进行分析后，可作为土地开发管理决策的实用辅助工具。本次提供的中部湿地数据为最后返回脉冲，并经过裸土地形的处理与滤波。由于2010年3月4日与5日的数据采集期间存在水位差异，合并后的数据集存在高程变化。