Ecosystem structure (DP3.30015.001)

Forests store and sequester a considerable proportion of the terrestrial global carbon budget. Forest canopy metrics are directly measurable with LiDAR sensors because laser pulses will be reflected from the uppermost canopy layers and remaining energy will penetrate to, and reflect from, under-story and the ground surface. The near simultaneous direct measurement of ground and canopy elevation allows the canopy height to be estimated through differencing. The CHM is generated by creating a continuous surface of canopy height estimates across the entire spatial domain of the LiDAR survey. The CHM is derived directly from the LiDAR point cloud. To produce the CHM, the point cloud is separated into classes representing the ground and vegetation returns. The ground classified points allow calculation of a height normalized point cloud to provide a relative estimate of vegetation elevation. A surface is then generated using the height normalized vegetation points to produce the CHM. For data collected with the Optech Gemini sensor, any canopy heights less than 2m are set to zero. For data collected with the Optech Galaxy or Riegl Q780 sensor, any canopy heights less than 0.7 m are set to zero.

Latency:
AOP data will be available 60 days after the final collection day at a site.

森林储存并固存了全球陆地碳收支中相当可观的一部分份额。森林冠层参数可通过激光雷达（LiDAR）传感器直接获取：激光脉冲会从最上层冠层反射，剩余能量则穿透冠层后，于林下植被及地表发生反射。对地表与冠层高程的近乎同步直接测量，可通过差值运算实现冠层高度的估算。冠层高度模型（CHM）直接源自激光雷达点云，其生成方式为在激光雷达测绘的全空间范围内构建连续的冠层高度估算表面。为生成冠层高度模型，需将点云划分为地表回波与植被回波两类；经分类的地表点云可用于计算高度归一化点云，以此得到植被高程的相对估算值，随后利用该高度归一化的植被点云生成表面，即可得到冠层高度模型。针对使用Optech Gemini传感器采集的数据，所有低于2米的冠层高度将被置零；针对使用Optech Galaxy或Riegl Q780传感器采集的数据，所有低于0.7米的冠层高度将被置零。
延迟说明：各站点的AOP数据将在该站点最终采集日起60天后对外提供。