Laboratoire de Météorologie Dynamique-IPSL/École Polytechnique, 91128 Palaiseau, France.
Sensors (Basel). 2010;10(8):7386-403. doi: 10.3390/s100807386. Epub 2010 Aug 6.
We have developed a new airborne UV lidar for the forest canopy and deployed it in the Landes forest (France). It is the first one that: (i) operates at 355 nm for emitting energetic pulses of 16 mJ at 20 Hz while fulfilling eye-safety regulations and (ii) is flown onboard an ultra-light airplane for enhanced flight flexibility. Laser footprints at ground level were 2.4 m wide for a flying altitude of 300 m. Three test areas of ≈ 500 × 500 m(2) with Maritime pines of different ages were investigated. We used a threshold method adapted for this lidar to accurately extract from its waveforms detailed forest canopy vertical structure: canopy top, tree crown base and undergrowth heights. Good detection sensitivity enabled the observation of ground returns underneath the trees. Statistical and one-to-one comparisons with ground measurements by field foresters indicated a mean absolute accuracy of ≈ 1 m. Sensitivity tests on detection threshold showed the importance of signal to noise ratio and footprint size for a proper detection of the canopy vertical structure. This UV-lidar is intended for future innovative applications of simultaneous observation of forest canopy, laser-induced vegetation fluorescence and atmospheric aerosols.
我们开发了一种新的机载紫外激光雷达，用于森林冠层，并在朗德森林（法国）进行了部署。它是第一个：（i）在 355nm 下工作，以 20Hz 的频率发射 16mJ 的高能脉冲，同时满足眼部安全规定，（ii）搭载超轻飞机，以提高飞行灵活性。在 300m 的飞行高度上，激光在地面的足迹宽 2.4m。我们对三个约 500×500m(2)的试验区进行了调查，这些试验区内有不同年龄的滨海松。我们使用了一种适用于该激光雷达的阈值方法，从其波形中准确提取详细的森林冠层垂直结构：冠层顶部、树冠底部和林下高度。良好的探测灵敏度使得可以观察到树冠下的地面回波。与地面林业测量员的地面测量进行的统计和一对一比较表明，平均绝对精度约为 1m。探测阈值的灵敏度测试表明，信噪比和足迹大小对于正确探测冠层垂直结构非常重要。这种紫外激光雷达旨在用于未来同时观测森林冠层、激光诱导植被荧光和大气气溶胶的创新应用。
