用机载激光测高仪对单木树冠进行自动提取和轮廓描绘,是获取森林信息的一种快速有效的方法。机 载激光测高仪可通过记录回波波形来描绘单树植被冠盖 等细节信息,但由于激光足印较小,很难给出树木种群的细节尺度参数,如树的冠盖大小、树径等。提出 把若干小激光足印复合成大激光足印的方法, 并通过高斯分解算法导出植被冠层高度、植被冠层反射率和中值能量高度等大尺度参数。实验结果表 明,通过把固定数量的小光斑激光足印复合成一个大光斑 激光足印的方法,能反演出更多的单树外围尺度参数,为植被垂直结构分析提供更多的可靠保证。

Automatic extraction and delineation of individual tree crown using airborne laser altimeter is an effective method to obtain forest information. The airborne laser altimeter can describe characterization of vegetation canopy structure by recording the time history of the return waveform within a small footprint for each laser pulse, but difficult to give out the large canopy metrics, like the canopy size and stem diameter. A collection of individual waveforms combined within a synthesized large footprint was used, through Gaussian decomposition of laser altimeter waveforms, to define three metrics: canopy height, canopy reflection ratio, and height of median energy. All three metrics were tested for reproducibility, the results show that combining several individual small-footprint laser pulses to define a composite “large-footprint” waveform is a possible method to depict the vertical structure of a vegetation canopy.