應用空載光達資料推測林木樹高與葉面積指數

Estimating Tree Heights and Leaf Area Index Using Airborne LiDAR Data

彭炳勳(Bing-Syun Peng) ； 陳朝圳(Chaur-Tzuhn Chen)

《航測及遙測學刊》 13卷2期 (2008/06) Pp. 85-100

https://doi.org/10.6574/JPRS.2008.13(2).2

摘要

空載雷射掃瞄系統（又稱光達系統）為近年新發展的遙測技術，林業研究上，光達系統已被證實適用於林木資源、生物量、冠層立體空間繪製，並且能誘導出單木層級的資料，包括單株立木位置及樹高等。本研究以阿里山地區立木基礎資訊以及溪頭與阿里山地區之葉面積指數資料，探討空載光達在單株立木高、林分高與葉面積指數之測量正確性與建立推估模式。結果顯示，研究區域63.21%之立木樹高相對誤差在20%以內，32.72%的立木樹高誤差絕對值在2m以內，平均林分高推估以樹冠高度模型為3m時，以15m × 15m 的林分面積，能獲取最佳之相關性(R2=0.979)；當點雲密度介於2-4ptsm^(-2)，由光達計算葉面積指數時，以15m × 15m (R2=0.993)為最高，顯示空載光達影像能有效用於葉面積指數之推估，為台灣林業研究提供一項新的遙測資訊。

關鍵字

空載光達系統 ； 雷射點雲穿透率 ； 林分結構 ； 葉面積指數

並列摘要

Airborne light detection and ranging (LiDAR) is an active remote sensing technique, which sends pulses of laser light toward the ground and detects the return times of back-scattered energy in order to determine ranges of the surface. The suitability of LiDAR in forestry is demonstrated by application such as assessment of timber resources and biomass, quantification of 3D canopy structures, as well as derivation of single trees properties like individual tree positions and tree height. In this study, we used the single tree height data was investigated in the Alishan area and LAI data was investigated in the Chitou and Alishan area, and use airborne LiDAR data to measured mean tree height, analyze the relationship between LAI and Laser Penetration Index (LPI) suitable raster cell size and estimation model.
The results of the study indicated that the laser single tree height overestimates the ground truth tree height, especially in compression tree. The laser mean height is computed as the arithmetic mean of the largest laser values within grid size of 15m, and the results was R2=0.993. The results was R2=0.979 when the LiDAR raster grid size was 15 × 15m 2. Therefore, LiDAR data is useful to estimate the LAI. The estimate map of LAI was obtained according to the results of regression analysis, and it can be found that the LiDAR point cloud of three-dimensional structure made the LAI values between forested region and non-forested region had significant differences. It shows that the LiDAR data have better detection ability for the forest canopy. It provides a new remote sensing technique for forestry investigation in Taiwan.

並列關鍵字

Airborne Laser Scanning System ； Laser Penetration Index ； Stand Structure ； Leaf Area Index