空載光達雷射穿透率指數與柳杉林葉面積指數之關係探討

Relationship between the Airborne Laser Penetration Index and Leaf Area Index by LiDAR Data Analysis of a Sugi Plantation

彭炳勳(Bing-Syun Peng) ； 謝依達(Yi-Ta Hsieh) ； 陳朝圳(Chaur-Tzuhn Chen)

《台灣林業科學》 23卷S期 (2008/10) Pp. s63-s73

https://doi.org/10.7075/TJFS.200810.0006

摘要

本研究主要目的在了解柳杉林生長地區之葉面積指數資料及空載光達影像之雷射穿透率指數兩者間的關連性，探討由光達影像推估葉面積指數之最適網格大小並建立葉面積指數推估模式。於溪頭及阿里山地區共計取得27筆柳杉(Cryptomeria japonica D. Don)樣區的葉面積指數資料，由光達影像萃取不同網格大小(1~50 m)中的點雲數量比值以取得雷射穿透率指數，用於探討不同網格大小對計算葉面積指數的影響。研究結果得知，當空載光達點雲密度介於2~4 pts m^(-2)，由光達影像計算葉面積指數時，以重新分類後的地面點與冠層點最適於穿透率之計算，LiDAR-LAI的推估空間尺度則以35×35 平方公尺(R^2=0.572)為最高，顯示光達影像能用於林份冠層結構之偵測，其立體空間分布之特性能提供台灣林業之研究與應用。

關鍵字

空載光達系統 ； 雷射點雲穿透率 ； 葉面積指數

並列摘要

The aim of this study was to understand the relationship between the leaf area index (LAI) and airborne laser penetration index (LPI) of a Sugi (Cryptomeria japonica D. Don) plantation. In a balanced experiment based on 27 field plots located in the Chitou and Alishan areas of central Taiwan, the LAI was determined in the field using an LAI-2000 instrument. For LiDAR data, different data trap sizes were used to compute the LPI, and the range of the raster cell size was 1~50 m. This study explored the effect of different raster cell sizes for calculating the LAI. The results of this study indicated when the LiDAR point cloud density was about 2~4 point (pt) m^(-2) and we calculated the LAI using LiDAR data, we derived the LPI model (vegetation points/all points) to obtain the best results of R^2=0.572 with a 35×35-m cell size. Therefore, LiDAR data were useful for estimating the LAI. This provides a new remote-sensing technology for forestry investigations in Taiwan.

並列關鍵字

airborne laser scanning system ； laser penetration index ； leaf area index