應用地面雷射掃描儀測算樹高之研究

A Study on Estimating Tree Heights from Terrestrial Laser Scanner Data

陳永寬(Yeong-Kuan Chen) ； 詹進發(Jihn-Fa Jan) ； 葉堃生(Kuen-Sheng Yeh) ； 鄭祈全(Chi-Chuan Cheng) ； 施瑩瑄(Ying-Hsuan Shih)

《航測及遙測學刊》 10卷4期 (2005/12) Pp. 327-336

https://doi.org/10.6574/JPRS.2005.10(4).2

摘要

應用空載光達(Airborne Lidar)在台灣密林地區進行點雲掃描蒐集，常因樹冠或地被植物覆蓋過密，阻擋光束進行而無法獲得足夠地表點雲資料，造成樹高估算偏誤。本研究選定陽明山區一針、闊葉樹混交林地，應用地面雷射掃描儀(Terrestrial Laser Scanner)於林下進行點雲掃描蒐集，實測立木位置與樹高，經點雲過濾、立木中心點搜尋等程序，自動估算樹高，並評估其準確度。結果發現，直立生長之優勢木，可簡易以最高點雲高程減去最低點雲高程，其差值即可正確推估樹高，誤差不超過全株實長之5%；但是被壓木或是不直立生長之林木樹高之推估成果則不盡理想，樹高推估之演算法有待改進。本研究亦發現，試區現場密集掃描之點雲，詳細記錄林地、林木、植被、樹冠、枝條、樹幹等，可轉算出地理座標，並進行三維展示。筆者等將進一步研發適當演算式，用以切取樹幹剖面、量度胸高直徑、分析枝梢率、量測樹冠直徑、估算地上部生物量等。

關鍵字

地面雷射掃描儀 ； 地面光達 ； 三維影像掃描儀 ； 空載光達 ； 樹高估算

並列摘要

The objective of this study was to estimate tree heights from point clouds scanned by a terrestrial laser scanner over a dense forest where the airborne lidar can not obtain enough ground return points. A 50m×50m sample plot was chosen in Yangminshan National Park where is located in northern Taiwan, and point clouds were then collected by utilizing Leica HDS3000 terrestrial laser scanner. Coordinates of each tree were surveyed by a total station and tree heights were estimated by subtract local minimum elevation from local maximum elevation by searching the point clouds within a specified radius at each surveyed tree location. True heights of trees in the sample plot were manually measured and were compared to the estimated tree heights. The result shows that the heights of dominate trees growing erectly can be estimated by simply subtracting the minimum elevation from maximum elevation, and the correctness of estimation are within 5% of the surveyed height, but results in other situations were not perform well. Other algorithm for point searching and tree height estimation must be then developed.

並列關鍵字

terrestrial laser scanner ； terrestrial lidar ； 3D image scanner ； Airborne Lidar ； tree height estimation