臺灣博碩士論文加值系統

台灣的森林占了本島一半以上的土地面積，其中蘊藏了豐富的生物資源，為了能有效的進行林分結構的量測來掌控森林生態系的變化，利用航遙測技術來獲取大範圍的森林資訊為目前的主要的趨勢。空載光達系統具有直接獲取高精度三維坐標的點雲以及部分穿透的特性，應用在森林中可達到快速量測林分結構的三維空間資訊，能得到在垂直方向的冠層高度以及樹冠密度變化，因此可用來估計樹冠高度模型(Canopy Height Model, CHM)和葉面積指數(Leaf Area Index, LAI)。因此，本研究主要目的是探討如何應用空載光達資料估計森林地區之樹冠高度模型和葉面積指數。
應用空載光達資料產製數值高程模型(Digital Elevation Model, DEM)及數值表面模型(Digital Surface Model, DSM)是目前成熟的空載光達資料處理程序，將DSM減DEM即可獲得CHM。而LAI的估計則透過雷射光(對樹冠層的)穿透率(LPI)之估算來推估，本研究採用五種LPI計算方法來估計LAI，並將成果與現地觀測得的資料進行迴歸分析，以驗證實驗成果。實驗區位在台灣東南部森林區範圍，採用三種全波形空載光達系統所得到的多重回波點雲和全波形點雲，共六種不同組合的點雲資料，分別進行樹冠高度模型和葉面積指數的估計，並進行成果之比較。其中，全波形點雲是利用小波為基礎的萃取方式，從光達儀器記錄的連續反射波形資訊中獲取而得，主要是希望透過波形中隱含的物理特性，萃取出較完整的點雲來代表森林結構。
經由研究成果發現，利用六種點雲資料在製作森林樹冠高度模型中最大的標準偏差約在1.5公尺左右，主要是在森林表面高度落差較大的地方有明顯的差異。而在葉面積指數估計方面，是利用離散的點雲計算出五種穿透率指標 : (1)地面點占全部點的比例; (2)地面點強度值和全部點強度值的比例；(3)地面點與所有雷射光束的比值；(4)改良自(1)的穿透率指標，增加對單一回波地面點的加權；(5)以全波形資料計算的雷射光照射地物間面積與非地面的面積比。再將各種穿透率指標，與使用LAI-2000於現地測得的葉面積指數進行迴歸比較。實驗成果顯示，使用經改良後的第四種穿透率指標對於葉面積指數有最佳的解釋能力。而相較於即時解算的多重回波點雲，使用全波形的光達點雲穿透率指標，可提升對LAI的估計，R2達到0.8以上。

Efficiently obtaining the information in forest region such as forest structure, forest ecosystems is important for forestry management. Remote sensing has been considered as a practical technology to acquire the data of a large area. Compared with spectral images, airborne light detection and ranging (LiDAR) can provide three dimensional coordinates directly, and the penetration characteristics of LiDAR system makes the possibility of seeing through the canopy. Therefore, the structure or the terrain under the canopy can be characterized by the LiDAR point cloud data.
The purpose of this study is to estimate the Canopy Height Model (CHM) and the Leave Area Index (LAI) of a dense forest area by using airborne LiDAR data. CHM is estimated by taking the difference of DSM and DEM derived from LiDAR data. Estimation of LAI is achieved based on the calculation of Laser Penetration Index (LPI). Five calculations of LPI were applied in this paper: (1.) The ratio between the number of ground points and that of all the points; (2.) the ratio between the intensities of ground points and that of all the points; (3) the ratio between the number of ground points and the number of laser beams; (4) a weighting method modified from index (1); and (5) the ratio between the area of ground points and that of all the points.
The study area is in a nature broadleaf forest of south Taiwan. In this study, we use three sets of airborne LiDAR data acquired with different full waveform LiDAR systems including Leica ALS60, Riegl LMS-Q680i and Optech Pegasus HD400. All of these LiDAR systems are capable of recording full waveform data, then we can get the waveform point clouds by the echo detector to do the comparison. Our experiments results show that the accuracy of CHM by different LiDAR data is about 1.5 meter. And the fourth LPI index has the highest coefficient of determination (about 0.8) and the estimation of LAI can be improved by using the waveform points.

摘要 I
Abstract II
致謝 III
目錄 IV
表目錄 VI
圖目錄 VII
第一章 緒論 1
1.1前言 1
1.2研究動機與目的 2
1.3研究方法與流程 4
1.4論文架構 5
第二章 森林樹冠高度模型及葉面積指數 7
2.1 樹冠高度模型(CHM) 7
2.2 葉面積指數(LAI) 8
2.2.1定義及意義 8
2.2.2 LAI估計方法 9
第三章 空載光達系統 14
3.1 系統原理 14
3.2 光達點雲資料性質 15
3.3 全波形光達系統 16
3.3.1 全波形資料性質 16
3.3.2 全波形響應偵測 17
3.3.3 全波形點雲 18
3.4 光達點雲資料處理 19
3.4.1 數值高程模型(DEM) 20
3.4.2 數值表面模型(DSM) 21
3.4.3 點雲穿透率 22
第四章 樹冠高度模型和葉面積指數的估計 23
4.1 樹冠高度模型估計 23
4.2 葉面積指數估計 25
4.2.1計算穿透率指標 26
4.2.2尋找最適合計算範圍 28
4.2.3葉面積指數的迴歸模式和評估方式 29
第五章 實驗成果與分析 31
5.1實驗資料 31
5.1.1實驗區域 31
5.1.2光達資料 32
5.1.3現地觀測資料 34
5.2樹冠高度模型成果分析 35
5.2.1單一光達資料之分析 36
5.2.2多種光達資料之分析 40
5.3葉面積指數估計成果分析 44
第六章 結論及建議 52
參考文獻 54
附錄 57
附錄一 空載光達點雲製作的DEM、DEM、CHM 57
附錄二 空載光達穿透率指標推估葉面積的直線迴歸模式 64

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