ENGLISH

20卷/4期

20卷/4期

華藝線上圖書館

Pages:

231-250

論文名稱

光達技術應用於人工林之經營與監測

Title

Application of LiDAR System for Monitoring and Management of Artificial Forest

作者

魏浚紘, 陳朝圳

Author

Chun-Hung Wei, Chaur-Tzuhn Chen

中文摘要

本研究利用地面光達探討如何以非破壞性方式,調查及監測森林樣區之立木三度空間資訊,及如何應用光達系統所量測之資訊應用於人工林經營。以自動化方式獲取疏伐作業所需之林分性態值資料,包括樹高、胸高直徑、樹冠高、立木位置圖等資料,並評估地面光達於人工林測計之可行性。結果顯示,透過地面光達系統確實可正確獲得立木資訊,對於永久監測樣區而言,以光達系統之不同拍攝位置,可消除掃瞄的遮蔽效應,藉由高密度的點雲資料,可直接測量立木樹高與不同樹幹位置之直徑,而單位體積之點雲資料量不同,會影響立木直徑推估之結果。而地面光達所獲得之樹高與樹徑之3D資料,可進行非破壞性之區分材積估算,並建立立木材積式。光達點雲資料之空間分布,所推估之樹冠高程模型,以樹冠高度之灰階值統計,藉由二值法所訂之閥值,可將林木與地表背景分離,獲取林冠孔隙之平面及垂直資料,此一林冠孔隙資訊可供為孔隙動態監測研究。地面光達所建立之林木測計、立木競爭指標、林冠孔隙及與疏伐監測資訊,可更準確的量化疏伐效益及增加林木狀態變化之資訊,對於人工林經營可提高森林資源調查效率,及擴充森林資源監測資訊。

Abstract

In this study, using 3D scanning Light Detection and Ranging (LiDAR) systems, which are the non-destructive methods, to investigate and monitor individual trees in artificial forest sample areas. Using ground-based LiDAR and traditional field survey data to obtain individual tree characteristic values which included tree height, diameter at breast height, canopy height, tree location map and evaluated the feasibility of ground-based LiDAR data in artificial forest areas. Results showed that the accurate information from the ground-based LiDAR system in permanent sampling plots, and different scanning stations could decrease occlusions. By using high density point cloud data, the height and diameter at different height of the tree could also be measured directly by the LiDAR systems. Different number of point cloud affected the accuracy of diameter. Results also showed that the systems could establish tree volume model non-destructively with tree height and DBH data obtained from ground-based LiDAR. Using threshold value to classify gap fraction, results showed that were accurate. Therefore, the results could be used to analyze the horizontal and vertical canopy structure, it was beneficial for the monitoring of plot dynamics in forest areas. Ground-based LiDAR could be used to determine tree measurements, tree competition and canopy gap which solve the problems of quantification and spatial research and also help with the stimulation of thinning operations. Results of this study were beneficial to artificial forest management and improved the forest resource inventory methods.

關鍵字

森林經營、疏伐作業、地面光達、三維雷射掃瞄、林分性態

Keywords

forest management, thinning operations, ground-based LiDAR technology, 3D laser scanning, stand characteristics

附件檔名

華芸線上圖書館

N / A

備註說明

N / A

Pages:

251-262

論文名稱

評估台灣常綠闊葉森林之衛星影像植生指標與空載光達穿透率之相關性

Title

Assessment of the Relationship between Satellite-Derived Vegetation Index and Lidar-Based Laser Penetration Index in Evergreen Broadleaf Forest

作者

李崇誠, 王驥魁, 洪子敏, 吳坤真

Author

Chung-Cheng Lee, Chi-Kuei Wang, Tzu-Min Hong, Kun-Jen Wu

中文摘要

由於空載光達系統其雷射光會穿透森林樹冠層到達地表,植生的密度會影響到穿透率程度之大小,而穿透率的推估方式為統計雷射光穿透森林冠層到達地面之比率,故穿透率越高所獲得的地面點相對增加,對於DEM產製有高度的影響,然穿透率屬於執行飛航任務事後獲得的資訊,本研究目的探討衛星影像植生指標與空載光達穿透率之關係,主要目的為提供光達掃瞄規劃之參考,在森林植生覆蓋度高的區域,可以增加入射森林之雷射光能量的方式來提升穿透率。本研究總共測試台灣南北兩個光達樣區,分別為北部金山的火山樣區與南部曾文水庫樣區,掃瞄面積分別為36km2與21km2,並取得Fomosat-2、SPOT-5、Worldview-2與GeoEye共7幅衛星影像,分別計算4種植生指標(NDVI、RVI、PVI與SAVI),拍攝時間與空載光達掃瞄時間相近,結果顯示衛星影像需經過大氣糾正處理消除水氣和地形之影響因子,並以Pearson相關性檢定其植生指標與穿透率之相關,結果為兩指數有顯著負相關性,表示當穿透率越高時植生指標相對減少,並以線性回歸探討兩者之關係,其R2值均高於0.8以上,代表衛星影像植生指標與空載光達穿透率有程度上之相關。

Abstract

The forest canopy affects the laser penetration rate of airborne LiDAR system (ALS). The denser the forest canopy, the higher the laser penetration rate, and vice versa. For an ALS survey project, with the goal to acquire sufficient ground surface points, the flight planning should be conducted according to the distribution forest canopy thickness. The information of forest canopy can be easily accessed via the satellite-derived vegetation index. In this study, we examined the correction relationship between the satellite-derived vegetation index and laser penetration index (LPI). The study area was 21 km2 located in Tseng-Wen Reservoir and 36 km2 located in Jin-Shan volcanic region. The ALS data were collected with an Optech HD400 instrument. The LPI is the ratio between the total number of laser pulses reaching at the ground surface and the total number of transmitted laser pulses. The vegetation indices were calculated from Formsat-2, SPOT-5, WorldView2 and GeoEye, all of which were acquired near the time of ALS data acquisition. This study calculated four vegetation indices, i.e., NDVI, RVI, PVI, and SAVI. The effect of atmospheric correction (conducted by ATCOR-3) were also discussed. The results show high linear correlation between LPI and LAI.

關鍵字

空載光達、森林穿透率、大氣糾正、衛星影像植生指標

Keywords

airborne LiDAR, laser penetration index of forest, atmospheric correction, satellite-derived vegetation index

附件檔名

華芸線上圖書館

N / A

備註說明

N / A

Pages:

263-277

論文名稱

地形計測方法應用於潛在大規模崩塌之判釋

Title

Potential Catastrophic Landslides Mapping by Using Geomorphometric analysis

作者

謝有忠, 侯進雄, 胡植慶, 費立沅, 陳宏仁, 邱禎龍, 詹瑜璋

Author

Yu-Chung Hsieh, Chin-Shyong Hou, Jyr-Ching Hu, Li-Yuan Fei, Hung-Jen Chen, Cheng-Lung Chiu, Yu-Chang Chan

中文摘要

莫拉克風災後,針對大規模崩塌的研究顯得刻不容緩。本研究利用中央地質調查所現有之1米數值地形資料,有別於傳統判釋方法,空載光達資料更能應用於坡地災害的分析。本研究以不同之地形計測方法來進行資料分析,其中透過融合坡度、地形陰影、地形開闊度等方法之結果,可以突顯細微地形特徵或變化處,此法不僅可提升崩塌地特徵之判釋速度,也能減少人為誤判而有效找出潛在大規模崩塌的位置,確實對潛在大規模崩塌的判釋和調查有很大的助益。未來搭配後續調查研究,進一步探討坡面地質災害的可能成因和規模或影響範圍,可為現今防救災策略上必需的重要資訊。

Abstract

Extreme weather events have induced more frequent geological hazards in Taiwan. The heavy rainfall brought by the Typhoon Morakot has triggered a large amount of landslides including the Xiaolin village which was demolished by a catastrophic Landslides. The study of such catastrophic landslides is urgently needed. It is considered that the creep phase of a landslides is a preparatory stage of progressive failure and gives enough signals before turning into a catastrophic landslides. This study used high-resolution airborne LiDAR-derived DEM data from the Central Geological Survey, MOEA. We used different geomorphometric analyses to process the high resolution and high accuracy DEM data including the hillshade, aspect, slope, eigenvalue ratio & openness. Among these geomorphometric analyses, which to converged openness, slope and hillshade method of the results, the capacity to discuss the possible cause and the influence analysis of the catastrophic Landslides in view of the slight terrain features has increased drastically through DEM processing. Our results indicate that over hundreds potential catastrophic landslides may present in southern Taiwan after the Typhoon Morakot event. The quantitative methods used in this study highlight the terrain features of the creep phase of catastrophic landslides and is helpful for landslide feature interpretation and hazard assessment.

關鍵字

數值地形模型、空載光達、地形測計學、大規模崩塌、自然災害

Keywords

airborne LiDAR, DEM, catastrophic landslides, Geomorphometry, natural hazard

附件檔名

華芸線上圖書館

N / A

備註說明

N / A

Pages:

279-299

論文名稱

應用空載光達資料自動化萃取建物邊界線

Title

Automatic Building Boundary Extraction From Airborne LiDAR Data

作者

洪曉竹, 曾義星, 朱宏杰

Author

Hsiao-Chu Hung, Yi-Hsing Tseng, Hone-Jay Chu

中文摘要

建物邊界線乃二維與三維圖資中重要的地物空間資訊,目前仍以航測立體測繪方式產製為主,產製效率不高。空載光達提供地物表面密佈的三維取樣點雲,隱含豐富的地物幾何特徵及三維空間資訊。理論上可從光達點雲萃取出屋頂面與牆面特徵,取其交會線特徵獲得建物邊界線,但空載光達點雲分佈於牆面的點通常較稀疏,不易萃取牆面特徵,以獲得建物邊界線。此外,由於屋頂面的附屬結構使得點雲分佈更雜亂,常使萃取得的邊界線特徵不連貫。本文針對上述課題提出自動化萃取建物邊界線之程序,演算法包含兩步驟,第一步驟是萃取三維平面點雲與邊界點偵測,結合多重回訊點,先獲得邊界線的候選點雲;第二步驟是透過Hough transform、直線擬合與線段分割等步驟萃取邊界線段。本研究選出十棟不同類型的建物進行測試,檢視邊界線萃取方法的成功率及效能,與現有地形圖比較之量化評估成果顯示,約70%的建物邊界線可被正確萃取出來,對屋頂結構線的正確萃取率也約可達85%,顯示出本研究所提出之演算法,對於從空載光達點雲資料萃取建物邊界線及結構線是有成效的。所萃取之建物邊界線及結構線乃三維建物模型重建的基本資料元素。

Abstract

Building boundary is one of the important components for the mapping of 2D digital topographic maps and the modeling of 3D city buildings. Photogrammetry is currently the common technique applied for building boundary generation,which are labor intensive. Airborne LiDAR data provides abundant3Dinformation of the scanned objects.The characteristics of objects are implicitly contained in the data set. Usually top surfaces, such as roofs, may have densely distributed points, but vertical surfaces, such as walls, usually have sparsely distributed points or even no points. Building boundaries, referring to the intersections of roof and wall planes are, therefore, not clearly defined in point clouds.To overcome this problem, this paper develops an algorithm to acquire building boundary from airborne LiDAR data. Threemajor process steps are included in the algorithm. Firstly the point clouds are classified as building points and non-building points. Then, octree-based split-and-merge segmentation is implemented to extract plane features.Second, those building points and coplanar points are used to trace the boundary points by concave-hull algorithm. Boundary points of coplanar point group and building points and the first and intermediate echo points of multi-return scan are selected as candidates of building boundary points. Finally, methods of the Hough transform, line fitting and line segmentation are applied to find line segments belonging to building boundaries. The experiment results show the effectiveness of the proposed method for automatic building boundary extraction from airborne LiDAR data, and that combining the information of the first and intermediate echo points of multi-return and the boundary points increases the completeness of boundaries. And, it is promising to use the extracted boundaries for 3D building modeling in the future.

關鍵字

空載光達、點雲、建物邊界萃取、建物模型重建

Keywords

airborne LiDAR, point cloud, building boundary extraction, 3D building reconstruction

附件檔名

華芸線上圖書館

N / A

備註說明

N / A

Pages:

301-316

論文名稱

利用衛星影像探討龜山島周圍海域熱液與地震的關係

Title

The Relationship between the Volcanic Activity and the Plume in Guishan Island with Satellite Image

作者

李聿文, 張中白, 任玄

Author

Yu-Wen Li, Chung-Pai Chang, Hsuan Ren

中文摘要

龜山島的後火山活動包含熱液和地震,熱液變化可能反應出活動的劇烈程度,所以本研究將地震當作活動指標,比對熱液變化與地震,借此得出熱液變化與火山活動之間的關係。龜山島東側的熱液因含有硫,顏色與周圍海水不同可被衛星影像偵測,衛星影像分析有三個的步驟:(1)去除陸地的千擾;(2)去除雲的干擾;(3)進行影像分類。分類出熱液後,使用相關係數與前後發生的地震比對,共有四種方式(1)熱液面積與地震數量;(2)熱液面積與地震規模;(3)熱液量與地震數量;(4)熱液量與地震規模。結果顯示熱液面積與前後1天和2天有較大的相關,且相較於前幾天的地震,後幾天發生的地震與熱液面積的關聯較大。

Abstract

Guishan Island is located at north eastern Taiwan belongs to Yilan County. According to geophysical and geochemical studies, it is an active volcano, and the latest eruption occurred in the Holocene (7 ka). The active hydrothermal vents and earthquake can be considered as manifestations of volcanic activity. There are some hydrothermal vents at eastern offshore, and the fluids from the vents are mostly made up of sulfur, which cause the discoloration of the ocean around Guishan Island. The discolored area is called plume which can be easily detected by satellite image. The shape and size of plume are disturbed by ocean currents or winds. In this study, we detect the plume area by three steps: (1) remove land area; (2) remove cloud area; (3) classification. First, ENVI is used to build a mask and remove land area. Followed by a fully constrained least squares approach, it is a mixed pixel classification method for concentration estimation in each pixel. Finally, the area of plume is calculated from the result of least square approach, and then compare with the number of earthquake events to find the relationship between them. In our experiment, 36 SPOT images in 2008 are adopted, and the result shows that the larger area of plume was occurred around the large cluster of events. The area of plume is related to earthquake but there isn't clear. After the correlation coefficient is calculated, the highest is in ±1day. It means maybe the earthquakes can cause the area of plume become larger.

關鍵字

龜山島、熱液、地震、光學式衛星影像、影像分類

Keywords

Guishan Island, hydrothermal vent, earthquake, satellite image, image classification

附件檔名

華芸線上圖書館

N / A

備註說明

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