ENGLISH

16卷/3期

16卷/3期

華藝線上圖書館

Pages:

特刊引言

論文名稱

測深光達原理與應用

Title

作者

史天元

Author

中文摘要

測深光達為以雷射掃描進行水域地形測量之作業技術,具有全波形記錄、多頻道掃描之特性。臺灣地區首度引進空載測深光達,為民國93年12月至94年10月間執行之內政部土地測量局(今國土測繪中心)「潮間帶地形測繪先導計畫」。該計畫之施測區域為「北自大肚溪出海口南岸端,南至員林大排出海口北岸端,東至南北端間海堤堤面中線為原則之連線往東200公尺止,西至當地最低潮位線起算至水深5公尺處」。此外,亦在北起通霄海岸,南至外傘頂洲海岸區域以測深光達施測。均因水質混濁,使得無水底反射之雷射回波值。為測試測深光達效能,另選擇宜蘭東澳及花蓮港地區進行測試。宜蘭東澳區域由於航線跨越山嶺高度達500公尺以上,而航高規劃僅400公尺,利用BN-2B定翼機因迴轉半徑較大故無法近岸施測,因此只能進行一條離岸邊較遠之航線,測得最深深度28公尺。花蓮港測區共計執行22條航線,測得最深深度37公尺,本區共進行兩組掃描參數之施測,包括航高300公尺、點雲密度3 x 3公尺及航高400公尺、點雲密度5 x 5公尺等兩組資料,進行航線間比對,比對成果符合25公分高程精度成果。 第二次引進為民國九十五至九十七年間,內政部「應用透水光達技術於近岸海域測繪工作案」,本特刊中王驥魁教授等所撰述者即為根據該案之成果。第三次引進為民國九十七年十二月至一百年四月間,內政部「以透水光達測繪技術測製東沙地區數值模型工作」計劃案,本特刊中有三篇論文即與此計畫相關。該計畫除順利完成東沙環礁約五百平方公里水域與澎湖測試地區之測繪外,亦曾就內陸水體如曾文水庫、南化水庫、與數段河道進行作業評估。但是內陸水體,在平原區有水質透光度不足之問題,在上游河段與水庫區,除優氧化造成之水濁問題外,飛行安全之顧慮亦為無法進行之主因。 綜合目前已有經驗,空載測深光達確實已達到實際應用階段。在淺水多礁、航行不便之處,空載測深光達是測繪水下地形唯一務實方案。以東沙環礁作業為例,航空測量具有快速、高效率之特色。但是,作業環境,尤其是水質之透光度,影響甚大。同時由於飛行時對地航高為300至400公尺,地形與人工建物如高壓電塔、跨河電纜、等,對飛安影響之顧慮,以及低空飛行時飛行器產生之噪音對居民生活品質之危害,均對空載測深光達之作業形成限制。另一方面,近三年中,有多種新型之機具開發成功,包含提升濁水穿透能力、提升測繪精度之機具,以及以10公尺以內水深作業為標的之「輕型」機具。未來儀器功能與價格,均將更具實用價值。因此,如何妥善引用空載測深光達技術,擬定針對極富開發價值之近岸淺水區測繪之策略,是當前面對之課題之一。

Abstract

關鍵字

Keywords

附件檔名

華芸線上圖書館

N / A

備註說明

N / A

Pages:

151-166

論文名稱

澎湖與東沙環礁測深光達作業探討

Title

On The 2010 Bathymetric Lidar Survey of Penghu and Dongsha Atoll

作者

史天元, 薛憲文, 蕭輔導, 陳雅信, 徐佳筠, 陳杰宗, 陳佳勳

Author

Tian-Yuan Shih, Shiahn-Wern Shyue, Fu-Daw Hsio, Ya-Hsing Chen, Chai-Yung Hsu, Jie-Chung Chen, Jia-Hsun Chen

中文摘要

摘 要 空載測深光達(Bathymetric Lidar,或稱透水光達),以航空器為載具,載運雷射掃瞄儀,進行水域水底地形測量之系統。掃瞄儀所使用之雷射光,為具穿透水體能力之綠光波段。 為引進空載測深光達作業技術,並獲取東沙環礁之水底地形資料,內政部於民國九十七年規劃澎湖及東沙環礁地區測量專案,並委由交通大學執行。本次測量採用AHAB HawkEyeⅡ系統,以Swearingen SA-226T航空器為載具,於民國99年8至9月間進行。實際完成東沙環礁約500平方公里,澎湖地區逾400平方公里之飛行測量。測量點間距(Nominal Point Space, NPS)約為3.5公尺。並擇定環礁東部約20平方公里區域,以較低航高獲取點間距2公尺之點雲。載資料品質管控工作上除了進行交叉航線及重疊航線之檢核外,並以船載聲納作業進行外部精度檢核,所獲取資料精度皆達國際海道測量組織(International Hydrographic Organization,IHO) 規範之一等要求。本文依據本計畫之作業經驗,整理描述飛航過程、資料編修處理、精度驗證、及產製成果等階段工作,並分析各階段之重要關鍵,期為未來相關工作之參考。

Abstract

Airborne Bathymetric Lidar systems utilize aircraft as the platform performing laser scan for surveying the underwater topography. The spectral band used for this laser is green, which can penetrate water and backscattered on the sea floor. This technology is best suited for area characterized as shallow and low water turbidity. Comparing with sonar based methods, airborne laser hydrography is featured with high efficiency and particularly suitable for areas with shoals and other risks for navigation. In order to fully utilize advanced technology for bathymetric mapping in Taiwan, and collect the bathymetric information of Dongsha atoll, Ministry of Interior planned a surveying project in 2008 for mapping Dongsha atoll and Penghu. This project is granted to National Chiao Tung University for execution. The aerial survey was performed with an AHAB Hawkeye II lidar system installed on a SA-226 aircraft, in August and September of 2010. 500 square kilometers in Dongsha, and about 400 square kilometers in Penghu were surveyed at spatial density of 3.5 meter by 3.5 meter. An area of 20 square kilometers located in the east portion of the atoll is surveyed with 2x2 meter resolution at lower flying height. Both cross flight and overlaps are compared for quality control. Sonar survey is also conduction for further validation. The survey result meets the IHO 1b specification. This article reviews the aerial surveying, data acquisition and editing, accuracy assessment and validation. The critical issues are discussed for the reference of future development and application of airborne bathymetric lidar in Taiwan.

關鍵字

全波形、航空測量

Keywords

Full waveform, aerial survey

附件檔名

華芸線上圖書館

N / A

備註說明

201208-16-151-166

Pages:

167-180

論文名稱

東沙島周圍海草分布特徵

Title

Distributional Characteristics of the Seagrasses Encircling the Dongsha Island

作者

孫筱雲, 柯佳吟, 李培芬

Author

Hsiao-Yun Sun, Chia-Ying Ko, Pei-Fen Lee

中文摘要

海草為淺海域水質與污染的敏感指標,透過萃取則可用於多類產品的開發,具有高度的生態與經濟價值。東沙島為茂密的海草床所環抱,出現的海草至少有六種,占全世界海草種數的10%,是為亞洲地區海草的分布重鎮。本研究結合東沙島周圍海草床的地面調查與測深光達資料(LiDAR),探討東沙島周圍海域海草的分布特性,並以橢球高(altitude)作為調查點平均水深的基礎,分析各項海草因子與水深之間的關係。調查結果顯示,水深範圍從0到6.8公尺處皆有海草分布,混生情形從單種到四、五種海草共存,在水深1到3公尺可觀察到最多種類的海草共存,水深1公尺內則多為單種或兩種海草混生;而在水深小於3公尺的樣點中,有超過93%出現海草,覆蓋度以50%到80%的頻度最高;從各種海草的分布來看,圓葉水絲草與泰來草的分布深度顯著小於水韭菜與鋸齒葉水絲草。整體而言,東沙島周圍海草大致呈現固定的種類分布,水深則是影響不同種類海草分布與共存之重要因子,並影響海草在東沙島周圍的地理分布。此外,由測深光達資料衍生之環境因子(如水深)有助於生物分布與生態監測研究。

Abstract

Seagrasses are as important indicator of water quality and pollution in the shallow-ocean zone and extracts from seagrasses can be used widely, leading them to a high value on both ecology and economy. Dongsha Island, surrounded by abundant seagrass meadow and composed of at least six species accounted for 10% of the world, is a main habitat for seagrasses in Asia. We combined field data of the seagrasses with environmental factors derived from LiDAR around the Dongsha Island to understand distributional characteristics of the seagrasses and to compare effects of water depth on seagrasses’ distributions. Our results indicated that, seagrasses were found in the depth of 0 to 6.8m, with the coexistence of 1 to 5 species. The highest number of seagrass species was coexisted in the depth of 1 to 3m while single or two seagrass species were often observed within depth of 1m. In the depth within 3m, the seagrass bed had the highest occurrence frequency, up to 93%, where the most sites had the leaf cover within 50% to 80%. We also found that the seagrasses Cymodocea rotundata and Thalassia hemprichii occupied the depths less than Cymodocea serrulata and Syringodium isoetifolium. Overall, the seagrasses encircled the Dongsha Island show specific preference, and their distributional characteristics and coexistence are affected most by water depth. The environmental data derived from LiDAR can be further useful on species distributions and ecological monitoring.

關鍵字

東沙島、海草、測深光達、分布

Keywords

Dongsha Island, seagrass, LiDAR, distribution

附件檔名

華芸線上圖書館

N / A

備註說明

201208-16-167-180

Pages:

181-192

論文名稱

空載測深光達於毛細波及重力波水面偵測之初探

Title

The Preliminary Study Of Airborne LiDAR Bathymetry On Capillary-Gravity Water Surface Detection

作者

趙鍵哲, 孟稚開

Author

Jen-Jer Jaw, Chih-Kai Meng

中文摘要

空載測深光達因其具備安全性與高效能的作業方式,使其成為執行淺海潮間帶三維地形圖資測繪有利的工具。然由於水體與水底材質分屬性質不同的介質體及反射體,為獲得正確的水底地形,須先掌握測深光達的正確雷射脈衝往返行經路徑,並從波形分析中分別偵測雷射脈衝碰觸水面及水底之時間點,此兩時間觀測量結合定位定向資料精度攸關水底三維地形測繪品質甚鉅。然而現階段對於水面模型幾何以及偵測水面時間點之相關研究仍顯薄弱,直接影響水底地形測繪品質的不確定性。本研究主要工作在瞭解及分析單一雷射脈衝至水面之交互作用;在水面模型方面考量水面局部變異顯著的毛細波及重力波。除了藉由改變系統掃描幾何與風速探討對水面回波波形在幾何與能量上之影響以外,亦歸結在不同系統掃描幾何及風速因素下較合宜且準確的波形時間偵測法。結果顯示中高風速下,以50% 上升時間演算法為較佳偵測方式;而於低風速下,以較低掃描角可獲取較明顯起伏之能量值。

Abstract

Airborne LiDAR Bathymetry has been proven as an ideal technique for safely and efficiently operating in both shallow water and tidal flat areas for 3-D topographic mapping tasks. Yet the crucial challenge for acquiring terrain of water bottom is to precisely capture the trajectory of laser pulse when travelling between different medium, in the air, water and at the water bottom. Therefore, the quality of mapping 3-D bottom terrain would depend on how well the waveform analysis on determining the timing hitting water surface and water bottom can be designated. The goal of this research is to focus on comprehending the reaction of laser pulse on water surface, mainly wind-induced capillary-gravity wave facets. In particular, laser scanning geometry and the wind factor that shape the waveform geometrically and radiometrically are analyzed and thus the better timing detection method can be advised. It is suggested that adopting 50% risetime point, among others, would render better timing detection results when operating under moderate to strong wind speeds. In addition, when provided with gentle wind speed, bathymetry scanned in a lower off-nadir angle would gain richer energy. Through this study, better understanding of laser-to-water interaction is realized. Last but not least, this work may contribute to highlighting the significance of water surface detection which current airborne LiDAR bathymetric systems overlook.

關鍵字

空載測深光達、波形、毛細波及重力波、時間偵測法

Keywords

Airborne LiDAR Bathymetry, Waveform, Capillary- Gravity Wave, Timing Detection Method

附件檔名

華芸線上圖書館

N / A

備註說明

201208-16-181-192

Pages:

193-201

論文名稱

評估應用透水光達於台灣近岸海域水深測繪

Title

Evaluation of Bathymetric LiDAR for Taiwan Coastal Water

作者

王驥魁, 陳桂嘉, 林志交

Author

Chi-Kuei Wang, Kuei-Chia Chen, Chih-Chiao Lin

中文摘要

透水光達(Airborne Laser Bathymetry, ALB)為近年海域測繪領域之先進技術,其利用空載雷射掃瞄儀搭配慣性導航儀(IMU)及全球定位系統(GPS),可快速且有效地獲得近岸海域(含潮間帶)的三維地形資料,故對於建立數值地型模型(Digital Terrain Model, DTM)以及分析地形之變化等相關研究實為一大幫助。本研究利用Hawk Eye II透水光達系統,評估台灣沿岸海域之水深資訊建這置成效,並以多音束掃瞄成果與其進行精度之分析。研究結果顯示,透水光達掃描系統與多音束掃瞄的測繪成果皆呈現一致性之趨勢,應用於近岸海域之測繪實屬可行。

Abstract

Airborne Laser Bathymetry (ALB), enabled by the combination of laser scanning system, inertia measurement unit (IMU), and global positioning system (GPS), is a recent achievement for coastal water mapping. It is especially suitable for generating the digital terrain model and monitoring the change of the tidal area. In this study, the Hawk Eye II system was employed for two coastal areas of Taiwan. And, the results were evaluated against independent multi-beam surveys. It shows that the bathymetry obtained by Hawk Eye II is consistent with that by multi-beam surveys.

關鍵字

透水光達、水深測量

Keywords

Airborne Laser Bathymetry, Hydrography

附件檔名

華芸線上圖書館

N / A

備註說明

201208-16-193-201

Pages:

203-217

論文名稱

水域測深方法暨原理探討

Title

An Investigation toward Sounding Method and Theory

作者

薛憲文, 史天元, 徐佳筠

Author

Shiahn-Wern Shyue, Tian-Yuan Shih, Chai-Yung Hsu

中文摘要

無論是基於對海洋及內陸水域經營管理或資源運用的需求,或是航行導航的需要,測深是探測水域之基本工作。從手持測量工具直到探測儀器問世,水深探測的方法與時漸進,如聲納利用聲波在水中傳導能量,測深光達則利用綠光雷射穿透水體。過去海洋測繪多利用船隻配合聲納做為主要測深工具,近期空載雷射掃瞄應用於近岸測繪,使得水深探測的範圍得以不受載具作業安全性之限制,而可以測繪近岸的淺水及多礁區域。本文主要探討比較聲納及測深光達兩種不同的測深方法之原理及作業方式。

Abstract

Navigation requirement speeds up people’s activity to ocean exploration, from manual lead line survey to echo sounding, methods of sounding improving with time. Such as sonar transport energy by sound wave and airborne bathymetric LiDAR uses doubled frequency green laser to penetrate water. In the past, bathymetric chart can be surveyed by means of echo sounder; laser scanning applications in shallow water expands the coverage of depth measurement without limitation of operational safety. In this article, shipborne sonar and airborne bathymetric LiDAR is investigated and their theory and operation method are introduced.

關鍵字

聲納、測深光達、水深

Keywords

Sonar, Airborne LiDAR Bathymetry, water depth

附件檔名

華芸線上圖書館

N / A

備註說明

201208-16-203-217

Pages:

219-228

論文名稱

測深光達波形與水深、底質關係觀察

Title

Exploration on Waveforms of Bathymetric Lidar

作者

林暐尊, 史天元, 張智安

Author

Wei-Tsun Lin, Tian-Yuan Shih, Tee-Ann Teo

中文摘要

測深光達(Bathymetric Lidar)以近紅外光及綠光之雷射掃描方式進行水域之水深及水底地形量測,藉由偵測水面及水底之回波時間間距求得空間距離以達探測水深效果。本研究使用東沙及澎湖之AHAB HawkEye IIb掃描數據及Coastal Survey Studio(CSS)軟體進行數據分析,以水面定義、水質濁度、底質種類及地形影響各方面進行探討,比較項目包含水深、信噪比量化數據,以及搭配相機影像判識之底質種類等差異。實驗結果顯示,由於HawkEye IIb系統對綠光訊號之時變增益處理,水深對波形狀態影響不顯著;混濁水質造成水體中有較強散射訊號,淺水區水面及水底訊號間衰減現象較不顯著,而於深水區域甚至可能無法測得水底回訊。波形狀態呈現則與陸域光達類似,波形強度受反射面材質影響,且反射面幾何形態亦造成波形寬度改變。依本文探討CSS軟體成果對應接收波形,盼作為未來測深光達波形處理時回波偵測、點雲分類等作業之參考。

Abstract

Bathymetric Lidar uses near infrared and green band lasers to acquired the water depth and underwater topography. The spatial distance can be estimated from the return signals of the surface and the bottom of water. Dongsha and Penghu are the test areas. The test data are acquired by AHAB HawkEye IIb and processed by Coastal Survey Studio (CSS) software. This study analyses the surface definition, water turbidity and bottom topography. The quantitative analysis includes water depth, signal-to-noise ratio and types of sea bottom. The experiment indicates that depths affected by waveform appearances are not obvious due to the Time-varied Gain (TVG). The turbid water makes stronger volume backscatter and decreases the attenuation effect, even leads to the bottom echo undetectable with deeper water. Waveform appearance is varied with types of reflective material and geometry, as well as influencing the strength and pulse width, respectively. This study analyses the relationship between waveform acquired by HawkEye IIb and results processed by CSS software. The experimental results may provide some evidences for further processing such as bathymetric Lidar echo detection, point cloud classification, and others.

關鍵字

測深光達、波形

Keywords

Bathymetric Lidar, Waveform

附件檔名

華芸線上圖書館

N / A

備註說明

201208-16-219-228

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