臺灣博碩士論文加值系統

本研究旨在驗證數位相機拍攝之影像透過影像特徵追蹤，應用於近岸表面流場分析之可行性。研究地點為有黃藍色相鄰且具鋒面特徵的陰陽海。現場所拍攝的數位影像必須進行幾何轉換、影像平滑化、邊緣偵測等影像處理。將邊緣偵測結果分別以主觀的目測法和客觀的最大交相關法判定影像特徵位移，並結合研究區域實際距離與影像像素比例尺，計算出鋒面特徵的移動速度，兩種方法所得結果相近。
將所得鋒面流速與前人以漂流浮標測得之資料比對後顯示在同為小潮期間、量測區域和潮段相近之情形下，退潮流速相差2％，且漲潮中段流速較滿潮時快。因此，利用數位相機影像透過影像特徵追蹤方法進行近岸表面流場分析應該可行。研究過程中，發現並非所有鋒面的移動速度皆能反應潮流，僅有位於西岸與碼頭西堤之中央以西，往北北東方向擴散且水舌厚度較薄之特徵，其鋒面移動速度較能反應出潮流流速。此外，於大小潮時流場之比較，小潮時潮流流速明顯低於大潮。


關鍵字：陰陽海、沿岸流場、特徵追蹤、最大交相關、數位影像

The purpose of this study is to verify the feasibility of feature tracking method on the images taken by a digital camera near the coastal area. This technology is applied to the surface circulaton at Yin-Yang Bay at the northeast of Taiwan with an obvious front of cloudy yellow fresh water and clear brine. The primary imagery taken at Yin-Yang Bay has to do geometric transformation, image smoothing and edge detection before works on feature tracking. Two feature tracking methods are used in this study: the subjective method of estimating distance among the sequence images by naked eyes, and the objective method of Maximum Cross Correlation (MCC). The results show that the velocities of surface currents at Yin-Yang Bay derived from both methods are similar and are compactable to the results of previous study. Under a similar condition of the end of ebb closing to neap tide, there is only 2% difference between this study and previous study. This indicates that the method developed in this study is suitable for coastal circulation research. From the feature tracking method, not every front velocity can perform the behavior of tidal current. Nevertheless, the front velocity in neap tide is slower than that in spring tide.



Keywords：Yin-Yang Bay, Coastal circulation, Feature tracking, Maximum cross correlation, Digital imagery

目錄
謝辭............................................................................................................I
摘要...........................................................................................................II
Abstract.....................................................................................................III
目錄……………………………………………………………………..IV
圖目錄…………………………………………………………………..VI
表目錄…………………………………………………………………..IX
第一章 緒 論 ………………………………………………………….1
1-1、前言 …………………………………………………………....1
1-2、研究動機與目的………………………………………………..2
1-3、文獻回顧……………………………………………………..…4
1-3-1 特徵追蹤之概念和應用…………………………………….4
1-3-2 研究環境背景介紹………………………………………….5
1-3-3 雨量、水文與潮汐………………………………………….7
1-3-4 風場………………………………………………………….8
第二章 影像拍攝與處理………………………………………………..9
2-1、陰陽海影像拍攝………………………………………………..9
2-2、數位影像處理…………………………………………………...11
2-2-1 幾何轉換……………………………………………………11
2-2-2 影像平滑化………………………………………………...16
2-2-3 邊緣偵測…………………………………………………...20
2-3、製作實際距離與影像像素的比例尺………………………….25
2-4、計算位移和速度……………………………………………….28
2-5、利用最大交相關法計算流速………………………………….30
第三章 結果與討論……………………………………………………33
3-1、水舌鋒面的種類和速度……………………………….………36
3-2、資料比對……………………………………………………….42
3-3、表面流場分析………………………………………………….47
3-4、陰陽海於大小潮時流場變化之比較………………………….52
3-5、C區渦狀水團成因之探討…………………………………….56
3-6、最大交相關法………………………………………………….58
第四章結論與建議……………………………………………………..61
4-1、結論…………………………………………………………….61
4-2、建議…………………………………………………………….63
參考文獻………………………………………………………………..64

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