Application of CCD Remote Sensing to Ocean Wave Field Observation

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Project title

Code/計畫編號

NSC98-2221-E019-061

Translated Name/計畫中文名

CCD遙測波浪適用於現場觀測研究

Funding Organization/主管機關

National Science and Technology Council

Co-Investigator(s)/共同執行人

周宗仁(計畫主持人)

Department/Unit

Department of Harbor and River Engineering

Website

https://www.grb.gov.tw/search/planDetail?id=1917517

Year

2009

Start date/計畫起

01-08-2009

Expected Completion/計畫迄

31-07-2010

Co-Investigator(s)

Ruey-Syan Shih

Bugetid/研究經費

798千元

ResearchField/研究領域

土木水利工程

"在一般的水工實驗室，平面水槽進行的水工模型試驗均必須使用大量波高計排列分區經多次重複實驗後始能獲得測試區域的平均波高資料，在時間、財力及人力上均需耗費相當大的資源，過去曾利用高感度CCD 來遙測水面變動，以一般的可見光卽投射燈作為光源，針對規則波場回歸出影像灰階值與實際波高值間的轉換函數。由於雷達遙感波浪與CCD 遙感波浪間，除擷取影像方法不同，雷達影像有雜訊存在及其他問題外，實驗水槽週遭條件單純，實際海面要考量的因素較複雜。雷達日夜均可觀測，但一般CCD 攝影機只能用於白天，若經費充裕，使用高感度紅外線CCD 攝影機(價格昂貴) ，亦可適用，兩者的分析理論是通用的。本研究擬以高解析度專業用CCD 來攝取平面水槽試驗之水面波浪變化之資料，以CCD 影像灰階值分析波高的經驗，利用雷達影像灰階值作為比對波高的對象，並以Longuet-Higgins(1956) 推導的波數譜理論分析海象特性。本計劃預定在實驗水槽對不規則波場進行實驗與分析，取得波高之轉換函數，未來在平面水工模型實驗如遮蔽實驗，每個條件的波浪，只造波一次，只須使用一支比對用的波高計卽可，利用CCD 取得連續影像就可分析，可節省大量的人力及時間。第二年擬從實驗室轉移到沿岸區域測試，雖然在室外週遭環境複雜，且光源為太陽光，光點位置強弱隨季節、時間及天氣而變，以及水面的反光等問題必須克服，但本研究為先驅的工作，研究成果將可作為未來持續發展CCD 遙測技術應用在現場觀測的參考。 " "Wave height measurements in a laboratory are generally accomplished by a great quantity of wave gauges which are indispensable for extrapolation to the whole area. However, the requirement of manpower and material resources are relatively high since the measurements have to be carried out in various locations repeatedly to cover the entire wave field in regions. Water surface fluctuations were formerly analyzed using image sequences from a CCD camera, a transfer function between the fluctuations and gray scale of images is therefore obtained, which the factor considered in real sea is still more complicated, relatively. Although general CCD cine-camera can only be used in the daytime, as radar can be observed day and night, yet, camera devices are less expensive as compared with radar devices. Based on the possession of experiences and analytical knowledge of the transfer function, and perceive the contrast between wave height fluctuations and gray scale using radar devices, together with the theory of statistical analysis of a random and moving surface derived by Longuet-Higgins, we expect through estimation the completion of a project of measured system using a CCD camera to sense the wave field characteristics in this study. The experiments would be carry out in the multidirectional wave basin with multidirectional random waves, anticipating the advantage of a CCD remote sensing acquiring the information of the whole wave field in one instant, which may decrease the cost of manpower and material resources quite substantially. In the second year of the project, we attempt to extend the technique in practice, i.e. the application of CCD remote sensing to ocean wave field observation. Nevertheless, accuracy may be influence by the reflection above the water surface and the source of light with various conditions, e.g. a sunny day, an overcast sky, glimmering in the mooring as well as in the evening, also varies with different season, all these factors must be overcome, still, this research may be the pioneer of CCD telemetering measurement technology and anticipate the consequences as consultation in the academia."

Keyword(s)

CCD 遙測技術
影像灰階值
波高轉換函數
波數譜理論
現場觀測
CCD remote sensing
gray scale
transfer function
wave field observation

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Application of CCD Remote Sensing to Ocean Wave Field Observation

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