本研究旨在以實驗方式探討大尺度質點影像量測法(large-scale particle image velocimetry，簡稱LSPIV)於分析大尺度水面流場之可行性及準確性，故選定兩種實驗尺度(試驗場尺度及現場尺度)加以研究。

本實驗利用數位攝影機於兩種實驗尺度擷取水面流場之影像，經數位化過程後，應用影像處理技術加以處理，再將處理後之影像讀入流場可視化及定量化程式(李，2003)，經流場相關計算分析後，可得二維水面瞬時流速場，並取1 sec時間內各組連續二維水面瞬時流速場之平均，即可獲得經1 sec時間平均之二維水面流速分佈圖。

經本研究得知，LSPIV於戶外所擷取之影像，先以同態濾波法對影像做處理後，再使用中值濾波法處理，其增強後的影像經流場相關計算分析，可得效果較佳之二維水面瞬時流場，但其中難免會產生誤判的速度向量，經使用中值濾波法對流場做處理後，其所得之結果更為良好。另外兩種實驗尺度之影像空間尺度校正誤差均小於2.5 %；單點流速驗證比較之差異均在7.5 %以內；空間平均流速驗證比較之差異均在8 %以內，且其分析結果符合受二次流效應影響之現象，故證實LSPIV法於分析大尺度水面流場，為一具可行性且有效力、可靠度高之遙測技術。

The purpose of this study is using experiment way to inquire into large-scale particle image velocimetry (LSPIV), and analyze the feasibility and accuracy for large-scale water surface velocity fields. So we choose this two experiment scales to discuss.

The experiment is taking advantage of digital camera to select the images of water surface between this two experiment scales. After digitalize processing, applying to image enhanced techniques to deal with, then loading the processed images into the program (Lee, 2003) which is making the cross-correlation analysis. So we can get two-dimension instantaneous velocity fields, and select 1 sec time-average for continuous two-dimension instantaneous velocity fields.

Through this research we can know, the images we pick from outdoor, which using Homomorphic filter and Medium filter to process. After making the cross-correlation analysis, we obtain more effective instantaneous water surface velocity fields. But it’s hard to avoid miss judging for velocity vectors. Undergo applying Medium filter to deal with velocity fields, we can get more better effect. In addition, this two experiment scales of spacial scale correction errors are less than 2.5 %, the diversities of single-point velocity comparison are all within 7.5 %, the diversities of spacial average velocity comparison are all within 8 %. And the analysis results conform to suffer the appearance of secondary flow effect influence. For this reason, it proves using LSPIV to analyze large-scale water surface velocity fields is a feasibility, effective and reliability remote technique.

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