從雷達影像萃取近岸海域表面流場之研究

A Study on the Extraction of Sea Surface Current from Nearshore X-band Radar Images

吳立中(Li-Chung Wu) ； 董東璟(Dong-Jiing Doong) ； 林家豐(Chia-Fong Lin) ； 高家俊(Chia-Chuen Kao)

《海洋工程學刊》 6卷2期 (2006/12) Pp. 81-94

https://doi.org/10.6266/JCOE.2006.0602.05

摘要

X-band雷達所觀測之海面影像隱含有表面流資訊在其中。利用雷達影像推算海面流場時，在深水區域，水深對流場計算結果之影響不明顯；但在近岸海域，水深會影響流場計算結果。本文研究目的為探討如何在流場分析過程中輸入適當的水深代表值，藉以從雷達影像中獲得正確的表面流場資訊。為達到此一目的，本文發展一套影像模擬法，依設定之波浪和流速條件產生影像序列，進一步透過迴歸分析獲得最佳水深代表值的經驗公式。為驗證結果的準確性，本文將影像求得之流速值與GPS漂流浮標量測之表面流速進行比對，結果顯示，在相對水深愈小的區域，代入本文所求得之水深輸入值，確實能從雷達影像中獲得更準確的表面流速資訊。

關鍵字

雷達 ； 流速觀測 ； 近岸海域

並列摘要

Sea surface information is possible to be extracted from the X-Band radar images. The value of representative water depth (RWD) is one of the most important factors in image process to derive surface current from radar images. It can not be ignored for the case of that the image is from shallow water area. The purpose of this paper is to study the estimation of RWD for the purpose of deriving the correct sea surface current from radar images. An image simulation method is developed to simulate images for further studies from various conditions of water depths, waves and currents. The optimal RWD is then determined by the criteria on minima bias of input and analyzed currents. An empirical formula is therefore derived to estimate the RWD. A field experiment is arranged to validity the result from image simulation. Sea surface current measured from GPS buoy is used for validation of present formula. It is shown that the result of sea surface current derived from radar images is improved by inputting RWD estimated from the empirical formula in this study. The improvement is significant at the coastal area with small relative water depth.

並列關鍵字

Radar ； Sea surface current measurement ； Nearshore area