波譜法遙測推算近岸水深

水深遙測常以可見光波段影像分析，利用電磁波在不同深度海域具有不同的海底反光，以獲取水深資訊。但由於臺灣東岸水深過深，西岸水污染嚴重，水質太混濁且分布不均，此法並不適用於臺灣近岸水深觀測。本研究嚐試以SPOT衛星影像，使用波浪傳遞原理，假設波浪傳遞中頻率守恆，但其波長因水深變化而改變，藉由此對應變化關係來推估近岸水深。此波譜法乃分析近岸海域波浪影像獲取波數能譜，以此波譜計算波長（或波數），再透過分散關係式（dispersion relation）推估水深，定量分析結果，水深平均誤差約在15％；海域水深推算之值經移動平均，消除隨機誤差後，其平均誤差可降至 8％∼ 10％。此法發揮經濟、安全、快速及廣域的遙測技術特性，提供概要水深分佈資訊，不失為臺灣近岸及不易作業海域的水深量測的可行方法。

關鍵字

波譜；遙測；水深

並列摘要

Besides conventional methods, remote sensing technology is another method to quickly map water depths of broad coastal zones. The images of visible band are available analyzed to obtain the information of shallow water depths owing to discriminating reflection of electromagnetic waves over the coastal zone with varied water depths. The visible band method is not suitable to eastern coastal zone of Taiwan due to its water depths almost beyond the penetrating depth of visible light and either western one because of high water turbidity. In this paper, the wave spectrum methodology is applied to bathymetry of shallow water. SPOT images were used to derive wave spectra and estimate water depths because of different lengths of waves over varied water depths. The bathymetry of shallow water is derived from wave spectra via the general dispersion relation of water waves. It bases on the hypothesis the waves keep their frequency uniform when they propagate from deep water into shallow water. Comparing with in situ water depths, the average error of estimating shallow water depths by wave spectrum bathymetric method is 15%. The moving average processing removes the random errors of water depths estimating by wave spectrum bathymetric method. Then the average error of water depths reduces to 8%∼10%. Wave spectrum bathymetric method takes advantages of remote sensing technology to obtain the synoptical bathymetry of shallow water in safety, economically and quickly. This method is a feasible approach over coastal zones of Taiwan with acceptable accuracy.

並列關鍵字

Wave spectrum ； Remote sensing ； Water depth

國際替代計量

波譜法遙測推算近岸水深

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