Spectrum Analysis of Ocean Wave Surface and Coastal Water Depths Derived from Satellite Images

• Main Authors: Leu Li-Guang, 呂黎光
• Other Authors: Kuo Yi-Yu
• Format: Others
• Language: zh-TW
• Published: 1998
• Online Access: http://ndltd.ncl.edu.tw/handle/15061030961027949212

博士 === 國立交通大學 === 土木工程研究所 === 86 === The remote sensing of ocean wave field is based on the analysis of waves spatial distribution, which is complementary to the conventional method of observing the coastal waves by measuring the time series of surface elevation at one or a few limited points. Coupling with the conventional method, ocean surface waves can be analyzed soundly both in temporal and spatial domain. ERS-1 (The first European Remote Sensing Satellite) SAR (Synthetic Aperture Radar) and SPOT (Satellite Probatoire d'' Observation de la Terre) images were used to analyze the wave field of Hwalien coastal water. The information of wavelength, wave direction, and wave spectrum were derived form wave images by way of Fast Fourier Transform (FFT). The difference between the image-derived wavelengths and those measured by the (directional) wave rider was not large, and also for the wave direction. Image spectra and in situ spectra correlated well with each other. Also, the wave energy distribution (spectral shape) and the spectral peaks were very similar. It proves that remotely sensing ocean surface waves is a feasible approach with acceptable accuracy. Following the spectrum analysis of wave image, the Wave Spectrum Bathymetric (WSB) method was developed and applied to estimate the coastal water depths. In cases study, the WSB method was used to analyzed two SPOT wave images, then to estimate the coastal water depths of Taichung Harbor. The coastal water depths were derived via change detection of wavelength and wave direction respectively. The average difference of coastal water depths derived from SPOT image and in situ data, was about 12% for wavelength change detection, and about 28% for wave direction change detection. The WSB method succeed in determining the coastal water depths. It takes advantages of remote sensing technology to obtain the synoptic bathymetry of coastal waters in safety, economically, frequently, and quickly. Also, the WSB method is very apt to determine the coastal water depth of high turbidity. It is worthy of developing soundly for the applications.