| Summary: | 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.
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