碩士 / 國立交通大學 / 土木工程學系 / 84 / Remote sensing is an outstanding technique for ocean wave
measurement,especially for the estimation of wave frequency and
direction. Directionalwave spectrum is important for
understanding the distribution of waveenergy, especially for the
application in random vibration of oceanstructure and wave
deformation. In this study, the SAR (Synthetic Aperture Radar)
data imaged from theESA (European Space Agency) Remote-Sensing
Satellite 1 (ERS-1) has beenused to evaluate the directional
wave spectrum. This method is developedto resolved the problems
encountered by the traditional measuring method.As an active
system, the SAR provides its own illumination and isindependent
on light resources like sunlight, thus permitting the wholeday
operation. Furthermore, microwave is able to penetrate the
weatherphenomena such as clouds, fog and precipitation, it thus
allows forall-weather imaging. It is especially convenient for
ocean observations. In this study, data pre-processing using
the concept of detrend wasperformed for the first stage. The
secondly, the two-dimensional F.F.T(Fast Fourier Transform)
algorithm was applied to create two-dimensionalwave spectrum in
Cartesian coordinate system. On the third stage,successive
formulas were undertaken to get the wave number spectrum inpolar
coordinate system. It was finally converted into
directionalfrequency wave spectrum. The most impressing result
of this research isthe improvement of the resolution, which has
been obtained by implementingthe algorithm of wave spectrum
analysis. The estimated results for wave spectrum analysis are
compared with theobservations measured by wave-rider. Five data
sets surveyed over the oceansurface to the east of Hualien
Harbor are used to evaluate the accuracy ofmethod in this study.
The verification procedure applies the Extension ofMaximum
Entropy Principle to obtain the directional wave spectrum in
orderto compare with the results created by analyzing SAR
imagery data. The results of comparison suggests that as long
as the significant waveheights measured by wave-rider are more
than 1.6 meters, the estimated peakfrequency coincides very well
with the observed one. Moreover, theirprofiles of directional
wave spectrum look quite similar. The error rangeswithin ?0%
for wave direction, but it need further verification.
Throughabove evaluation, this study confirms the feasibility of
estimating oceanwave spectrum using SAR imagery data.
| Identifer | oai:union.ndltd.org:TW/084NCTU0015020 |
| Date | January 1996 |
| Creators | Kao, Yi-Lang, 高義郎 |
| Contributors | Kuo Yi-Yu, 郭一羽 |
| Source Sets | National Digital Library of Theses and Dissertations in Taiwan |
| Language | zh-TW |
| Detected Language | English |
| Type | 學位論文 ; thesis |
| Format | 70 |
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