Bathymetry Determination Based on Abundant Wavenumbers Estimated from the Local Phase Gradient of X-Band Radar Images

A phase gradient (PG)-based algorithm is proposed in this study to determine coastal bathymetry from X-band radar images. Although local wavenumbers with the same spatial resolution of the wave field can be obtained from the wave field using the PG method, only a single wavenumber result can be extr...

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Autores principales:	Laurence Zsu-Hsin Chuang, Li-Chung Wu, Yung-Da Sun, Jian-Wu Lai
Formato:	article
Lenguaje:	EN
Publicado:	MDPI AG 2021
Materias:	wave dispersion relation directional pass filter nearly monocomponent wave fields Science Q
Acceso en línea:	https://doaj.org/article/2c34dcd6417146bdbf2188a4ac8a2fdf
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spelling	oai:doaj.org-article:2c34dcd6417146bdbf2188a4ac8a2fdf2021-11-11T18:51:00ZBathymetry Determination Based on Abundant Wavenumbers Estimated from the Local Phase Gradient of X-Band Radar Images10.3390/rs132142402072-4292https://doaj.org/article/2c34dcd6417146bdbf2188a4ac8a2fdf2021-10-01T00:00:00Zhttps://www.mdpi.com/2072-4292/13/21/4240https://doaj.org/toc/2072-4292A phase gradient (PG)-based algorithm is proposed in this study to determine coastal bathymetry from X-band radar images. Although local wavenumbers with the same spatial resolution of the wave field can be obtained from the wave field using the PG method, only a single wavenumber result can be extracted from each location theoretically. Due to the influence of unavoidable noise on the wave field image, single wavenumber estimation often shows high uncertainty. This study combines a bandpass filter and directional pass filter to produce different nearly monocomponent wave fields from X-band radar images and then estimates more wavenumbers from these wave fields using the PG method. However, the distributions of wavenumbers in higher-frequency bins still show high variance because the strength of wave signals is weak. We confirmed that the uncertain wavenumber–frequency pairs can be improved using the Kalman filter and are more consistent with the dispersion relation curve. To decrease the influence of inaccurate wavenumbers, we also use the strength of the wave signals as the weights for the least-squares fit. Although the depth errors from shallow-water areas are still unavoidable, we can remove the inaccurate depth estimation from shallow-water areas according to the coefficients of determination of the fitting. In summary, the algorithm proposed in this study can obtain a bathymetry map with high spatial resolution. In contrast to the depth result estimated using a single wavenumber of each frequency bin, we confirm that more wavenumbers from each of the frequency bins are helpful in fitting the dispersion relation curve and obtaining a more reliable depth result.Laurence Zsu-Hsin ChuangLi-Chung WuYung-Da SunJian-Wu LaiMDPI AGarticlewave dispersion relationdirectional pass filternearly monocomponent wave fieldsScienceQENRemote Sensing, Vol 13, Iss 4240, p 4240 (2021)
institution	DOAJ
collection	DOAJ
language	EN
topic	wave dispersion relation directional pass filter nearly monocomponent wave fields Science Q
spellingShingle	wave dispersion relation directional pass filter nearly monocomponent wave fields Science Q Laurence Zsu-Hsin Chuang Li-Chung Wu Yung-Da Sun Jian-Wu Lai Bathymetry Determination Based on Abundant Wavenumbers Estimated from the Local Phase Gradient of X-Band Radar Images
description	A phase gradient (PG)-based algorithm is proposed in this study to determine coastal bathymetry from X-band radar images. Although local wavenumbers with the same spatial resolution of the wave field can be obtained from the wave field using the PG method, only a single wavenumber result can be extracted from each location theoretically. Due to the influence of unavoidable noise on the wave field image, single wavenumber estimation often shows high uncertainty. This study combines a bandpass filter and directional pass filter to produce different nearly monocomponent wave fields from X-band radar images and then estimates more wavenumbers from these wave fields using the PG method. However, the distributions of wavenumbers in higher-frequency bins still show high variance because the strength of wave signals is weak. We confirmed that the uncertain wavenumber–frequency pairs can be improved using the Kalman filter and are more consistent with the dispersion relation curve. To decrease the influence of inaccurate wavenumbers, we also use the strength of the wave signals as the weights for the least-squares fit. Although the depth errors from shallow-water areas are still unavoidable, we can remove the inaccurate depth estimation from shallow-water areas according to the coefficients of determination of the fitting. In summary, the algorithm proposed in this study can obtain a bathymetry map with high spatial resolution. In contrast to the depth result estimated using a single wavenumber of each frequency bin, we confirm that more wavenumbers from each of the frequency bins are helpful in fitting the dispersion relation curve and obtaining a more reliable depth result.
format	article
author	Laurence Zsu-Hsin Chuang Li-Chung Wu Yung-Da Sun Jian-Wu Lai
author_facet	Laurence Zsu-Hsin Chuang Li-Chung Wu Yung-Da Sun Jian-Wu Lai
author_sort	Laurence Zsu-Hsin Chuang
title	Bathymetry Determination Based on Abundant Wavenumbers Estimated from the Local Phase Gradient of X-Band Radar Images
title_short	Bathymetry Determination Based on Abundant Wavenumbers Estimated from the Local Phase Gradient of X-Band Radar Images
title_full	Bathymetry Determination Based on Abundant Wavenumbers Estimated from the Local Phase Gradient of X-Band Radar Images
title_fullStr	Bathymetry Determination Based on Abundant Wavenumbers Estimated from the Local Phase Gradient of X-Band Radar Images
title_full_unstemmed	Bathymetry Determination Based on Abundant Wavenumbers Estimated from the Local Phase Gradient of X-Band Radar Images
title_sort	bathymetry determination based on abundant wavenumbers estimated from the local phase gradient of x-band radar images
publisher	MDPI AG
publishDate	2021
url	https://doaj.org/article/2c34dcd6417146bdbf2188a4ac8a2fdf
work_keys_str_mv	AT laurencezsuhsinchuang bathymetrydeterminationbasedonabundantwavenumbersestimatedfromthelocalphasegradientofxbandradarimages AT lichungwu bathymetrydeterminationbasedonabundantwavenumbersestimatedfromthelocalphasegradientofxbandradarimages AT yungdasun bathymetrydeterminationbasedonabundantwavenumbersestimatedfromthelocalphasegradientofxbandradarimages AT jianwulai bathymetrydeterminationbasedonabundantwavenumbersestimatedfromthelocalphasegradientofxbandradarimages
_version_	1718431693111558144

Bathymetry Determination Based on Abundant Wavenumbers Estimated from the Local Phase Gradient of X-Band Radar Images

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