40
Multiscale Hydrologic Remote Sensing: Perspectives and Applications
photographic imagery and the observed reduction of ocean wave phase speed with
decreasing water depth (Williams 1946). Since then, the same basic principle has
been applied successfully with different algorithmic implementations, especially
since the development of operational ground-based video imagery systems (for a
review, see the work of Stockdon and Holman 2000; Holamn and Stanley 2007).
Similar techniques have also been applied in wave flume experiments for the determination of the local bathymetry (e.g., Catalán and Haller 2008). In addition, significant results on this topic have been acquired from airborne optical measurements
(Piotrowski and Dugan 2002; Dugan et al. 2003).
In parallel with these optical-based methods, microwave imaging of the wave field
has been developed. Grazing incidence radars have been built and used for research
purposes, leading to a broader understanding of the physics of sea clutter, which
underpins the interpretation of image data captured from marine radars (Wetzel
1990). Crombie (1955) was the first to record the phenomenon of radar backscattering from sea waves, after which it became a main investigation issue when Wright
(1966) published his oceanographic observations based on ground-based radars.
Since then, the backscattering mechanism from the ocean surface has been studied
theoretically and experimentally for many years (Barrick 1968; Hasselmann 1971;
Krishen 1971; Plant 1977; Alpers and Hasselmann 1978), and many other methods
for the first 30 years of research were summarized by Hasselmann et al. (1978), but
still there is ongoing research (Lee et al. 1995; Hyunjun and Johnson 2002; Haller
and Lyzenga 2003; Catalán et al. 2008).
Despite the absence of one commonly accepted theory for the backscattering
mechanism, the imaging of the wave field with radars has been in use since the early
1960s. Oudshoorn (1961) was monitoring the wave field in the challenging area of
the harbor mouth at Rotterdam in order to monitor the transformations and interactions of the wave field due to the constructions. Several more researchers (Wright
1965; Wills and Beaumont 1971; Evmenov et al. 1973) have published photographs
of radar scopes showing waves. The analysis of these kinds of photos for the quantitative extraction of wave properties was introduced by Mattie and Lee (1978) and
ameliorated by Heathershaw et al. (1979). Making use of digitized radar images,
the 2-D (Hoogeboom and Rosenthal 1982) and 3-D spectra of spatial radar images
were calculated (Young et al. 1985). The development of stable spectral analysis
was originally applied to ship-based radar data by Ziemer and Rosenthal (1987)
and gradually led to the development of WaMoS I (Ziemer 1991, 1995; Ziemer and
Dittmer 1994). Similar systems with WaMoS II have been presented by several
research groups (Hirakuchi and Ikeno 1990) and companies (Gronlie 1995; Borge
et al. 1999; Reichert et al. 2007).
In the last decade, improvements in this field were made possible to establish
effective methodologies for the monitoring of the wave field, develop robust algorithms for spectral analysis of image sequences, and commercialize several different
ground-based radar systems. These improvements led to creating several methodologies for bathymetry reckoning that have been published based on the wave celerity
inversion. Bell (1999) tried to trace the motion of the wave crests by spatial cross
correlation in time; the distribution of the wave phase speeds is estimated and the
depth is calculated by using the linear dispersion relationship; the tidal signal is
Multiscale Hydrologic Remote Sensing: Perspectives and Applications
photographic imagery and the observed reduction of ocean wave phase speed with
decreasing water depth (Williams 1946). Since then, the same basic principle has
been applied successfully with different algorithmic implementations, especially
since the development of operational ground-based video imagery systems (for a
review, see the work of Stockdon and Holman 2000; Holamn and Stanley 2007).
Similar techniques have also been applied in wave flume experiments for the determination of the local bathymetry (e.g., Catalán and Haller 2008). In addition, significant results on this topic have been acquired from airborne optical measurements
(Piotrowski and Dugan 2002; Dugan et al. 2003).
In parallel with these optical-based methods, microwave imaging of the wave field
has been developed. Grazing incidence radars have been built and used for research
purposes, leading to a broader understanding of the physics of sea clutter, which
underpins the interpretation of image data captured from marine radars (Wetzel
1990). Crombie (1955) was the first to record the phenomenon of radar backscattering from sea waves, after which it became a main investigation issue when Wright
(1966) published his oceanographic observations based on ground-based radars.
Since then, the backscattering mechanism from the ocean surface has been studied
theoretically and experimentally for many years (Barrick 1968; Hasselmann 1971;
Krishen 1971; Plant 1977; Alpers and Hasselmann 1978), and many other methods
for the first 30 years of research were summarized by Hasselmann et al. (1978), but
still there is ongoing research (Lee et al. 1995; Hyunjun and Johnson 2002; Haller
and Lyzenga 2003; Catalán et al. 2008).
Despite the absence of one commonly accepted theory for the backscattering
mechanism, the imaging of the wave field with radars has been in use since the early
1960s. Oudshoorn (1961) was monitoring the wave field in the challenging area of
the harbor mouth at Rotterdam in order to monitor the transformations and interactions of the wave field due to the constructions. Several more researchers (Wright
1965; Wills and Beaumont 1971; Evmenov et al. 1973) have published photographs
of radar scopes showing waves. The analysis of these kinds of photos for the quantitative extraction of wave properties was introduced by Mattie and Lee (1978) and
ameliorated by Heathershaw et al. (1979). Making use of digitized radar images,
the 2-D (Hoogeboom and Rosenthal 1982) and 3-D spectra of spatial radar images
were calculated (Young et al. 1985). The development of stable spectral analysis
was originally applied to ship-based radar data by Ziemer and Rosenthal (1987)
and gradually led to the development of WaMoS I (Ziemer 1991, 1995; Ziemer and
Dittmer 1994). Similar systems with WaMoS II have been presented by several
research groups (Hirakuchi and Ikeno 1990) and companies (Gronlie 1995; Borge
et al. 1999; Reichert et al. 2007).
In the last decade, improvements in this field were made possible to establish
effective methodologies for the monitoring of the wave field, develop robust algorithms for spectral analysis of image sequences, and commercialize several different
ground-based radar systems. These improvements led to creating several methodologies for bathymetry reckoning that have been published based on the wave celerity
inversion. Bell (1999) tried to trace the motion of the wave crests by spatial cross
correlation in time; the distribution of the wave phase speeds is estimated and the
depth is calculated by using the linear dispersion relationship; the tidal signal is