Coastal zone is the interaction area between the ocean and the land, and it is one of the most important residential areas of human. Coastal area management and planning is necessary in utilizing coastal space and resources. Coastal zone changed rapidly in recent decades in Tangshan, China. In this research, a total of 11 Landsat images were selected for studying the coastal change in Tangshan during the last 35 years. Results showed that the coastline length increased by 114.05 km, while land area increased by 449.76km2 from 1975 to 2010. The main period of coastal increasing in Tangshan occurred during 2005–2010, and the primary area changes happened in Caofeidian District and Jingtang Port. The main reason of the rapid coastal changes in Tangshan was the human activities of industrial and commercial district construction and harbor construction.
Submarine sand waves are visible in optical sun glitter remote sensing images and multiangle observations can provide valuable information. We present a method for bathymetric mapping of submarine sand waves using multiangle sun glitter information from Advanced Spaceborne Thermal Emission and Reflection Radiometer stereo imagery. Based on a multiangle image geometry model and a sun glitter radiance transfer model, sea surface roughness is derived using multiangle sun glitter images. These results are then used for water depth inversions based on the Alpers–Hennings model, supported by a few true depth data points (sounding data). Case study results show that the inversion and true depths match well, with high-correlation coefficients and root-mean-square errors from 1.45 to 2.46 m, and relative errors from 5.48% to 8.12%. The proposed method has some advantages over previous methods in that it requires fewer true depth data points, it does not require environmental parameters or knowledge of sand-wave morphology, and it is relatively simple to operate. On this basis, we conclude that this method is effective in mapping submarine sand waves and we anticipate that it will also be applicable to other similar topography types.
The spatial and temporal variability of sea surface temperature (SST) in the Zhejiang Coastal Waters of the East China
Sea is investigated with long time series of cloud-gap free SST imagery. The SST dataset is reconstructed with Data
INterpolating Empirical Orthogonal Function (DINEOF) method using daily MODIS Aqua SST images. An EOF
analysis technique is further used to reveal the regional temporal and spatial SST variability at seasonal to inter-annual
timescales. The first three EOF modes cumulatively account for more than 84% of the total SST variance. The first mode
explains 71.5% of the total SST variability and it is dominated by an annual cycle. The second mode accounts for 10.3%
of the SST variance and it reveals a warm/cold pattern in the coastal shelf sea. The third mode, accounting for 2.4% of
the SST variance, indicates a pattern describing the synoptic-scale variability.
This study focuses on the large sand waves in the Taiwan Banks. Our goals are to observe the sand waves as completely as possible, to obtain their direction, wavelength, density, and ridge length, to analyze their spatial distributions, and to understand the effects of the current field and water depth on the sand waves. This study demonstrates the possibility of using HJ-1A/1B sun glitter imagery with a large swath width and rapid coverage in studying sand waves. Six cloud-free HJ-1A/1B optical images with sun glitter signals received during 2009 to 2011 were processed. The sand waves were mapped based on their features in the images; their direction, wavelength, density, and ridge length were measured and analyzed. We identified 4604 sand waves distributed in an area of 16,400 km2. The distributions of sand waves and their characteristics were analyzed, and the differences of sand waves between the northwestern subregion and the southeastern subregion are reported. Further analysis and discussion of the relationships between spatial distribution of the sand waves and both the tidal current field from a numerical simulation and water depth led to some interesting conclusions. The current field determines the orientation of the sand wave, while the hydrodynamic conditions and water depth influence the shape, size, and density of sand waves to a certain degree.
Measurements of sea surface currents are important in understanding the dynamic of ocean processes especially in coastal waters, and satellite remote sensing has been used to derive sea surface advective velocities with visible or infrared imagery. Yet satellite remote sensing suffered from lack of high temporal imagery in dynamic coastal waters and from frequent cloud cover. In this study, using measurements from the Geo-stationary Ocean Color Imager (GOCI), we observed the sea surface currents in the East China Sea on 29 May 2011 by applying the Maximum Cross-Correlation (MCC) technique. The hourly ocean color images on 29 May 2011 (8 images per day from 8:30 am to 15:30 pm) showed water pattern movement and evolution through the course of a day, and 7 sequence sea surface velocity fields were derived. The results show that there were significant diurnal changes of the sea surface currents in the coastal waters. The average current velocity was 30~40 cm/s during the measurements, with maximum velocity of 50~60 cm/s observed between 9:30 and 10:30 am. The short-term changes of the surface velocities are mainly a result of the horizontal dilution due to tides. The case study here demonstrates the unique value of a geostationary satellite ocean color sensor in revealing short-term dynamics in coastal waters.
According to SAR imaging mechanism of underwater bathymetry, a 3-D hydrodynamic model based on SELFE (Semi-implicit
Eulerian-Lagrangian Finite Element) is applied to demonstrate the temporal variations of the channel bathymetry
changes. A microwave radar imaging of oceanic surface’s program of M4S is used to simulate the variation of
normalized radar cross section (NRCS) induced by the ocean surface current. The simulation is carried out to study the
effect of water depth changes and current variations on SAR imaging of channel bathymetry. The depth of channel is
defined between 5 m to 17 m with an interval of every two meters. Six time of tide are used in the current variation
simulation. The NRCS variation demonstrated in the simulated images are compared with in situ data, historical
bathymetric maps and calibrated SAR images. All the four kinds of images manifest similar changes of channels, which
proves that there is agreement between the simulation model used in this paper and other data. Simulation results also
show that bigger depth change induces bigger NRCS variation. In the time of maximum ebb tide, simulated relative
NRCS is bigger than others.
Coastline change, erosion-accretion evolution, and their relationship in the Pearl River Estuary (PRE) of China over the past 25 years are analyzed using six remote-sensing images from 1986 to 2011 and two nautical charts. Due to land reclamation in the period from 1986 to 2011, the total length of the PRE coastline increased by 149.2 km, which is equivalent to a growth of 0.57% per year, and the coastal land increased by 251.76 km 2 , which is equivalent to a growth of 0.23% per year; in addition, water depth change showed a trend in that foreshores became shallower, while deep channels became deeper. Areas where the coastline extended seaward had deposition to some extent, except for deepwater ports. Human activities played an important role in coastline change and erosion-accretion evolution in the PRE, which intervened with the natural variation of coastline and erosion-accretion. In addition, pollutants from the reclamation land became the major factors of coastal water pollution, which may significantly influence the environment of the PRE in a negative way.
In this article, EOS MODIS ocean color and sea-surface temperature data were used to study the influence of coastal upwelling on a red tide in the Zhejiang Coastal Waters in the summer of 2007. Several cloud-free and date-continued ocean color and sea-surface temperature images during the red tide event were selected and processed in this study. According to the field observations of the red tide, pixels with chlorophyll concentration higher than a certain value were considered as the red tide waters in the ocean color images. And the coastal upwelling in the Zhejiang Coastal Waters was measured by applying a temperature threshold approach from the sea-surface temperature images. Then, the temporal and spatial distributions of the red tide and the coastal upwelling were contrastively analyzed. Results show that there exists a high degree of correlation in spatial distribution between the coastal upwelling and the red tide. The coastal upwelling affects the spatial cover of the red tide according to their spatial correlation and the upwelling plays a crucial role in the development of the red tide in term of water temperature. The upwelling in the Zhejiang Coastal Waters is an important dynamic factor for the formation of red tides there.
The satellite-borne synthetic aperture radar (SAR) has been proven to be a valuable tool for high resolution ocean surface wind measurements. However, oceanic surface phenomena observed by SAR and oceanic processes which can cause the change of backscatter in SAR imagery will influence the SAR wind retrieval. Upwelling is one of the main factors, and it is prevalent in the East China Sea. It smooths the sea surface which results in a lower backscatter cross section in SAR imagery. In this study, using sea surface temperature and chlorophyll2-a data derived from Earth Observing System (EOS) MODIS, the low backscatter features in ENVISAT advanced synthetic aperture radar (ASAR) imagery are analyzed. A CMOD4 algorithm is adopted to retrieve the sea surface wind speed from SAR imagery. Results show that the wind speed is negatively biased due to the low normalized radar cross section associated with the upwelling. In order to resolve the impact of coastal upwelling on SAR wind retrieval, combined with high resolution numerical meteorological model wind field data, a wind speed correction method is proposed by using linear robust regression. To demonstrate the applicability of this method, underestimated wind speeds retrieved from ENVISAT ASAR images in the upwelling areas of Zhejiang coast and the sea area near northeast of Taiwan are corrected. Results show that the accuracy of upwelling region SAR wind retrieval data has been improved.
Spaceborne synthetic aperture radar (SAR) plays an important role in sea surface wind field. Upwelling is a common
oceanic phenomenon which influences the wind retrieving from SAR imagery. It smoothes the sea surface and its
backscatter cross section in SAR images is low. The sea surface wind retrieved directly from SAR imagery in upwelling
region will be underestimated. In this article, using sea surface temperature (SST) and chlorophyll2-a derived from EOS
MODIS, the low backscatter features in ENVISAT ASAR image are analyzed along the Zhejiang Coast in the East
China Sea. And CMOD4 algorithm is adopted to retrieve sea surface wind speed, using wind directions from interpolated
NCEP / NCAR reanalysis data. Results show that wind speed is negatively biased due to the low Normalized Radar
Cross Section (NRCS) associated with the Zhejiang Coastal Upwelling. Based on statistical method, the quantitative
relationship between SAR-derived wind speeds and high resolution numerical meteorological model results is
established. Then using this quantitative relationship, the underestimated wind speeds in upwelling region are corrected
and the impact of coastal upwelling on SAR wind retrieval is quantitatively evaluated.
This paper focuses on the topography measurement of island with satellite remote sensing. In this paper, remote
sensing stereo images from Cartosat-1 satellite are used to survey the topographic information of island. Ground
control points (GCPs) data are collected through on-site measurement. Then, some distributed GCPs are selected for
remote sensing image processing. The digital elevation information (DEM) is extracted from Cartosat-1 remote
sensing data by DEM extraction processing. And then, contour, slope and aspect are calculated based on DEM
information. Finally, some ground control points is selected to validate the accuracy of topographic information. The
results show that the accuracy of topographic information obtained 4.32m at horizontal position and 6.24m at vertical
elevation accuracy.
This paper focuses on the wetland of Ximen Island special marine protected areas in Yueqing Bay, Zhejiang, China.
In this paper, four remote sensing images from Landsat-7, SPOT-4, SPOT-5 and WorldView-2 satellites are collected.
These images are used for wetland investigation and analysis. Wetland information of island and tidal flat is derived
from the remote sensing images. Wetland in island includes aquaculture water, pond water, paddy fields and
reservoirs. Tide wetland includes vegetation areas, breeding areas, mud tide flat and water. The results mainly showed
that the area of island wetland is 1,281,973.04 square meters, accounting for 18.09% of the whole island area, and that
the mangroves communities distribute along the coast of Ximen Island.
The synthetic aperture radar (SAR) has been proven to be a valuable tool for high resolution ocean surface wind measurements, which is especially important for coastal waters. However, oceanic surface phenomena observed by SAR and oceanic processes which can cause the change of backscatter in SAR imagery will influence the SAR wind retrieval. Upwelling is one of the main factors and it is prevalent in summer along the Zhejiang Coast. It smoothes the sea surface
which results in the lower backscatter cross section in SAR imagery. In this article, using sea surface temperature (SST) and chlorophyll2-a data derived from EOS MODIS, the low backscatter features in ENVISAT ASAR imagery are analyzed along the Zhejiang Coast in the East China Sea. And then CMOD4 algorithm is adopted to retrieve the sea surface wind speed, using wind directions from interpolated NCEP / NCAR reanalysis data. The result of wind speed is
negatively biased due to the low Normalized Radar Cross Section (NRCS) associated with the Zhejiang Coastal Upwelling. In order to resolve impact of the coastal upwelling on SAR wind retrieval, combining high resolution numerical meteorological model wind field data, a wind speed correction model is proposed using linear robust
regression. Results show that the accuracy of SAR wind retrieval is improved in upwelling region.
In this article, EOS MODIS sea surface temperature (SST) data are used to observe the Zhejiang Coastal Upwelling in
the East China Sea. MODIS SST data in summer from 2007 to 2009 are selected and processed. Based on the
upwelling's temperature features in SST imagery, a temperature threshold approach is established to measure the
physical parameters of the upwelling. And then the temporal and spatial characteristics of the upwelling are analyzed.
Results show that the upwelling distributes along the Zhejiang Coast running from south to northeast, and covers an
average area of 11,000 square kilometers. The mean temperature of the upwelling is about 25~28°C, and its temperature
difference from surrounding non-upwelling waters is in the ranges of 2~4°C. The upwelling appears in June and
develops to its strongest period in July and August, and then it weakens and vanishes in late September. Three years of
observational results reveal that the upwelling has short-time, seasonal and interannual variances. The upwelling is also
closely related to the coastal topography.
A new method for mapping shallow water topography surface currents from SAR image is introduced based on the
shallow water topography SAR imaging mechanism. M4S (presented by Romeiser R.) was used to forward simulate
radar signatures of the oceanic features over the ocean surface. The first guessed surface currents can be estimated from
the normalized radar cross section (NRCS) of the shallow water topography profile in the SAR image according to the
Apers-Hennings linear theory, the NRCS induced by the varying shallow water topography surface currents could be
simulated by the forward simulating model. The wind speed and shallow water topography surface currents gradients are
modified using the iterative method until the simulated radar signals close to the NRCS calculated from SAR image. By
this method, the wind speed and the surface currents can be retrieved finally. This method is tested on an ERS-2 SAR
image in the Taiwan Shoal. Results show that the simulated shallow water topography radar signal is consistent with the
NRCS extracted from SAR image, and their correlation coefficient is up to 90%, which means that this method is
convergent and applicable.
This paper discusses the relationship between the observations of submarine sand wave SAR images in Taiwan shoal and
sea surface wind. A total of 43 SAR images over 11 years are collected and 496 profiles of sand wave SAR images are
used, the wind are estimated from blended wind data and current direction is from mode. Results show submarine sand
waves are observed by SAR under wind speed of 10 m/s, only littlie are imaged above 10 m/s. The number of observed
sand waves reaches its maximum under the adverse wind direction, while the crosswind has its minimum. These support
that low and middle wind speed and adverse wind direction are favorable for SAR imaging submarine sand waves, high
wind speed and crosswind are unfavorable. The comparison between monthly mean wind speed and sand waves
observed by SAR also shows a strong correlation between both, which is lower wind speeds, the higher probability of
sand waves observed by SAR. This may indicate that the higher observation of the sand waves by SAR is partly due to
wind speed.
The submarine sand waves of the Taiwan Shoal in the coastal area of China have been observed with ERS-1 SAR
images. A numerical model for shallow water bathymetric survey by SAR has been used to derive the heights and the
slopes of the submarine sand waves while a feature tracking method has been applied to measure the movement of the
submarine sand waves with sequential images. The results show that the submarine sand waves align parallel to the east
direction with a height scale of 2-6m and a slope scale of 2°-14°. The lengths and widths of the submarine sand waves
are about 500-5000m and 200 to 2000m respectively. The submarine sand waves move towards the south and the
southeast. The displacement of the submarine sand waves varies between 20 to 450m with an average value of about
146m.
A new method for retrieving shallow water topography surface currents from SAR image is introduced based on the
shallow water topography SAR imaging mechanism. M4S was applied to forward simulate radar signatures of the
oceanic features over the ocean surface. The first guessed surface currents can be estimated from the normalized radar
cross section (NRCS) of the shallow water topography profile in the SAR image according to the AH linear theory, the
NRCS induced by the varying shallow water topography surface currents could be simulated by the forward simulating
model. The wind speed and shallow water topography surface currents gradients are modified using the iterative method
for the simulated radar signals close to the NRCS calculated from SAR image. Finally, the wind speed and the surface
currents can be retrieved. This method is tested on an ERS-2 SAR image in the Taiwan Shoal. The result shows that the
simulated shallow water topography radar signal is consistent with the NRCS measured from SAR image, and their
correlation coefficient is up to 90%, which means that this method is convergent and applicable.
This paper presents the progress toward marine applications of synthetic aperture radar (SAR) data and a review of the
SAR satellite program in China. The technique development includes the development of algorithms and of
methodology for extracting oceanographic parameters from SAR data. Marine applications range from environmental
monitoring to oceanographic research. Two series of SAR satellites have been planned. The first SAR satellite of the
Environmental and Disaster Monitoring Satellite series (HJ series) will be launched in 2009 while the first SAR satellite
of the Ocean SAR Satellite series (HY-3 series) is in planning phase. A description is given of the instruments and their
plateforms.
Fully polarimetric synthetic aperture radar (SAR) data has been found to have many potential marine applications. This
paper investigates in the polarization phase information for ship detection using Space-borne Imaging Radar-C/X-band
SAR (SIR-C/X-SAR) data. It is shown that there exits large difference in polarization phase between ships and sea
surface. The HH-VV polarization phase difference has largest ship-sea contrast among all polarization phase differences.
An algorithm for ship detection has been proposed based on the ship-sea contrast in polarization phase information. The
results have indicated that the polarization phase difference information can be used to detect ships with high accuracy.
In this paper, we propose a new ship detection model on SAR imagery. The model uses the Pearson distribution system
to simulate the backscattering distribution from ocean surface on SAR imagery. In the Pearson distribution system, four
distributions including the pearson distributions of type I, III, IV and VI are employed in the model. Using these four
distributions, we form a CFAR equation. A distribution selected machine basedβplane is used to select which
distribution is adopted for specify SAR imagery. We can get four equations and get the threshold of gray level. Then,
using the threshold, the model can find ships from SAR images.
Red tides occurred frequently in the East China Sea in recent years. A red tide dominated by Prorocendrum donghaiense and Karenia mikimotoi happened in the Zhejiang Coastal Waters in late-May 2005. EOS MODIS water color data were utilized in extracting the red tide information. Sea surface temperature data derived from NOAA AVHRR and EOS MODIS were also analyzed to understand the possible formation mechanism of this red tide. The relationships between the red tide and related oceanographic features were discussed based on image data. The results indicate that the red tide was associated with several oceanographic processes, such as coastal front. This study showed that the combination of remote sensing data of water color and sea surface temperature can be useful in studying and understanding the oceanography of red tides.
Based on the Kelvin ship wake mode, the ocean wave mode and the two-scale mode for electromagnetic scattering from
rough surfaces, we propose a new method of simulation for Kelvin ship wake imaging by multi-look direction SAR. We
have simulated the VV normalized radar backscattering cross-section (NRCS) of the ship wakes from different look
directions in 2-D space firstly. The results show that the transverse waves can be viewed clearly when the radar look
direction is parallel to the ship's track direction, while the divergent waves can be viewed clearly when the radar look
direction is perpendicular to the ship's track direction. When the radar look direction is neither perpendicular nor parallel
to the ship's track direction, Kelvin arms are imaged as a bright line and a dark line according to the relationship between
spread direction of crest waves and ship's track direction. The waves whose track direction is more parallel to the ship's
track direction can be imaged as a brighter line. Moreover, the simulation results also draw this conclusion another, when
radar look direction is more near perpendicular to the ship's track direction, the angle between two Kelvin arms is
smaller as a result of these circumstances gunpoint at the stern wave scattering cross-section is as large as bow wave. It's
show that the simulated results agree quite well with the ERS-1/2 images.
The Zhejiang-Fujian coastal front is an important front in the East China Sea. The frontal parameters have been measured using an improved front-following algorithm with Advanced Very High Resolution Radiometer (AVHRR) data. The Frontal parameters including position width mean SST SST difference and gradient of the front have been retrieved.
Thermal infrared images from the NOAA AVHRR taken over 12 years between 1991 and 2002 have been used to study the sea surface front ofthe South China Sea Warm Current in the southern Taiwan Strait. Information about the location length width and strength of the front has been retrieved. The temporal and spatial variations of the front have been discussed.
Multiparameter (multifrequency and/or multipolarization) synthetic aperture radar (SAR) data collected by JPL AIRSAR and SIR-C are used to analyze ocean features such as ocean waves oil slicks ship wakes ocean fronts and underwater topography in the China Seas. Suggestions to the choices of frequency and polarization for the mapping of these features are given based on the analyses.
Multi-parameter synthetic aperture radar (SAR) are significant approaches for acquiring multi-factor information of ocean. It is known to require real and quantitative detection of sea shallow bottom topography and coastal zones and so on that are the parts as complex oceanic objects. The basic principles on multi-parameters SAR remote sensing are introduced at the first in the paper. Imaging mechnisms and the technologies of their studies by multi-parameter SAR are described. Information extraction of ocean shallow bottom topographies etc and their some results are dealt with in detail. Discussions and conclusions are conducted at the end of the paper.
The dynamic and random processes of ocean features and their multi-element mixs make the detections of ocean phenomena and information seperations so much complicated. The multi-parameter synthetic aperture radar (SAR), including multi-frequencies, multi-polarizations, multi-incident angles multi-resolutions and multi-swaths etc., are quite significant approaches in order to obtain a lot of oceanic multi-elements and the parameter estimations of these elementss according to SAR images. In the paper, the complication of the ocean processes and their application needs as well as multi-parameter SAR remote sensing abilities are briefly introduced at the first. The remote sensing principles and methodologies of multi-parameter SAR studying on complicated oceanic dynamic features are described. Multi-parameter SAR simulations and detections of sea surface waves, internal waves, currents and sea surface winds etc. are studied in detail. The further development of multi-parameter SAR systems and their potential in ocean applications is discussed and concluded at the final.
China is one of the largest oceanic countries in the world. China Seas, particularly southern CHina sea areas, is often dominated by rainy, foggy and cloudy weather that it is difficult to detect the near-real time, continuous marine environmental conditions, such as wind fields, surface waves, surface current and tidies, meso-scale eddies, fronts and coastal dynamic changes etc. SAR becomes a powerful tool for observing oceanic phenomena. In the paper, SAR, imaging, remote sensing methods and information extraction of oceanographic features are presented and analyzed in detail. The end of the paper, the potential of SAR images in marine applications is summarized.
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