scholarly journals Automatic Extraction of Offshore Platforms in Single SAR Images Based on a Dual-Step-Modified Model

Sensors ◽  
2019 ◽  
Vol 19 (2) ◽  
pp. 231 ◽  
Author(s):  
Jing Zhang ◽  
Qi Wang ◽  
Fenzhen Su
Keyword(s):  
Northern South China Sea ◽  
River Estuary ◽  
Image Data ◽  
Offshore Platform ◽  
Beibu Gulf ◽  
Automatic Extraction ◽  
Offshore Platforms ◽  
Sar Images ◽  
Modified Model ◽  
Radar Images

The quantity and location of offshore platforms are of great significance for marine oil spill monitoring and offshore oil-gas development. In the past, multiphase medium- and low-resolution optical or radar images have been used to remove the interference of ship targets based on the static position of a platform to extract the offshore platform, resulting in large demands and high image data costs. According to the difference in shape between offshore platforms (not elongated) and ships (elongated shapes) in SAR (synthetic aperture radar) images, this paper proposes an automatic extraction method for offshore platforms in single SAR images based on a dual-step-modified model. First, the two-parameter CFAR (constant false alarm rate) algorithm was used to detect the possible offshore platform targets; then, the Hough transform was introduced to detect and eliminate ship targets with linear structures. Finally, the final offshore platform was obtained. Experiments were carried out in four study areas in the Beibu Gulf basin and the Pearl River estuary basin in the northern South China Sea. The results show that the method has a good extraction effect in the above research area, and the extraction accuracy rate of offshore platforms is 86.75%. A single SAR image can obtain satisfactory extraction results, which greatly saves on image data cost.

scholarly journals Identification of Eggs and Spawning Zones of Hairtail Fishes Trichiurus (Pisces: Trichiuridae) in Northern South China Sea, Using DNA Barcoding

2021 ◽  
Vol 9 ◽  
Author(s):  
Gang Hou ◽  
Youwei Xu ◽  
Zuozhi Chen ◽  
Kui Zhang ◽  
Wangsu Huang ◽  
...  
Keyword(s):  
South China Sea ◽  
Continental Shelf ◽  
South China ◽  
Water Mass ◽  
Northern South China Sea ◽  
River Estuary ◽  
Late Summer ◽  
Beibu Gulf ◽  
Spawning Grounds ◽  
China Sea

Commercially important hairtails, Trichiurus spp., are widely distributed throughout China’s marine waters. Because eggs of these species are difficult to identify and the taxonomy of the group has recently been resolved, their spawning grounds in the northern South China Sea (SCS) are not well known. We identified three Trichiurus species (T. japonicus, T. nanhaiensis, and T. brevis) using DNA barcodes in spring and late summer–autumn ichthyoplankton surveys of 2019 in the northern SCS. Egg distributions reveal that the spawning grounds of T. japonicus and T. nanhaiensis occur mainly from the central and southern Beibu Gulf, along Hainan Island, to the waters off the Pearl River Estuary, and that egg densities are higher in spring than in late summer-autumn. Spawning of T. japonicus commonly occurs along the continental shelf, T. nanhaiensis along the continental shelf to slope (over seabed depths of 42–380 m), and T. brevis mainly in shallow water. Considering the salinity and temperature data, we found that the eggs of Trichiurus were associated with specific water masses. In spring, eggs of T. japonicus and T. nanhaiensis occurred at central and southern Beibu Gulf water mass (CSBGWM) and South China Sea surface water mass (SCSWM). While in late summer-autumn, eggs of T. japonicus and T. nanhaiensis mainly occurred in the waters of SCSWM. Our findings reveal that the occurrence of Trichiurus eggs and their spatial and temporal distribution are determined by hydrological conditions.

A preliminary study on sediment records of possible typhoon in the northern South China Sea during the past 6500 yr

The Holocene ◽  
2021 ◽  
pp. 095968362110032
Author(s):  
Pingyuan Li ◽  
Mingkun Li ◽  
Huayang Gan ◽  
Zhen Xia
Keyword(s):  
South China Sea ◽  
South China ◽  
Southern China ◽  
Northern South China Sea ◽  
River Estuary ◽  
Pearl River Estuary ◽  
Human Beings ◽  
China Sea ◽  
The Pearl River ◽  
China Coast

Typhoon is an important meteorological phenomenon that affects the living and development of human beings on the southern China coast. However, there is still lack of clarity in the paleo-typhoon history and its influence on the evolution of the ancient human settlement environment since the mid-Holocene. Here, we identify six typhoon-like deposits from a core retrieved from the northern South China Sea shelf, close to the Pearl River Estuary, based on accelerated mass spectrometry 14C dating, grain size, and geochemistry. The sand fractions, CaO, Sr, SiO2/TiO2, and SiO2/Al2O3 were used to indicate the typhoon-like deposits. Results show that the ages with high-frequency typhoons are present ~200–300 cal yr BP, ~800–1000 cal yr BP, ~1500–1700 cal yr BP, ~2000–2100 cal yr BP, ~2400–2500 cal yr BP, and ~2700–3000 cal yr BP. Our results are comparable to the records from adjacent regions. Significantly, the vast tides occurred in the duration of ~2700–3000 cal yr BP in southern China, which probably caused the ancestors’ migration to the inland. Further studies are needed to deeply study the paleo-typhoon history in the southern China coast to verify our results.

Storm-induced circulation in the Pearl River Estuary of China during super Typhoon Koryn

2012 ◽  
Vol 47 (3-4) ◽  
pp. 314-332 ◽  
Author(s):  
Liqun Tang ◽  
Jinyu Sheng ◽  
Yuhan Cai
Keyword(s):  
Northern South China Sea ◽  
River Estuary ◽  
Pearl River Estuary ◽  
Horizontal Resolution ◽  
Pearl River ◽  
Study Region ◽  
Near Surface ◽  
The Pearl River Estuary ◽  
Super Typhoon ◽  
The Pearl River

This study presents a numerical investigation of storm-induced circulation and hydrographic distributions over the Pearl River Estuary (PRE) in South China's Guangdong Province during super Typhoon Koryn in June 1993. The nested-grid modelling system used in this study has three downscaling subcomponents: an outer-most sub-model with a coarse horizontal resolution of ∼7 km for simulating surface elevations and depth-mean currents forced by wind and tides over China Seas from Bohai Sea to the northern South China Sea; and an inner-most sub-model with a fine resolution of ∼1.2 km for simulating the three-dimensional estuarine circulation and hydrographic distributions in the PRE and adjacent waters. A parametric vortex is inserted into the coarse-resolution (0.5°) numerical weather forecast products to better represent the atmospheric pressure and wind stress associated with Koryn. Model results demonstrate that large surface elevations and intense surface currents are generated over the area of influence of the storm. Lagrange velocities of near-surface particles are also used to examine the effect of the storm on the movements and dispersion of near-surface particles over the study region.

scholarly journals A Proposed Approach to Determine the Edges in SAR images

2020 ◽  
pp. 185-192
Author(s):  
Rabab Farhan Abbas
Keyword(s):  
Edge Detection ◽  
Electromagnetic Waves ◽  
Operator Method ◽  
Bézier Curve ◽  
Bezier Curve ◽  
Edge Image ◽  
Sar Images ◽  
Wavelet Method ◽  
Radar Images ◽  
Sobel Operator

Radar is the most eminent device in the prolonged scattering era The mechanisms involve using electromagnetic waves to take Synthetic Aperture Radar (SAR) images for long reaching. The process of setting edges is one of the important processes used in many fields, including radar images, which assists in showing objects such as mobile vehicles, ships, aircraft, and meteorological and terrain forms. In order to accurately identify these objects, their edges must be detected. Many old-style methods are used to isolate the edges but they do not give good results in the  determination process. Conservative methods use an operator to detect the edges, such as the Sobel operator which is used to perform edge detection where the edge does not appear well.      The proposed method which combines Ridgelet transform, Bezier curve and Sobel operator is used to detect edges very efficiently. Ridghelet transform resolves the harms in the wavelet transform and it can well detect the edges in images. Bezier curve can profit gradual variation of the data and their mutability. Hence, the efficiency of the edged image is improved and, when used with Sobel operator, the quality of the edge image become very good. The data show that the advocated method has superior fallouts over the Sobel edge detection and the wavelet method in both subjective and impartial experiments. While the Peak Signal to Noise Ratio(PSNR) values were equal to 9.3812, 9.8918, 9.6521 and 9.0743using the Sobel operator method and to10.2564, 10.7927, 10.5612and 10.8633 using the wavelet method, they were increased in the proposed method to 12.6542, 12.9514, 12.8574 and 12.3013 respectively.

scholarly journals Multi-Temporal Data Fusion in MS and SAR Images Using the Dynamic Time Warping Method for Paddy Rice Classification

Agriculture ◽  
2022 ◽  
Vol 12 (1) ◽  
pp. 77
Author(s):  
Tsu Chiang Lei ◽  
Shiuan Wan ◽  
You Cheng Wu ◽  
Hsin-Ping Wang ◽  
Chia-Wen Hsieh
Keyword(s):  
Neural Network ◽  
Time Series ◽  
Decision Tree ◽  
Data Fusion ◽  
Dynamic Time Warping ◽  
Image Data ◽  
Synthetic Aperture ◽  
Time Warping ◽  
Radar Images ◽  
Dynamic Time

This study employed a data fusion method to extract the high-similarity time series feature index of a dataset through the integration of MS (Multi-Spectrum) and SAR (Synthetic Aperture Radar) images. The farmlands are divided into small pieces that consider the different behaviors of farmers for their planting contents in Taiwan. Hence, the conventional image classification process cannot produce good outcomes. The crop phenological information will be a core factor to multi-period image data. Accordingly, the study intends to resolve the previous problem by using three different SPOT6 satellite images and nine Sentinel-1A synthetic aperture radar images, which were used to calculate features such as texture and indicator information, in 2019. Considering that a Dynamic Time Warping (DTW) index (i) can integrate different image data sources, (ii) can integrate data of different lengths, and (iii) can generate information with time characteristics, this type of index can resolve certain classification problems with long-term crop classification and monitoring. More specifically, this study used the time series data analysis of DTW to produce “multi-scale time series feature similarity indicators”. We used three approaches (Support Vector Machine, Neural Network, and Decision Tree) to classify paddy patches into two groups: (a) the first group did not apply a DTW index, and (b) the second group extracted conflict predicted data from (a) to apply a DTW index. The outcomes from the second group performed better than the first group in regard to overall accuracy (OA) and kappa. Among those classifiers, the Neural Network approach had the largest improvement of OA and kappa from 89.51, 0.66 to 92.63, 0.74, respectively. The rest of the two classifiers also showed progress. The best performance of classification results was obtained from the Decision Tree of 94.71, 0.81. Observing the outcomes, the interference effects of the image were resolved successfully by various image problems using the spectral image and radar image for paddy rice classification. The overall accuracy and kappa showed improvement, and the maximum kappa was enhanced by about 8%. The classification performance was improved by considering the DTW index.

scholarly journals Apparent source levels and active communication space of whistles of free-ranging Indo-Pacific humpback dolphins (Sousa chinensis) in the Pearl River Estuary and Beibu Gulf, China

2016 ◽  
Author(s):  
Zhi-Tao Wang ◽  
Whitlow Au ◽  
Luke Rendell ◽  
Ke-Xiong Wang ◽  
Hai-Ping Wu ◽  
...  
Keyword(s):  
River Estuary ◽  
Pearl River Estuary ◽  
Pearl River ◽  
Beibu Gulf ◽  
Apparent Source ◽  
Communication Space ◽  
The Mean ◽  
Active Communication ◽  
The Pearl River ◽  
Free Ranging

Background. Knowledge of species-specific vocalization characteristics and their associated active communication space, the effective range over which a communication signal can be detected by a conspecific, is critical for understanding the impacts of underwater acoustic pollution, as well as other threats. Methods. We used a two-dimensional cross-shaped hydrophone array system to record the whistles of free-ranging Indo-Pacific humpback dolphins (Sousa chinensis) in shallow-water environments of the Pearl River Estuary (PRE) and Beibu Gulf (BG), China. Using hyperbolic position fixing, which exploits time differences of arrival of a signal between pairs of hydrophone receivers, we obtained source location estimates for whistles with good signal-to-noise ratio (SNR≥10 dB) and not polluted by other sounds and back-calculated their apparent source levels. Combining with the masking levels (including simultaneous noise levels, masking tonal threshold, and the Sousa auditory threshold) and the custom made site-specific sound propagation models, we further estimated their active communication space (ACS). Results. Humpback dolphins produced whistles with average root-mean-square apparent source levels (ASL) of 138.5 ± 6.8 (mean ± standard deviation) and 137.2 ± 7.0 dB re 1μPa in PRE (N=33) and BG (N=209), respectively. We found statistically significant differences in ASLs among different whistle contour types. The mean and maximum ACS of whistles were estimated to be 14.7 ± 2.6 (median ± quartiledeviation) and 17.1± 3.5 m in PRE, and 34.2 ± 9.5 and 43.5 ± 12.2 m in BG. Using just the auditory threshold as the masking level produced the mean and maximum ACSat of 24.3 ± 4.8 and 35.7± 4.6 m for PRE, and 60.7 ± 18.1 and 74.3 ± 25.3 m for BG. The small ACSs were due to the high ambient noise level. Significant differences in ACSs were also observed among different whistle contour types. Discussion. Besides shedding some light for evaluating appropriate noise exposure levels and information for the regulation of underwater acoustic pollution, these baseline data can also be used for aiding the passive acoustic monitoring of dolphin populations, defining the boundaries of separate groups in a more biologically meaningful way during field surveys, and guiding the appropriate approach distance for local dolphin-watching boats and research boat during focal group following.

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