全极化SAR图像中溢油极化特征研究

相比于单极化SAR图像,全极化SAR图像不仅能体现海面目标的几何特征、后向散射特征,还能体现目标的极化特征。因此,在溢油检测方面,极化SAR更具优势。特征提取作为溢油检测的关键步骤,直接影响到溢油检测的精度。在本文中,我们分析了全极化SAR图像中海面溢油的极化特征,如极化散射熵、平均散射角等。并提出了新的极化特征P,该特征参数能够反映海面目标电磁散射过程中布拉格散射机制和镜面散射机制的比例。为了研究极化特征溢油检测的能力,本文基于SIR-C/X-SAR和Radarsat-2全极化SAR图像开展了相关实验,并对比分析了溢油的多种极化特征。实验结果显示,在中低风速情况下,C波段溢油探测效果优于L波段;本文提出的极化特征P对海面散射机制敏感;基准高度和特征参数P在C波段比其他极化特征更适于溢油检测。     

Approximate evaluation of the distortion to the peak ocean wavelength and direction derived from SAR image spectra

A calculation procedure using the modulation transfer function approach is presented to estimate the distortions to the values of the peak ocean wavelength and direction derived from SAR images of these waves. The distortions are calculated for ranges of SAR parameters which are typical for aircraft and satellites, and ocean wave parameters which reflect sea states which can be imaged by these SARs. The calculated distortions are discussed in terms of overall trends, effect of particular SAR and wave parameters, and qualitatively compared with observed differences between SAR and in situ measurements.     

Characterization of natural hydrocarbon seepage in the South Caspian Sea off Iran using satellite SAR and geological data

Abstract

Two groups of oil slicks have been repeatedly detected in the Southern Caspian Sea, off Cape Sefidrud and close to the Iranian coast of the sea on the synthetic aperture radar (SAR) images acquired by the Sentinel-1A and Sentinel-1B satellites in April–June 2018. Analysis of the SAR images together with bathymetry, geological and geophysical data in geographic information system showed that these manifestations (oil slicks) visible on the sea surface have natural origin, related to the bottom seepage phenomenon and are associated with existing hydrocarbon system. Oil slicks are concentrated over the continental slope and related to local geological formations of the sedimentary cover having oil deposits related to paleo-delta of Sefidrud River. Our evidence shows that two seeps in this area are active and repeating. It is concluded that the SAR is an excellent tool for monitoring of seepage phenomenon. Moreover, results indicate that the use of remote methods to identify offshore natural oil seeps related to existing active petroleum system can be considered as a well-accepted approach to support oil and gas exploration in frontier areas such as the South Caspian Basin.     

Mathematical modeling of the terrigenous sedimentation in the Sea of Azov

Based on balance calculations with the use of a spatially detailed mathematical model for transport and sedimentation of the particulate matter adjusted to the conditions of the Sea of Azov, particular spatiotemporal features of the terrigenous sedimentation in the second half of the 20th century are recognized. The general tendency for the deceleration of the accumulation of terrigenous sediments and for the decrease in the areas with a negative balance of the terrigenous matter is related to the 2.5-fold fall in the volumes of the matter supplied from land. During the period considered, the intensity of the sedimentation decreased from 1000 to 400 g/m²/year. The accumulation of terrigenous sediments proceeds in the regions where the sources of the matter supply are concentrated and where features of the bottom morphology and hydrodynamical activity are favorable for the sedimentation: in Taganrog and Temryuk bays. In the central part of the sea, the intensity of the sedimentation comprises a value of about 300 g/m²/year. In Taganrog Bay and in the sea proper, areas with a negative balance of terrigenous sedimentary matter increased up to 30%.     

灰度共生矩阵纹理特征对SAR海冰漂移监测的增强性能研究

海冰漂移监测对气候变化分析、船只航行、海上石油平台等海上活动安全作业具有重要意义。当前主流的SAR海冰漂移监测方法多是基于SAR灰度图开展的,其受噪声、环境等因素的影响较大,导致其在海冰漂移探测时,特征失配率高,匹配正确率低。针对这一问题,本文尝试利用SAR海冰纹理特征来增强海冰漂移探测性能。首先对比分析了8种纹理特征对海冰漂移探测中特征匹配的增强性能,筛选出能够有效增强特征匹配性能的最优纹理特征;其次进一步分析了海冰类型、入射角和分辨率对基于纹理特征的海冰漂移探测性能增强的影响。实验结果表明,均值是最优的纹理特征,与SAR强度图相比,特征匹配正确率提高了约7%。     

基于模型相似度拟合的海杂波统计方法

本文提出一种基于模型相似度拟合的海杂波统计方法。首先根据合成孔径雷达(SAR)图像计算瑞利分布、对数正态分布、韦布尔分布、K分布、G0分布5种经典的海杂波分布的概率密度函数,然后根据模型间的相似度准则拟合得到新的海杂波分布模型。文章利用四景不同类型的真实SAR数据对算法的拟合性能进行了评价,结果显示利用该算法得到的拟合模型与真实SAR数据的平均Kullback-Leibler距离仅为0.015 84,远优于其他分布模型。基于该拟合模型的恒虚警率舰船检测算法对四景SAR数据的平均检测精度达到95.75%,在控制虚警和漏检方面均优于采用其他模型的同类方法。     

基于影像纹理特征和外部风向的星载 SAR 海面风场反演研究

在合成孔径雷达(Synthetic Aperture Radar,SAR)海面风场反演中,基于风条纹影像纹理特征的海面风向反演方法精度高,但是依赖于图像风条纹的存在,而外部风向信息与SAR资料时空分辨率不易匹配、精度较低,从而影响大面积、高分辨率海面风场反演的精度。针对此问题,提出一种将SAR图像风条纹线性纹理特征与外部风向信息相结合的星载SAR海面风向获取方法,在SAR影像线性纹理特征明显的区域采用二维连续小波变换得到高精度的海面风向,其余区域采用与之时空相匹配的数值预报模式风向填充;并利用地球物理模型函数进一步得到海面风速,进而实现高精度、大范围海面风场的反演。为验证本文方法的有效性,利用ENVISAT/ASAR数据进行风场反演试验,并将反演结果与浮标实测数据进行比对。结果表明:在线性纹理特征明显的区域,小波方法的反演精度优于快速傅里叶变换(FFT)法和数值预报模式风向;外部风向精度略低,但与SAR观测资料时空匹配性较好,弥补了风条纹风向的不足。二者的结合为星载SAR海面风场反演的业务化应用提供了支持。     

中国海草资源分布现状、退化原因与保护对策

海草床是三大典型的近海海洋生态系统之一,具有极高的生态服务功能。然而,截至2015年我国近海海草资源分布现状尚不明晰,严重制约了我国海草床保护与修复工作的开展。2015～2021年,笔者通过实地调查,借助船只走航、声呐探测、遥感等技术手段,重点对我国近海海草资源的分布面积、种类及主要威胁进行了全面普查,并据此提出我国海草床管理与可持续利用对策。结果表明,我国近海海域海草床面积共为26 495.69hm²,可划分为:温带海域海草分布区和热带-亚热带海域海草分布区;我国现有海草4科9属16种。其中,温带海域海草床面积为17 095.01 hm2,主要分布在辽宁、河北、天津和山东沿海,分布有2科3属5种,以鳗草(Zosteramarina)和日本鳗草(Z.japonica)为优势种,其中唐山乐亭-曹妃甸海草床面积达9 025.56 hm2,是我国面积最大的海草床;热带-亚热带海域海草床面积为9 400.68 hm2,主要分布在福建、广东、广西和海南沿海,分布有4科8属12种,以泰来草(Thalassia hemprichii)、海菖蒲(Enhalus acoroides...     

利用RADARSAT-1数据提取海水养殖区面积

利用2001年胶州湾RADARSAT-1数据,探讨了SAR影像在海水养殖面积监测方面的可行性。选择适当成像参数、天气与海况等环境条件下成像的遥感数据,进行SAR影像的几何校正、图像增强等图像处理,提取养殖区面积信息。选取胶州湾西北部大沽河口至红岛间的海域作为实验区,对处理后的影像进行养殖区面积的提取,结合常规调查数据对该海域养殖类型变迁分析,结果表明1999到2001年间有4.634×106m2海域由底播养殖区转变成水面养殖区。     

Oil seeps in the southeastern Black Sea studied using satellite synthetic aperture radar images

One of the tasks being completed while oil pollution monitoring in the Black Sea, was a study of natural seepage. Two known oil seeps are located in the southeastern section, the Georgian sector, from which crude oil enters the marine environment. The archives of European Space Agency and ScanEx Research and Development Center have a considerable quantity of synthetic aperture radar (SAR) images acquired in 1993–2011 by the ERS-1/2, Envisat, and Radarsat-1 satellites, on which seep oil slicks are clearly visible in this region. Processing of the collected SAR images with detected slicks in combination with the geoinformation approach has revealed a link of these slicks with the bottom sources on the local sedimentary structure in the Southeast Black Sea; their analysis provides both new insight into this phenomenon and new information to help understand nature of these oil seeps. On the basis of an analysis of collected SAR images and detailed bathymetric data, information on the source positions on the bottom and estimates of oil volumes entering the sea surface are obtained.     

基于SAR图像雨团足印的海面风向提取方法

利用地球物理模式函数进行SAR海面风速反演时,需以风向作为地球物理模式函数的输入。本文应用了一种利用SAR图像上雨团足印顺风一侧比逆风一侧明亮的图像特征的海面风向提取方法,以进行海面风速反演。4景RADARSAT-2卫星SAR示例数据风向提取结果相对于ASCAT散射计的风向均方根误差满足不大于16°。分别以本文方法提取的风向和ASCAT散射计风向作为输入,利用地球物理模式函数CMOD5进行海面风速的SAR反演,两者的风速反演结果基本一致,其均方根误差差值不超过0.3 m/s。本文利用SAR图像雨团足印信息的风向提取方法准确可靠,可应用于SAR海面风速反演。     

基于双极化SAR图像的U-Net海冰多分类模型

北极多年冰在近几十年有明显的减少趋势,与北极海冰的厚度、体积和夏季最小海冰范围的减少密切相关。合成孔径雷达(synthetic aperture radar, SAR)具有全天时、全天候成像能力,基于SAR卫星影像的海冰分类对监测北极多年冰具有重要意义。基于深度学习U-Net模型,以SAR图像的双极化信息为模型输入,构建了像素级的海水、一年冰和多年冰多分类模型。与已有SAR图像海冰分类方法(支持向量机、随机森林和卷积神经网络)进行对比,基于双极化SAR图像的U-Net海冰分类模型的准确率、平均重叠度和Kappa系数,分别达到了90.73%、0.831和0.849,优于其他对比模型,分别提升了4.08%～19.04%, 0.063～0.321和0.111～0.335。此外,针对SAR图像水平-垂直极化(horizontal-vertical polarization, HV)有明显的条状热噪声和水平-水平极化(horizontal-horizontal polarization, HH)受入射角效应而亮度不均匀的特点,设计敏感性实验,研究HV噪声、入射角和灰度共生矩阵(gray leve...     

A synthetic aperture radar sea surface distribution estimation by n-order Bézier curve and its application in ship detection

To dates,most ship detection approaches for single-pol synthetic aperture radar(SAR) imagery try to ensure a constant false-alarm rate(CFAR).A high performance ship detector relies on two key components:an accurate estimation to a sea surface distribution and a fine designed CFAR algorithm.First,a novel nonparametric sea surface distribution estimation method is developed based on n-order Bézier curve.To estimate the sea surface distribution using n-order Bézier curve,an explicit analytical solution is derived based on a least square optimization,and the optimal selection also is presented to two essential parameters,the order n of Bézier curve and the number m of sample points.Next,to validate the ship detection performance of the estimated sea surface distribution,the estimated sea surface distribution by n-order Bézier curve is combined with a cell averaging CFAR(CA-CFAR).To eliminate the possible interfering ship targets in background window,an improved automatic censoring method is applied.Comprehensive experiments prove that in terms of sea surface estimation performance,the proposed method is as good as a traditional nonparametric Parzen window kernel method,and in most cases,outperforms two widely used parametric methods,K and G0 models.In terms of computation speed,a major advantage of the proposed estimation method is the time consuming only depended on the number m of sample points while independent of imagery size,which makes it can achieve a significant speed improvement to the Parzen window kernel method,and in some cases,it is even faster than two parametric methods.In terms of ship detection performance,the experiments show that the ship detector which constructed by the proposed sea surface distribution model and the given CA-CFAR algorithm has wide adaptability to different SAR sensors,resolutions and sea surface homogeneities and obtains a leading performance on the test dataset.     

Atmospheric frontal gravity waves observed in satellite SAR images of the Bohai Sea and Huanghai Sea

In the satellite synthetic aperture radar (SAR) images of the Bohai Sea and Huanghai Sea, the authors observe sea surface imprints of wave-like patterns with an average wavelength of 3.8 km. Comparing SAR observations with sea surface wind fields and surface weather maps, the authors find that the occurrence of the wave-like phenomena is associated with the passing of atmospheric front. The authors define the waves as atmospheric frontal gravity waves. The dynamical parameters of the wave packets are derived from statistics of 9 satellite SAR images obtained from 2002 to 2008. A two-dimensional linear physical wave model is used to analyze the generation mechanism of the waves. The atmospheric frontal wave induced wind variation across the frontal wave packet is compared with wind retrievals from the SAR images. The CMOD-5 (C-band scatterometer ocean geophysical model function) is used for SAR wind retrievals VV (transmitted vertical and received vertical) for ENVISAT and HH (transmitted horizontally and received horizontally) for RADARSAT-1. A reasonable agreement between the analytical solution and the SAR observation is reached. This new SAR frontal wave observation adds to the school of SAR observations of sea surface imprints of AGWs including island lee waves, coastal lee waves, and upstream Atmospheric Gravity Waves (AGW).     

一种增强型YOLOv3的合成孔径雷达(SAR)舰船检测方法

近年来,海战场成为现代战争的主要作战区域之一,舰船目标逐渐成为海上重点监测对象,能否快速准确地识别海战场舰船目标的战术意图,给指挥员的决策提供必要的支持,这关系到一场海上战役的成败。随着合成孔径雷达(synthetic aperture radar, SAR)成像技术的不断发展,大量SAR图像可用于舰船目标检测与识别。利用SAR图像进行舰船目标检测与识别,已经成为重要的海洋应用之一。针对传统SAR图像舰船检测方法准确率较低的问题,本文在YOLOv3的基础上,结合感受野(receptive fieldblock,RFB)模块,提出一种增强型的SAR舰船检测方法。该方法在最近公开的SAR图像舰船检测数据集上平均准确率值达到了91.50%,与原YOLOv3相比提高了0.92%。实验结果充分表明本文提出的算法在SAR舰船的检测中具有较好的检测效果。     

Growth and gonad production of the sea urchin Hemicentrotus pulcherrimus in the fucoid bed and algal turf in northern Japan

To clarify the differences in the growth and gonad size of the sea urchin Hemicentrotus pulcherrimus among algal sere, the study was conducted in June and July, and September 1998 at three fucoid beds in Oga and at three algal turfs in Hachimori, Akita Prefecture in northern Japan. The most rapid growth was observed in a large perennial fucoid bed at the climax stage. Growth in a small perennial Chondrus ocellatus‐dominated bed in algal turfs in the seral stage was then high. The slowest growth was observed in the small perennial Dictyopteris divaricata‐ and Laurencia spp.‐dominated beds which are known to possess chemicals which act as feeding deterrents against the sea urchins. The gonad index (gonad wet weight × 100/body wet weight) at a fucoid bed was high where standing crops exceeded 3 kg·m^?2. The gonad index in the Laurencia bed was lower than those at fucoid beds. These results suggest that growth and gonad production are affected by algal sere and differ among species of small perennial algae in the seral stage with or without chemical defense.     

Spatial structure within a dense bed of the brittle starOphiura sarsi (Ophiuroidea: Echinodermata) in the bathyal zone off otsuchi,Northeastern Japan

Photographic observations of the brittle starOphiura sarsi were conducted at a depth of approximately 280 m in the Pacific Ocean off tsuchi, northeastern Japan. Bottom photographs showed that this ophiuroid occurred in high densities, uniformly covering the sea floor and that other megafauna was rare. The mean density and biomass of ophiuroids in the dense bed were estimated to be 373 m^–2 and 124 g m^–2, respectively. Ophiuroids comprised 99% of all megabenthic organisms in terms of number of individuals, and megafaunal assemblage of the dense bed showed very low species diversity.O. sarsi exhibited a regular spatial pattern avoiding contact with conspecific neighbors. This regular spatial pattern was disrupted by certain other organisms, around which halo-like, bare areas were observed. The size and shape of these halo-like areas varied and were apparently related to the body size and/or motility of the organisms. In the present observation areaO. sarsi covered 96% of the sea bottom, and the remaining 4% was occupied by other organisms and their halo-like bare areas.     

基于面向对象和模糊逻辑的SAR溢油检测算法

星载合成孔径雷达(Synthetic Aperture Radar,SAR)具有全天时、全天候的工作能力,已被众多学者认为是非常适合探测海面溢油污染的遥感器。然而在SAR影像中经常出现"类油膜"现象,这严重干扰了SAR溢油检测的精度。因此,如何有效区分SAR影像中的油膜和类油膜,对提升溢油检测精度具有重要意义。本文利用面向对象图像分析的方法,从20景ENVISAT ASAR影像中提取了较多的溢油和类油膜样本,对其基于对象的形状、物理和纹理特征进行了综合分析,找出了适合区分溢油和类油膜的特征量。利用特征分析的结论,本文建立了一种基于模糊逻辑的溢油检测算法。该算法可以有效区分SAR影像中的溢油和类油膜,还可以给出暗斑被判定为溢油的概率。溢油检测实验说明,本文方法能够得到令人满意的效果。     

Subaqueous debris flow deposits in Baffin Bay

Thin-bedded debris flow deposits are an important constituent of the marine Quaternary, sequence in NW Baffin Bay, covering about 30,000 km² of sea floor. Individual debris flows traveled over a slope as low as 0.4° and a distance of several hundred kilometers. Some debris flows have generated turbidity currents. Debris flow deposits observed in the cores displayed distinctive downslope trends in grain size, bed thickness, and sorting, and showed variations in structures and sequences of sedimentary structures with poorly to moderately well-developed gravel fabric, showing the long axes of clasts aligned nearly parallel to the bedding plane.     

“龙王”台风SAR遥感研究

利用0519号"龙王"台风SAR遥感图像,结合NCEP/QSCAT混合风场海面风向反演了高分辨的台风海面风速。基于高分辨率的SAR台风海面风场的风速剖面,对台风期间台湾海峡及周边海域海面风场的小尺度特征及变化进行了分析,结果表明,地形对风场特征的形成有显著作用,它导致台风海面风场结构发生变形以及澎湖列岛附近低风速尾流区、台湾岛的中央山脉北端下风面"角流"区和台湾岛西北海岸背风槽(或诱生低压)等现象的形成及台风期间福建省沿海区的大风天气。