基于数学形态学图像分割的波向检测

根据波浪图像的纹理特征,提出了一种基于数学形态学图像分割的波向检测方法,该方法首先利用顶帽变换和底帽变换,得到增强的波浪纹理图像,然后对图像波谷进行应用标记的分水岭分割,最后利用波谷形态方向提取出波浪方向,实验结果证明该算法能够有效地实现波向检测。     

地理信息的快速检索与捕捉

本文介绍了将海图图形信息和拓扑关系信息用链索引结构存放在同一个海图文件中的一种较复杂的数据结构,并提出了采用速查标记BITMAP、坐标极值、数据实体细检索的三级要索检索方法,大大提高了地理信息的检索与捕捉速度。较详细地给出了各类要素的速查标记BITMAP的生成算法,最后介绍了在一个系统中进行地理信息快速检索与捕捉的具体实现过程。     

改进BP算法在风暴潮极值水位预报中的应用

提出1种基于改进BP算法的风暴潮极值水位预报方法。首先针对现有人工神经网络BP算法存在的缺陷,引入Cauchy训练方法计算连接权的调整,解决BP算法的局部极小点和网络瘫痪的问题。然后结合山东海区水文观测站每年的台风风暴潮资料,应用该改进算法建立台风强度、风速和台风移速与风暴潮极值水位的非线性网络预报模型,对该站极值水位进行预报。实验结果表明,该算法具有很好的稳定性和准确性,为风暴潮预报分析提供了1种可靠的技术手段。     

基于纹理特征的围填海SAR图像分水岭分割方法

本文提出了一种基于纹理特征的围填海SAR图像分水岭分割方法,首先对机载MiniSAR图像进行灰度共生矩阵纹理滤波,获得纹理特征图像,再对纹理特征图像进行分水岭算法分割,将获得的形态学重建图像进行门限阈值分割,得到最后的二值化分割结果。该方法一方面通过调整灰度共生矩阵纹理滤波的窗口大小,抑制了斑点噪声的影响;另一方面,利用分水岭算法对边缘模糊杂乱图像的优势,提高了围填海信息提取的准确性。实验结果表明,本方法对高分辨率SAR图像围填海监测图像的分割效果良好。     

希尔伯特-黄变换的端点延拓

希尔伯特-黄变换(HHT)是近年来发展起来的一种新的时间序列信号分析方法.该文在对HHT深入研究与充分肯定的基础上,发展了信号的镜像闭合延拓和包络的极值延拓两种方法.通过几个典型的例子检验了两种方法,并与Huang等(1998,1999)进行了比较,得到了令人满意的结果.镜像闭合延拓法根据信号端点的分布特性,把镜子放在具有对称性的极值位置,通过镜像法把镜内信号映射成一个周期性的信号,不存在端点,从根本上避免了经验模态分解和希尔伯特变换的端点问题.极值延拓法简单易行,具有与镜像闭合法相当的效果,在处理非对称波形信号时更显其优越性.     

变分同化研究中最速下降算法的一个改进

对于变分同化中经常遇到的多极值问题，一般的优化算法无法解决。以最速下降算法为例，提出一种改进方法，在迭代到某个极值点时，自动跳出该极值点附近去寻找下一个极值点，直到找到满意的最小值点为止。原则上这种改进算法可推广应用到其它优化算法中。     

基于互信息和相关比算法的声呐图像配准

针对互信息算法在配准图像过程中易陷入局部极值的问题,提出了一种新的算法,即将互信息和相关比按一定的标准组合在一起,生成一种新的测度算法,并将该算法应用到了多波束图像和侧扫声呐图像的配准中。该组合算法可以改善互信息测度易陷入局部极值的弊端,稳定性更强。通过实验验证,新的组合算法是准确的,可以较好地实现存在较大畸变的多波束和侧扫声呐图像的配准,配准速度和精度优于互信息算法和相关比算法,新的组合算法是对原有算法的改进和优化。     

Weibull分布参数的粒子群算法估计

基于广西涠洲岛海洋监测站3个方向的年极值波高观测资料,在假设其服从Weibull分布的基础上,运用最小二乘法,矩估计法和最速下降法对Weibull分布的参数进行估计,同时引入粒子群算法确定Weibull分布的3个参数,对文中4种方法得出的拟合结果及运算效率进行比较分析,说明了粒子群算法在估计极值分布参数中的优势.     

一种光照变化条件下的自适用权重局部立体匹配算法

基于Census变换的局部立体匹配算法,对于光照变换具有较高的鲁棒性,但在图像内视差不连续区域存在匹配误差,导致前景膨胀现象。本文提出一种新的在RGB空间基于稀疏Census变换的自适应权重的局部立体匹配算法。通过在RGB 3个彩色通道分别进行稀疏Census变换,根据颜色距离和空间距离,计算在局部窗口中各个像素的权重,从而进行聚合。实验结果表明,该算法能够有效消除前景膨胀现象,提高了对视差不连续区域的匹配准确度,同时提高了光照变换的鲁棒性。     

极值分布参数的非线性估计及其工程应用

本文基于高斯—牛顿法,在理论频率与实际频率残差平方和最小这一适线准则下,实现了三种极值分布参数的非线性估计。该算法计算精度高,收敛速度快,对观测数据拟合程度较佳。文中对三种极值分布与P-Ⅲ型分布、对数正态分布进行了适线比较,所做工程算例表明;极值Ⅱ型所得小概率设计参数最大,极值Ⅰ型次之,威布尔分布最小,P-Ⅲ型与对数正态分布居中。本文采用的分布参数拟合方法同样适用于其它线型。     

基于ZY-3遥感影像的不同地貌水边线提取方法

水边线的精确提取对于沿海地区的经济开发和海域的使用管理具有重要意义。以雷州半岛东北部为研究区域,利用2017年资源三号(ZY-3)卫星数据为数据源,基于不同海岸地貌特征为划分依据,运用阈值分割法、神经元网络分类法和面向对象法对多光谱数据的人工海岸、砂质海岸、淤泥质海岸和红树林海岸进行水边线提取。通过目视解译提取融合图像的海岸线为基线,将提取的水边线与基线进行定性、定量分析。研究结果表明,对于人工岸线,神经元网络分类法最优,均方根误差为6.4m;对于砂质岸线,阈值分割法最优,均方根误差为5.4m;对于淤泥质及红树林岸线,面向对象法最优,均方根误差分别为23.3m和15.2m。该研究对于不同岸线的提取具有重要的借鉴和指导意义。     

Digital Tide-Coordinated Shoreline

The shoreline is one of the most important features on earth's surface. It is valuable to a diverse user community. But the dynamic nature of the shoreline makes it difficult to be represented in a naturally dynamic style and to be utilized in applications. The officially used shoreline, for example in nautical charts, is the so-called tide-coordinated shoreline. It is also the shoreline that makes the computation of shoreline changes and associated environmental changes meaningful. Mapping of the tide-coordinated shoreline has been very costly. On the other hand, instantaneous shorelines extracted from different data sources may be available. Also, high-resolution satellite and airborne imagery have the capacity of stereo imaging and can be used to extract instantaneous shorelines at a high accuracy and low cost. This article proposes an approach to derivation of digital tidecoordinated shorelines from (a) those instantaneous shorelines and (b) digital coastal surface models and a digital water surface model. Some preliminary study results, analysis, and the potential of the approach are discussed.     

Digital Tide-Coordinated Shoreline

The shoreline is one of the most important features on earth's surface. It is valuable to a diverse user community. But the dynamic nature of the shoreline makes it difficult to be represented in a naturally dynamic style and to be utilized in applications. The officially used shoreline, for example in nautical charts, is the so-called tide-coordinated shoreline. It is also the shoreline that makes the computation of shoreline changes and associated environmental changes meaningful. Mapping of the tide-coordinated shoreline has been very costly. On the other hand, instantaneous shorelines extracted from different data sources may be available. Also, high-resolution satellite and airborne imagery have the capacity of stereo imaging and can be used to extract instantaneous shorelines at a high accuracy and low cost. This article proposes an approach to derivation of digital tidecoordinated shorelines from (a) those instantaneous shorelines and (b) digital coastal surface models and a digital water surface model. Some preliminary study results, analysis, and the potential of the approach are discussed.     

Instantaneous Shorelines as an Intermediate for Island Shoreline Mapping based on Aerial/Satellite Stereo Images

Island shoreline mapping based on field measurements by collecting visually discernible features is costly and even unrealistic to be implemented in practice because of the nonuniqueness, fuzziness, and ambiguity of shoreline features. The MHHW (the mean higher high water) shoreline, i.e., the intersection of the coastal profile with the MHHW, is recommended to be chosen as a significant shoreline indicator of an island. An approach for mapping the MHHW shoreline using the aerial/satellite stereo images is proposed. In the proposed procedure, first, the height difference between the instantaneous shoreline and the MHHW shoreline is calculated by the ocean tide model; then the orthometric/normal height of the instantaneous shoreline is determined from the stereo images; last, the instantaneous shoreline is used as an intermediate for determination of the height of the MHHW shoreline. The proposed procedure is applied to the MiaoZiHu Island located in the East China Sea. Preliminary experimental result shows that in ideal cases, the horizontal positional accuracy of the extracted shoreline can reach 0.2 m from aerial images of 0.1 m resolution.     

空间分辨率对海岸线时空演变遥感分析的影响——以渤海湾为例

文章针对中低分辨率遥感影像难以提取海岸线中小尺度变化的实际问题,以渤海湾为例,利用2010—2020年SPOT5、GF-1/6、ZY-3等高分辨率遥感影像,采用数字海岸线分析和分形维数方法获取渤海湾海岸线位置变迁速率和复杂度变化过程;针对目前渤海湾海岸线变迁分析研究多基于中低分辨率遥感影像的问题,结合同时期的Landsat影像,分析遥感影像空间分辨率对渤海湾海岸线变迁速率和分形维数的影响。研究结果表明,遥感影像空间分辨率差异对分形维数的影响较小,但对不同类型的岸线变迁速率影响显著;渤海湾海岸线在2010—2020年的变化呈现出由剧烈过渡至相对稳定的状态,伴随着海岸线位置的变化,岸线的分形维数呈现出先上升再至平稳的趋势。相关研究成果能够为渤海湾地区海洋资源利用优化、海岸线及滩涂湿地等自然资源保护提供数据支持。     

Google Earth: A New Resource for Shoreline Change Estimation—Case Study from Jaffna Peninsula,Sri Lanka

Abstract

Estimation of shoreline change using satellite images is considered as a very effective method because the coastline is found highly dynamic. This study focuses to develop a methodology to detect shoreline changes using satellite imageries obtained from Google Earth platform. The study was carried out in north-east coastline of Jaffna in Sri Lanka. Shorelines from 2002 to 2017 were delineated on the multi-temporal satellite images in the Google Earth software by visual interpretation and change was detected using Digital Shoreline Analysis System in ArcGIS. Tidal variation, digitizing error, and geometric errors were considered to calculate the uncertainty. Mean End Point Rate, mean Shoreline Change Envelop, mean Net Shoreline Movement, and mean Weighted Linear Regression Rate were used as main shoreline change statistics. Result shows that there is net shoreline accretion of 6.13?±?8.74 m with an annual rate of deposition of 0.5?m/year. During the study period, 76.12% of the observed shoreline is found accreted while the 23.88% of the shoreline is eroded. Mean Uncertainty of the shoreline is 3.73?±?0.59 m. The study revealed that the satellite images from Google Earth platform can be used for time series analysis of shorelines after appropriate corrections.     

Hurricane impact and recovery shoreline change analysis of the Chandeleur Islands,Louisiana, USA: 1855 to 2005

Results from historical (1855–2005) shoreline change analysis conducted along the Chandeleur Islands, Louisiana demonstrate that tropical cyclone frequency dominates the long-term evolution of this barrier island chain. Island area decreased at a rate of −0.16 km²/year for the relatively quiescent time period up until 1996, when an increase in tropical cyclone frequency accelerated this island area reduction to a rate of −1.01 km²/year. More frequent hurricanes also affected shoreline retreat rates, which increased from −11.4 m/year between 1922 and 1996 to −41.9 m/year between 1982 and 2005. The erosional impact caused by the passage of Hurricane Katrina in 2005 was unprecedented. Between 2004 and 2005, the shoreline of the northern islands retreated −201.5 m/year, compared with an average retreat rate of −38.4 m/year between 1922 and 2004. A linear regression analysis of shoreline change predicts that, as early as 2013, the backbarrier marsh that serves to stabilize the barrier island chain will be completely destroyed if storm frequency observed during the past decade persists. If storm frequency decreases to pre-1996 recurrence intervals, the backbarrier marsh is predicted to remain until 2037. Southern portions of the barrier island chain where backbarrier marsh is now absent behave as ephemeral islands that are destroyed after storm impacts and reemerge during extended periods of calm weather, a coastal behavior that will eventually characterize the entire island chain.     

基于高分遥感的西沙群岛典型海岛时空变化分析

高分辨率卫星遥感技术已成为有效监测海岛动态变化的主要手段。本文以西沙群岛社区驻地海岛、领海基点所在海岛和自然保护区所在海岛为研究对象，利用 2005 年以来的高分辨率卫星遥感影像，分析了各类海岛的时空变化情况。结果表明：社区驻地海岛变化普遍较大，特别是永兴岛、赵述岛、筐仔沙洲和银屿，主要都是由于吹沙填岛和岛上开发利用活动日益增多造成的，变化主要发生在 2012 年三沙市成立之后；领海基点所在海岛和自然保护区所在海岛相对较稳定，岛上地形、地貌及植被等基本保持原有的自然状态，变化区域主要分布在各个海岛的端头，主要是由自然因素导致的。海滩岩对海岛起到了极大的保护作用，海滩岩发育好的海岛基本保持稳定状态，而没有海滩岩发育或海滩岩被破坏的海岛则变化较大。     

基于水深分段选择因子的多光谱影像反演水深

岛礁周边海底地形精密测量是海洋测绘的难点问题之一,利用多光谱卫星能精确测定岛礁周边水深地形,是传统岛礁水深测量有效的补充方式之一。本文以蜈支洲岛周围水域为研究区域,提出了基于BP神经网络水深分段选取反演因子的方法,利用WorldView-2数据和多波束实测数据建立多模型,整合预测的各段水深获得海底地形。实验表明,本文方法能充分利用水体的光谱特性,与单一BP神经网络模型结果相比,MRE降低了6.4%,RMSE降低了1.2 m,是一种可行的多光谱水深反演的方法     

遥感水深反演海图修测应用研究

卫星遥感技术可以应用于浅海水下目标探测，是特殊区域碍航物探测的有效手段。结合海岛礁的特殊地理环境和测绘需求，采用高分辨率卫星影像进行浅水深反演试验，提出的高分辨率预处理方法实用、有效；并与海图数据结合，进行水深标定和海图修测应用分析。研究结果表明，针对南海岛礁，应用高分辨率卫星影像可以获取岛礁分布和轮廓、概略等深线信息、潜在航道以及水下障碍物信息等，能达到修测海图的目的。