共查询到20条相似文献，搜索用时 115 毫秒
1.
Due to the need of rapid and sustainable development in China’s coastal zones, the high-resolution information theory using data mining technology becomes an urgent research focus. However, the traditional pixel-based image analysis methods cannot meet the needs of this development trend. The paper attempts to present an information extraction approach in terms of image segmentation based on an object-oriented algorithm for high-resolution remote sensing images. An aim of the author’ research is to establis... 相似文献
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A detection model of underwater topography with a series of SAR images acquired at different time 总被引：1，自引：1，他引：0
underwater topography is one of oceanic features detected by Synthetic Aperture Radar. Underwater topography SAR imaging mechanism shows that tidal current is the important factor for underwater topography SAR imaging. Thus under the same wind field condition, SAR images for the same area acquired at different time include different information of the underwater topography. To utilize synchronously SAR images acquired at different time for the underwater topography SAR detection and improve the precision of detection, based on the detection model of underwater topography with single SAR image and the periodicity of tidal current, a detection model of underwater topography with a series of SAR images acquired at different time is developed by combing with tide and tidal current numerical simulation. To testify the feasibility of the presented model, Taiwan Shoal located at the south outlet of Taiwan Strait is selected as study area and three SAR images are used in the underwater topography detection. The detection results are compared with the field observation data of water depth carried out by R/V Dongfanghong 2, and the errors of the detection are compared with those of the single SAR image. All comparisons show that the detection model presented in the paper improves the precision of underwater topography SAR detection, and the presented model is feasible. 相似文献
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Quality Control of ARGO Data Based on Climatological T-S Models 总被引：1，自引：0，他引：1
By implementing the ARGO program, a large number of T-S profiles can be observed in the world ocean. However, it is very difficult to examine changes of the sensitivity of the sensors equipped at the ARGO floats, because it is difficult to understand their condition in the sea and the reliability of the data. Quality control must be done in order to avoid the wrong conclusion deduced from the wrong data.One of the realistic methods for quality control of the ARGO data is the comparison with the local climatology. High quality climatological T-S models in northwest Pacific have been built based on the Nansen bottle data and CTD data for the quality control in NMDIS. The models are used to check the ARGO data in this area and have got good result. 相似文献
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Using data of wind speed, air temperature and humidity recorded simultaneously on board and the on the small buoy, the latter is considered as criterion, the paper has discussed the influence of the body of ship on the meteorological data. Owing to the disturbance and the influence of heat radiation from the body of ship, the temperature observed on board is higher by about 2癈 than on buoy, and the relative humidity lower by 10%, wind speed observed on the mast is not only irregular but is less than that on the buoy, the error of which would be 3 m/s. The paper therefore suggests that the data observed on the deck in daytime, especially in fair weather after midday, is less reliable. The reliability of data decreases simultaneously with the increase of the body of ship in size.In addition, this paper also proposes that more reasonable observing points chosen on board should be the key to obtain reliable data. By analysis, it is believed that the meteorological data observed on ship's bow or upwind outs 相似文献
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Dong Guohai Li Yucheng Wang Yongxue
Lecturer Doctor Dalian University of Technology Dalian
Professor Dalian University of Technology Dalian 《中国海洋工程》1995,(1)
- A large amount of experimental analysis and systematical theoretical calculation has been done by the authors to solve the problem of wave transformation and breaking, considering the effect of both current and topography, but only the wave energy loss due to spilling breaker in the surf zone has been discussed in this paper. Based on test result analysis and calculation with the Stream Function Wave Theory, the wave velocity field at breaking points has been obtained, and it is used to calculate the wave heights after breaking by the VOF (Volume of Fluid) method, in which the governing equations are continuity equation and Navier-Stokes Equation for imcompressible fluids. In the present paper, the improved VOF technique is used to calculate the wave heights of stable regular waves after breaking. Results fit the test data well, which shows that the VOF method is suitable to numerical simulation of regular waves after breaking. Besides, the breaker coefficient B of regular waves in the bore model is a 相似文献
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Surface elevation is the basic data for geo-science. It is difficult to retrieve tidal-flats’ elevation from single Remote Sensing (RS) image because of the complicated sediment dynamical environment and huge spatial difference in tidal-flats’ moisture content. A Digital Elevation Model (DEM) construction method for inconstant inter-tidal zone based on high tempo-resolution MODIS data set in a short period is proposed in a case study on the Dongsha Sandbank of the Jiangsu Radial Tidal Sand-ridges. In the present study, a batch-preprocessing method based on image partition to handle massive MODIS 1B images is developed and applied to 8163 scenes of MODIS images. The dataset of short-period and multi-temporal MODIS images for inter-tidal flats’ DEM inversion is selected and the usability of MODIS dataset is analyzed. Shorelines of the Dongsha Sandbank are extracted by use of batch supervised classification. In accord with tidal-level forecasted by the Chenjiawu Tidal Gauge Station at the overpass moment of each RS image, DEMs of inter-tidal flats in January and summer(Jul, Aug and Sept), 2003 were built under ArcGIS9.2. Studies show that: (1) The dataset of short-duration and multi-phase MODIS images can be used to retrieve the historical DEM of tidal-flats at changeful tidal flats. (2) Analysis on usability of MODIS images from Aqua and Terra indicates that there are more usable and high-quality MODIS images in spring, autumn and winter, but less in summer. Therefore, the period for building inter-tidal flats’ DEM is suggested to be one month in spring, autumn and winter and three months in summer. 相似文献
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You Yuming Hou Min Senior Engineer River Harbour Department Nanjing Hydraulic Research Institute Nanjing Assistant Engineer River Harbour Department Nanjing Hydraulic Research Institute Nanjing 《中国海洋工程》1992,(3)
- The data of landsat TM of multi-temporal for Lingdingyang Estuary, Pearl River in China is firstly used with suspended sediment concentration of field measurement to establish a correlative model equation. After the ratio processing of TM data and atmospheric correction, the images of suspended sediment concentration of different temporals are exported from the image processing systems AREIS II and III. These images express the characteristics of suspended sediment distribution, the mode of sediment transport and the extent of dispersion under the actions of tidal current and wind condition of different seasons. 相似文献
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Determinded in this paper are 18 isotherms of Cu2 and Pb2 partitioning between liquid and solid (kaolinite, illite and montmorillonite), all proved to be "ion exchange-precipitation" isotherms. This is a new type of isotherms in marine chemistry. We have used the modified BET and T6th equations to describe them. In this paper, we proposed the third expression, i. e. de Boer-Zwikker equation. Theoretically, this method has a proper chemical model. Practically, it is simple and easy to compare with experimental data. 相似文献
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A study of oil spill detection using ASAR images 总被引：5，自引：3，他引：2
The oil spilled worldwide causes ecological disasters that result in enormous damages to the quality of marine environment, and great expenses on clear-up operations are needed. Due to its wide coverage and day-night all-weather observation capability, Synthetic Aperture Radar (SAR) is an important tool for oil spill monitoring and detection. C-band SAR is well adapted to detect oil pollution because oil slicks dampen the Bragg waves and reduce radar backscattering coefficients. In order to detect the area of oil slicks, the algorithm consists of these steps:Preprocessing, Masking of land areas, Detection of dark spots, Spot feature extraction, Dark spot classification. In this paper, the authors examined two coastal regions around Hong Kong and Yantai, China. The obtained results performed on Envisat ASAR images have demonstrated that it is efficient to detect oil spill around the coastal regions. The methodology still needs to be refined with the collection of more SAR data in the near future. 相似文献
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This paper describes a new framework for object detection and tracking of AUV including underwater acoustic data interpolation, underwater acoustic images segmentation and underwater objects tracking. This framework is applied to the design of vision-based method for AUV based on the forward looking sonar sensor. First, the real-time data flow (underwater acoustic images) is pre-processed to form the whole underwater acoustic image, and the relevant position information of objects is extracted and determined. An improved method of double threshold segmentation is proposed to resolve the problem that the threshold cannot be adjusted adaptively in the traditional method. Second, a representation of region information is created in light of the Gaussian particle filter. The weighted integration strategy combining the area and invariant moment is proposed to perfect the weight of particles and to enhance the tracking robustness. Results obtained on the real acoustic vision platform of AUV during sea trials are displayed and discussed. They show that the proposed method can detect and track the moving objects underwater online, and it is effective and robust. 相似文献
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相位差测深声呐(Phase Differencing Bathymetric Sonar,PDBS),也被称作干涉式声呐(Interferometric Sonar),可以同步采集水深点云数据和双频侧扫声呐图像,完全适用于大范围的近海人工鱼礁探测。本文采用基于PDBS原理的Edge Tech 6205地形地貌一体化测量设备对莱州湾某海域海洋牧场投礁区进行全覆盖探测,获取了高精度水深数据以及双频侧扫声呐图像。对水深数据进行地形特征变量计算,精细刻画了研究区的微地形地貌特征,并结合侧扫声呐图像通过多数据融合实现了对鱼礁边界的精准识别。在此基础上利用地理信息系统中的空间分析方法对人工鱼礁的水下物理参数进行计算和统计,并探讨了研究区地形地貌的成因及其演化模式,最后论证了基于PDBS的近海人工鱼礁探测技术具有高效率、低成本、高精度等诸多优势。研究结果表明,研究区水深介于4.1~7.3 m,鱼礁分布区有较大的海底起伏且在礁体周围存在明显的沉降和冲刷现象;鱼礁总占地面积约占研究区的14.04%,总空方量共计2 528.22 m3,鱼礁高度介于1.26~3.63 m且呈正态分布。本研究为近海人工鱼礁探测提供了数据和技术支撑,具有较强的实践意义。 相似文献
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基于小波变换的声纳图像边缘特征检测研究 总被引：1，自引：0，他引：1
声纳图像的边缘特征检测是其目标识别技术的重要技术基础。声纳图像背景复杂、噪声污染严重,而传统的边缘检测方法对图像噪声非常敏感,所以针对这一特点,利用小波变换易于消除噪声、运算方便的数学特征,提出了一种基于小波变换的声纳图像边缘特征检测算法。由计算机仿真结果可以得到,与传统的边缘检测算法相比,此算法在有效地抑制噪声的同时,还可以得到较高的边缘定位精度,能够很好地检测到原始声纳图像的边缘。 相似文献
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Abstract The paper describes a general mathematical model for the determination of depths, using “stereoscopic”; Side Scan Sonar images. It is based on the assumption that the attitude and position parameters of the sensor can be continuously recorded or reconstructed by calculation. 相似文献
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Sonar image segmentation based on GMRF and level-set models 总被引：2，自引：0，他引：2
We propose two new level-set models to address the segmentation problem in sonar images. Local texture features, extracted using the Gauss-Markov random field model, are integrated into level-set energy functions to dynamically select regions of interest. Then, new two-phase level-set and multiphase level-set models are obtained by minimizing each new energy function, and the selection of model parameters is analyzed. The proposed models do not require re-initialization, which is usually a very costly procedure. Segmentation experiments on both synthetic and real sonar images show that the proposed two level-set models are accurate and robust when they are applied to noisy sonar images. 相似文献
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旁侧声呐在海底探测中的应用和工作船动态定位施工技术 总被引：1，自引：0，他引：1
随着海洋工程建设及海上事故和海难的增多,日益增加的海底障碍物给海上安全生产和航运带来了前所未有的挑战和安全隐患,需要进行海上搜寻和水下探摸与处理。旁侧声呐和动力定位船的配合使用是处理这类问题的最佳选择,但租用动力定位船费用昂贵,成本很高。而根据工作区的实际情况利用渔船改装的动态定位船操作简单,且费用低廉,被海洋工作者广泛采用。本文介绍了旁侧声呐在海底障碍物探测中的应用和渔船改装的GPS动态定位船进行水上定位的工作原理和施工方法。装备GPS导航软件的渔船可以指示船只的实时位置。通过改变锚绳长度来改变船只位置的动态定位技术适用于水下搜寻和探摸处理工作。 相似文献
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This paper is concerned with the application of active contour methods to unsupervised binary segmentation of high-resolution sonar images. First, texture features are extracted from a sidescan image containing two distinct regions. A region-based active contour model of Chan et al. [J. Vis. Commun. Image represent, vol. 11, pp. 130-141,2000] is then applied to the vector-valued image extracted from the original data. Our implementation includes a new automatic feature selection step used to readjust the weights attached to each feature in the curve evolution equation that drives the segmentation. Results are shown on simulated and real data. The influence of the algorithm parameters and contour initialization are also analyzed. 相似文献
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基于灰度直方图和几何特征的声纳图像目标识别 总被引：2，自引：0，他引：2
目标形状因子和长、宽、高等几何特征,与目标类别具有很大的关系,而灰度直方图也是目标物理特性的直接表现。根据采用马尔可夫随机场理论分割后的声纳目标和阴影图像,利用其灰度直方图曲线进行目标的聚类分析,再利用几何特征进行类别识别,经实测的数据验证,取得了较好的效果。证明该方法可有效表征不同目标的物理特性,从而区分不同类别的目标,避免了目标绝对反向散射强度的复杂计算,增强了抗噪性。以搜寻目标的几何特征为输入参数,可迅速锁定要搜寻的目标,借助其它探测手段,实现目标的自动识别。 相似文献