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Generalization is a comprehensive process. It is not simply a question of an algorithm, such as simplification, selection, displacement, and so on. Only after geometric shapes and topological properties have been understood fully, can a sound and automated generalization process be possible. This article proposes a new theoretical model for sounding generalization in digital nautical charts. First, with the aid of Delaunay triangulation, a tree structure is introduced for a hierarchical representation of the marine topography. Then, an analytical algorithm for the recognition and the measurement of the marine topography is developed through the use of the tree structure. Finally, all of the techniques mentioned above are integrated into a model for sounding generalization, of which results are illustrated with the aid of several examples. 相似文献
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Wenhao Yu 《Marine Geodesy》2018,41(1):68-85
Sounding acts as the main feature in a digital nautical chart as it describes the concerned marine topography for the safety of navigation. Unlike the geometry-oriented selection of point feature, the generalization of soundings for chart compiling is expected to be context-oriented, which means bathymetry complexity variations across the study region should be preserved in the sounding selection process. However, such variations are not explicitly accessible to automated systems. This paper proposes an approach that effectively analyzes and measures bathymetry complexity from sounding data, with a focus on topography variations among different regions. The presented approach first divides the exploring region into several subregions, by adopting techniques of computational geometry and graph theory. Then, the approach quantitatively measures the bathymetry complexity of the subregions from grid-based digital terrain model. Finally, a composite bathymetry complexity index integrating aspects of steepness and depth variation is developed to guide the operation of sounding selection in different subregions. Generally, when seafloor is rugged with steep slopes, the number of soundings is high. While in flatter areas, a smaller amount of soundings is retained. The potential of our approach is demonstrated by an application to a real data set. 相似文献
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利用最小二乘向量机(LS-SVM)算法构造海底趋势面的过程中,由于算法解缺乏稀疏性,使得异常测深训练样本对最终构造的函数模型也产生影响。为了解决该问题,在对留一样本交叉检核法研究的基础上提出了LS-SVM稀疏算法,由于留一样本交叉检核法求解的残差序列可以有效地表示函数预测值偏离实际水深的程度,因此利用该原则重新修剪后的样本数据不仅使算法具有稀疏特性,而且构造的函数模型更合理。为了检验算法的有效性,选取实测的多波束测深数据进行验证,计算结果表明留一样本交叉检核法能够合理地筛选出对函数模型构造贡献程度大的测深训练样本,使得构造的函数模型更合理。 相似文献
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在分析和借鉴传统的水深综合理论和方法的基础上,开展水深数据的层次性分析,对水深数据进行分类、定级和聚合等处理方法研究。在满足制图综合规范的基础上,按照水深分类数据的重要性和特征性排序,重组综合方法使用顺序和结构,从而构建层次水深综合模型。该模型能够实现水深综合的流程控制,兼顾水深综合的质量要求,为进一步开展水深自动综合的实用性研究提供了理论和技术支持,具有一定实用价值。 相似文献
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CUBE算法及其在多波束数据处理中的应用 总被引:5,自引:0,他引:5
阐述了一种基于表面生成的多波束数据处理方法——CUBE(Combined Uncertainty and Bathymetry Estimator)算法,用该方法可以对观测区域网格节点"真实"水深及相关误差进行估计。与从测量水深中选择出"最佳"数据的手工交互方式的多波束数据编辑手段不同,CUBE算法具有很强的抗差性和较高的效率,适合于实时多波束数据处理。对南海某测区多波束数据处理结果表明,在没有人工干预的情况下,利用CUBE算法去噪生成的海底DTM图与手工编辑生成的相当吻合。CUBE算法和手工编辑方法综合对比得出,CUBE算法能够很好地保留水深地形细节,在计算效率、误差评估、实时处理等方面比手工编辑方法具有较大的优势。 相似文献
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多波束数据的海底数字地形模型构建 总被引:11,自引:0,他引:11
提出大批量多格式原始多波束数据的DTM构建方法,以满足大区域、大比例尺海底地形制图的需要。在多种格式原始多波束数据接口和系统内部标准数据结构的基础上,通过对数据文件、数据种类和数据运算量的有效组织管理,实施边读入、边权重配赋的网格插值,分析了高斯、指数和距离平方反比权重函数的适用性,及最小值、最大值和平均值的实用性。在权重配赋网格插值基础上,提出分形fBM和张力样条配合使用的方程式插值方法,保证DTM数据的有效外延和地形分辨。整套算法效率高,并能有效保证DTM的精度,对存储在外部介质的数据遍历一次即可完成网格插值。 相似文献
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HYPACK综合导航定位系统是广泛应用于海洋工程水下地形地貌测量的数据采集和处理软件,它支持多种定位设备和测深设备的数据采集和处理。如何正确提取所需的数据、满足不同工程测量的特殊要求,是我们在实际使用中经常碰到的问题。分析了实测HYPACK数据,以VISUAL C 6.0为平台进行程序开发,实现了在HYPACK记录的原始文件中特定数据的处理,如航迹(点位)坐标、水深值、潮位数据等。所开发的程序实现了数据的图形可视化和由数据向DXF格式的转换,实现了数据编辑和图形效果的交互。 相似文献
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The knowledge of the bedrock topography (instead of the ocean-floor relief) is required in various geoscience studies investigating the evolution and structure of the oceanic lithosphere. The gross density structure and thickness of marine sediments were obtained from ocean drilling data or seismic surveys. Alternatively, marine gravity data corrected for the ocean and sediment density contrasts can be used for a detailed mapping of the bedrock topography. In this study, we compute and apply the sediment stripping correction to marine gravity data. The sediment density distribution is approximated by a 3-D density model derived based on the analysis of density samples from the Deep Sea Drilling Project. Methods for a spherical harmonic analysis and synthesis are utilized in computing the sediment stripping correction. Results show that this correction varies between 0 and 32 mGal. We also demonstrate that the approximation of heterogeneous sediment structures by a uniform density model yields large errors. The spectral analysis reveals a high correlation (>0.75) between the sediment-stripped marine gravity data and the bedrock topography. The application of the sediment stripping correction to marine gravity data enhanced the gravitational signature of the sediment-bedrock interface. 相似文献
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为了研究内波对多波束测深的影响,通过对内波建模,分别对四个区间的声线跟踪情况进行了研究分析。在此基础上,推导了针对曲线型梯度结构的声线跟踪模型,并根据该模型进行了仿真分析。仿真简单模拟了采用常梯度声线跟踪模型对曲线型梯度结构声速剖面进行声速改正的声线跟踪过程。采用仿真数据绘制了声线跟踪前后的声线示意图,并对归算前后的波束脚印位置进行了比较分析。仿真结果说明内波会给多波束的边缘波束带来大量尖峰状的浅点,而这些浅点难以用传统的声速改正模型消除。推导的针对曲线型梯度结构的声线跟踪模型可为内波的进一步研究提供理论依据,最后对未来的研究进行了展望。 相似文献
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海底地形对开展海洋科学调查和研究十分重要。以多波束为主的回声测深技术测量成本高且效率低,几十年来仅实现了全球约20%的海床测绘。对于空白区(特别是深海区域),可以借助重力异常和重力垂直梯度异常进行回归分析反演得到,但该方法得到的比例因子鲁棒性不强。为了解决这一问题,同时考虑到两种重力数据在表征海底地形长短波长的不同优势,本文结合滑动窗口赋权和稳健回归分析来反演海底地形。在太平洋皇帝山海域(35°~45°N,165°~175°E)的实验结果表明:在船测检核点处,本文构建模型的标准差为61.02 m,相比于单一重力数据反演模型,精度分别提高了14.92%(重力异常)和2.08%(重力垂直梯度异常),能较好地反映皇帝海山链的地形走势。 相似文献
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阐述了使用多波束测深系统对东海大桥轴线水下地形扫测的技术方法,采用GPS实时动态测量、多站位同步验潮、测深精度的有效控制等方法,使大桥轴线水下地形测量和扫海工作的质量与效率明显地提高。扫测成果为东海大桥桥墩的打桩施工和主通航孔的方向确定提供了科学数据与决策依据。 相似文献
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J. J. Becker D. T. Sandwell W. H. F. Smith J. Braud B. Binder J. Depner 《Marine Geodesy》2013,36(4):355-371
A new 30-arc second resolution global topography/bathymetry grid (SRTM30_PLUS) has been developed from a wide variety of data sources. Land and ice topography comes from the SRTM30 and ICESat topography, respectively. Ocean bathymetry is based on a new satellite-gravity model where the gravity-to-topography ratio is calibrated using 298 million edited soundings. The main contribution of this study is the compilation and editing of the raw soundings, which come from NOAA, individual scientists, SIO, NGA, JAMSTEC, IFREMER, GEBCO, and NAVOCEANO. The gridded bathymetry is available for ftp download in the same format as the 33 tiles of SRTM30 topography. There are 33 matching tiles of source identification number to convey the provenance of every grid cell. The raw sounding data, converted to a simple common format, are also available for ftp download. 相似文献