共查询到20条相似文献，搜索用时 281 毫秒
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针对当前海图制图过程中作业人员识别特殊水深效率低下、易发生错漏等缺点,借鉴坡度的概念,定义了图示坡度及其计算方法;通过分析海图水深大小与其之间间隔距离的关系,借鉴当前海道测量学中对特殊深度的分级标准,对特殊水深的判断及分级标准设计了明确的量化分级指标,提出了一种海图特殊水深的定量识别分析方法。实验结果表明:所提方法能准确识别特殊水深;作业效率明显高于当前普遍使用的手工识别方法;将特殊水深分为强、中、弱三个等级,可为以后给不同等级的特殊水深设计有区别的海图符号提供参考依据。 相似文献
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本文通过对Delaunay三角网的利用和对TIN(Triangulated Irregular Network不规则地形三角网)的化简方法实现了对海图中特征水深注记的选取;并在此基础上建立了具有水深注记分区选取、人机交互选取水深注记、菱型网设置、三角网检测等多项功能的海图水深注记自动综合子系统。 相似文献
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针对当前海图抽选过程由于缺乏有效的海图抽选算法,而造成抽选效率不高甚至有可能漏选海图的问题,按照海图抽选原则并利用海图比例尺及海图覆盖区域信息,对船舶航行区域进行分级处理,提出了一种基于航行区域分级的海图自动抽选算法,阐述了该算法的基本思路和实现步骤,并通过实验验证了该算法的可行性。 相似文献
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Soundings on nautical charts provide information about the shape of the ocean bottom between chart depth curves. A single chart may have thousands of soundings posted on it. This article describes a system for automatic cartographic sounding selection. In this system, a new algorithm for automated selecting soundings is developed. The algorithm is employed in such a way that it can guarantee (a) fast and accurate selecting sounding, (b) processing the circular depth curves, (c) solving the overplotting problems between depth curves and soundings, and (d) keeping selected soundings “prettier.” The system was intensively tested using real data sets, and its superiority has been revealed by the testing results. 相似文献
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Soundings on nautical charts provide information about the shape of the ocean bottom between chart depth curves. A single chart may have thousands of soundings posted on it. This article describes a system for automatic cartographic sounding selection. In this system, a new algorithm for automated selecting soundings is developed. The algorithm is employed in such a way that it can guarantee (a) fast and accurate selecting sounding, (b) processing the circular depth curves, (c) solving the overplotting problems between depth curves and soundings, and (d) keeping selected soundings “prettier.” The system was intensively tested using real data sets, and its superiority has been revealed by the testing results. 相似文献
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The NOAA National Ocean Service hydrographic surveys run between 1930 and 1965 have been digitized from the paper smooth sheets. The surveys since 1965 have been collected, processed, and stored in digital form. The new multibeam systems have been used since 1984 to cover over 100,000 square nautical miles of the Exclusive Economic Zone with overlapping swaths of digital soundings. Each of these multibeam surveys may contain millions of soundings. None of the above data has been assigned quality control tags by NOS, but they are stored by survey number, with indexes showing what younger data are available to supersede older data in any area. Large digital databases, such as the Master Seaftoor Digital Database, are planned in connection with the Defense Hydrographic Initiative. It will be necessary to assign quality control ratings to the soundings in the databases. The detailed survey data may be indexed in the master database but maintained in distributed databases. The databases could supply historical sounding data in digital form for the planning, collection, processing, and evaluation of new survey data. During the compilation of some bathymetric maps and nautical charts, it is necessary to junction and combine the newer multibeam surveys having total bottom coverage, with the more widely spaced historical data. Precedence is given to the newer hydrographic data, with some older data being removed as needed in order to provide a smooth transition between data sets. In applying multibeam data to nautical charts, it is necessary that actual soundings be positioned properly with respect to bottom contours, which may have been drawn using gridded values. The junctioning of historical and newer data sets is expected to be aided by the use of interactive cartographic workstations. 相似文献
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Nigel R. L. Gooding 《Marine Geodesy》2013,36(3-4):197-203
Abstract The historical development of positioning in relation to the nautical chart is described. Present nautical charts are largely based on geodetic surveys which date from the nineteenth and early twentieth centuries. This gave rise to the use of many local datums and there has been a need to provide the mariner with information to enable him to transfer his position from one chart to an adjacent one on a different datum. The availability of the Global Positioning System (GPS) and the World Geodetic System 1984 (WGS84) datum enables positioning on a single worldwide datum to become a reality. The important factors affecting the adoption of WGS84 as the datum for nautical charts—namely, data availability and the practical and political considerations—are discussed. New developments in the use of nautical charts, the electronic chart display and information systems, and the delineation of international boundaries and territorial limits all give rise to the requirement for improved positional accuracies. Recent experience in the use of GPS both in the provision of control for shore stations of electronic position‐fixing systems and the provision of position for hydrographic surveys is briefly discussed. 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