An algorithm for automatic cartographic sounding selection

Soundings on nautical charts provide information about the shape of ocean bottom between chart depth curves. A single chart may have thousands of soundings posted on it. This paper describes a new algorithm for selecting soundings automatically. At first,the problem encountered in automatic cartographic sounding selection is presented. Then the authors give the principle of the new algorithm,and the implementation is illuminated in detail. At last the experiments prove the rationality and efficiency of the new algorithm.     

An algorithm for automatic cartographic sounding selection

Soundings on nautical charts provide information about the shape of ocean bottom between chart depth curves. A single chart may have thousands of soundings posted on it. This paper describes a new algorithm for selecting soundings automatically. At first, the problem encountered in automatic cartographic sounding selection is presented. Then the authors give the principle of the new algorithm, and the implementation is illuminated in detail. At last the experiments prove the rationality and efficiency of the new algorithm.     

An ontology-driven multi-agent system for nautical chart generalization

ABSTRACT

On nautical charts, undersea features are portrayed by sets of soundings (depth points) and isobaths (depth contours) from which map readers can interpret undersea features. Different techniques were developed for automatic sounding selection and isobath generalization. These methods are mainly used to generate a new chart from the bathymetric database or from a larger scale chart through selection and simplification. However, a part of the process consists in selecting and emphasizing undersea features formed by groups of soundings and isobaths on the chart according to their relevance to maritime navigation. Hence, automation of the process requires classification of features and their generalization through the application of a set of operators according not only to geometric constraints but also to their meaning.

The objective of this work is to conceive a multi-agent system (MAS) for nautical chart generalization that is driven by the knowledge on the generalization process and the undersea features and their relationships. First, this work provides a feature-centered ontology modeling of the generalization process. Then, the MAS structure is introduced where agents access cartographic knowledge stored in the ontology. The MAS makes use of measure algorithms to evaluate constraint violations on the chart in order to decide which generalization operators to apply. The whole model has been implemented to provide generalization plans on a real case study.     

A fast algorithm of cartographic sounding selection

An effective strategy and framework that adequately integrate the automated and manual processes for fast cartographic sounding selection is presented. The important submarine topographic features are extracted for important soundings selection, and an improved “ influence circle” algorithm is introduced for sounding selection. For automatic configuration of soundings distribution pattern, a special algorithm considering multi-factors is employed. A semi-automatic method for solving the ambiguous conflicts is described. On the basis of the algorithms and strategies a system named HGIS for fast cartographic sounding selection is developed and applied in Chinese Marine Safety Administration Bureau （CMSAB）. The application experiments show that the system is effective and reliable. At last some conclusions and the future work are given.     

海图水深注记的基准更新方法研究

建立统一、规范的深度基准体系是海洋测绘成果应用的基本保证。为了消除目前海图应用中水深注记基准面不一致的影响,本文在以往研究成果的基础上,提出了以平均海面基准为中介的海图新旧深度基准的转换体系,并以某实验海区水深数据为例,构建了基于深度基准面更新模型的海图水深注记的更新方法。经试验验证效果良好。     

实时水深模型的一种构建方法

水深是表达海洋深度变化的基础数据,实时水深是舰船航行和海岸带军事行动的重要影响因子。本文从实用角度出发,采用海图水深作为静态水深,基于余水位订正的预报水位作为动态水位,提出了一种顾及实时水深区域变化特征的实时水深模型。实验表明,该模型实现了实时水深的快速求取,一定程度上可以满足航海和军事应用需求。     

顾及潮汐变化的动态可航水域表示模型及方法研究

自20个世纪90年代末起,GIS技术开始得到广泛的应用。随着应用领域的不断扩展和相关研究的日益深入,GIS技术的发展出现了新的趋势:时间被引入到空间分析中来,随之而产生了TGIS,时间的引入为GIS技术的发展注入了新的活力。本文所研究的就是TGIS技术在近岸海上航行中的应用问题:以电子海图显示系统为平台,在引入潮汐等随时间变化较为显著且影响较大的相关要素的前提下,通过建立实时水深模型、动态等深线勾绘模型和区域生成模型等与时间要素密切相关的数学模型,实现舰船可航水域表示模型的动态实时快速构建。     

An Ontology of the Submarine Relief for Analysis and Representation on Nautical Charts

Abstract

A nautical chart is a kind of map used to describe the seafloor morphology and shoreline of adjacent lands. One of its main purposes is to guarantee safety of navigation. As a consequence, the construction of a nautical chart follows very specific rules. The cartographer has to select and highlight undersea features according to their relevance to navigation. In an automated process, the system must be able to identify and classify these features from the terrain model. This paper aims therefore to define ontologies of the submarine relief and nautical chart that will be at the root of a model-oriented generalization process. To the best of our knowledge, no ontology has been defined to formalize the geographical and cartographic objects for nautical chart representation. Thus, a bottom-up approach was developed to extract and model knowledge derived from standards established by the International Hydrographic Organization (IHO) and cartographers’ expertise. The submarine relief ontology formalizes undersea features describing the submarine relief. Four concepts (composition, morphometric class, shape value and depth value) are introduced to describe properties and relationships between undersea features. The cartographic representation ontology of nautical charts will define several concepts (chart, features, isobathymetric lines and soundings) for the representation of undersea features on the chart.     

苏南运河镇江段航道3维可视化技术及其应用研究

航道3维可视化对全面掌握运河河底地形地貌,保障运河水上交通安全具有重要意义。本文以3维可视化苏南运河镇江段航道为例,阐述如何在实现航道周边场景3维渲染的基础上,利用航道数字测深数据,创建基于格网的数字水深模型,进而生成河底数字高程模型的过程,并对航道3维可视化技术的实际应用进行了探讨。     

联合不确定度的多期水深剖面分析方法及应用

单波束测深技术在近海及河口水深测量中被广泛应用,但受动态海洋环境的影响,很难有效获取不同时期同一位置的水深数据,这给快速变化的近海地形的准确对比与分析造成很大困难。针对该技术问题,本文提出了一种联合不确定度的多期水深剖面分析方法。通过初始不确定度计算、水深及不确定度传递、卡尔曼滤波更新等步骤构建时序地形剖面,并基于假设检验完成剖面地形演变分析。用两期次河口区单波束数据对算法进行了验证。结果表明,本文方法获取了可与实际地形剖面有效对比的水深剖面,并可对地形骤变区域作出准确评估,对于快速变化的河口水下三角洲尤其是航道区域的演变分析具有实际的应用价值。     

不同函数拟合水体后向散射波形对激光测深精度的影响

为了提高激光测深数据处理结果的精度,在原有的激光测深回波信号拟合方法的基础上,结合信号形成的物理过程,提出使用指数函数模拟激光测深水体后向散射回波成分的方法。利用Wa-LiD（Water LiDAR）工具生成了多组模拟数据集以对比和检验提出的新方法。对于每个可探测回波,海面回波和海底回波均使用高斯函数进行拟合,水体后向散射波形分别使用三角形、四边形、指数函数进行拟合。实验结果显示,指数函数测深误差统计量明显优于三角形和四边形拟合方法,且更适用于拟合不同水质和水深条件下水体后向散射回波信号。同时检验了体积散射函数取180°时数值对测深回波信号探测结果的影响。     

海底地形的识别与水深的综合

水深综合是数字海图综合的重要方面,也是其难点之一,在分析水深综合原则的基础上,提出了基于地形特征识别的综合模型,以分解其诸多约束条件,来实现水深的自动综合。     

Feature‐Driven Generalization of Isobaths on Nautical Charts: A Multi‐Agent System Approach

A nautical chart provides a schematic view of the seafloor where isobaths (contour lines joining points of same depth) and depth soundings are generalized to highlight undersea features that form navigational hazards and routes. Considering that the process is ultimately driven by features and their significance to navigation, this article proposes a generalization strategy where isobath generalization is controlled by undersea features directly. The seafloor is not perceived as a continuous depth field but as a set of discrete features composed by groups of isobaths. In this article, generalization constraints and operators are defined at feature level and composed of constraints and operators applying to isobaths. In order to automate the process, a multi‐agent system is designed where features are autonomous agents evaluating their environment in order to trigger operations. Interactions between agents are described and an example on a bathymetric database excerpt illustrates the feasibility of the approach.     

数字海图水深注记的自动综合研究

以海图中水深综合的基本原则为依据,模拟人在制图综合时的思维方式,提出一种新的水深注记自动综合的模式--表达、识别与综合,并通过试验验证该综合模式的实用性和有效性,为自动制图综合的研究开创新的理论与研究方法.     

利用拟构模型面调控水深模型点选取的航海DDM构建

针对传统方法难以确保所建模型的深度保证率满足航海安全要求的问题，提出了一种利用拟构模型面调控水深模型点选取的航海数字水深模型（digital depth model，DDM）构建方法。定义了已选、待选、拟选水深点以及拟构模型面的概念，并利用待选水深点来定量评估模型面的深度保证率与表达度，实现了水深自动选取过程中的DDM质量动态监控。在此基础上，通过构造水深选取中的质量评估综合算子，利用该算子来定量调控水深点的选取，确保所构DDM的深度保证率能达到规定指标要求。实验结果表明:（1）与传统方法相比，所提方法能确保所建模型的保证率满足航海安全要求；（2）对于深度保证率均能满足航海安全要求的水深点，所提方法较传统方法能从一定程度上提高模型在此处的表达度。     

多波束异常测深数据检测方法实践

由于现有的交互式滤波和自动滤波不能满足大区域、高密度多波束测深数据滤波的需要,为此,本文给出了易于改善自动化滤波的趋势面法和基于抗差M估计的选权迭代加权平均法。前者适合于显著粗差的探测,对小粗差不敏感;后者由于对被检测点邻域内的观测点具有选择性,加之采用迭代实现推值,因而对于粗差具有较强的探测能力,检测和滤波结果较趋势面法更为合理。     

基于航路二叉树的航线自动生成方法

针对航线自动生成中存在贪婪性的弱点,提出了基于航路二叉树的航线自动生成算法。实验结果表明,所提方法能克服现有航线自动生成算法中的贪婪性,提高航线最优化结果的质量。     

基于BDS反演海上气象要素的研究

海洋大气环境对舰船航行及作战有至关重要的影响,海上空中气象信息的获取依赖于探空手段的发展,然而舰船海上探空技术受制于常规方法和仪器设备的局限性而存在诸多现实问题,大大降低了舰船远海航行安全性及舰载武备的使用效能。本文针对该问题提出舰基BDS反演海上气象要素技术,研究基于地基BDS气象要素反演理论实现海上舰基反演技术的可行性,分析了海上反演气象要素存在的主要问题,并对解决相关问题的关键技术提出了研究设想。      

海洋测深数据的抗差Kalman滤波

从线式测深模式要求出发,构建了海洋水深测量过程中的测船位置滤波模型和深度数据的滤波模型,并在此基础上,给出了测线上位置数据和深度数据Kalman滤波的一般解和抗差解,并结合海洋水深测量特点,构建了满足水深数据剔除异常值的截断权函数和滤波方案,实例分析表明,抗差滤波方法能够有效地控制测船位置粗差,在选择截断权函数情况下,抗差滤波方法能够有效地剔除水深跳点和假水深。     

CUBE曲面滤波参数联合优选关键技术及应用

CUBE(combined uncertainty and bathymetry estimator)算法是国际上主流的多波束测深异常值自动探测与处理算法,在国内外被广泛应用,但对其核心算法和参数知之甚少,不利于该项技术的国产化。本文详细阐述了CUBE算法的基本原理、数学模型、关键参数和处理步骤,进而建立了CUBE曲面滤波参数联合优选方法。通过选取典型地形区、参数试验、对比分析等步骤完成参数的联合优选,并用台湾浅滩实测数据进行了验证。结果表明,优化后的参数可有效提升多波束数据自动处理的精度和效率。本文成果可应用于国产多波束测深处理软件的深化研发以及多波束实测数据处理。