基于Kriging算法实现等高线制式转换

地图上等高线的等高距主要有英美制（英尺、码）和公制（米）两种制式，不同制式间的等高线转换，其实质是等高线重构。克里金（Kriging）算法是对空间分布的离散数据进行无偏、线性最优内插估计的一种较理想的插值方法。论述了Kriging算法的基本原理，并以VB＋Surfer为二次开发环境，实现了等高线制式由码至米的转换，分析了该方法应用的主要特点。     

MicroStation环境下等高线综合工具箱的开发

主要讨论了如何在MicroStaion环境下进行等高线综合工具箱的研制和开发，重点介绍了等高线综合工具箱的关键组成部分——算法库的建立过程，总结了开发过程中的注意事项。     

用数学形态学变换提取地性线的一种方法

地性线是非常重要的地形结构信息,应用领域十分广阔。采用单纯的矢量方法提取的地性线往往不连续,比较零碎。阐述了利用数学形态学的流域分割算法提取地性线的原理,介绍了基于等高线,采用矢量栅格混合算法提取地性线的具体步骤,最后,给出了结论,实验结果表明,采用本文提出的算法是可行的,提取的地性线有较好的连续性。     

等高线数据压缩的量子分割方法

一、引言 数字化的等高线数据占据了很大的计算机存贮空间。同时,基于这些数据的显示和处理也需要花费大量的时间。因此,数字化等高线数据的压缩,对于地理信息系统的数据处理是非常重要的。为此,本文提出了等高线数据压缩的量子分割方法,同时进行了实验性研究。该方法编程简单、使用方便且适用于微机。 当大量的等高线数据经过计算机处理、输出显示时,采用全部数据点进行插值的方法是非常耗费时间的。但是从处理过程看,还没有更合适的方法。在各种坐标数据中,假设有多组同方向矢量,那么从通过等高线的具有同一方向矢量的连续数据群中,起始点与终点之间可以插值,插值对象所     

在CAD中实现等高线自动内插的一种方法

针对实际工作中内插等高线这一问题,分析了内插等高线算法的基本原理以及实际绘图时可能遇到的几种特殊情况,给出了用ObjectARX语言实现该算法的程序,提出了一些需要注意的问题。该算法及程序可以解决大部分地形图等高线的内插问题,在实际工作中具有较高的实用价值。     

空间信息系统原理(三)数字高程模型及其数据结构

简要介绍了DTM的提出和应用情况,并对数字地面模型(DTM)、数字高程模型(DEM或DHM)、数字地形模型(DGM)等三个概念进行了论述,说明了它们的区别和联系,详细论述了离散点、不规则三角形、等高线、断面线和规则格网等几种数字高程模型的数据结构,并对不同数据结构的数字地面模型的特征进行了比较。     

基于加权最小二乘曲面拟合的规则格网DEM

数字高程模型（DEM）是描述地表起伏形态特征的空间数据模型。DEM完全可以代替传统使用等高线对地形表面的描述，进而满足对等高线数据相同的各种需求。内插是DEM的核心问题，它是DEM各种应用的基础。介绍了加权最小二乘曲面拟合法构建规则格网DEM的理论和方法。试验结果表明：加权最小二乘曲面拟合算法具有插值结果较精确、处理效率较高和模拟地表效果较好等优点。     

基于ArcInfo的海图等高线自动制图综合研究

等高线制图综合是海图生产中工作量比重较大的一项工作,通常采用人工处理的方式,效率较低,影响成图速度。根据海图等高线制图综合特点,利用ArcInfo系统相关功能,研究提出了一套相对较好的等高线自动制图综合方法,并在实际作图过程中得到了较好的应用,提高了海图生产效率。     

分形几何在海底火山地形中的应用

对最近取得的中国南海大陆坡上的火山地形的等高线进行分维测量 ,发现火山及其附近的等高线具有稳定的分维数。利用分维数可以将火山及其附近的地形分成三类 :火山口附近、较陡峭的火山腰部和火山附近较平坦的海底。它们的分维数均低于大陆上等高线的一般分维值 ,平均为 1 .1 1 8。说明玄武岩火山即便不很古老 ,仍可具有标度不变性 ,并且与附近海底一起接受了较厚的海底沉积后 ,又具有了略为不同的分维数。     

等高线自动绘制中断层处理的新方法

提出了一种断层处理新方法——分块法与断层恢复法合成算法，这种方法兼有分块法与断层恢复法的优点同时又克服了其不足，较好地解决了含逆断层时煤层底板等高线自动绘制及任意边界的构网问题，使绘出的等值线图误差较小，更加符合实际。     

离散点数据自动绘制等深线方法探究

提出用反距离插值法将多波束离散数据点插值成规则格网DEM数据,再根据海图生产规范自动绘制不等间距相对光滑的DEM。将自动绘制的等深线与一般软件生成的等深线、海底地形图成果等深线进行比较分析得出：文中方法绘制的等深线相比以前有较大改善且更符合地形,可作为人工绘制的参考线。     

海洋地磁测量资料的虚拟检查线调差方法

在海洋磁力测量中,因受测量环境及各项改正的残余量等因素的系统性影响,不同测线间存在着不同程度的系统差,这种测线系统差会使测区磁场水平不统一,导致磁异常等值线图失真。为此,研究了基于虚拟检查线的海洋地磁测量数据调差方法,该方法尝试在不使用检查线数据情况下,沿垂直于测线方向选取一定数量的虚拟检查线,根据测线数据拟合出各条虚拟检查线上场的分布规律,并将测线方向拟合前后残差的平均值作为各条测线上的测线系统差,对各条测线数据进行改正。仿真计算与分析表明:对于磁异常变化较平缓的测区,该方法可以有效消除测线系统差;当磁异常变化剧烈时,该方法可以部分消除测线系统差。     

基于曲线特征的等深线自动综合方法研究

从等深线的特点及其制图综合的基本原则与方法出发,提出了一种基于曲线特征的Douglas-Peucker改进算法,在此基础上构建了等深线自动综合方法。该方法通过对曲线特征点的提取和弯曲特征的分析,可以自动确定等深线综合的数量指标和最小分界指标,经试验验证取得了较好的综合效果。     

Hydrostatic stability calculations by pressure integration

It is the purpose of this paper to present a new method for the calculation of hydrostatic properties of intact and damaged ship hulls and other floating structures. The geometry of the floating structure is modelled as a set of compartments, bounded by flat panels. Hydrostatic properties are derived by pressure integration on these panel elements. By application of Greens integration theorem the area integration is transformed into line integrals around the contour of each element. The line integrals can be expressed analytically such that the final result is that all the hydrostatic properties can be determined as a summation of easily evaluated expressions. This calculation procedure has the advantage of being well suited for computer calculation, and is easily applied to truly arbitrarily shaped floating structures. Another advantage is that it is based on a geometrical model which is equally suited for finite element strength analysis and hydrodynamic calculations based on a panel method. The application of the procedure is demonstrated by an example.     

Prediction of Long-Term Extreme Response of Fish Cage Using Environmental Contour Method

The fish cage design requires accurate predictions of long-term extreme loads and responses. Compared with the time-consuming full long-term analysis method integrating all the probability distribution of the short-term extremes,the environmental contour method gains much attention in predicting the long-term extreme values due to the less computational effort. This paper investigates the long-term extreme response of a fish cage using the environmental contour method. The fish cage is numerically simulated based on the lumped-mass method and the curved beam theory. Based on the one-dimensional(1D) and two-dimensional(2D) environmental contour, the extreme responses,including the surge and heave motions, mooring force, and vertical bending of the floater, are predicted for different return periods and compared with the full long-term analysis results. Results indicate that the 1D method greatly underestimates the extreme values. The 2D environmental contour method with a higher percentile level, namely90%, provides reasonable estimations and seems to be suitable for the long-term value analysis. Sensitivity studies show that the mooring arrangement and the bending stiffness have great effects on the bending moment and the mooring force and the mooring line pre-tension has minor effects on the fish cage response.     

基于A~*算法的海底地形等深线模型构建方法研究

介绍了DEM原理和构建方法,利用现有矢量海图中的水深要素及海岸线岛屿要素,对生成电子海图海底规则网格数据进行研究。计算机辅助虚拟三维海底地形,运用线性八叉树场景进行分解寻求其规律性,用A*算法最好最优地勾绘出等深线,从而建立海底地形等深线模型,为实现电子海图海底三维可视化奠定了基础。最后对算法进行分析与完善。     

基于Hough变换原理的海冰厚度识别方法

作为主要海冰参数之一的海冰厚度对海冰灾害评估和极地船舶与冰区海洋工程结构设计具有重要意义。采用船侧视频图像对海冰厚度进行自动识别是提取海冰参数的重要方式。本文采用基于Hough变换的机器视觉方法对海冰翻转过程中的表面轮廓线进行识别,从而自动获取海冰厚度参数。根据海冰图像特征制定了图像边缘识别?近似线段识别?海冰轮廓线段组识别的计算流程。在线段组识别过程中,根据海冰的几何特征建立了由夹角、长度及间距参数相关联的3个识别参数所组成的判断条件。为验证方法的可靠性,将该方法用于“雪龙”号第八次北极科考的走航实测数据中,结果表明,3个识别参数均具有最优阈值。当低于最优值时提高阈值可增加有效识别率;而高于最优值时提高阈值则会导致误判率增大,采用最优阈值可使冰厚识别率达到90%以上。因此,采用基于Hough变换的冰厚识别方法可实现对海冰厚度的实时监测。     

Effects of the asymmetric riser and bilge keel arrangements on FPSO green water assessment

This article aims to report important findings on how the asymmetric riser and bilge keel arrangements affect the motion response and green water assessment by using a real FPSO conversion project. Recently, the authors have proposed a practical approach for short-term and long-term green water prediction. In this paper, the method has been further extended to include the effect of truncated bilge keel by using Morrison elements. Numerical studies are conducted focusing on the effect induced by asymmetric riser arrangement and truncated bilge keels. Comparisons of short-term and long-term results between different models indicate that the FPSO’s motion is significantly affected by asymmetrically arranged appendages and attachments in a complicated way. The relative wave elevation is also affected by appendages and attachments, but not the same trend as the motion response. The effect of the asymmetric arrangement of risers and bilge keel on long-term relative wave elevation response has been captured by both traditional contour line approach and response-based analysis, but some discrepancy identified between the results from the two methods indicates the limitation of the traditional contour line approach.     

Visualising the spatial extent of predicted coastal zone inundation due to sea level rise in south-west Western Australia

Visualising coastal zone inundation is crucial for both a quick assessment of coastal vulnerability and a full understanding of possible implications to population, infrastructure and environment. This study presents a simple but effective method of assessing the spatial extent of coastal zone inundation due to predicted sea level rise using commonly available elevation and image data as well as GIS software. The method is based on the geometrical principle of matching the raised sea level with the corresponding elevation contour line on land. Results for a test area along the south-west coast of Western Australia (∼200 km of coast line) show that a sea level rise of less than 0.5 m over the 21st century will have only minor impact but will become important when added to an extreme sea level event (e.g. storm surge). Both century-scale (∼0.5 m) based on tide gauge records and larger (>few metres) longer-term sea level rise predictions based on the melt of ice covered areas show essentially the same areas that are most vulnerable. Furthermore, the effectiveness of the method is demonstrated by the detection of areas that can be protected by relatively small flood protective structures at river and estuary entrances, thus providing valuable information for policy makers and local councils.