Design and implementation of a 3D ocean virtual reality and visualization engine

In this study,a 3D virtual reality and visualization engine for rendering the ocean,named VV-Ocean,is designed for marine applications.The design goals of VV-Ocean aim at high fidelity simulation of ocean environment,visualization of massive and multidimensional marine data,and imitation of marine lives.VV-Ocean is composed of five modules,i.e.memory management module,resources management module,scene management module,rendering process management module and interaction management module.There are three core functions in VV-Ocean:reconstructing vivid virtual ocean scenes,visualizing real data dynamically in real time,imitating and simulating marine lives intuitively.Based on VV-Ocean,we establish a sea-land integration platform which can reproduce drifting and diffusion processes of oil spilling from sea bottom to surface.Environment factors such as ocean current and wind field have been considered in this simulation.On this platform oil spilling process can be abstracted as movements of abundant oil particles.The result shows that oil particles blend with water well and the platform meets the requirement for real-time and interactive rendering.VV-Ocean can be widely used in ocean applications such as demonstrating marine operations,facilitating maritime communications,developing ocean games,reducing marine hazards,forecasting the weather over oceans,serving marine tourism,and so on.Finally,further technological improvements of VV-Ocean are discussed.     

Model of wind-generated ambient noise in stratified shallow water

In order to build a rapid ocean ambient noise model adapted for a stratified shallow water, a hybrid model of normal mode method (for far field) and ray method (for near field) is suggested which combines the advantages of both methods. Since the near field of wind-generated noise is not sensitive to the sound speed profile, the sound speed profile is regarded as a constant; which makes the model rapid and accurate. The simulation results are in agreement with those of the wave model.     

GPU accelerated marine data visualization method

The study of marine data visualization is of great value. Marine data, due to its large scale, random variation and multiresolution in nature, are hard to be visualized and analyzed. Nowadays, constructing an ocean model and visualizing model results have become some of the most important research topics of ‘Digital Ocean'. In this paper, a spherical ray casting method is developed to improve the traditional ray-casting algorithm and to make efficient use of GPUs. Aiming at the ocean current data, a 3D view-dependent line integral convolution method is used, in which the spatial frequency is adapted according to the distance from a camera. The study is based on a 3D virtual reality and visualization engine, namely the VV-Ocean. Some interactive operations are also provided to highlight the interesting structures and the characteristics of volumetric data. Finally, the marine data gathered in the East China Sea are displayed and analyzed. The results show that the method meets the requirements of real-time and interactive rendering.     

基于本体论的海洋流场语义分析与表达研究

随着海洋观测技术的不断发展,人类获取的海洋数据也快速增长,由于海洋流场是整个海洋系统物质流和能量流输送的主要渠道,基于这些观测数据进行海洋流场迁移变化规律分析及可视化表达研究,对所有涉海领域均具有非常重要的意义。然而,由于海洋时空大数据集合的多源性和异构性等原因,至今尚未有令人满意的海洋流场数据集成共享和动态可视化分析工具,从而导致这些异源异构数据难以实现统一标准下的集成组织与语义共享。为了实现海洋流场语义层次上的统一描述,本文在分析了海洋流场多维特征、拓扑特征、模糊特征等基础上,基于本体论的语义构建思想,提出并构建了基于四元组O=（C,P,R,I）的本体组织基础结构,其中C表示概念集合、P表示属性集合、R表示概念间的关系集合、I表示实例集合,通过对概念、属性、关系结构的进一步定义,共同组合构成了海洋流场整体本体结构。为了给出清晰的本体语义建模过程,以海流现象局部本体构建为例,在对成因性、空间性、时间性、运动性等本体属性分析的基础上,进行了海流概念、本体属性、语义关系的描述和定义,从而为海洋流场组织提供一个规范性框架。进而借助OWL语言本体建模的优势,以地转流为例进行了其形式化表达和本体类构建。研究结果表明,基于本体的海洋流场语义分析方法能有效地解决传统海洋现象描述中的异构问题,可为海洋信息共享与集成研究提供参考。     

Web-based spatiotemporal visualization of marine environment data

With long-term marine surveys and research, and especially with the development of new marine environment monitoring technologies, prodigious amounts of complex marine environmental data are generated, and continuously increase rapidly. Features of these data include massive volume, widespread distribution, multiple-sources, heterogeneous, multi-dimensional and dynamic in structure and time. The present study recommends an integrative visualization solution for these data, to enhance the visual display of data and data archives, and to develop a joint use of these data distributed among different organizations or communities. This study also analyses the web services technologies and defines the concept of the marine information gird, then focuses on the spatiotemporal visualization method and proposes a process-oriented spatiotemporal visualization method. We discuss how marine environmental data can be organized based on the spatiotemporal visualization method, and how organized data are represented for use with web services and stored in a reusable fashion. In addition, we provide an original visualization architecture that is integrative and based on the explored technologies. In the end, we propose a prototype system of marine environmental data of the South China Sea for visualizations of Argo floats, sea surface temperature fields, sea current fields, salinity, in-situ investigation data, and ocean stations. An integration visualization architecture is illustrated on the prototype system, which highlights the process-oriented temporal visualization method and demonstrates the benefit of the architecture and the methods described in this study.     

基于交通轨迹数据的三维动态噪声地图

噪声信息具有空间传播和随距离衰减变化的特征,采用三维动态可视化形式表达噪声地图可以体现该特征。本文针对噪声的空间分布与强度变化提出一种噪声地图表达的方法,基于Bertin符号参量分析,以具有高度可变的方柱并配以深浅变化的颜色作为噪声符号,动态传递噪声信息。为进行多尺度地图展示,在不同地图等级下设有相应细节层次的符号尺寸和定位排列方式。噪声地图以Web端Mapbox为展示平台,基于交通噪声模型和GPS轨迹数据,对上海黄浦区某区域一时间段内的噪声情况进行模拟表达,实现噪声数据的立体动态化显示。三维动态的表达扩展了噪声数据的表现维度,多维度、多参量的立体动态符号不仅可准确刻画噪声的分布,而且从视觉观感上提高了受众的兴趣度和专注度,这为研究噪声的热点分布、传递趋势等空间规律提供了可视化参考。     

跨平台嵌入式数字地图可视化中间件设计与应用

本文在分析嵌入式环境下平台差异和计算、存储与显示等资源有限对数字地图可视化限制性的基础上,基于中间件思想,提出了跨嵌入式操作系统平台的数字地图可视化中间件EMD_MW（Embedded Map Display_MiddleWare）,设计了操作系统抽象层、服务框架层和功能层中间件体系结构。利用操作系统抽象层,提取与数字地图可视化相关的操作系统消息转发和图形图像绘制接口进行抽象,屏蔽了不同嵌入式操作系统之间的异构性;利用服务框架层屏蔽了数据存储差异性,扩展了基本图形绘制接口;通过功能层提供数字地图显示各类接口,并详细阐述了EMD_MW的抽象层、服务框架和功能层的设计和实现,给出了基于EMD_MW的几种工程应用。本文设计的跨平台嵌入式数字地图可视化中间件,已在多个嵌入式地理信息应用系统中得到检验,表明该中间件具有良好的跨平台特性,较好地解决了不同嵌入式平台下的数字地图显示问题。     

基于Web服务的海洋矢量场远程可视化研究

目前,GIS大部分空间数据的静态网络可视化共享及其服务器端数据集中管理提供底层数据服务的方式,不仅难以满足与日剧增的多源异构海量空间数据共享需求,同时从应用角度也难以满足对动态性较强的海洋环境信息进行实时可视化共享的需求。而网络Web服务和网格技术的快速发展及其与网络GIS的有机结合,使得分布式、一站式的空间数据实时动态网络可视化共享成为可能。因此,本文针对海洋矢量场信息,深入分析其网络实时动态可视化需求及相应的技术难点,并以Web服务为基础,探讨了在Web服务与网络GIS技术基础上建立一站式海洋环境矢量场网络动态可视化共享系统的技术方法和具体系统结构。文章最后以海洋流场数据为例,具体采用ArcGIS Server的网络服务技术,以及Arc Engine的高效可视化技术,具体实现海洋流场的网络动态可视化共享平台。实践证明,基于Web服务的海流网络可视化系统较好地满足了用户对矢量场数据网络共享与可视化的需求。     

基于二维小波自适应阈值的海洋磁场资料去噪方法

构建海洋三维磁空间背景场模型时,解析延拓是实现不同高度磁场数据相互转换的关键。针对向下延拓数据中的高频信息极易被延拓算子放大,并包含在延拓后的磁场资料中,降低了三维磁空间背景场模型的构建精度,引入二维小波自适应阈值去噪方法,在不同小波分解阶层中设定自适应阈值,在向下延拓前去除磁测数据中的高频噪声,改善向下延拓结果。理论模型试验与实例分析表明,在不同噪声条件下,二维小波自适应阈值法可有效提高数据的信噪比,去噪效果优于传统的快速傅里叶（FFT）平滑法,从而有效改善频域迭代向下延拓结果,为三维磁空间背景场模型构建提供基础。     

Dynamic visual simulation of marine vector field based on LIC——a case study of surface wave field in typhoon condition

Line integral convolution(LIC) is a useful visualization technique for a vector field. However, the output image produced by LIC has many problems in a marine vector field. We focus on the visual quality improvement when LIC is applied in the ocean steady and unsteady flow field in the following aspects. When a white noise is used as the input in a steady flow field, interpolation is used to turn the discrete white noise into continuous white noise to solve the problem of discontinuity. The "cross" high-pass filtering is used to enhance the textures of streamlines to be more concentrated and continuity strengthened for each streamline. When a sparse noise is used as the input in a steady flow field, we change the directions of background sparse noise according to the directions of vector field to make the streamlines clearer and brighter. In addition, we provide a random initial phase for every streamline to avoid the pulsation effect during animation. The velocities of vector field are encoded in the speed of the same length streamlines so that the running speed of streamlines can express flow rate. Meanwhile, to solve the problem of obvious boundaries when stitching image, we change the streamline tracking constraints. When a white noise is used as an input in an unsteady flow field, double value scattering is used to enhance the contrast of streamlines; moreover, the "cross" high-pass filtering is also adopt instead of two-dimensional high-pass filtering. Finally, we apply the above methods to a case of the surface wave field in typhoon condition. Our experimental results show that applying the methods can generate high-quality wave images and animations. Therefore, it is helpful to understand and study waves in typhoon condition to avoid the potential harm of the waves to people's lives and property.     

Simulation of Spark Source Wavelet Under Multibubble Motion

Marine spark sources are widely used in high-resolution marine seismic surveys.The characteristic of a wavelet is a critical part in seismic exploration;thus,the formation and numerical simulation of spark source wavelets should be explored.In studies on spark source excitation,the acoustic field generated by the interaction between bubbles constitutes the near-field wavelet of a source.Therefore,this interaction should be revealed by studying complex multibubble motion laws.In this study,actual discharge conditions were combined to derive the multibubble equation of motion.Energy conservation,ideal gas equation,and environmental factors in the discharge of spark source wavelets were studied,and the simulation method of an ocean spark source wavelet was established.The accuracy of the simulation calculation method was verified through a comparison of indoor-measured signals using three electrodes and the spark source wavelet obtained in the field.Results revealed that the accuracy of the model is related to the number of electrodes.The fewer the number of electrodes used,the lower will be the model's accuracy.This finding is attributed to the statistical hypothesis factor introduced to eliminate the coupling term of the interaction of the multibubble motion equation.This study presents a method for analyzing the wavelet characteristics of an indoor-simulated spark source wavelet.     

Damage localization of marine risers using time series of vibration signals

Based on dynamic response signals a damage detection algorithm is developed for marine risers. Damage detection methods based on numerous modal properties have encountered issues in the researches in offshore oil community. For example, significant increase in structure mass due to marine plant/animal growth and changes in modal properties by equipment noise are not the result of damage for riser structures. In an attempt to eliminate the need to determine modal parameters, a data-based method is developed. The implementation of the method requires that vibration data are first standardized to remove the influence of different loading conditions and the autoregressive moving average (ARMA) model is used to fit vibration response signals. In addition, a damage feature factor is introduced based on the autoregressive (AR) parameters. After that, the Euclidean distance between ARMA models is subtracted as a damage indicator for damage detection and localization and a top tensioned riser simulation model with different damage scenarios is analyzed using the proposed method with dynamic acceleration responses of a marine riser as sensor data. Finally, the influence of measured noise is analyzed. According to the damage localization results, the proposed method provides accurate damage locations of risers and is robust to overcome noise effect.     

顾及空间冲突的等级道路网变比例尺二次规划模型

变比例尺可视化技术被广泛应用于城市路网的地图制图,其基本思想是采用较大比例尺突出显示城区的密集道路,较小比例尺显示并不重要但对路网布局起辅助作用的周边道路。目前,不少研究是通过使用坐标转换公式及参数组合对路网进行变换,以得到较理想的变比例尺效果。然而,这类方法常难以避免路网较大的变形和道路要素的空间冲突。鉴此,本文结合顾及道路等级的形变约束规则和基于支持向量机的线相交约束规则,建立了二次规划算法的等级道路网变比例尺模型,动态优化道路网变比例尺的效果。本文以广州市增城区规划建设的“一核三区”道路网作为试验对象,分别与可调“放大镜”式地图投影和Focus+Glue+Context模型进行比较。实验结果表明,本模型能得到较为理想的变比例尺效果,且具有良好的自适应性和实用价值,为地图变比例尺可视化研究提供一种可控制地图变形过大和解决空间冲突问题的新方法。     

基于MapInfo的福建省经济数据可视化研究

通过信息可视化平台的多维显示数据,揭示数据之间的关联以及隐藏在数据后面的信息,使数据为人们提供更多、更有价值的信息,正是信息分析处理的发展趋势。本文结合可视化开发中集成地图的原理、方法和对象模型,对经济数据特点及其可视化系统开发的关键技术、功能进行了分析。     

海洋标量场时空过程远程动态可视化服务研究

随着多源、大面海洋遥感数据及其反演产品呈指数形式增加,利用网络实现远程长时间序列的海洋标量场动态可视化查询、分析,成为海洋信息服务的迫切需求之一。本文在深入分析现有海量数据网络动态可视化技术及海洋标量场时空变化过程的特点时,针对海洋标量场数据探讨标量场的点过程和面过程的网络可视化表达。并以海表温度数据为例,介绍了从MODIS的海表温度反演产品到网络发布的整个处理流程,构建了中国台海区域海表温度场时空过程的网络可视化原型系统。在该原型系统中,实现了海表温度场任意点位的温度查询,任意点位温度时间变化的过程曲线,温度场面过程时空过程动态演进可视化分析等功能。同时该原型系统可以为其他海洋标量场的时空过程可视化提供技术与方法借鉴。     

基于室内定位数据的群体时空行为可视化分析

室内定位数据记录了用户在室内空间活动的时空轨迹,是研究人群室内行为的重要信息源。室内数据时空耦合、分布复杂,可视化分析可以更好地揭示其规律。然而,与室外数据不同,室内数据具有时空粒度细、定位精度高等特点,与POI之间的空间关系更为明确,其轨迹受到室内设施和空间的制约,出现高维和不规则的特征,而这给室内行为研究提供依据的同时,又给可视化分析带来一定的挑战。现有的可视化方法主要应用于室外定位数据,关注轨迹自身的活动轨迹分析,往往忽略了所经过POI语义信息表达。针对这一问题,首先分析室内空间结构与定位数据的特征,阐述室内空间可视化分析的特殊性;在此基础上,面向室内人群的时空分布、移动模式及相关POI之间的对比、关联分析的需求,细化可视化分析的内容,明确可视化分析与展示的对象,并设计数据结构;从数据结构、可视化方法、展示图件及用户交互4个层次构建时空行为可视化分析模型;基于上述方法,采用WebGIS和WebGL技术综合设计和实现了面向商场定位的商场客流分析系统;最后,通过某一大型商场的用户定位数据进行可视化分析,从而验证了研究成果的正确性和有效性。     

电子地图的信息组织及可视化机制

对多媒体电子地图的信息组织及可视化机制进行了研究,提出了多媒体电子地图的空间信息和多媒体信息的组织方法,结合电子地图的特点,论文还提出将数字制图模型与数字景观模型相结合、矢量栅格数据混合的空间数据组织方法。在研究空间数据与非空间数据组织的基础上,论文又对多媒体电子地图的信息可视化机制进行了研究。最后,论文以多媒体电子地图著作工具软件Atlas2005为例对论文的研究内容进行了说明。     

面向GTP的三维地质模型空间剖切方法与应用

广义三棱柱（GTP）是近年来提出并被广泛应用于三维地质建模领域的一种较为成熟的空间数据模型,可满足大多数地质钻孔数据的三维地质建模的要求。然而,现有针对GTP模型的三维空间剖切分析方法,仍无法适用于偏斜钻孔数据所建三维地质模型高效多次任意剖切、不能支持较为复杂的地质模型空间分析的问题。本文通过对GTP剖切算法改进研究,提出了采用动态四面体剖分法减小数据冗余;鉴于GTP形态较为复杂,可对剖切后保留多面体进行拓扑关系的重组,解决任意多次剖切问题;将多次“面-体”形式的单剖切运算组合为一次“体-体”形式的复合剖切运算的方法,可高效实现对三维地质模型空间分析。本文着重面向GTP体元的多重任意切剖平面的剖切问题,在分析了GTP体元特征的基础上,弥补了三维地质建模领域中对GTP体元任意、多重剖切方法研究的不足。应用实例表明,上述改进算法可以提高GTP剖切计算速度,并能够快速实现巷道掘进模拟,以及空间开挖模拟等复杂的空间分析功能。     

基于光滑粒子流体动力学算法的海浪建模仿真研究

针对传统海浪建模方法中存在海洋表面真实感差、计算复杂的问题,本文进行了基于光滑粒子流体动力学算法（SPH）与移动立方体算法（MC）相结合的海浪建模仿真研究。通过基于空间网格的粒子分配,建立了粒子群单向列表存储结构,在海浪粒子物理量计算时,实现了其光滑核半径内粒子群的快速检索,并基于拉格朗日流体控制方程,进行了海浪粒子受力分析及状态计算;在模拟海浪与环境障碍物碰撞时,将碰撞问题简化为粒子在一定时间段内所经过的路径与障碍物表面三角面片是否相交来进行判定,并假设粒子为理想刚体,采用改进的欧拉方法实现了粒子新位置的动态计算;为增强海浪流体模拟的真实感,在移动立方体节点密度动态计算基础上,依据确定的海浪表面密度阈值,耦合MC算法进行了海浪表面的动态提取,从而实现了海浪三维表面建模与动态演变仿真。通过模拟验证了该算法的时效性与可行性,可为海洋环境信息三维可视化提供一定的参考。     

面向多粒度时空对象数据模型的网络电子地图生成方法

传统网络电子地图生成是以要素进行组织的,在表达地理实体动态变化、关联关系以及多粒度特征时存在一定的局限性。而多粒度时空对象数据模型旨在解决现实世界到对象所组成的事物空间之间的映射这一科学问题,为时空实体的可视化提供了新的思路,为展示地图要素间复杂关联、多维动态等特征提供了模型基础和数据保证。本文将多粒度时空对象数据模型引入网络电子地图生成当中,渐进得改变了以往网络电子地图依靠图层数据生成的模式,基于多粒度时空对象的概念、模型框架以及数据存储与管理方式,提出了2种网络电子地图生成方法。一种是利用多粒度时空对象数据重建图层,为现有网络制图工具提供“中间件”,使其能够调度和使用多粒度时空对象数据;另一种是将多粒度时空对象数据和地图符号进行绑定,使网络电子地图不再依赖于图层而能根据多粒度时空对象动态更新,同时便于将对象之间的关系、组成结构等非结构化属性特征进行可视化。同时,本文通过实验验证了2种方法的可行性,为多粒度时空对象在网络电子制图领域的应用进行了有效实践。