基于ASP技术的WebGIS系统开发方法研究

随着互联网技术的发展,WebGIS已成为GIS的发展趋势。本文比较了WebGIS的各种实现技术,研究了在ASP引擎支持下开发WebGIS系统的基本方法,构建了基于ASP的WebGIS系统结构,简要分析了基于ASP技术开发WebGIS系统的优越性。     

基于WebGL的三维WebGIS应用研究

基于WebGL技术进行3D WebGIS开发中的WebGL机制、坐标系统、坐标变换、数据组织等关键技术问题进行了研究.分析与设计了以虚拟地球形式基于WebGL技术的3D WebGIS原型系统;最后,实现了具有三维地图浏览、兴趣点搜索定位以等功能的3D WebGIS,验证了基于WebGL构建3D WebGIS的优越性.     

WebGIS在美国南加州数字城市建设中的应用实例分析

从介绍WebGIS技术在南加州一个成功应用项目--加州橙县土地公共文档查询显示和电子商务系统的技术路线和体系结构入手,分析了当前几个主要WebGIS软件的基本特点和存在的技术问题.在此基础上,引入了可以改善目前WebGIS技术领域内弊端的一种新方法--基于SVG矢量图形格式的WebGIS技术,同时给出了这一技术的基本思路和优点,并通过系统的开发实践证明其响应速度、功能与图形效果.这一WebGIS应用展示了基于SVG格式的WebGIS技术的强大活力.通过与其他系统的无缝集成,如与电子商务系统,文档管理系统,以及办公自动化系统等,WebGIS将GIS技术的应用推上一个新台阶,使得GIS技术在数字化城市的建设中发挥更大的作用.     

基于SuperMapISJava技术杨凌WebGIS实现

建立城市WebGIS是实现城市管理自动化、科学化、网络化和智能化的一种趋势.以杨凌为研究对象,探索了网络地理信息服务的体系结构,重点探讨基于SuperMap IS Java技术构造网络地理信息系统的方法,说明了WebGIS的实现技术、实现流程及其功能.结果表明,本系统可以为广大用户提供各种空间信息服务,具有良好的可扩展性.     

基于RIA的WebGIS系统设计与实现

本文研究了基于Silverlight技术的WebGIS系统,分析了基于RIA技术的WebGIS系统的优势。在此基础上,设计并实现了基于Silverlight技术的WebGIS系统,该系统建立在GeoDatabase空间数据模型之上,以REST风格为服务发布模式。研究表明,本文研究成果为WebGIS的发展提供了一个新的解决方案。     

C++Builder下WebGIS服务器端应用程序的开发与实现

近几年来,WebGIS技术在全世界各行各业中得到了迅猛发展及广泛应用.同时,随着Web技术及开发手段的不断发展,也推动了WebGIS专业开发工具的不断发展,出现了很多WebGIS专业开发工具.利用专业开发工具开发WebGIS虽然具有很多优点,但也有很多不成熟的地方,很难通过无缝集成实现应用系统的特殊功能.在对空间数据及空间分析要求不高的情况下,应用C++Builder可以迅速开发出满足特殊要求的WebGIS系统,并在灵活性、可扩展性等方面都有无可比拟的优点.     

基于Silverlight的工业经济地理信息系统设计与实现

为了提高WebGIS响应效率,满足用户对高交互性和炫酷界面的需求,提出采用RIA（丰富互联网应用程序）技术改善WebGIS传统结构模式存在的问题,介绍各种RIA技术并对比总结其优缺点,详细分析新兴的微软Silverlight技术特点,针对应用系统功能需求,利用Silverlight技术在ArcGISServer10平台上设计并实现基于RIA的成都市工业经济GIS系统,验证Silverlight在WebGIS富客户端的可行性。     

MapNotes的设计与开发

MapNotes是一个嵌入式的WebGIS基础平台,利用它,二次开发人员可以根据各自需求开发出各种具体的WebGIS应用系统,在Internet/Intranet上发布地图和各种与空间位置有关的信息.MapNotes采用的是典型的服务器端策略的WebGIS解决方案,它由管理系统(MapAdmin)、GIS内核(MapCells)和ASP包3部分组成.MapNotes的开发采用了一种先进的面向对象的软件工程方法--统一软件开发过程(USDP).     

基于开源的轻量级WebGIS开发框架的研究与实现

介绍了当前WebGIS的发展趋势和WebGIS开发技术和框架,分析了优势和不足.通过选择合适的开源技术库构建了一个轻量级的WebGIS开发框架,并详细介绍了该框架的组成.利用该技术框架开发了我国水产生物资源分布查询系统.结果表明,使用该框架开发能够快速构建跨平台的GIS应用.     

基于J2EE/XML的分布式WebGIS平台系统设计与实现

分析了目前WebGIS各种实现模式的优缺点以及利用J2EE构建分布式WebGIS的优越性;提出了一种基于J2EE/XML构建的四层体系结构的分布式DragonMapWeb系统;并就该系统,分别探讨了与其相关的系统构架、EJB类组织、数据模型、关键技术、功能设计等问题.     

Noisy Data Smoothing in DEM Construction Using Least Squares Support Vector Machines

Since spatial datasets are subject to sampling errors, a smoothing interpolation method should be employed to remove noise during DEM construction. Although least squares support vector machines (LSSVM) have been widely accepted as a classifier, their effect on smoothing noisy data is almost unknown. In this article, the smoothness of LSSVM was explored, and its effect on smoothing noisy data in DEM construction was tested. In order to improve the ability to deal with large datasets, a local method of LSSVM has been developed, where only the neighboring sampling points around the one to be estimated are used for computation. A numerical test indicated that LSSVM is more accurate than the classical smoothing methods including TPS and kriging, and its error surfaces are more evenly distributed. The real‐world example of smoothing noise inherent in lidar‐derived DEMs also showed that LSSVM has a positive smoothing effect, which is approximately as accurate as TPS. In short, LSSVM with a high efficiency can be considered as an alternative smoothing method for smoothing noisy data in DEM construction.     

小波变换的异常地质体识别

针对工程勘探中识别异常地质体的问题,该文提出了一种采用一维二进小波分析寻找局部物性陡变点,叠加在视电阻率增强表达图像上进行异常地质体识别的数据挖掘方法。该方法主要基于数据处理,对解释人员的经验背景知识依赖程度低。在滇中引水前期工程勘探中,该方法被应用于2号剖面线的地质异常区域识别,识别的结果除了能基于地质资料进行合理性的解释外,与常规物探解释成果相比,该方法能够得到更为精细化的可视化表达成果,为地质工程中的预测预报提供决策支持。     

Automatic interpretation of digital maps

In the past, the availability and/or the acquisition of spatial data were often the main problems of the realization of spatial applications. Meanwhile this situation has changed: on one hand, comprehensive spatial datasets already exist and on the other hand, new sensor technologies have the ability to capture fast and with high quality large amounts of spatial data. More and more responsible for the increasing accessibility of spatial data are also collaborative mapping techniques which enable users to create maps by themselves and to make them available in the internet. However, the potential of this diversity of spatial data can only hardly be utilized. Especially maps in the internet are represented very often only with graphical elements and no explicit information about the map’s scale, extension and content is available. Nevertheless, humans are able to extract this information and to interpret maps. For example, it is possible for a human to distinguish between rural and industrial areas only by looking at the objects’ geometries. Furthermore, a human can easily identify and group map objects that belong together. Also the type, scale and extension of a map can be identified under certain conditions only by looking at the objects’ geometries. All these examples can be subsumed under the term “map interpretation”. In this paper it is discussed how map interpretation can be automated and how automatic map interpretation can be used in order to support other processes. The different kinds of automatic map interpretation are discussed and two approaches are shown in detail.     

Continuing Research Needs Resulting from the SDTS Development Effort

For more than a decade, efforts to develop and specify the U.S. Spatial Data Transfer Standard (SDTS) have on many occasions encountered limitations in both theory and "gaps in our knowledge" which have hindered its development. This work examines broad categories of these limitations from the perspective of research needs, to encourage further research on these topics. Areas in need of further study include fundamental concepts, the specification and use of spatial objects, spatial data quality, entity definitions, the data transfer mechanism, and international comparison of transfer mechanisms. In many cases recent research progress has been made in these areas and this progress is pointed out. A number of high-priority research areas are identified. It is hoped that this work will encourage more research effort to be directed towards these areas, which will benefit not only the development of spatial data transfer standards but also the spatial data sciences in general.     

基于特征元的符号库数据结构及算法探讨

空间数据符号化是GIS中数据可视化的重要手段,是目前GIS实现过程中计算机时间开销最大的工作之一.提高空间数据符号化效率,是提高GIS软件性能的重要方面,本文提出考虑全局优化、面向符号对象整体、基于特征元的算法设计思想.据此提出一种基于特征元的符号库的数据结构及实现算法.实验表明,运用该算法及相关数据结构的空间数据符号化软件不仅效率优于传统算法,而且扩展了符号库法实现空间数据符号化的功能.     

Instantaneous Precise GPS Positioning under Geomagnetic Storm Conditions

Due to the maximum of the solar cycle, ionospheric activity increased considerably last year. At frequent times warning were sent out announcing geomagnetic storms disturbing the ionospheric electron content. In this article the influence of such geomagnetic storms on fast and precise GPS positioning (for surveying applications at midlatitude regions) is studied. And here with “fast” it is aimed at the shortest observation time possible: carrier ambiguity resolution and position estimation using only one single epoch of data. To apply this instantaneous data processing technique successfully to GPS baselines of medium length (up to 50 km), additional ionospheric information is inevitable, not only under geomagnetic storm but also under more quiet conditions. However, in this article it will be shown that under geomagnetic storm conditions, even for rather short baselines (<10 km), for which the ionospheric delays under more quiet conditions could be neglected, one has to account for significant relative ionospheric delays. Therefore an important facet of this contribution is the investigation of how to process baselines of varying length in a more uniform way, making use of a permanent GPS network (if available in the surveying area) and a stochastic modeling technique of the ionospheric delays. ? 2001 John Wiley & Sons, Inc.     

A Snake-based Approach for TIGER Road Data Conflation

The TIGER (Topologically Integrated Geographic Encoding and Referencing) system has served the U.S. Census Bureau and other agencies' geographic needs successfully for two decades. Poor positional accuracy has however made it extremely difficult to integrate TIGER with advanced technologies and data sources such as GPS, high resolution imagery, and state/local GIS data. In this paper, a potential solution for conflation of TIGER road centerline data with other geospatial data is presented. The first two steps of the approach (feature matching and map alignment) remain the same as in traditional conflation. Following these steps, a third is added in which active contour models (snakes) are used to automatically move the vertices of TIGER roads to high-accuracy roads, rather than transferring attributes between the two datasets. This approach has benefits over traditional conflation methodology. It overcomes the problem of splitting vector road line segments, and it can be extended for vector imagery conflation as well. Thus, a variety of data sources (GIS, GPS, and Remote Sensing) could be used to improve TIGER data. Preliminary test results indicate that the three-step approach proposed in this paper performs very well. The positional accuracy of TIGER road centerline can be improved from an original 100 plus meters' RMS error to only 3 meters. Such an improvement can make TIGER data more useful for much broader application.     

导航电子地图数据增量更新研究

随着经济建设的快速发展,人们出行对地图的需求越来越大．特别是导航电子地图得到了广泛应用,随之而来的就是导航地图数据的定位精度和现势性问题．而动态增蜮更新是解决地图现势性的唯一途径。但是长期以来受终端硬件性能瓶颈的影响。进展不大．而当前随着微电子技术的迅猛发展,导航终端硬件设备的处理运算和存储能力的提高,导航仪硬件设备成本下降．为实现导航电子地图动态增鳋更新提供了可能．本文就导航电子地图数据更新模式进行探讨。     

改进的差值扩张和平移矢量地图可逆水印算法

在传统差值扩张水印算法的基础上,对水印嵌入和数据恢复公式进行了改进,无需计算顶点对之间的均值,即可在提取水印的同时,实现数据的完整恢复。仿真实验结果表明,与传统算法相比,改进的差值扩张和平移算法具有更大的嵌入容量和有效信息载荷,数据误差更可控,保密性更好。     

GIS中多用户环境下数据共享一致性问题研究

讨论了GIS中多用户环境下数据一致性问题,着重研究了由于某个用户修改其他用户已读数据所产生的不一致以及由于用户UNDO/REDO后产生的不一致。对于前者,本文提出了一种“通知-重读”法。