【作者】 韩双旺；

【导师】 王心源；

【作者基本信息】 安徽师范大学 ， 地图学与地理信息系统， 2007， 硕士

【摘要】 数字地球的发展要求GIS必须实现数据共享,必须发展WebGIS技术,而网络技术的崛起为GIS的发展注入了新的活力。GIS与网络技术融合以形成一个基于Internet技术的GIS集成平台自然成为当前GIS研究领域的一个重要方向和热点话题。但是目前的WebGIS产品大都是基于传统的GIS系统软件,利用CGI或Server API构造,一般需在后台运行一个或多个GIS应用程序。这种模式只解决了在Web上发布空间信息的问题,并没有针对Web应用环境进行重新设计和优化,因此在功能和效能上不能满足人们的需求。另外,当今WebGIS在空间数据模型上存在缺陷,而XML具有数据来源的多样性、多种应用的灵活性、柔韧性和适应性,为WebGIS带来新的机遇。随着WebGIS的快速发展,在WebGIS中以矢量的方式快速传输、浏览电子地图,是当前GIS研究的一个热点。而基于XML的SVG正好可以解决WebGIS中矢量发布的问题。ASP.NET是MicroSoft.NET的一部分,具有强大的Web开发功能。SVG是一种基于XML的用来描述二维矢量图形和矢量/栅格混合图形的标记语言,本质上是XML在网络上表达图形图像的一种扩展应用程序。利用ASP.NET强大的Web应用开发功能与SVG矢量传输与显示功能,可构建功能较为强大、性能较为优化、数据较为安全和开发成本较为低廉的WebGIS。本文设计了一种基于ASP.NET与SVG技术的WebGIS平台解决方案。通过对该方案具体实现的研究,可得出如下结论:(1)把ASP.NET,Web Service技术和SVG技术结合起来引入WebGIS的设计与实现,可达到ASP.NET强大的Web开发功能和利用SVG实现地图矢量传输与显示的很好结合;同时,通过对已定义的Web Service进行发布和注册还可以实现本系统GIS数据库服务器上数据资源的共享,也可以通过搜索Internet上已发布和注册的相关Web Service,通过对其引用而实现异地数据的集成。(2)把ASP.NET的多级缓存机制与安全性实现机制引入WebGIS的设计与实现,可通过客户端缓存和服务器端缓存提高WebGIS整体运行效率的同时,保证开发的WebGIS能在Internet上安全运行。(3)地理数据按集成结构或以XML/GML方式保存在数据库服务器端的相应数据库中,服务器收到客户端的请求后,通过对其分析,对于集成结构的数据库,可利用已定义的Web Service实时地从数据库中抽取相应范围的数据并将其转换成XML/GML数据;对于XML/GML数据库,则直接利用Web Service进行抽取;然后对以上两种情况下得到的XML/GML数据通过XSLT转换成SVG,并通过GZIP压缩将其压缩为SVGZ后发送到客户端浏览器显示,如果用户没有请求新的数据,用户只是进行放大、缩小、漫游等操作,那么可只针对已随.aspx页面下载到客户端的SVGZ文件,而无需再次传输这些数据,在矢量传输数据量小的基础上,进一步减少了传输的数据量,进一步提高了传输与显示效率。所以这种方法不仅保证了后台数据的安全可靠也具有较高的效率。(4)采用集成结构的空间数据库来组织和存储GIS数据或采用XML/GML数据库存储GIS数据,从而利用RDBMS对空间数据和属性数据实现统一管理,为客户端提供效率较高的地理信息查询服务,同时也提高了对GIS数据的管理和维护效率。另为,可通过将不同数据源进行模式映射和转换而存储为XML/GML数据而实现多源数据的集成。最终通过将不同格式的空间数据转换成基于文本格式的XML/GML,使异构空间数据集成于XML/GML这一格式,由此实现空间数据之间的共享与互操作。(5)无需购买昂贵的诸如MapXtreme,ArcIMS等WebGIS开发软件,便可实现WebGIS,开发成本低廉。通过开发具体的WebGIS,证明该方案具有数据容易集成和共享,传输数据量小,传输速度快,性能较为优化、数据较为安全和开发成本较为低廉等特点。更多还原

【Abstract】 The development of digital earth demand GIS must realize data share and develop WebGIS technology, and the growing up of network technology has injected new vigor into development of GIS. GIS and network technology merge so as to form the integrated platform of GIS that based on Internet technology naturally become an important direction and hot Question for present GIS research field.But present WebGIS products are mostly based on traditional GIS systems software that is constructed using CGI or Server API and generally need to operate backstage one or more GIS application program. This kind of mode has only solved the problem of publishing space information on Web, it has not redesigned and optimized for the Web environment, so it can’t meet people’s demands on function and efficiency. In addition, the nowaday WebGIS exist defect on the space data model, and XML has the variety of the source of data and agility, flexibility and adaptability of many kinds of application, it brings the new opportunity for WebGIS.With the fast development of WebGIS, fast transmiting and viewing the electronic map by way of vector in WebGIS is a focus that GIS research at present. And SVG based on XML can just solve the problem that the vector is published in WebGIS.ASP.NET is a part of MicroSoft .NET, it has powerful developing function of Web. SVG is one kind of markup languages that is used describing two dimension vector graphics and vector/grid mixed graphics, it is a kind of expansion application program that XML expressed the graphics and picture in the network in essence. Utilizing ASP.NET strong function of Web development and the vector transmiting and displaying function of SVG, we can comparatively construct WebGIS that the function is strong, performance is comparatively optimizing and data is safe and the development cost is cheap.This thesis has designed a kind of WebGIS platform solution based on ASP.NET and SVG technology.Through the research to the specific realization of the solution, can educe the following conclusion:(1) It introduce ASP.NET, Web Service and SVG technology into the design and realization of WebGIS, it realize very good combination of powerful Web developing function of ASP.NET and vector transmiting and displaying of the map through using SVG, at the same time, through publishing and registering the Web Service that is already defined can also realize sharing of the data resources on GIS database server of this system, we can also search relevant Web Service that has published and registered in Internet to realize integration of the other land data through citing it.(2)Designing and realizing WebGIS by introducing multistage cache and security mechanism of ASP.NET, not only improve the whole operational efficiency of WebGIS through the cache of client and server, but also guarantee WebGIS that is developed in this way to run safely in Internet.(3)The geographical data are kept in the corresponding database of the database server according to the integrated structure or XML/GML way, after the server receives the request from client, for the integrated structure database, real-timely extracting the data of the corresponding range from the database by analysis and changing it into XML/GML by Web Service that has been defined, for XML/GML database, direct extracting the data,then changing XML/GML that has been gained by the front two way into SVG through XSLT and transmiting SVGZ to the client browser to display after the compresseing of GZIP for SVG, if user does not have new data asked, user is just carrying on enlarging, shrinking, roaming operation etc, then these oprations can only use SVGZ file that has been already download to the client with .aspx pages, and not need transmiting these data moreover, on the basis that the data amount of the vector transmitting is small, it has further reduced the transmitted data amount,it has further improved transmitting and displaying efficiency. So the way not only can guarantee background data is safe and reliable but also has higher efficiency.(4)The solution adopt the space database of the integrated structure to organize and store GIS data or adopt XML/GML database to store GIS data, thus utilize RDBMS to achieve unified management for the space data and attribute data, it offer geographical information query service with higher efficiency for the client, at the same time, it improve management and maintenance efficiency for GIS data.Another, it can realize integration of the data of many sources through carrying on the mode mapping and changing the different data source into XML/GML data. Finally, converting different space data to XML/GML based on text form, thus integrating the different structure space data to the form of XML/GML, thus realizing sharing and operating each other between the space data.(5)Do not need to buy expensive WebGIS development software, such as MapXtreme, ArcIMS etc. we can realize WebGIS, the development cost is cheap.Through developing concrete WebGIS, it has proved the solution has the characteristic that data is easily integrated and shared, the amount of transmitted data is small, transmiting velocity is fast, performance is comparatively optimizing and the data is comparatively safe and the development cost is cheap etc.更多还原