Internet GIS method for processing geographic information of multiple data sources

AbstractThis paper introduces the Internet GIS method for obtaining, managing and processing various data sources and the principles and functional features of Internet GIS designed with this method.

 KeywordsInternet GIS; interoperability; Java/jdbc; customer/Server
Classification NumberP208

Internet GIS Approach to Multisource Data and Geoprocessing
Yuan Xiangru(National Laboratory for Information Engineering in surveying, mapping and remote sensing,
Wtusm, 129 luoyu Road, Wuhan, China, 430079) Gong jianya Chen Lili Han Haiyang

Abstract most of recent researchers believe that a lack of awareness, and problems of accessibility of spatial data are significant bottlenecks to increasing numbers of users and applications. it is not easy for users to get spatial attribute from image of WWW Geographic Information System (www gis ). in order to solve these problems, the vector graphic seamless link with main database model and new www gis system have been developed with Java and JDBC. this paper introduces Internet GIS Approach to mutlisource data and geoprocessing, And the principle and functions of Internet GIS.
Key words　Internet GIS approach; interoperability; Java/JDBC; Client/Server

With the rapid development of geographic information systems, the demand for obtaining, storing, and sharing digital geographic space data is growing. Many engineering-oriented GIS applications believe that GIS data is isolated information, and data is independently acquired, stored, and analyzed to meet the needs of a single project and program. Data is rarely shared, leading to data collection and storage redundancy and inefficiency. The increasing demands of GIS users have promoted the development of GIS. An organization is committed to developing a complete database and meeting the needs of GIS applications through Agency departments. You are encouraged to use the public digital information for free or at minimum cost in the Internet environment.
Two traditional methods for obtaining information-server application interface method and plug-in method-construct the client distributed space data query and Interconnected Network Acquisition System (Peng, 1997 ). The images obtained from the server do not have spatial attributes and are not easy to operate. In these methods, CGI (Common Gate Interface) is written on the HTTP server as a path to return appropriate files and generate an online file transmission path. Operations on all spatial data are completed on the server side. Currently, HTML2.0 supports geographic information data files. files obtained from CGI files or programs cannot be embedded with vector data. An image in GIF or JPEG format is the only format returned by spatial data. In this way, image processing is time-consuming, such as scaling, roaming, online plotting, and model analysis services, because each time a message is sent to the server, the server needs to search for the database, perform operations, generate GIF, and then send it to the viewer. Undoubtedly, this is a very heavy burden on network transmission and database servers (Lin, 1997 ).
To solve these problems, the author developed a World Wide Web Geographic Information System Based on the vector graphics distributed model using Java and JDBC. Compared with the traditional method, this method can be obtained and managed from the database server through the World Wide Web, including geofile (Fox Pro), geodb (Microsoft SQL Server) multiple data sources, such as ARC/INFO, Mapinfo, DXF, and MGE, are directly transmitted to the client. You can easily manipulate the vector data, including roaming, scaling, querying, and analyzing. On the client, you can operate data as on the server. This method also provides geographic information processing functions, such as map feature analysis, query, spatial analysis, thematic drawing, distance analysis, and table operations. Internet GIS provides great flexibility and interoperability between GIS users and spatial data services.

1. Internet GIS principles

For General GIS software, it is used for the production, management and maintenance of geographic information data. Currently, the most influential GIS software include ARC/INFO, Mapinfo, and MGE. Most of the users who use the software are geographic information production departments. The Geographic Information Production Department produces these geographic information to allow the majority of users to use it for paid use to achieve geographic information sharing. If the geographic information data is shared by users around the world in a simple way, it will bring good economic benefits to the geographic information production department and users. Users who use geographic information data can be divided into three categories: ① use the raw data of geographic information data; ② use the intermediate results of geographic information data; ③ use the final chart of geographic information data.
Internet GIS can be defined as a geographical information system that allows global users to use geographic information data on the Internet. Internet GIS provides special data sales methods for geographic information data production departments and provides different levels of geographic information data sharing and services to meet different needs of three types of users. It makes geographic information a reality for global users. The principle is shown in Figure 1.

Figure 1 principles of Internet GIS
Fig.1 the principle of Internet GIS

The basic requirements of Internet GIS are as follows:
1) Interoperability application environment. Users can use special tools and necessary geographic information data on any software or hardware platform to solve the problem.
2) share data space. Multiple Analysis and drawing applications are supported using models.
3) heterogeneous data browsing. Study and obtain information on the Internet to analyze available resources.
Internet GIS is based on the vector graphics distributed model, that is, the user operates on the geographical information data of the vector graphics; the tasks of the geographic information database server, web server, JDBC server, and client are separated; computing is distributed on the Internet. The geographic information database server and client are multiple and distributed on the Internet to achieve interoperability between multiple data sources.

2 obtain and manage multiple data sources

Internet GIS is mainly used to provide links and bridges between geographic information production departments and Internet users. In addition to the production, update and maintenance of geographic information data, it also has all other features and functions of general geographic information systems. Obtaining and managing multiple geographic information data sources is the primary feature of Internet GIS. Geographic information systems such as ARC/INFO, Mapinfo, and MGE all have their own geographic information data formats. Internet GIS must be able to obtain and manage the data formats of existing Geographic Information Systems and share existing geographic information data.
The JDBC and extended JDBC data organization component of Internet GIS is responsible for obtaining data from the database server. It contains many sub-parts, such as geostar Data Acquisition sub-parts and ARC/INFO Data Acquisition sub-parts. Currently, it supports the following data formats: ① geostar internal data format, including geodb (miscosoft SQL Server) and geofile; ② Mapinfo's MIF data format and internal data format; ③ ASC ⅱ of MGE load data format and dgn data format; ④ e00 data format of ARC/INFO and coverage data format; ⑤ DXF data format of AutoCAD.
Geographic information data formats can be divided into three categories: ① file data formats formed in the form of non-relational databases, such as ARC/INFO, Mapinfo, and MGE; ② geographical data formats formed in the form of relational databases, such as geodb; ③ geometric objects are stored in the form of files, and attribute objects are stored in the form of geographical information data in the form of relational databases, for example, geofile.
The above three data sources of different formats must be completed using different components. The JDBC Data Organization module is used to obtain the geographical information data of relational databases, and the JDBC Data Organization module is extended to obtain the geographic information data of non-relational databases. The third category should be implemented through the combination of JDBC and extended JDBC Data Organization components.
After running the client, the system lists all the relevant database service domain names (or URLs) and geographic information data directories that users can use. End users use standard SQL statements or extended SQL statements to find directories of interest to users from these geographic data sources and return data to form a data layer. On the basis of the layer, JDBC and the extended JDBC server obtain data from the database server, transfer the data to the client, and form a graph.
You do not need to transmit all the data on the database server to the client over the Internet. Instead, you can use SQL statements or extended SQL statements to select a data set that you are interested in and transmit it to the client, this is the biggest advantage of using JDBC and extending the JDBC data organization part. This reduces the data transmission volume and server load, thus improving the efficiency.
For client users, you can use several visual and intuitive methods to obtain geographic information data from multiple data sources through JDBC and extended JDBC Data Organization components: ① index graph method. You can select a map that you are interested in on the index map to obtain geographical information data from the database server, for example, a China Digital Map. ② Data source and Map Name list method. The system lists all the geographic information data sources and image frames on the database server selected by the user on the client. ③ Geometric method. The geographical information layer that users care about is extracted from the database server through geometric segmentation. ④ SQL statement method. On the JDBC server, the SQL statement obtains the geographic information data required by the user from the database server.
The geostar sub-part of the JDBC data organization component obtains data from the SQL server of the database server through SQL statements, transmits data to the client over the Internet, and displays data graphics on the client. The background is the Netscape Browser, it displays relevant information and provides a Java virtual machine. For the coverage data of ARC/INFO, expand the ARC/INFO sub-part of JDBC data organization to obtain data from the database server and transmit the data to the client through the Internet to form a graph. The procedure of Mapinfo's MIF data is similar to that of Arc/Info's coverage data. The difference is that it uses the Mapinfo sub-part of the extended JDBC data organization part. For more information about the legends, see [2].
After obtaining geographic information data through JDBC and extended JDBC Data Organization components, you need to manage these vector data. Data management is implemented by components, as shown in figure 2, such as displaying components, drawing parts, analyzing parts, and data management parts. Component-based data management reflects the object-oriented features, including inclusiveness, diversity, inheritance, and dynamic connectivity. When the system is running, all parts are not downloaded from the server to the client at a time, but only the parts in use by the user. Other parts are dynamically downloaded and run from the server when the user needs them. The system can provide many functions and complete functions during design, but only the components that arrive at the client are required by the user, which helps relieve the burden on the Internet and the client, it is of great significance to the actual project.

Figure 2 system organization
Fig.2 the construction of the system

3. Geographic Information Processing and features

The Internet GIS method provides powerful functions for Spatial Data Query and operations. First, it provides the ability to search for Images Based on attributes. In the SQL query operation, you can find the features with special conditions and list these features in an Attribute Table. Secondly, it implements spatial relationship query, and queries the objects through a specific geometric image, such as points, lines, rectangles, circles, and polygon. By comparison, another method of Spatial Query within a certain range is in the buffer zone around the point, line, and area.
It also provides many data statistics and graphical representation methods. For example, the methods for describing data of different levels and regions, the range description method, and the individual description method. The system not only provides users with a variety of symbols, such as bars, pie charts, and curves in statistical graphs, but also has the ability to design special symbols.
Internet GIS provides distance analysis and topic plotting functions for Geographic Information Processing of multiple data sources. Topic charts include two-dimensional or three-dimensional pie charts, bar charts, isographs, trend charts, hierarchical statistical charts, and texture filling charts. This provides a powerful method for analyzing and displaying data from multiple data sources. In addition, you can use a local printer on the client to output results of various analysis, query, drawing, and table operations.
The main features of Internet GIS are as follows:
1) distributed model based on vector graphics. That is, vector graphics, task separation, distributed computing, distributed servers and clients, and multi-data source interoperability.
2) You can conveniently perform operations on geographic information data on the client, such as roaming, scaling, querying, and analyzing.
3) it can run on all platforms and operating systems with Java virtual machines. You can start the system on any 10 thousand Tib browser, such as the Netscape browser and the Internet Explorer e browser. After the system is started, it has nothing to do with the browser.
4) with Java and JDBC, you can obtain geographic information data from Relational geographic information databases (such as Sybase, SQL server, and Oracle) and non-relational geographic information databases.
5) strong security. You can obtain geographic information data, but the data cannot be stored on the client.
6) The operation is simple and convenient. No installation is required. You can start the instance by knowing the IP address or domain name of the system.
7) Obtain and manage multiple geographic information data sources, such as GeoFile, GeoDB, Arc/Info, MapInfo, DXF, and MGE.
8) spatial analysis capabilities, such as analysis, query, spatial analysis, thematic drawing, distance analysis, and table operations.
9) supports multiple languages and can run in multiple languages at the same time, such as Chinese, English, and Japanese.

4 Conclusion

With the rapid development of Internet technology, the Internet Geographic Information System will further affect the publishing of geospatial data and the development of GIS software. The Internet GIS method based on the vector graphics distributed model is an effective method for obtaining, managing, and processing geographic information from multiple data sources over the Internet. It proves the feasibility and practicality of sharing and using geographic information data for global users on the Internet, it also provides a new method for Interoperability GIS and a high degree of flexibility between GIS users and geographic information data services.

* The National Natural Science Foundation of China and the National Ninth Five-Year Plan fund for key scientific and technological breakthroughs, numbered 49525101 and 95d0203.
Author profile: Yuan Xiangru, male, 30-year-old, doctoral student, is currently engaged in Internet Geographic Information System Research.
【Author】: Yuan Xiangru, Yan jianya, Chen Lili, Han Haiyang, State Key Laboratory of surveying and remote sensing information engineering, Wuhan ing Technology University, No. 129, Luyu Road, Wuhan, 430079

References
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