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A Comparative Assessment of Internet GIS Server Systems
WebGIS system architecture
Initial approaches to deploy the Web mapping application, the system architecture for the Web-based GIS, infrastructure requirements and necessary skills should be considered. The WebGIS system architecture can be illustrated as a Client-Server web deployment. However, there is need for additional technology to provide a Webmapping application, either at just the server-side or at both the server-side and the client-side. The Web server itself is not able to do any geo-processing then it has to pass on requests from the client to map server (WebGIS software) for geo-processing. There are several standard interfaces such as the Common Gateway Interface (CGI) and server Application Programming Interfaces (APIs) to enable the communication between Web server and map server. The diagram below illustrates a generalized view of a web-deployed mapping application.  Figure 1. Webmapping system architecture The interaction based on request and respond scenario of client-server. A server-side application communicates with the map server to provide the request information. The updated map is returned to the browser embedded in the HTML page or applet. Generally, the web system architecture can be categorized by means of the thickness of users. Thin Client Approach The thin client architecture focuses on the server-side which most of data and analysis procedure was processed on demand on the server. Data transmitted to the web-client are in standard HTML format embedded with typical GIF, PNG or JPG images that can be views in any web browsers. The disadvantage of the server-side solutions are primary associated with limited user interface. In WebGIS, there are many applications in which users need to interact with the spatial data before an action take place. These include of dragging windows, selecting the features or area of interest. It is inefficient to do this by using a standard Web interfaces (Gerardo, 2000, URL). Therefore this solution is the simply way for build up the web map applications running on any standard browser. Thick Client Approach A Thick client is at the other end of the spectrum. To support displaying the results of geo-processing at the client-side several technologies have been developed such as plug-ins, ActiveX controls and Java-applets. GIS plug-ins are small software applications installed at the client-side to extend browser capabilities to handle GIS data formats that current HTML cannot recognize. Some simple GIS functionality can be built into the plug-in or applet and performed locally. The execution requires no server-side geo-processing, thus reducing data transfer over the Web. Unlike in the case of the thin-client architecture where rendered maps are transmitted as images files, the geo-data in the thick-client approach are transmitted in the form of the more compact vector data structure (Gerardo, 2000, URL). The advantages of the WebGIS client-side solutions are the abilities to enhance user interface and serving map by illustrating in vector form. In general, the disadvantages associated with the client-side solutions relate to distribute the software and data. No software either Java or ActiveX run on all computer platforms that exist on the Internet.
A Comparative Assessment of WebGIS software The research plays an attention on currently available three WebGIS software packages among the various initiatives. These discussions provide an overview of these three software packages emphasized on their features and capabilities in order to develop the webmapping applications. The research also describes about the proficiency of the software in order to meet the challenges set by the benchmark items. We have deployed the applications with these products and will use this paper as an opportunity to share our experiences and observations. |
