The costs associated with the implementation of a GIS are often perceived as prohibitive. This is particularly true of small and medium enterprises, which operate under tight budgetary constraints. The paper proposes a technical solution, which can help to mitigate the problem and enable the organization to derive the benefits of implementing a GIS. The paper describes the development of a low-cost Internet enabled graphics viewer, which has been successfully implemented in an intranet-enabled GIS Application.
Network capability of current Internet GIS applications
The Internet has emerged to new heights within the last few years especially in developing countries. Also it is inexpensive and ubiquitous and renders "information like water". This makes it a perfect vehicle for carrying the GIS to the users across the globe.
Current version of HTTP protocol does not support direct transfer of vector data type, which most of the GIS applications require. Hence the Internet users are not able to analyze and display vector data. As a result, GIS applications require:
- More time for transfer of data between client and the server
- Extra burden for repeated processing, like map Navigation, visualization and analysis.
This mainly happens because of the system architecture used. Typically the process involved is that the user sends a query to the GIS server, which initiates a function to convert the vector data into raster format. The raster file is then returned to the browser for display.
What LTGIS Tool can do for GIS applications on the Internet/Intranet?
The heavy network traffic caused by frequent data transmission in existing Internet-enabled GIS systems, served as a catalyst to developed a new solution, which will enable users to download objects from the network GIS server to their local machines and make use of them locally. This will solve the problem of data transfer.
The LTGIS Tool - A Internet enabled GIS
Microsoft Visual Basic 6.0, Win32 API, and XML
Win NT 4.0, Microsoft Internet Information Server 4.0
Hardware/Software Requirement for the client
Component of LTGIS Tool
- The user system should have minimum 32 MB RAM computer (64MB recommended)
- Pentium Processor
- The application could be best viewed in Internet Explorer 5.0 with 800 * 600 resolution.
The LTGIS tool has two major components,
I. The Data Converter
II. The Viewer
I. The Data Converter
The data converter component resides on the server and is responsible for converting the data from a standard DXF file to the LTGIS data format, which is readable by the Viewer, deployed onto the client machine.
II. The Viewer
The Viewer is an ActiveX control, which displays the drawing files (vector maps) with basic entity like line, arcs, point and text. The viewer is capable of rendering the vector data directly, which is downloaded from the server when the user accesses the map for the first time. Thereafter, there is no transaction between the server and the client for any of the vector map data unless user requests for a different map or retrieves attribute data.
The Viewer accepts the data from the Server in the form of XML strings. Hence the Viewer can display any data format. Once the Viewer receives the data there is no interaction with the server as far as the basic GIS functionality is concerned. The map navigation and other GIS functionalities are performed at the client end. Hence the process reduces the network traffic and increases the overall performance of the application.
Figure 2: The Viewer
The functionalities supported by the Viewer (Fig. 2) are listed in next page.