Going Open in WebGIS
Malaysia University of Science and Technology
Dr. Woon Wei Lee
Malaysia University of Science and Technology
This paper investigates the possibility of adopting open standards and technologies for the development of geographic information systems (GIS) particularly for the web. The GIS market has traditionally been monopolized by several key players that make up a large segment of commercially available systems and raises the issue of interoperability. GIS software is often high in cost and restricts access to the select few who can afford it. Adopting an open standard is one of the solutions but are the current open source libraries and software sufficiently mature to be used for web mapping applications? An extensive review was conducted and the findings are presented in this paper on existing open source libraries and software to determine their impact in the development of GIS. This also includes several standards that are adopted by the Open Geospatial Consortium (OGC) which will shape the future growth of remote sensing. In contrast with popular belief in the difficulty of developing using open source software, we developed and documented a simple proof of concept WebGIS system. This paper is based on actual reviews on selected open source libraries, software and published materials, including white papers, standards documentation and journals.
The use of open source based software has always attracted keen interest in the tech community. Not too long ago, the phrase “open source” was usually associated with a high learning curve and there was also difficulty and complications when integrating with existing systems. The same cannot be said now with many successful open source software products such as Linux, Open Office and Mozilla. The advancement of the Internet has lead to people who share common interests to group together and form communities dedicated to collaborative software development and pooling of knowledge.
1.1 Open Information Sharing
With the dominance of commercial based software, there is minimal sharing of spatial information as the information is locked in with the system. Moving from one system to another is often difficult with each system having a proprietary format that cannot be read by the other. The difficulties arise when information from two different sources needs to be integrated and this cannot be done due to incompatibility between the respective data formats.
1.2 Web-GIS System
A WebGIS system can be modelled using the client-server architecture. A thin client approach is where most of the processing work is done on demand in the server and the client does not perform any task other than to display the data on screen. The thin client system comprises two parts, the client and the server and this model will be used for our simple demonstration later in this paper.
The advantage of this is that users will not be required to install any additional software apart from a standard web browser. Since processing will be done on the server side, clients will not need a powerful machine to access the services offered, though this would also mean that the server would be subject to additional and often heavy loads. However, in order to reduce server loading, the HTTP server, database and WebGIS software do not necessarily have to reside on the same server and can be distributed across the Internet.
2.0 Going the Open Way
Standardization means that everyone agrees to a common system. The Open Geospatial Consortium (OGC) is the organization that is responsible for setting these standards through an open process. In the old GIS paradigm, clients usually need a separate interface to access different vendors’ systems. The lack of an open standard discouraged vendors from having a common system. The open standards that are introduced in this chapter are steps taken by industry to help eliminate the problem of users being trapped in technology stovepipes . We will review some of the successful standards and tools that are paving the way in making GIS more accessible to the open source community
2.1 Open Web Service (OWS)
Geoprocessing is a task that requires specialized software and sometimes hardware. A system that is capable of performing spatial tasks is often difficult to maintain and expensive. In  it was argued that the solution would be to use a distributed development platform to separate the data and actual processing into two separate servers using a web service. A web service is a program that makes itself accessible over the Internet using XML as a messaging system. The OGC envisioned OWS to be a system where users can access geospatial data through a single interface regardless of the platform being used. The OWS suite includes three principal types of georeferenced information services which are Web Map Server (WMS), Web Coverage Server (WCS) and Web Feature Server (WFS). This discussion is focused on building a system that is compliant to OGC’s WMS and WFS specifications.