will allow an application to seamlessly combine data drawn from different locations.

"If you're going to route an emergency vehicle properly, you've got to have all of those available in one data set in one location, or at least made to look transparent as if it's one data set," he said.

Extra Horsepower

Under an enterprise GIS server architecture, all aspects of the GIS, including mapping, spatial analysis and database management, run on a central server. Users working on thin clients -- PCs or other devices equipped with browsers -- use a local- or wide-area network to access those GIS applications.

Staff needing more sophisticated functions can access the system from a "thick" client machine, which runs some of the necessary software locally. The architecture also supports handheld systems that interact with the server while connected to the network, but that also function while disconnected.

ArcGIS Server includes full geographic analysis functions, high-end cartography and other capabilities, uses standards-based application programming interfaces and supports extensible markup language/simple object access protocol (XML/SOAP), Java and .NET, Maguire said.

The EGIS approach promises many advantages of other Web-based systems -- scalability, easy access and inexpensive maintenance -- while delivering full GIS functionality because, according to ESRI, instead of trying to adapt a desktop system to the Web environment, the ArcGIS Server was designed for the Internet.

Not Quite Yet

The Kansas Data Access and Support Center (DASC), like its Oregon counterpart, provides a GIS clearing-house for state and local agencies. Unlike Oregon's GEO, the DASC currently has no plans to procure and deploy ArcGIS Server.

"I don't think many people are, because it's pretty new," said Kenneth Nelson, GIS coordinator at the Kansas Geological Survey and manager of the DASC, while acknowledging that future customer requests might push the DASC to consider an enterprise GIS server in the future.

The DASC, housed at the University of Kansas in Lawrence, currently uses ArcIMS to distribute interactive maps and basic GIS applications to users via the Web. Nelson said ArcIMS is an easy and cost-effective way to allow people who aren't trained professionals to use the data, which was previously only useful to GIS professionals with the expertise to locate the data they wanted, and download, unzip and import it into the applications they were running on the desktop.

An enterprise GIS server would allow the state to deliver all functions currently available in the ArcGIS family of products over the Internet, Nelson said.

While the enterprise GIS server approach offers a major advantage, Kansas will not deploy it in the near future because DASC staff simply have too many other projects on their to-do lists.

"The investment in time to get up and running and develop applications in that environment is pretty large," Nelson said, because ArcGIS Server is more expensive than ArcIMS, and applications developers must climb a steep learning curve before they can use it.

So far, DASC staff members have developed all the applications that clearing-house users have requested. But as more users at state and local agencies come to understand the power of geographic data, it's very likely they will start asking for applications that strain the limits of ArcIMS, Nelson said.

"I think as their needs mature, that will probably push us toward that server technology, where they're trying to do more sophisticated query or analysis or more sophisticated data development."

Merrill Douglas  |  Contributing Writer