A simple map client view of the Lawrence Imagery map service.

The world of GIS and spatial data is growing by leaps and bounds. Faster, more powerful software that is easier to deploy than ever is resulting in users doing tremendous things with GIS technology worldwide. The Internet, distributed systems, and other GIS networks are connecting this growing world of users, as well as providing a better means for making data accessible around the globe. And as the GIS community expands, the question is: How can people wade through the vast stores of spatial data to get the information important to them? Conversely, how can data producers effectively make their datasets available to those who need them most?

Questions such as these have been the driving force behind an innovative data distribution solution, one that's been making quite a stir in the GIS and information technology (IT) communities: Mapdex (www.mapdex.org).

Mapdex is an extensive database portal searchable by spatial layers, fields, and map service names. Ever evolving, the project provides users with access to a large and growing number of map services. For the GIS community, this is a tremendous boon; specialists in many industries can locate and use data already created. They can also learn about its origin, date of creation, scale, and a myriad of metadata variables.

"I found that there is much GIS data available to the general public and GIS users through Internet map servers, but I also found that users would not find this information easily by using traditional search engines," says Jeremy Bartley, assistant GIS coordinator and Geoinformatics Project lead of the Kansas Geological Survey at the University of Kansas. "The public needed a way to search the actual data behind the interactive maps, and this was the impetus behind Mapdex."

Mapdex provides an index of publicly available ArcIMS services comprising approximately 1,715 servers, serving approximately 30,000 map services, and containing approximately 475,000 GIS layers. It brings together a previously disparate network of GIS services, searchable from one location, that can be tapped into by the GIS community using just a few keyword searches and mouse clicks.

A user has searched for all layers with "photo or aerial or ortho or doqq" in the layer name in and around the geographic area of Lawrence. Kansas.

"Geospatial One-Stop and the National Map are excellent services, but these only search sites that have full metadata, which omits many servers and services," explains Bartley. "I wanted to effectively extend the traditional search to an even wider array of GIS data. When I discover a public map server, information about that server and its associated map services would be stored in its native XML structure in Oracle9i's XMLDB database. This database is the Mapdex database. I think it is a great resource for the GIS community, especially since it is becoming common for GIS specialists to spend more time searching for data than they do creating it."

The Mapdex Web Portal

In the course of developing a Web portal for current and future Kansas Geological Survey project work, Bartley discovered a method for extending and refining Web searches to include a vast number of publicly available GIS data and Web services. Using the Google and Yahoo! search APIs, he programmatically searched for possible map server keywords, such as "mapping," "interactive map," "pan," "zoom," and "GIS," looking for possible Web databases with treasure troves of publicly accessible data. Each time he discovered a Web site with GIS data available, he included it in his Mapdex database. He then queried each of the possible map server sites to determine whether they were publishing public map services.

Once the information is stored, Mapdex uses ArcIMS 9 to reproject each layer's envelope coordinate to a geographic projection. This allows users to search spatially for data. Currently, only 30 percent of map services have defined a valid projection. Only sites that have a defined projection are able to be searched spatially.

Mapdex Web site. Users can search by server, service, layer, column, or geography.

Mapdex was developed using standards-based ArcIMS and WMS 1.1.1 technologies. Mapdex runs using ArcIMS 9 on a Windows 2000 Server with Apache 2.x and Tomcat 4.x.

"The wide use of ArcIMS allowed us to build the Mapdex portal," says Bartley. "We have been able to leverage ArcIMS software's large user community to provide access to each of the participant's datasets, as well as large national datasets, such as national scale orthophotography, satellite, and digital elevation models, that could not be served using a single, centralized architecture. In our own GIS shop, ArcIMS is the solution of choice for delivering dynamic maps, data, and services via the Web. It provides a highly scalable framework for publishing our GIS data and combining it with our other partner organizations."

Users can find requests by server, service, projection, layer names, and geography. When users search by geography, Mapdex uses Esri's ArcWeb Public Services to geocode location addresses and place-names.

Bartley and his team developed a simple front-end viewer for Mapdex that allows easy searching and quick mapping of spatial data. In addition, users can go into ArcGIS and add the relevant server to their ArcGIS project. Currently in development, an advanced map viewer will soon allow users to overlay different maps on a single screen and perform more advanced cartography. This will provide a richer degree of functionality to those who need fast searches and quick, accurate mapping functionality in near real time.

Style sheets have been written to graphically display the output from getclientservices requests.

For instance, emergency responders will be able to locate and integrate a myriad of map servers in separate locations and orthophotos, parcel data, and street infrastructure data can be assembled to provide a common operating picture of emergency commanders entering a disaster location and in need of making quick tactical decisions.

"Mapdex will continuously evolve, offering more services and data as they go online," says Bartley. "It's a fast and easy way to find interactive GIS sites where organizations are making their data available to the public. The more data goes online, the easier people can locate it, and the more GIS can make a difference in all ways of life, and then even more and more data will be available and accessible. And as the GIS network grows, we'll continue to refine Mapdex's capabilities."

The Mapdex team comprises Jeremy Bartley, Praveenkumar Ponnusamy, Asif Iqbal, and Amber Reynolds. For more information, contact Jeremy Bartley, assistant GIS coordinator and Geoinformatics Project lead, Kansas Geological Survey, University of Kansas (tel.: 785-864-2126, e-mail: jbartley@kgs.ku.edu), or visit www.mapdex.org.