Computers & Geosciences, Volume 26, Number 5, 2000

Another Node On the interNet

Sheena K. Beaverson and Robert J. Krumm
Illinois State Geological Survey
Champaign, Illinois

John Butler
University of Houston
Houston, Texas 77204

From The Associate Editor

When ANON was initiated one goal was to focus on how individuals and organizations were using the Internet as an integral part of their efforts. This month Sheena K. Beaverson and Robert J. Krumm describe their work in developing an online catalog of imagery for the state of Illinois.

The Illinois Natural Resources Geospatial Data Clearinghouse: An Online Data Catalog Maintained by the Illinois State Geological Survey

The Illinois Natural Resources Geospatial Data Clearinghouse serves as a gateway to GIS data and imagery for Illinois. The project is a multi-agency effort by the Illinois Department of Natural Resources (DNR) Scientific Survey divisions and is associated with the National Spatial Data Infrastructure (NSDI) clearinghouse. The Illinois Clearinghouse is housed at the Illinois State Geological Survey (ISGS) In Champaign, IL, and maintained by ISGS staff. Available county and statewide Data sets and documentation (metadata) include: geology, water resources, nature preserves, wildlife areas, environment, land cover, Digital Raster Graphic (DRG) files, elevation, Public Land Survey, political boundaries, roads, census information, and much more. Other features include a metadata generation tool, information about upcoming metadata workshops, a hotlist of other online DNR data-related features, and a table listing DNR aerial photography holdings.

The clearinghouse was brought on-line on July 1, 1997 and currently serves more than 1,800 downloadable GIS data sets in Arc/Info export file format, described by over 130 complete metadata documents. An additional 100 "skeleton" metadata files represent searchable entries from our working list. Data and metadata are accessible through straightforward browse pages and keyword search functions. The browse pages for statewide and county data are augmented with short abstracts, complete metadata, and GIF images that give a visual snapshot of each data layer. Users have the ability to conduct keyword searches of the metadata database either locally at the Illinois Clearinghouse or remotely from the primary (NSDI) gateway.

In April, 1999, DRG images of all the U.S. Geological Survey (USGS) topographic quadrangle maps for Illinois were made available in a variety of projections and at the following scales: 1:250,000, 1:100,000, and 1:24,000. The DRG files are georeferenced images produced by scanning USGS topographic maps. This widely-used and recognized map format provides large and intermediate-scale, base map coverage essential for many digital mapping initiatives. These files can be selected via imagemap indexes, by name, or by USGS index number, and are available in georeferenced TIFF format.

The Clearinghouse project has been very successful. From July 1, 1997 to July 1, 1999 the site has had 91,900 hits in 73,300 user sessions, and had averaged 3,000 users per month. Metadata documents were accessed over 56,900 times and 72,500 data sets (roughly 48 gigabytes) were downloaded. In the ten months that the DRGs have been available free for download, roughly 10,000 files have been downloaded, equaling 25.5 gigabytes of distributed data. This activity represents new data distribution, and these values exclude in-house access by ISGS staff. Although Internet statistics of this sort are imprecise, they indicate that the Illinois Natural Resources Geospatial Data Clearinghouse is receiving a great deal of attention and is providing convenient data access to our digital data consumers. At present, the project is sustained as a part of the ISGS's internal GIS database operations. In the longer-term, we hope the Clearinghouse will be recognized by the state as an essential service and supported appropriately. Meanwhile, funding has been pursued from state initiatives and third parties, to significantly expand the on-line data catalog.

In 1999, state and federal agencies with interests in Illinois entered into a joint funding agreement with the U. S. Geological Survey to purchase the full set of Digital Orthophoto Quadrangles (DOQs) for Illinois. DOQs are digital map layers made >From aerial photographs that have been registered to map coordinates. Created from 1998/99 photography, these map coverages will be the most up-to-date, large-scale geographic base data available for Illinois. DOQs are well suited for virtually any mapping project, digital or otherwise. Over the next two years, the State of Illinois, through the ISGS, will receive one set of these data. External funding is Currently being sought by the ISGS to support the processing necessary to archive and distribute the 4,135 Illinois Digital Orthophoto Quarter Quadrangles. The ISGS plans to distribute compressed versions of the 1998/99 DOQ data files on-line, free for download, at the Illinois Natural Resources Geospatial Data Clearinghouse. The uncompressed data all will be offered for sale on CD-ROMs.

Access to DOQs will enable GIS and remote sensing professionals to more readily develop projects that foster sustainable use of natural resources and will increase scientists' capacity to address the world's changing food and agricultural demands. Thus, the application of DOQs to natural resource protection, mapping, and monitoring will likely yield a significant economic impact.

The llinois Natural Resources Geospatial Data Clearinghouse can be visited at: