Chicago Urban Area (CUA) orthoimagery data have been created for the counties of Cook, DuPage, Kane, Lake, McHenry, and Will in northeastern Illinois in two projections. These are Universal Transverse Mercator (UTM) with a NAD83 datum, Zone 16 and Illinois State Plane East Zone (SPE) with a NAD83 datum. Data were created using US Geological Survey Urban Area specifications on true-color film during the leaf-off period of spring, 2005 at a 1 foot by 1 foot resolution. Each data tile was created utilizing multiple aerial images. Images were captured on the following dates in 2005: March 28, April 4, April 8, April 14, and May 4. Programmatic details for CUA data were outlined in Illinois GIS Notes, Winter 2005.
Compressed data are LizardTech's MrSID Generation 2 .sid files. Target compression ratio was 8:1; one compressed file is roughly 9 megabytes in size.
A statewide collection of both 2005 CUA data (40 Gigabytes) and 2005 National Aerial Photography Program (NAPP) data requires about 100 Gigabytes of storage space. We do not plan to distribute compressed data files by any other means (cd-rom, zip drives, portable drives, ftp download, etc).
The ArcIMS interactive map was created for the Universal Transverse Mercator data by loading the original GeoTIFF files into ArcSDE.
Contact theto obtain indiviual, uncompressed Illinois 2005 orthoimagery files. Note that one statewide collection of uncompressed 2005 CUA data (310 to 320 Gigabytes) and 2005 NAPP data would require about 1 Terabyte of storage space.
Project funding was contributed by:, Illinois Department of Military Affairs, , the , and the .