Illinois National Aerial Photography Program (NAPP) Digital Orthophotography quarter Quadrangle (DOQ) data have been created for 96 counties in two projections. These are Illinois Universal Transverse Mercator (UTM) with a NAD83 datum and State Plane (SP) with a NAD83 datum. This data collection excludes the counties of Cook, DuPage, Kane, Lake, McHenry, and Will in northeastern Illinois. Imagery was collected using NAPP specifications using black and white film during the leaf-off period of spring, 2005 at a 1.5 foot by 1.5 foot (half meter) resolution. Programmatic details for Illinois NAPP data were outlined in Illinois GIS Notes, Winter 2005.
U.S. Geological Survey Surdex Corporation and Science Applications International Corporation (SAIC) Illinois State Geological Survey