Flights flown between July 12, 1939 and October 1, 1939 by Midwest Aerial Surveys, Inc., for the U. S. Dept. of Agriculture, Agricultural Adjustment Administration. Photos numbered BXB-1-2 through BXB-4-6. Scale not given. Stereoscopic coverage. Only indexes are georeferenced.
Marshall County (Ill.) (W 89°38′--W 89°03′/N 41°09′--N 40°55′)
Illinois State Geological Survey
248 remote-sensing images, 861 megabytes, average file 3.5 megabytes
Scanned from 9 x 9 contact prints (nominal scale ca. 1:20,000) on Crosfield 646IE drum scanning system at 750 dpi. Quality assurance target not published but available by contacting the Illinois State Library Map Dept. MrSID files compressed at a target ratio of 12:1. Uncompressed TIFF images on cd available from the Illinois State Library Map Dept.