Flights flown between July 16, 1939 and October 1, 1939 by Midwest Aerial Surveys, Inc., for the U. S. Dept. of Agriculture, Agricultural Adjustment Administration. Photos numbered BXA-1-11 through BXA-3-114. Scale not given. Stereoscopic coverage. Only indexes are georeferenced.
McHenry County (Ill.) (W 88°42′--W 88°12′/N 42°30′--N 42°09′)
Illinois State Geological Survey
303 remote-sensing images, 1.03 gigabytes, 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.