51. Radio direction finding chart 21 DF and 22 DF. 22 DF. Aeronautical chart for radio direction finding, lat. 38°-49°, long. 87°-105°. Scale 25 m. = 0.8 in., scale 1:2,000,000. Bookmark Corporate/Agency Authors: Coast and Geodetic Survey and Commerce Dept. Publisher: Coast and Geodetic Survey Date: [July 1947] SuDoc number: C 4.9/5:22 DF/947-2