Topography in Illinois from aerial photographs by Kelsh plotter, Aerial photographs taken 1956. Field check 1957, Topography in Indiana by planetable surveys 1940-1941, Culture revised from aerial photographs taken 1956. Field check 1957.;Contour interval 10 feet.;Relief shown by contours and spot heights.;1 map, colored;45 x 35 cm.;1:62,500