Base map: USGS Cleveland, Ohio; Pa., U.S., Ont., Can. (4th ed. 1972 rev.) "Areal density of photo linears occurring within a 5000 meter square grid." Includes location maps. Title assigned by cataloguer. prepared ... by Richard A. Struble and David A. Hodges. Scale 1:250,000 ; Transverse Mercator projection Depths shown by bathymetric isolines.