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