above map was assembled from the four 45o-quads of the
National Geophysical Data Center (NGDC) public domain maps.
NGDC maps were generated from digital data bases of seafloor and
land elevations on a 2-minute latitude/longitude grid. Assumed
illumination is from the west; shading is computed as a function of
the east-west slope of the surface with a nonlinear exaggeration
favoring low-relief areas. A Cylindrical Equidistant projection was
used for the World image; the resolution of the gridded data varies
from true 2 minutes for the Atlantic, Pacific, and Indian Ocean
floors and all land masses to 5 minutes for the Arctic Ocean floor.