MARC21       008e'18-21  Relief
     Values: 
              #   No relief shown
              a   Contours
              b   Shading
              c   Gradient tints
              d   Hachures
              e   Bathymetry/soundings
              f   Form lines
              g   Spot heights
              h   Color [obs.]
              i   Pictorially
              j   Land forms
              k   Bathymetry/isolines
              z   Other relief type